Sigma Nutrition Radio
The podcast for lovers of nutrition science! Listen to detailed discussions with researchers and leading experts about the science of nutrition, dietetics and health.
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#620: BPC-157 and Peptide Medications: What Do We Know? – Jordan Feigenbaum, MD
09/15/2026
#620: BPC-157 and Peptide Medications: What Do We Know? – Jordan Feigenbaum, MD
Commonly people are talking about “peptides” to refer to a heterogeneous group of peptide medications or investigational compounds. These are increasingly promoted for injury recovery, tissue repair, performance and longevity, with BPC-157 attracting particular attention. But what evidence supports the claims made about these compounds? How should animal studies, biological mechanisms and personal anecdotes be interpreted? What is currently known about their safety? And what do recent regulatory discussions actually mean for their medical status and availability? In this episode, physician and Barbell Medicine founder Dr. Jordan Feigenbaum examines the evidence surrounding BPC-157 and other peptide medications, alongside the wider questions of risk, access and informed decision-making. Timestamps [00:13] What we want to address [04:47] Interview start [05:29] What do we mean by “peptides”? [10:32] BPC-157 evidence [16:49] Sourcing of peptides [20:19] The gray zone of pro-peptide communication [24:16] Risk sourcing vs drug effects [26:25] FDA lists and compounding [31:05] Risk tolerance and informed consent [43:02] Why did pharma abandon peptide research? [47:44] Harm reduction debate [51:48] Practical takeaways [56:20] Key Ideas segment (Premium members only) Episode Resources Go to Join the for free Subscribe to Enroll in the next cohort of our course Instagram: Book: Related episode: Further reading: Ruenzi M, Stolte M, Veljaca M, et al. Efficacy and safety of PL 14736 (BPC 157) in patients with active ulcerative colitis. Gastroenterology. 2005. Meeting abstract; full study not published.
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#619: How Much Fish Should a Healthy Diet Contain?
09/08/2026
#619: How Much Fish Should a Healthy Diet Contain?
Most dietary guidelines recommend eating one to two servings of fish per week, often specifying that at least one serving should be oily fish. But how directly is that recommendation supported by evidence? And does adding fish to the diet improve outcomes? This episode examines where current fish-intake recommendations originated, why findings may appear contradictory, and what substitution analyses can tell us about replacing fish with alternative options. It also considers evidence from pescatarian and vegetarian cohorts, including whether adding fish would improve an already high-quality diet and whether removing it from a plant-forward diet is likely to provide further benefit. Timestamps [00:20] Setting out the question at hand [03:26] Overview of typical fish intake recommendations [07:10] Is there good evidence for suggested intakes? [08:10] Historical context [13:22] Key evidence: DART trial and cohort data [19:27] Analysis from Mohan et al. [25:04] Comparator issue: what is fish replacing? [30:52] Fish protein vs. plant protein [44:29] Vegetarian vs. pescatarian cohorts [55:20] Conclusions [01:00:50] Key Ideas segment (Premium-only) Episode Resources (with full study reference list) Join the for free Subscribe to Subscribe to Alan’s Enroll in the next cohort of our course
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#618: How Wellness & Optimisation Culture Can Commodify Science – Nick Tiller, PhD
09/01/2026
#618: How Wellness & Optimisation Culture Can Commodify Science – Nick Tiller, PhD
Wellness and optimisation culture increasingly presents itself as “science-based”. But citing studies, using technical language, or having scientific credentials does not guarantee that the underlying evidence is being represented accurately. In this episode, exercise science researcher Dr. Nick Tiller, discusses how science can be selectively packaged, overstated, and used to support commercially attractive health claims. It explores the difference between science communication and science commodification, why scientific scepticism is distinct from cynicism, how anecdotes and mechanistic explanations can mislead, and why a single peer-reviewed study should never be treated as definitive evidence. The conversation also looks further upstream at problems within science itself, including low statistical power, p-hacking, publication bias, questionable research practices, and academic incentives that may favour novelty and positive findings. These issues can then be amplified through media, social platforms, and the wellness industry until tentative findings become confident recommendations. Timestamps: [03:14] Interview start [06:22] The health and wellness “lie” [08:38] Optimization and the illusion of control [11:14] Science communicators vs commodifiers [14:21] Vitamin D hype case study [20:54] Spotting misinformation online [24:50] Skepticism not cynicism [28:47] Guidelines for debunking [33:46] Spotting the grift pattern [41:25] Bad science in academia [54:47] Key ideas segment (Premium-only) Episode Resources: Go to Join the for free Subscribe to Enroll in the next cohort of our course – How Skepticism (not Cynicism) Can Raise Scientific Standards and Reform the Health and Wellness Industry – The Nontechnical Summary: A New Initiative to Enhance the Translation of Sports Science Research and Reduce the Spread of Misinformation
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#617: What Does Effective Athlete Support Look Like in Practice? – Gemma McGuinness
08/25/2026
#617: What Does Effective Athlete Support Look Like in Practice? – Gemma McGuinness
Effective athlete support requires more than delivering technically correct nutrition advice. It depends on understanding the athlete’s wider environment, anticipating the pressures that disrupt good intentions, and building flexible routines that remain useful across training, competition, travel and everyday life. This episode explores how practitioners can move beyond rigid prescriptions, use “good, better, best” options, measure meaningful progress, and create environments in which athletes can communicate openly about difficulties. It also examines identity, transitions out of sport, and why sustainable support should develop an athlete’s autonomy rather than dependence on the practitioner. To discuss all this is Gemma McGuinness, registered performance nutritionist, former professional footballer and co-founder of Verus Performance. Timestamps: [02:38] Interview start [03:48] Nutrition beyond performance [10:10] Identity and food choices [18:47] Standards versus perfectionism [24:52] Planning that actually works [28:32] Measuring progress in athletes [33:37] Where discipline can cause problems [38:40] Building high performance environments [45:37] Key ideas (Premium-only) Links: Join the for free Subscribe to Enroll in the next cohort of our course Instagram:
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Fiber: Independent Benefits or Just a Proxy for Healthy Foods?
08/18/2026
Fiber: Independent Benefits or Just a Proxy for Healthy Foods?
This episode answers one of the questions raised in the most recent Q&A episode on . The full episode includes the following questions: Fiber: Independent effect or proxy for healthy foods? Exposure frequency for matched dose of red meat MTHFR gene mutations and 5-MTHF Typical fish oil supplements vs pharmaceutical-grade products Health impacts of saturated fat in coconut products Do I need to consume whole grains? Could the increasing use of AI pose a threat to doing rigorous science? To listen to the entire episode (plus the back catalogue of all Premium-exclusive episodes) . For episode info and mentioned research .
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#616: More Testing, Better Health? Harms of Overdiagnosis & Overtreatment - Austin Baraki, MD
08/11/2026
#616: More Testing, Better Health? Harms of Overdiagnosis & Overtreatment - Austin Baraki, MD
Medical screening is often framed as an uncomplicated good: if disease is found earlier, treatment can begin earlier and outcomes should improve. This episode examines why that reasoning is incomplete. Screening can produce benefit, but it can also generate false positives, incidental findings, overdiagnosis, overtreatment and diagnostic cascades. Dr. Austin Baraki discusses the distinction between screening people without relevant symptoms and investigating a clinical problem, the probabilistic interpretation of test results, biases that can make screening appear more effective than it is, and the importance of shared decision-making before a test is ordered. Timestamps: [03:35] What screening means [06:36] Choosing what to screen [11:59] Sensitivity and specificity [16:54] Predictive value and prevalence [22:16] Harms of screening and testing [31:02] Overdiagnosis and biases [41:40] The $50,000 physical [44:49] Overdiagnosis vs false positives [53:03] Overtreatment and surveillance [57:22] Clinician action bias [01:02:30] What to screen for Links: (with resources) Join the for free Subscribe to Enroll in the next cohort of our course Instagram: Twitter:
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#615: Why Processing Doesn’t Determine the Healthfulness of Plant-Based Diets – Alysha Thompson, PhD
08/04/2026
#615: Why Processing Doesn’t Determine the Healthfulness of Plant-Based Diets – Alysha Thompson, PhD
What does the evidence actually show when we look at plant-based dietary patterns through the lens of food processing? And does classifying foods as “ultra-processed” meaningfully change how we interpret the relationship between plant-based diets and long-term health outcomes? A recent large prospective cohort analysis examined both healthful and unhealthful plant-based dietary patterns, and importantly, stratified the contributing foods based on whether they were classified as ultra-processed or non-ultra-processed. In this episode, the study’s lead author Dr Alysha Thompson, discusses the many intesresting aspects to the analysis. These include how the dietary indices were constructed, the challenges of applying NOVA classification to self-reported dietary data, the role of residual confounding in observational nutrition research, and the extent to which we can or cannot infer independent effects of processing from these findings. We also consider the broader implications for the use of processing-based classifications in nutrition science and whether this adds meaningful explanatory value beyond traditional assessments of diet quality. Timestamps [03:02] Interview start [05:08] The key research question [07:52] Study design [17:25] Building diet scores [21:11] NOVA classification challenges [25:04] Key findings [38:30] NOVA debate and stance [43:44] Adjustments and mediators [48:11] Future research directions [54:37] Key ideas (premium-only) Resources: Join the for free Subscribe to Enroll in the next cohort of our course Paper:
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#614: The Human Skills of Nutrition Coaching – Krista Scott-Dixon, PhD
07/21/2026
#614: The Human Skills of Nutrition Coaching – Krista Scott-Dixon, PhD
In nutrition and health coaching, one of the central challenges is understanding how people actually change, particularly when life is complex, motivation fluctuates, and behaviour is shaped by emotion, identity, environment, and relationships. In this episode, Dr. Krista Scott-Dixon discusses the human skills that underpin effective coaching practice. We discuss the importance of the coach–client relationship, the role of therapeutic alliance, and how concepts from counselling and psychology can be used appropriately within scope of practice. The discussion also explores autonomy-supportive coaching, self-regulation, compassion, acceptance, feedback, and the meta-skills practitioners need in order to improve over time. Timestamps [06:10] What makes a competent practitioners? [11:17] Scope of practice line [17:49] Therapeutic alliance [23:33] Applying compassion and acceptance [31:18] LLMs vs human connection [34:40] Meta skills for practitioners [38:51] Getting better feedback [44:23] Collaboration and autonomy [55:44] Key ideas recap Links: Join the for free Subscribe to Enroll in the next cohort of our course Past episode #326: Krista’s website: Instagram: The textbook: Applied Nutrition Coaching and Counseling:
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#613: Supplement Safety & Medication Interactions – Giulia Guerrini, MPharm
07/14/2026
#613: Supplement Safety & Medication Interactions – Giulia Guerrini, MPharm
Supplement safety is often discussed in very general terms, but in practice the risks depend heavily on the individual. A supplement that is reasonable for one person may be inappropriate for another based on their medications, health conditions, dose, formulation, or the other products they are already using. This becomes especially important when supplements interact with medications or underlying medical conditions. Some interactions can change how a drug is absorbed, metabolised, transported, or cleared from the body. Others can amplify or oppose the drug’s clinical effect, such as increasing sedation, lowering blood pressure or blood glucose, or affecting bleeding risk. In this episode, Giulia Guerrini, a GPhC-registered pharmacist and researcher at Examine, talks about how clinicians and practitioners can think more systematically about supplement safety, side effects, contraindications, and drug–supplement interactions. Timestamps: [02:39] Interview start [05:21] Why context matters [06:38] Timing and formulation [12:58] Rating interaction risk [22:39] Berberine benefits and interactions [27:33] Adaptogens quality concerns [30:15] Melatonin safety questions [36:30] Stacking supplements risks [41:50] Quality control and regulation [55:35] Key ideas segment (premium-only) Links: – For health & nutrition professionals. Includes the Supplement Navigator (safety and interaction checking), plus all other Examine tools (study summaries, supplement database, in-depth guides, etc.) – For anyone wanting to make evidence-based decisions about supplements and health. Includes: 100+ study summaries a month. The full supplement database. In-depth guides. ExamineAI. Doesn’t include the Supplement Navigator. Subscribe to
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#612: Does Sweet Taste Exposure Actually Develop Preference? – Prof. Katherine Appleton
07/07/2026
#612: Does Sweet Taste Exposure Actually Develop Preference? – Prof. Katherine Appleton
A common idea is that repeated exposure to sweet taste strengthens our preference for sweetness, which then drives greater intake of sweet foods and drinks. This idea is often used in arguments about fruit, low-calorie sweeteners, diet drinks, and the supposed need to “reset” taste preferences by avoiding sweetness altogether. But does the evidence actually support that causal chain? In this episode, Prof. Katherine Appleton, Professor of Psychology at Bournemouth University, discusses what is known about sweet taste exposure, sweet preference, and how these concepts are measured in the scientific literature. Timestamps: [04:23] Interview starts [07:35] Sweetness terms explained [10:17] Sweet liker phenotypes [14:03] Liking vs wanting vs preference [19:18] Trial evidence overview [23:48] Policy and practical impact [30:41] Why we eat foods Links: (incl. links to studies) Join the for free Subscribe to Enroll in the next cohort of our course
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#611: Electrolyte Mythology: Wellness Marketing vs. Evidence - Zoë Rom & Kylee Van Horn
06/30/2026
#611: Electrolyte Mythology: Wellness Marketing vs. Evidence - Zoë Rom & Kylee Van Horn
Electrolytes have become one of the most heavily marketed areas of modern sports nutrition and wellness. What was once a relatively specific tool for certain endurance athletes has increasingly been reframed as an everyday requirement for hydration, energy, focus, productivity, and general health optimisation. But how much of this messaging is grounded in physiology, and how much is an example of industry taking a real mechanism and extending it far beyond the evidence? In this episode, we examine why many common use cases are unlikely to require an electrolyte product. Along the way, we explore how wellness marketing, biohacking culture, diet communities, and social media narratives can turn narrow sports nutrition applications into broad claims that many people come to accept as true. To discuss this topic, Danny is joined by Zoe Rom, a science and environmental journalist, and Kylee Van Horn, a sports dietitian, to discuss how these claims are shaped by marketing, culture, and the attention economy. Timestamps: [04:00] Interview start [07:03] Wellness industry rebrand [09:16] Electrolytes 101 [16:02] Fear marketing and vague symptoms [22:50] When athletes actually need them [28:19] Salt fix and anti science narratives [33:53] Keto biohacking and identity [43:42] How to evaluate your need [48:43] Who should skip electrolytes Links: Go to Join the for free Subscribe to Enroll in the next cohort of our course podcast – Endurance Sports Nutrition
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SNP51: Understanding Blood Glucose Reponses
06/23/2026
SNP51: Understanding Blood Glucose Reponses
This is a Premium-exclusive episode. Go to the Premium feed to listen. Or subscribe to . Blood glucose is easy to measure, but not always easy to interpret. This Premium-only episode brings together insights from several previous guests to examine blood glucose responses in more detail. We discuss the misuse of clinical thresholds, the difference between OGTT results and free-living CGM data, and whether “flatter” glucose curves are actually better in normoglycemic people. The episode also covers when repeated high glucose excursions may be worth investigating, how sugar intake should be interpreted in context, and why skeletal muscle and exercise play such an important role in glucose regulation. Overall, the aim is to clarify what glucose responses can tell us, what they cannot tell us, and how to avoid pathologizing normal physiology. Links: Join the for free Subscribe to Enroll in the next cohort of our course
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#610: Rock, Paper, Salmon – Errors in Interpreting Food Substitution Models
06/16/2026
#610: Rock, Paper, Salmon – Errors in Interpreting Food Substitution Models
When considering the health impact of foods, it is important to consider “compared to what?”. Increasing the amount of a certain food or nutrient in the diet, typically implies a displacement of another. While comparisons are more obvious in trials, in epidemiology food substitution models can be useful to help us determine the health effects of increasing/decreasing intake of a food, food group or nutrient. However, these models are often misinterpreted and miscommunicated as if they are a game of “rock, paper, scissors”, where one food beats another, and the losing food must be removed from the diet or considered harmful to health. In this episode we discuss the problem of treating substitution analyses as food-ranking contests, rather than context-dependent comparisons shaped by the comparator, the unit of substitution, the baseline diet, and the outcome being studied. Timestamps: [01:30] Misuse of "compared to what?" [06:39] What substitution models do [10:43] Specified vs unspecified substitution [16:57] Why the units used matter [26:45] Example: organic vs conventional produce [31:22] When substitutions are useful [34:35] If legumes beat fish, does that mean fish intake should be zero? [44:31] Naive vs bias-adjusted: artificial sweeteners case study [49:14] Checklist: how to interpret food substitution analyses Links: (all study references linked) Join the for free Subscribe to Subscribe to Enroll in the next cohort of our course Episode #472: Episode #589:
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#609: Unprocessed Red Meat & Cancer Risk
06/09/2026
#609: Unprocessed Red Meat & Cancer Risk
Unprocessed red meat and cancer risk remains one of the most debated topics in nutrition science, partly because the evidence is often presented in overly simplistic terms. The key question is not whether to adopt a vague “balanced” position on red meat, but whether the evidence clearly identifies intake levels at which colorectal cancer risk increases and whether controlled human trials support plausible mechanisms for that risk. A second issue is whether claims that fibre, vegetables, or an otherwise “healthy diet” can neutralise high red meat intake are actually supported by the mechanistic evidence, or whether they overstate what dietary context can plausibly offset. In this episode, Danny and Alan examine the evidence base by moving beyond the usual epidemiology-only debate. They discuss why regional intake patterns and dose thresholds matter, then explore controlled human feeding studies showing how higher red meat intake can increase endogenous N-nitroso compound formation, faecal water genotoxicity, and other mechanistic biomarkers linked to colorectal carcinogenesis. Timestamps: [01:11] Defining the exposure and outcome [02:34] Carcinogen labels explained [07:54] Epidemiology and dose thresholds [14:04] Interpreting null findings [19:09] Bingham 1996 nitroso study [25:20] Hughes dose response trial [33:49] Cross 2003 heme iron mechanism [42:55] Fecal water genotoxicity [55:42] Tumor mutational signatures [59:38] What we can conclude now [01:04:10] Practical intake recommendations [01:08:41] Key ideas segment (premium-only) Links: (includes links to studies mentioned) Subscribe to Join the for free Enroll in the next cohort of our course
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#608: Performance Nutrition in Elite Rugby – James Morehen, PhD
06/02/2026
#608: Performance Nutrition in Elite Rugby – James Morehen, PhD
Performance nutrition in elite sport is often discussed in terms of meal plans, supplements, and macronutrient targets. However, effective practice in professional environments depends just as much on education, trust, communication, and the ability to translate scientific principles into decisions athletes can act on under real-world constraints. In this episode, Dr James Morehen discusses his work across elite rugby, football, and combat sports, with particular attention to the demands of professional rugby. The conversation explores how practitioners support athletes in a high-impact collision sport, including fuelling for training and match play, managing body composition without reducing athletes to arbitrary numbers, addressing recovery from muscle damage and injury, and developing practical systems around game-day nutrition. The episode also provides insight into the realities of building a career in performance nutrition, including the importance of applied experience, interdisciplinary collaboration, and learning how to coach athletes rather than simply prescribe to them. Timestamps: [03:31] Interview starts [10:26] Educating athletes on nutrition [13:55] Breaking into elite sport [26:26] Physiological demands of rugby [30:53] Energy needs and timing [38:28] Body composition measurements: utility? [46:16] Game day fuelling strategy [01:07:09] Key ideas (premium-only) Links: Join the for free Subscribe to Enroll in the next cohort of our course James’ Instagram: James’ LinkedIn: Related episodes:
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#607: Gut Health & Microbiome Testing: What Evidence Do We Actually Have? – Emily Leeming, PhD
05/26/2026
#607: Gut Health & Microbiome Testing: What Evidence Do We Actually Have? – Emily Leeming, PhD
Gut health has become a major focus in nutrition, medicine, and consumer wellness, but the term is often used loosely. Claims about microbiome testing, probiotics, fermented foods, fibre, and “boosting” the gut microbiome are now common, yet the evidence behind these claims varies substantially. In this episode, Dr. Emily Leeming examines what gut health actually refers to, why it cannot be reduced to the microbiome alone, and where current microbiome science is being applied before it is ready. The discussion covers the limits of commercial stool testing, the difficulty of defining a healthy microbiome, and the practical strategies most strongly supported by current evidence. Timestamps: [02:48] Interview start [04:17] Defining gut health [09:03] What is a "healthy microbiome"? [15:25] Microbiome testing - any clinical utility? [24:08] Interpreting microbiome studies [34:39] "30 plants a week" is not evidence-based [39:53] Serotonin and gut brain [45:34] Fiber research frontier Links/Resources: (w/ links to mentioned studies) Join the for free Subscribe to Enroll in the next cohort of our course Dr. Leeming’s newsletter:
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PMOS (PCOS) and Diet: What Can Nutrition Realistically Do? - SNP#50
05/21/2026
PMOS (PCOS) and Diet: What Can Nutrition Realistically Do? - SNP#50
In this episode, we examine what nutrition can realistically do in the condition historically known as PCOS, now renamed polyendocrine metabolic ovarian syndrome, or PMOS. We begin by explaining why the name change matters: the condition is not defined by ovarian cysts, but is better understood as a broader endocrine-metabolic and ovarian syndrome involving insulin resistance, androgen excess, ovulatory dysfunction, metabolic risk, and psychological burden. We then assess the nutrition evidence, including energy restriction, weight loss, carbohydrate quality, glycaemic index and load, protein intake, fat quality, appetite regulation, fertility outcomes, and phenotype differences. Rather than seeking a single “PCOS diet”, the episode asks which dietary features may plausibly help, how strong the evidence is, and where uncertainty remains. This is a Premium-exclusive episode. To listen to the full episode, subscribe to . Links: Go to Subscribe to Join the for free
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#606: Practical Nutrition Strategies for Fat Loss – Luke Hanna
05/19/2026
#606: Practical Nutrition Strategies for Fat Loss – Luke Hanna
Body composition goals, particularly bodyfat loss, are among the most common reasons people seek support from a nutritionist or health and fitness professional. While the principles are well established, the challenge is helping individuals apply them consistently in real-world conditions. Many people struggle due to hunger, unrealistic expectations, emotional eating, inconsistent routines, or overly restrictive dieting approaches. These challenges can make fat loss difficult to sustain, even when someone understands what they “should” be doing. In this episode, Luke Hanna discusses practical strategies for improving body composition, including food diaries, energy-density manipulation, preloads, mindful eating, and realistic goal-setting. The discussion emphasizes identifying individual barriers, collaborating with clients, and building repeatable behaviours that support both fat loss and long-term maintenance. Luke Hanna holds a Master’s degree in Obesity and Clinical Nutrition from University College London and a degree in Sport and Exercise Science from the University of Portsmouth. He currently works as a nutrition coach and personal trainer. Timestamps: [03:15] Interview [05:39] Client assessment basics [11:59] Alternatives to tracking [13:57] Volume eating [18:56] Preloads before meals [22:25] Snacking and hunger types [26:44] Habits and food environment [30:40] Managing expectations [33:51] Transition to maintenance [39:09] Key ideas (premium-only) Links: (with resources) Join the for free Subscribe to Instagram:
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#605: Fasting, Nutrient Timing & CGMs: Interpreting the Evidence – Prof. James Betts
04/23/2026
#605: Fasting, Nutrient Timing & CGMs: Interpreting the Evidence – Prof. James Betts
Fasting, nutrient timing, chrono-nutrition, and continuous glucose monitoring are all topics that have generated substantial interest, but they are also areas where exaggerated claims can easily outpace the underlying evidence. In many cases, tentative hypotheses are presented as if they were already well-established conclusions, despite the fact that the research base is often more mixed and context-dependent than popular narratives imply. It is one thing for an idea to appear biologically coherent. It is another for that idea to translate into meaningful, reliable effects in real-world interventions. In this episode, Professor James Betts discusses how to think clearly about these topics, why common errors in interpretation can lead to overstated conclusions, and what is required to properly evaluate whether an observed effect reflects a true intervention effect rather than baseline differences, inappropriate comparisons, within-group changes, or mechanistic signals being mistaken for meaningful health outcomes. Timestamps: [04:24] Background into Prof. Betts' research [07:28] Evidence in fasting research over past 5-6 years [10:15] Hype vs evidence in intermittent fasting [16:44] Spotting spin in study conclusions [17:31] Common statistical red flags [24:45] Methods matter in fasting trials [31:10] Exercise nutrient timing [38:32] CGMs what they measure, misuse and patterns [53:59] Key ideas (premium-only) Links: Go to (study links, bio, etc.) Join the for free Subscribe to Enroll in the next cohort of our course
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#604: How To Interpret Nutrition Research – David Allison, PhD
05/05/2026
#604: How To Interpret Nutrition Research – David Allison, PhD
How should we decide what counts as trustworthy evidence? Scientific rigor is not a single characteristic of a study, but a chain of decisions made from the moment a question is conceived to the point at which findings are communicated to the public. Errors can occur at every stage: the question may be ill-posed, the design may be incapable of answering it, the measurements may be weak, the analysis may be inappropriate, the interpretation may overreach, and the public-facing communication may become distorted. In this episode, Dr. David Allison, PhD discusses the deeper methodological issues that shape the field’s conclusions. The discussion moves from the philosophy of scientific inquiry to the practical realities of study design, statistical analysis, interpretation, and dissemination. Timestamps: [03:30] Interview start [06:17] What is true scientific rigor? [10:06] Study design and analysis problems in nutrition [12:56] The DINS error [14:14] Conflation of heterogeneity in response vs. in outcomes [17:31] Misunderstanding of p-values and hypothesis testing [27:01] Incorrect labelling of “responders” and “non-responders” [34:49] Errors related to analysis of secondary outcomes [45:01] How can nutrition science improve as a field? [51:30] Key ideas segment (Premium-only) Links: (with list of episode resources) Subscribe to Enroll in the next cohort of our course
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#603: Should Dietary Fiber Be Considered Essential? – Andrew Reynolds, PhD
04/28/2026
#603: Should Dietary Fiber Be Considered Essential? – Andrew Reynolds, PhD
Dietary fiber is widely recognized as an important component of a healthy diet, yet it is not typically classified as an essential nutrient. In this episode, Dr. Andrew Reynolds explores whether that distinction still holds, arguing that the traditional criteria used to define essentiality may be outdated when applied to modern nutrition science. The discussion moves beyond simply acknowledging the benefits of fiber and instead examines whether it meets the foundational requirements of an essential nutrient. This includes considering its physiological roles, the body’s inability to synthesize it in sufficient quantities, and whether low intake leads to a meaningful and reversible dysfunction. Drawing on evidence from prospective cohort studies, randomized controlled trials, and mechanistic research, Reynolds outlines the strength of the evidence linking higher fiber intakes to reduced risk of cardiovascular disease, type 2 diabetes, colorectal cancer, and premature mortality. Reynolds presents a compelling case that fiber may play a fundamental role in maintaining normal physiological function and therefore warrants reconsideration within the framework of essential nutrients. Timestamps: [03:50] Interview starts [05:53] Understanding essentiality [09:26] Could there be a deficiency-state for fiber? [15:38] What are fiber guidelines based on? [23:52] Fiber and chronic disease risk: dose-response [28:59] Different types of fiber [37:21] Fermentation and SCFAs [42:55] Research priorities ahead [50:04] Low fiber health risks [58:02] Key Ideas segment (Premium-only) Related Resources: Go to Join the for free Subscribe to Enroll in the next cohort of our course
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#602: Avoidant/Restrictive Food Intake Disorder (ARFID) – Megan Hellner, DrPH, RD & Katherine Hill, MD
04/21/2026
#602: Avoidant/Restrictive Food Intake Disorder (ARFID) – Megan Hellner, DrPH, RD & Katherine Hill, MD
Avoidant/Restrictive Food Intake Disorder (ARFID) is an eating disorder diagnosis characterized by a persistent restriction or avoidance of food intake that results in clinically significant consequences (medical, nutritional, and/or psychosocial), but without the weight- and shape-driven psychopathology typical of anorexia nervosa and bulimia nervosa. In this episode, Megan Hellner and Katherine Hill outline how ARFID presents across the lifespan, why it is frequently missed in routine healthcare, and what an evidence-informed assessment and treatment pathway can look like in practice. A central theme is that ARFID is not synonymous with “picky eating” and not confined to any one body size. Patients may present at any point on the weight chart, including those who are weight-stable or in larger bodies, and the condition can begin in early childhood and persist into adulthood. The episode also highlights ARFID in athletes and physically active people, where restricted dietary variety and/or low intake can contribute to low energy availability and RED-S-like presentations, sometimes without an obvious intent to lose weight. Timestamps [03:48] Interview start [06:23] What is ARFID? DSM-5 definition vs “picky eating” [09:36] Clinical red flags: when restriction becomes a disorder [11:37] ARFID isn’t always underweight: missed cases & diagnostic pitfalls [16:46] ARFID presentation profiles: low interest, sensory sensitivity, fear [18:59] Comorbidities & nutrition consequences [25:16] Evidence-based ARFID treatment [29:16] How to expand foods without pressure [32:28] Weight restoration, stabilization, and long-term maintenance [35:44] What research still needs [38:16] Differential diagnosis & referral Links/Resources (with links to papers and ARFID resources) Subscribe to Join the for free Enroll in the next cohort of our course
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#601: Gallstones & Gallbladder Conditions: Impact of Diet – Angela Madden, PhD RD
04/14/2026
#601: Gallstones & Gallbladder Conditions: Impact of Diet – Angela Madden, PhD RD
This episode examines what we actually know (and importantly, what we do not know) about diet in relation to gallstones and gallbladder conditions. Much of the public-facing guidance around gallstones focuses on “avoiding fatty foods”, yet Dr. Angela Madden explains that this long-standing practice sits on surprisingly weak direct evidence, particularly when judged against the standards typically expected for clinical dietary recommendations. A central theme is the need to separate two distinct questions: dietary factors that influence the risk of developing gallstones (prevention), versus dietary strategies intended to reduce symptoms or complications once gallstones exist (management). While the prevention literature suggests plausible, consistent associations with overall diet quality and lifestyle factors, the specific question of prescribing a low-fat diet to manage symptomatic gallstones lacks robust randomized trial evidence. Dr Angela Madden is a clinical researcher in nutrition and dietetics at the University of Hertfordshire, where she established and led the nutrition and dietetics subject group and now focuses her research on improving nutritional assessment, dietary interventions, and patient-centred outcomes in clinical and public health settings. Timestamps [02:09] Discussion with Dr. Angela Madden begins [06:53] Understanding the gallbladder [08:08] Gallbladder disorders and their prevalence [13:42] Risk factors and pathophysiology [22:15] Dietary factors and gallstone formation [27:20] Exploring dietary fat and gallstones [34:09] Broader dietary considerations [45:44] Practical dietary recommendations Related Resources Go to Join the for free Subscribe to Enroll in the next cohort of our course Cochrane Review: Related episode: 513: Kidney Stones & Diet – Deepa Kariyawasam, RD
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Coevolution With Foods? Multivitamins? Eating Too Early? – Ask Me Anything (SNP49)
04/07/2026
Coevolution With Foods? Multivitamins? Eating Too Early? – Ask Me Anything (SNP49)
In this episode, Danny answers questions submitted by Premium subscribers. Questions Answered in This Episode: [00:05:13] Is eating too early (relative to chronotype) metabolically problematic? [00:16:55] Can plant-based diets reverse cardiovascular disease? [00:32:54] Are multivitamins useful insurance, or a waste with a good diet? [00:44:56] Does coevolution with foods determine human compatibility and benefit? [00:56:25] How should consumers choose supplement formulations and brands? [01:04:46] Folate vs folic acid: differences and best choice for women of childbearing age? [01:12:37] How reliable is omega-3 content in farmed salmon, especially imported frozen salmon? [01:19:18] How accurate are food labels for metabolizable energy and absorption, especially across processing levels? [01:23:58] Protein needs in breastfeeding and general rehabilitation (non-sport injury)? To listen to the full episode, . Related Resources (with full resource list) Subscribe to Resources for this episode:
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#600: Finite Knowledge, Infinite Ignorance
03/31/2026
#600: Finite Knowledge, Infinite Ignorance
“The more we learn about the world, and the deeper our learning, the more conscious, specific, and articulate will be our knowledge of what we do not know, our knowledge of our ignorance. For this, indeed, is the main source of our ignorance — the fact that our knowledge can be only finite, while our ignorance must necessarily be infinite.” – Karl Popper To mark Sigma Nutrition’s milestone 600th episode (and 12-year anniversary), Danny and Alan examine several areas in which their views have changed, softened, strengthened, or remained stable over the lifespan of the podcast. The discussion is therefore not only about nutrition itself, but also about the process of scientific reasoning: how positions are formed, what type of evidence can shift them, and why changing one’s mind is often a sign of better thinking rather than inconsistency. The episode therefore serves as both a review of several specific nutrition controversies and a lesson in scientific epistemology. They discuss topics such as red meat, protein, dietary cholesterol, omega-3s, flavonoids, and sodium. Timestamps [11:04] Time-restricted eating [19:32] Protein intake, quality & dosing [35:04] Cocoa flavanols and cognition [51:38] Unprocessed red meat [01:05:23] Omega-3 supplementation [01:23:10] Dietary cholesterol [01:44:41] Sodium J-curve myth [01:53:41] Energy balance model Links (with study links & resources) Join the for free Subscribe to Enroll in the next cohort of our course
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#599: Does Unprocessed Red Meat Increase Diabetes Risk? – Gil Carvalho, PhD MD & Mario Kratz, PhD
03/24/2026
#599: Does Unprocessed Red Meat Increase Diabetes Risk? – Gil Carvalho, PhD MD & Mario Kratz, PhD
This episode examines whether unprocessed red meat has a causal role in (1) type 2 diabetes risk and intermediate measures of glucose intolerance (insulin resistance, beta cell dysfunction, glycemic markers) and (2) cardiovascular disease (CVD) risk. While there is commonly observed risk signal from observational cohorts, there exist short-term randomized controlled trials (RCTs) that show largely null effects on glucose homeostasis. This had led to differing opinions and interpretations of the evidence base. Some feel that in the context of an otherwise healthy diet, there isn’t much to suggest concern about consuming unprocessed red meat. While others are of the view that there does exist a risk and that limiting or even avoiding consumption is prudent. The crucial concept of replacement effects is discussed. Increasing red meat intake always means decreasing something else or increasing total energy intake. Therefore, interpreting evidence requires specifying the comparator food(s), the background dietary pattern, the dose, the cut (lean vs fatty), and how the meat is prepared. To discuss their interpretations of this contentious evidence base, Dr. Mario Kratz and Dr. Gil Carvalho join the podcast to go through the studies most directly related to these questions. Timestamps [06:20] Red meat’s impact is debated [10:54] Mechanisms linking meat to diabetes [15:31] Cohort evidence on diabetes risk [24:43] Differences between cohorts and threshold effects [33:13] RCT evidence and substitution trials [45:49] Why comparator foods matter [50:43] RCT examples and mixed results [01:00:30] Is there cardiovascular risk beyond saturated fat? [01:08:10] Epidemiology patterns and dose thresholds [01:11:36] Personal recommendations and risk tolerance [01:16:19] Key ideas Related Resources (study links, guest bios, additional resources) Join the for free Subscribe to Enroll in the next cohort of our course Mario’s YouTube channel: Gil’s YouTube channel:
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#598: How Do Exercise & Diet Interact to Improve Glycaemic Control? – Jenna Gillen, PhD
03/17/2026
#598: How Do Exercise & Diet Interact to Improve Glycaemic Control? – Jenna Gillen, PhD
This episode examines how exercise and nutrition interact to influence glycaemic control, with particular focus on the postprandial period (i.e., the hours after eating) and on “time-efficient” exercise strategies such as low-volume interval training. Dr. Jenna Gillen outlines the physiological basis for why muscle contraction can acutely reduce post-meal glucose excursions, why repeated sessions can accumulate into longer-term improvements in insulin sensitivity, and why the nutrition context (pre- and post-exercise feeding, carbohydrate availability, and energy balance) can meaningfully alter observed outcomes. A key translational thread is that many clinically relevant improvements may come from small, feasible doses of activity; especially post-meal walking and brief “exercise snacks” used to interrupt sedentary time. However, the discussion considers who these interventions matter for most (and least). Postprandial glucose rises are normal in healthy individuals, whereas reducing exaggerated excursions is most relevant for those with insulin resistance, prediabetes, or type 2 diabetes (T2D). Dr. Jenna Gillen is an Assistant Professor of Exercise Physiology in the Faculty of Kinesiology & Physical Education at the University of Toronto. Timestamps [02:42] Dr. Gillen’s research focus [04:11] Understanding glycemic control [10:07] Fasted vs. fed state exercise [11:10] Post-meal exercise benefits [20:10] Low volume interval training [26:27] Interval training and blood glucose [31:29] Energy balance and insulin sensitivity [36:32] Exercise and nutrition interactions [40:11] Practical exercise recommendations [43:56] Key ideas segment (Premium-only) Links (with links to papers) Join the for free Subscribe to Enroll in the next cohort of our course See
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#597: Behavioral Psychology in Diet & Health Counselling – David Creel, PhD, RD
03/10/2026
#597: Behavioral Psychology in Diet & Health Counselling – David Creel, PhD, RD
In clinical practice effective nutrition, exercise, and obesity care is rarely about identifying the single “best” plan on paper. Instead, sustainable change depends on behavioral psychology: understanding the person’s context, motivation, barriers, and patterns, then co-designing practical steps that can actually be implemented in real life. David Creel PhD, RD is a clinical psychologist and registered dietitian working in weight management at the Cleveland Clinic. Dr. Creel discusses how clinicians can bridge the gap between “optimal recommendations” and what is most likely to create actual behaviour change. This includes a combination of using collaborative communication, self-monitoring, skill-building, relapse prevention planning, and a multidisciplinary framework. Behavioral and psychological factors shape food choices, physical activity, and adherence far more than knowing the newest guideline. In addition, the modern obesity treatment landscape (including GLP-1 receptor agonists) increases the need for structured behavior-change support: people may experience new hope and new fear (especially fear of weight regain), and the key clinical question becomes how to use these tools to build durable habits and reduce relapse risk over the long term. Timestamps [03:09] Start of interview [05:31] Challenges in nutrition and exercise recommendations [11:01] Behavior change in real-world practice [16:32] Self-monitoring and its importance [23:48] Non-scale victories and positive body image [25:58] Focusing on body capabilities over aesthetics [27:20] Integrating activity into lifestyle [30:30] Exercise snacking and practical tips [33:36] Impact of GLP-1 receptor agonists [38:24] Addressing fear of weight regain [41:24] Effective multidisciplinary obesity treatment Related Resources Join the for free Subscribe to Enroll in the next cohort of our course LinkedIn: X/Twitter:
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#596: Why Do Omega-3 Trials Show Mixed Results?
03/03/2026
#596: Why Do Omega-3 Trials Show Mixed Results?
Omega-3 fatty acids (particularly EPA and DHA) have a long history in nutrition and cardiovascular medicine, yet the clinical trial literature is often perceived as inconsistent. This episode examines why some randomized trials show clear benefit while others show null or mixed findings, and how differences in trial design, dose, population risk, and outcome selection can materially change what we observe. A key theme is separating (1) the persistent cultural narratives around omega-3s (including origin stories that do not hold up well to modern evidence) from (2) the more precise, mechanistic and clinical questions about where supplemental EPA/DHA may reduce cardiovascular risk. The discussion focuses heavily on understanding heterogeneity: why “omega-3 supplementation” is not a single, uniform exposure, and why subgroup patterns (e.g., secondary prevention, higher baseline triglycerides, and higher doses) may explain much of the apparent conflict in the evidence. Note: This discussion is taken from a previous episode of the podcast. The audio has been remastered and improved, and now study notes and full transcript are available. Timestamps [04:10] Omega-3 historical context and Inuit studies [08:38] Mechanisms of omega-3 benefits [12:49] VITAL and ASCEND trials analysis [23:41] GISSI-Prevenzione trial insights [26:44] REDUCE-IT trial and residual risk [32:19] Significance of baseline triglycerides [37:57] 2018 Cochrane review [46:02] Hu et al. meta-analysis [01:00:27] Practical takeaways for omega-3 supplementation [01:03:55] Key ideas segment (premium subscribers only) Related Resources (with links to mentioned studies) Join the for free Subscribe to Enroll in the next cohort of our course Alan Flanagan’s
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#595: Neuroplasticity and Reducing Risk of Cognitive Impairment – Dr. Majid Fotuhi
02/24/2026
#595: Neuroplasticity and Reducing Risk of Cognitive Impairment – Dr. Majid Fotuhi
Conversations about brain health have been dominated by a competing mix of fatalism and over-promising, with aging framed as inevitable decline and “brain optimisation” sold through weak evidence. So how should we think about cognition across the lifespan? In this episode, we explore the idea that neuroplasticity does not disappear in adulthood, but instead continues to respond, for better or worse, to repeated behaviours and exposures. Much of what is labelled age-related cognitive decline may in fact reflect an accumulation of modifiable risk factors. We also dig into how to critically evaluate brain-health claims and how lifestyle pillars such as exercise, sleep, diet, stress reduction and cognitive training fit into a coherent framework. The discussion extends to emerging multimodal intervention programs, their promising signals and their clear limitations, and to a broader, multifactorial view of Alzheimer’s disease that moves beyond a narrow amyloid-centric model. Finally, we examine the role of genetics, including ApoE4, and why genetic risk does not equate to biological destiny, even later in life. Dr. Majid Fotuhi is a neurologist and an adjunct professor at the Johns Hopkins Mind/Brain Institute. He earned his medical degree from Harvard Medical School and completed a Ph.D. in neuroscience at Johns Hopkins University. That was followed by internship and neurology residency at Johns Hopkins Hospital. Timestamps [03:41] Understanding neuroplasticity [05:22] Risk factors for cognitive decline [07:07] Evidence-based interventions for brain health [09:37] The five pillars of brain health [10:42] Dr. Fotuhi’s multimodal program [19:09] Measuring cognitive function [24:43] The role of amyloid and tau in Alzheimer’s [27:53] Genetics and lifestyle in brain health [30:03] Debunking myths and overhyped claims [36:08] Key ideas segment (premium subscribers only) Related Resources (with links to studies mentioned) Join the for free Subscribe to Enroll in the next cohort of our course Dr. Fotuhi’s book:
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