Sigma Nutrition Radio

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)
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Dr. Fotuhi's book: The Invincible Brain

This is a Premium-exclusive episode of the podcast. To listen to the full episode you need to be subscribed to Sigma Nutrition Premium.
This episode examines dietary fiber through the lens of a practical, clinically relevant question: if higher fiber intakes are consistently associated with reduced chronic disease risk, what intake level should we be aiming for to meaningfully improve health outcomes?
The discussion deliberately spans from common online claims that fiber is "not essential" (and therefore unnecessary), through to mechanistic reasoning and the highest-quality evidence we have for hard outcomes and accepted intermediate cardiometabolic endpoints.
Across the episode, we'll hear from six expert perspectives to integrate epidemiology, controlled feeding studies, and clinical guideline contexts.
We will consider how the dose–response patterns, fiber type/source, individual tolerance, and the limitations of nutrition trials all influence what can be recommended with confidence.
Timestamps
[03:51] Addressing the claim "fiber is not an essential nutrient"
[11:23] Carbohydrate quality and fiber
[17:16] Dietary recommendations for fiber
[20:01] Portfolio diet and cardiovascular health
[26:48] Comparing fiber sources
[36:07] Epidemiological evidence on fiber
[41:57] Understanding fiber intake and coronary heart disease
[43:23] Fiber intake and colorectal cancer
[54:06] Diet swap study: south african vs. african american diets
[01:01:47] High fiber diets and diabetes
[01:16:18] Challenges in fiber intake and IBS
[01:21:45] Concluding thoughts on fiber intake
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Dr. José Areta and colleagues recently carried out a human intervention study examining how a pronounced, short-term energy deficit interacts with an aerobic training stimulus to shape endocrine, metabolic, and skeletal muscle proteomic adaptations.
The core premise is that "low energy availability" is often discussed in a largely unidirectional risk framework, yet human physiology evolved under intermittent energy scarcity, and therefore adaptive responses may be more nuanced than "energy deficit equals impaired adaptation."
The study used tightly controlled diet and exercise, repeated muscle biopsies, and dynamic proteomic profiling to quantify both abundance and synthesis rates of hundreds of individual muscle proteins. This enables a more granular view of "muscle quality" and phenotype than traditional bulk muscle protein synthesis measures.
The findings were incredibly interesting and could have implications for how we view the impact of energy deficits and exercise response.
We discuss the implications for athletes who routinely encounter transient within-day or multi-day energy deficits, for weight loss contexts, and for broader questions around healthspan and ageing biology.
Timestamps
[02:27] Guest introduction
[03:28] Research background and study design
[12:18] Study findings: weight loss and endocrine responses
[15:47] Muscle adaptations and proteomic analysis
[21:47] Interpreting the results: evolutionary and practical implications
[26:57] Mitochondrial proteins and muscle adaptation
[28:44] Energy deficit as a stressor
[34:26] Case study: female tour de france athlete
[40:20] Implications for clinical populations
[41:44] Future research directions
[46:48] Key ideas segment (Premium subcribers only)
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X: @jlareta

While the term "hyperpalatable" has been used frequently for considerable time to refer to foods that are so appealing and tasty that they drive overeating, this term hasn't been well-defined nor has there been a universal standard for what it means.
One researcher who set out to create an objective definition for hyper-palatable foods (HPFs) is Dr. Tera Fazzino. Using specific defined thresholds of sugar, fat and salt combinations, Dr. Fazzino and colleagues have looked at the impact of consumption of these HPFs.
In this episode, we delve into defining HPFs and their nutrient profiles, whether they have addictive-like properties, how HPFs differ from (and overlap with) ultra-processed foods (UPFs), the mechanisms by which these foods drive overconsumption, and the broader public health implications.
Tera Fazzino, PhD, is an associate professor of psychology at the University of Kansas. Her research focuses on addiction, obesity, and eating-related behaviors.
Timestamps
[03:39] Interview begins
[05:05] Attempting to define hyper palatability
[10:03] Nutrient combinations in hyper palatable foods
[14:54] Prevalence of hyper palatable foods
[17:43] Debate on ultra processed foods
[30:02] Mechanisms behind hyper palatability
[35:06] Addiction theory and hyper-palatable foods
[43:38] Early exposure and long-term effects
[50:53] Key ideas recap
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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 slogans and thresholds. What does 0.8 g/kg represent, and just as importantly, what does it not? At what point do higher intakes stop meaningfully improving muscle-related outcomes? And where do concerns about kidney function, longevity, and chronic disease fit when we look at long-term data rather than isolated mechanisms?
Rather than treating protein as a single number to defend or dismiss, this conversation places intake in context: training status, ageing, health outcomes, source and optimising for specific goals.
Timestamps
[05:19] Discussion starts
[07:18] Setting the scene: protein intake and health
[09:38] Health outcomes and protein intake
[10:27] Mechanistic measures vs. longitudinal outcomes
[15:47] The RDA: purpose and limitations
[19:19] Higher protein recommendations: where do they come from?
[21:48] Protein intake for athletes and general population
[27:25] Dose response and optimal protein intake
[44:59] Statistical errors in Morton meta-analysis
[46:07] Comparing meta-analyses: Morton, Tagawa, and Nunez
[56:23] Mechanistic claims and protein intake
[59:49] Nitrogen balance and protein requirements
[01:11:55] Protein sources and health outcomes
[01:18:13] Summarizing optimal protein intake
[01:24:31] Key ideas segment (premium subscribers only)
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Dr. Helms: MASS Research Review
Muscle & Strength Pyramids books
Instagram: @helms3dmj

Dr. Nagra: Instagram: @dr.matthewnagra
Dr. Nagra's website