Sigma Nutrition Radio

Can broad-spectrum vitamin and mineral supplements improve anxiety, depression or emotional regulation?

In this Premium-exclusive episode, we examine three randomised, placebo-controlled trials from Professor Julia Rucklidge's research group: NoMAD, investigating anxiety and depressive symptoms in adults; NUTRIMUM, examining depressive symptoms during pregnancy; and BEAM, studying irritability and emotional dysregulation in adolescents.

These studies offer an opportunity to explore some central challenges in interpreting nutrition and mental health research. What does "faster improvement" mean when groups reach similar outcomes by the end of a trial? How should improvements in overall functioning be weighed against results from depression-specific measures? And how much confidence should we place in a large treatment effect found within a small subgroup?

Links:

• Go to episode page
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Studies discussed:

• NoMAD trial – Blampied et al., 2023
• NUTRIMUM trial – Bradley et al., 2024
• BEAM trial – Rucklidge et al., 2026

• Related episodes:

• #117: Prof. Julia Rucklidge – Role of Micronutrients in Mental Health & Psychiatric Disorders
• #473: Diet & Depression (What Do We Actually Know?) – Nicole Lippman-Barile, PhD

Claims about "improving the gut microbiome" are widespread, but what would improvement actually mean? How do we establish which microbial changes contribute to disease, and which simply reflect it?

Research on bacterial metabolism of medications raises questions about how the microbiome might influence treatment efficacy and toxicity. What would it take to translate these findings into reliable tests and effective therapies?

In this episode, gastroenterologist and researcher Prof. Harry Sokol examines these questions, discusses the development of Faecalibacterium prausnitzii as an investigational treatment, and considers what current evidence can tell us about dietary advice and commercial microbiome testing.

Timestamps

•

[02:50] Harry Sokol's work

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[04:36] Defining healthy microbiome

•

[06:48] Do we have causal evidence?

•

[11:05] FMT evidence

•

[15:29] Diet-microbiome claims

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[20:45] Emulsifiers & IBD research

•

[22:54] Microbiome-drug interactions

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[30:23] Bacteria as a drug?

•

[38:09] Microbiome testing

•

[44:36] Key ideas segment (Premium-only)

Introduction

Claims about "improving the gut microbiome" are widespread, but what would improvement actually mean? How do we establish which microbial changes contribute to disease, and which simply reflect it?

Research on bacterial metabolism of medications raises questions about how the microbiome might influence treatment efficacy and toxicity. What would it take to translate these findings into reliable tests and effective therapies?

In this episode, gastroenterologist and researcher Prof. Harry Sokol examines these questions, discusses the development of Faecalibacterium prausnitzii as an investigational treatment, and considers what current evidence can tell us about dietary advice and commercial microbiome testing.

Timestamps

•

[02:50] Harry Sokol's work

•

[04:36] Defining healthy microbiome

•

[06:48] Do we have causal evidence?

•

[11:05] FMT evidence

•

[15:29] Diet-microbiome claims

•

[20:45] Emulsifiers & IBD research

•

[22:54] Microbiome-drug interactions

•

[30:23] Bacteria as a drug?

•

[38:09] Microbiome testing

•

[44:36] Key ideas segment (Premium-only)

On this episode:

• Host: Danny Lennon
• Guest: Prof. Harry Sokol

Episode Resources:

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Exeliom Biosciences
• Book: MICROBIOME: Science, Promises and Lies
• Instagram: @harry_sokol
• LinkedIn: Prof. Harry Sokol

Can an athlete reduce the environmental impact of their diet while still meeting the demands of training, competition and recovery? Peter Res argues that these aims can be compatible, provided dietary changes are planned around the athlete's needs.

The discussion looks at practical changes athletes can make to make their diets more environmentally sustainable. This includes tips on increasing the contribution of plant proteins, maintaining adequate energy intake, and making plant-rich eating practical within sporting environments.

Timestamps

•

[04:21] Peter Res' background

•

[05:22] Defining sustainability metrics

•

[08:17] Biggest diet change to make it more environmentally sustainable

•

[09:23] Is local and organic actually better?

•

[13:44] Athlete fears about protein

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[18:07] Barriers for athletes

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[19:37] Fueling high calorie needs

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[21:26] Micronutrients

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[24:02] Performance effects

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[26:32] Athletes as role models

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[30:17] Easy first steps

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[34:21] Premium-only: key ideas segment

Links:

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• LinkedIn: Peter Res
• Fork Ranger
• Related episodes:

• #320: Hannah Ritchie, PhD – Environmental Impacts of our Diet: Climate, Carbon Footprint & Land Use
• #446: How Climate Change Impacts Nutrient Status
• #584: EAT-Lancet: Does the Planetary Health Diet Improve Human Health?

•

Men commonly feel that if their testosteone isn't "optimized" and high, they are missing out on greater health in a variety of ways. But what can a testosterone result actually tell us? How can results be interpreted with appropriate nuance that is needed? How low is low enough to be problematic?

In situations where a test flags testosterone as low, there is a belief this means automatically starting testosterone replacement therapy. While TRT can be an excellent intervention in appropriate cases, when is it actually likely to benefit someone, and when is it not?

For many people the decision seems straightforward: get a blood test, see whether testosterone is a little low, and start TRT. However, this simplistic thinking is full of potential issues that are important to understand.

Dr. Austin Baraki returns to discuss how testosterone testing should inform treatment decisions, what benefits to expect, and the questions surrounding fertility and long-term safety.

Timestamps:

•

[03:50] Dr Austin Baraki's work

•

[06:33] When and why test?

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[10:36] Probability and context impacts interpretation

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[14:13] What labs measure

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[21:15] Specific vs nonspecific symptoms

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[28:35] Primary vs secondary hypogonadism

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[32:30] Lifestyle vs TRT decisions

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[35:21] TRT risks

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[39:32] Testing timing and variability

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[41:55] Androgen receptor genetics

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[44:28] Free vs total testosterone

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[48:57] Low-normal results: what now?

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[57:45] TRT risks?: heart and prostate

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[01:03:55] Side effects and monitoring

Links:

• Go to episode page & resources
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Instagram: @austin_barbellmedicine
• Barbell Medicine
• McCormack & Holmes, 2020 – Your results may vary: the imprecision of medical measurements
• #417: Austin Baraki, MD – What Do Nutrient Blood Tests Actually Tell Us?: Understanding Biomarkers
• #334: Austin Baraki, MD – Potential Harms of Screening, Overdiagnosis and Overtreatment

Body composition testing is widely used in research, sport and clinical practice. But what are these methods actually measuring, and how much confidence should we place in the numbers they produce?

In this episode, we examine the assumptions behind common approaches including DXA, bioelectrical impedance, and skinfold measurements. We discuss the distinction between accuracy and reliability, the value and limitations of repeated measurements, and how coaches, clinicians, researchers and individuals can select an appropriate method and interpret the data without overstating its precision.

Joining Danny to discuss these issues is Professor Grant Tinsley, Professor of Human Performance at Texas Tech University and Director of its Energy Balance and Body Composition Laboratory.

Timestamps:

•

[03:04] Grant Tinsley's research

•

[05:25] What body composition means

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[08:50] Skeletal muscle mass vs. fat-free mass vs. lean soft tissue

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[11:51] How different methods estimate body composition

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[23:38] Group vs individual accuracy

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[31:09] Standardizing testing conditions and assessments

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[36:36] Reliability testing thresholds

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[40:08] Understanding phase angle in bioelectrical impedence results

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[45:02] Consumer devices

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[50:55] Not all benefit from monitoring

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[54:14] Using data wisely

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[01:02:55] Key Ideas (premium-only)

Links/Resources:

• Go to episode page (references, bio, study notes)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course

Why do some foods feel difficult to stop eating, while others can be highly enjoyable without prompting the same tendency to overconsume? Answering this requires a clearer understanding of food reward, including the distinction between liking a food, wanting it, and perceiving it as easy to overeat.

In this episode, we examine how nutritional composition, sensory characteristics, learned beliefs and the eating context may shape hedonic overeating. It also considers the limits of using broad food categories to explain complex eating behaviour.

Discussing all this is Professor Graham Finlayson, professor of Psychobiology at the University of Leeds, whose research focuses on human appetite, food reward and the psychological processes involved in eating behaviour and weight control.

Timestamps

• [04:02] Prof. Finlayson's research
• [06:06] Food reward
• [07:13] Liking versus wanting
• [12:43] Measuring wanting in research
• [15:27] Does wanting predict overeating?
• [16:36] Study on hedonic overeating
• [23:19] Perception and context effects
• [26:24] Does ultra processing classification add anything?
• [36:09] Key takeaways and future work
• [40:35] Premium key ideas

Links/Resources:

• Go to episode page
• Subscribe to Sigma Nutrition Premium
• Join the Sigma newsletter for free
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Study: Finlayson et al., 2025 – Food-level predictors of self-reported liking and hedonic overeating: Putting ultra-processed foods in context

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

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[20:19] The gray zone of pro-peptide communication

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[24:16] Risk sourcing vs drug effects

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[26:25] FDA lists and compounding

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[31:05] Risk tolerance and informed consent

•

[43:02] Why did pharma abandon peptide research?

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[47:44] Harm reduction debate

•

[51:48] Practical takeaways

• [56:20] Key Ideas segment (Premium members only)

Episode Resources

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Barbell Medicine
• Instagram: jordan_barbellmedicine
• Book: Signal: What Testosterone Levels Are Telling You About Your Health
• Related episode: #524: Strength & Fitness Levels for Reducing Chronic Disease Risk & Promoting Health Ageing – Jordan Feigenbaum, MD
• Further reading:

• Emerging use of BPC-157 in orthopaedic sports medicine: a systematic review. 2025.
• 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.

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

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[07:10] Is there good evidence for suggested intakes?

•

[08:10] Historical context

•

[13:22] Key evidence: DART trial and cohort data

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[19:27] Analysis from Mohan et al.

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[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

• Go to episode page (with full study reference list)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Subscribe to Alan's Alinea Nutrition Education Hub
• Enroll in the next cohort of our Applied Nutrition Literacy course

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 episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Dr. Tiller's website
• Tiller & Phillips, 2023 – How Skepticism (not Cynicism) Can Raise Scientific Standards and Reform the Health and Wellness Industry
• Tiller et al., 2024 – The Nontechnical Summary: A New Initiative to Enhance the Translation of Sports Science Research and Reduce the Spread of Misinformation

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:

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Instagram: @gemmcguinnness
• Verus Performance
• Davey Nutrition
• Gemma's Substack

This episode answers one of the questions raised in the most recent Q&A episode on Sigma Nutrition Premium.

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) become a member of Sigma Nutrition Premium.

For episode info and mentioned research go to the episode page here.

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:

• Go to episode page (with resources)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Instagram: @austin_barbellmedicine
• Twitter: @AustinBaraki

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:

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Paper: Plant-Based Diets, Ultra-Processed Foods, and Risks of Mortality and Major Chronic Diseases: A Prospective Cohort Study

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:

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Past episode #326: Adaptability & Autonomy in the Nutrition Coaching Process
• Krista's website: https://kristascottdixon.com/
• Instagram: @stumptuous
• 1% Better Academy
• The textbook: Applied Nutrition Coaching and Counseling:

• ebook version
• US
• Canada
• UK
• International

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:

• Free trial of Examine Clinician Edition – 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.)
• Free trial of Examine+ – 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.
• Go to episode page
• Subscribe to Sigma Nutrition Premium

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:

• Go to episode page (incl. links to studies)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course

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 episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Your Diet Sucks podcast
• Fly Nutrition – Endurance Sports Nutrition

This is a Premium-exclusive episode. Go to the Premium feed to listen. Or subscribe to Premium.

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:

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course

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:

• Go to episode page (all study references linked)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Subscribe to Alinea Nutrition Education Hub
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Episode #472: Compared To What?
• Episode #589: Causal Inference in Nutrition Science – Daniel Ibsen, PhD

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:

• Go to episode page (includes links to studies mentioned)
• Subscribe to Sigma Nutrition Premium
• Join the Sigma newsletter for free
• Enroll in the next cohort of our Applied Nutrition Literacy course