Fructose has often been labeled a uniquely damaging nutrient, blamed for obesity, diabetes, and other metabolic diseases. But does fructose truly have unique harmful effects or are the risks associated with it related to context and quantity?

The episode explores how fructose is metabolized in the body, why it gained a reputation for being problematic, and what the scientific evidence says about fructose in our diets. You will gain insight into why fructose was singled out in the past (e.g., its unique pathway in the liver and lack of insulin response), and how newer studies put those concerns into context.

It covers important nuances for practitioners and health-conscious individuals, especially given public confusion and fear around fructose (even in fruit).

Dr. Scott Harding, Ph.D., is an Associate Professor of Nutritional Biochemistry in the Department of Biochemistry at Memorial University of Newfoundland. His research explores the complex interactions between diet, metabolism, and chronic disease, with a particular emphasis on the metabolic effects of dietary sugars (especially fructose), the role of fats and phytosterols in lipid metabolism, and how public health policies like sugar taxation influence population health outcomes.

• [02:58] Dr. Harding’s academic background
• [08:45] Fructose metabolism in detail
• [12:51] Fructose in diet and public health
• [23:07] Current research
• [29:53] Identifying biomarkers for fructose overconsumption
• [31:12] Fructose impact on health
• [40:58] The food matrix
• [45:10] Personalized nutrition and future research directions
• [54:06] Key ideas segment (premium-only)

• Subscribe to Sigma Nutrition Premium
• Join the Sigma email newsletter for free
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Related podcast episodes: #476, #468, #155
• See Sigma's "Recommended Resources"

Vitamin 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.

• [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

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

The idea that saturated fat might be harmful to our health has sparked controversy for decades. In recent years, counter-narratives have surged: suggesting that concerns over saturated fat were overblown, that LDL cholesterol doesn’t matter, or that the original diet-heart hypothesis has been debunked. These claims have become especially popular in online wellness spaces and certain dietary communities, often wrapped in compelling but misleading rhetoric.

So what does the best available evidence actually say? And how should we think about saturated fat, LDL cholesterol, and cardiovascular risk in the current day?

In this wide-ranging interview, originally recorded for the Chasing Clarity podcast, Alan and Danny explore the scientific consensus around saturated fat’s impact on blood lipids, why LDL and apoB are central to atherosclerotic disease, and how dietary patterns can meaningfully reduce risk.

Importantly, they also address some of the most persistent myths and half-truths that fuel confusion, from flawed interpretations of the Seven Countries Study to misrepresentations of newer meta-analyses.

• [03:41] How do we know saturated fat impacts LDL-C?
• [05:28] Metabolic ward studies and key findings
• [11:13] The Keys equation and subsequent research
• [17:17] Epidemiology and long-term studies
• [31:48] The Seven Countries Study
• [44:25] Understanding the impact of saturated fat on blood lipids
• [47:23] Historical and research perspectives on saturated fat
• [50:43] Practical dietary strategies for improving blood lipids
• [53:48] The Portfolio Diet and other dietary interventions
• [58:07] The role of pharmacology in managing blood lipids
• [01:00:58] Addressing misconceptions and common claims
• [01:13:57] Key ideas segment (premium-only)

• Subscribe to Sigma Nutrition Premium
• Join the Sigma email newsletter for free
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Alan Flanagan’s Alinea Nutrition Education Hub
• Related episodes to add to your podcast queue: 532, 525, 515, 493, 481, 439