#592: How Much Protein is Actually Healthy? – Eric Helms, PhD & Matt Nagra, ND
Sigma Nutrition Radio
In this episode, the discussion turns to a deceptively simple question that sits at the centre of countless nutrition debates: how much protein do we actually need? On one side, there are confident claims that very high protein intakes are not just beneficial but essential for maximising strength, performance, and muscle mass. On the other, equally strong assertions that the current RDA is entirely sufficient for most people, and that going beyond it is unnecessary or even harmful. Dr. Eric Helms and Dr. Matthew Nagra work through what the evidence actually tells us when we step away from...
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#591: Maintaining Functional Capacity with Age – Brendan Egan, PhD
Sigma Nutrition Radio
Maintaining the ability to carry out everyday tasks and live independently is often described as a cornerstone of healthy ageing. But what actually happens to muscle strength, power, and functional ability as we get older? And how inevitable is their decline? At what point do changes in muscle function really begin to matter for day-to-day life? Is loss of strength an unavoidable consequence of ageing itself, or does it reflect something more modifiable? If declines are not fixed, what kinds of training or lifestyle interventions genuinely make a difference, and how strong is the evidence...
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#590: Is the Nutrient Density of Crops Declining? – Edward Joy, PhD
Sigma Nutrition Radio
Nutrient density refers to the concentration of vitamins and minerals in crops relative to their yield. There are widespread claims that today’s fruits, vegetables, and grains contain fewer micronutrients than in decades past, often linked to modern farming practices or soil degradation. This issue is important because if staple crops become less nutritious, it could silently undermine dietary quality and contribute to micronutrient deficiencies (“hidden hunger”) in populations. Dr. Edward Joy is uniquely qualified to address this topic. As a senior research fellow in food systems and...
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Does Processing Really Make Food Unhealthy? (SNP47)
Sigma Nutrition Radio
This is a Premium-exclusive episode of the podcast. To listen to the full episode you need to be subscribed to . Recently we (Danny Lennon & Alan Flanagan) were invited to ‘Processing the Evidence’, a “behind closed doors” workshop to discuss the latest scientific evidence on the role of processed foods in human health. The event was organized by Professors Ciarán Forde and Vincenzo Fogliano of Wageningen University in the Netherlands. The workshop attendees included a range of prominent researchers across a range of domains related to food processing,...
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#589: Causal Inference in Nutrition Science – Daniel Ibsen, PhD
Sigma Nutrition Radio
This episode explores how asking better questions and using stronger methods can resolve much of the confusion in nutrition science. Dr. Daniel Ibsen discusses why nutrition research often produces conflicting results and how careful methodological thinking can clarify true diet-disease relationships. Nutrition science has unique challenges – diets are complex, people self-report their food intake imperfectly, and we can’t easily run long-term diet experiments on people. Dr. Ibsen explains how embracing concepts like food substitution analysis, the “target trial” framework, and...
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#588: Menstrual Cycle “Syncing”: Do the Claims Hold Up to Evidence? – Expert Panel
Sigma Nutrition Radio
How much do hormonal fluctuations really influence performance and recovery? Should women be adjusting their training and nutrition based on the menstrual cycle? And do female athletes need different protein strategies or recovery protocols than men? These are questions that have fuelled countless online claims, from rigid “cycle syncing” programmes to supposedly gender-specific nutrition rules. But how much of that is actually grounded in evidence? In this episode, the conversation tackles those debates head-on, exploring what we truly know about female physiology, adaptation, and...
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#587: How Should Nutrition Be Taught in Medical Training? – Akash Patel
Sigma Nutrition Radio
This episode centers on the critical gap in nutrition education within medical training and efforts to bridge it. Guest Akash Patel, a medical student who led a pilot nutrition curriculum, discusses why doctors receive little formal training in nutrition despite poor diet being a major driver of disease. With diet-related conditions (obesity, diabetes, cardiovascular disease, etc.) contributing heavily to morbidity and healthcare costs, the conversation highlights a pivotal push to better equip physicians in nutritional knowledge and counseling. Patel’s work comes at a turning point: there...
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#586: The Manufactured Collapse of Expertise
Sigma Nutrition Radio
Never before has there been greater access to information about nutrition and health. But never before has there been such a low barrier to being seen as an “expert”. There are large numbers of people getting information from, and basing their health decisions on, people who don’t have direct expertise in the field in which they are talking about. Moreover, some promote the lack of domain expertise as a feature, not a bug. They claim that those that were conventionally seen as domain experts are either brainwashed, lazy in their thinking, or outright corrupt. And the solution is instead...
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SNP46: Reviewing Six Key Insights from the Year’s Conversations
Sigma Nutrition Radio
This is a Premium-exclusive episode of the podcast. To listen to the full episode you need to be subscribed to . Each year, the conversations on Sigma Nutrition Radio aim to examine the ideas that shape how we understand nutrition, health, and human behavior. This episode brings together the key insights from those discussions, revisiting the most important themes, emerging evidence, and shifts in understanding from the past year. Across topics such as dietary guidelines, ultra-processed foods, sleep, metabolism, environmental exposures, and the psychology of eating, this review...
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#585: Why We Think Poorly: Reason, Emotion, and Evidence-Based Reasoning
Sigma Nutrition Radio
We take a look at critical thinking in science and healthcare, examining how we often fall prey to cognitive biases, emotional reasoning, and flawed thinking. Drawing from six different experts in their respective fields, the episode explores why we sometimes believe we are being rational when in fact our conclusions aren’t truly evidence-based. The discussion spans what genuine evidence-based practice means, how domain expertise matters, and how factors like identity, beliefs, and emotions can derail objective reasoning. Timestamps [02:56] Dr. David Nunan on evidence-based medicine...
info_outlineVitamin A is often one of the less-discussed micronutrients in relation to bone health, taking a back seat to nutrients like calcium and vitamin D. Yet this fat-soluble vitamin plays a fundamental role in skeletal development, remodeling, and mineral homeostasis. It influences gene expression in both osteoblasts and osteoclasts, and contributes to the regulation of bone turnover throughout the lifespan.
But what makes vitamin A particularly interesting, and controversial, is that its effects on bone appear to follow a double-edged pattern. While it’s essential for bone formation, several large epidemiological studies have suggested that chronically high intakes of preformed vitamin A may actually increase the risk of osteoporosis and fracture, especially when consumed as retinol from supplements or high-liver diets. And yet, the picture is not so clear-cut.
This raises compelling questions:
- Is the concern over vitamin A and bone health justified, or is it a case of context-dependent risk?
- Can vitamin A, when combined with adequate levels of D and K, actually support bone strength?
- And are there thresholds above or below which risk increases?
In this episode, we explore the human evidence on vitamin A and skeletal health, looking not only at fracture outcomes and bone mineral density data, but also at nutrient interactions, mechanistic plausibility, and the implications for supplement use in well-nourished populations.
Note: This is a Premium-exclusive episode, so you will only hear a preview on this public feed.
Timestamps
- [00:23] Vitamin A and bone health: an overview
- [02:50] Forms of vitamin A: retinol and carotenoids
- [04:16] Mechanisms of vitamin A in bone physiology
- [17:52] Nutrient interactions: vitamin A, D, and K
- [31:03] Practical takeaways and recommendations
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