#559: Skin Health & Nutrition – Thivi Maruthappu, PhD

·45 min·4 clips

A study found that using factor 50 sunscreen correctly doesn't reduce vitamin D production at all.

This episode features host Danny Lennon and Dr. Thivi Maruthappu, a consultant dermatologist and nutritionist, exploring the evidence and controversies around diet and skin health. Dr. Maruthappu leads a nutritional dermatology department at King's College London and authored the book "Skin Food." They aim to clarify topics often clouded by anecdotes and misinformation due to a general lack of high-quality studies. The conversation first addresses sunscreen, distinguishing its use for skin cancer prevention versus anti-aging, noting UVA and UVB have different roles. Dr. Maruthappu cites a study from Guys Hospital and Boots showing proper sunscreen use does not inhibit vitamin D production. For skincare ingredients, she highlights strong evidence for topical ceramides, retinol, and vitamin C, but notes poor evidence for topical vitamin E. A significant problem is young audiences using inappropriate products due to social media marketing. Regarding diet, she observes clinical patterns like dry skin from iron deficiency or eczema flares from low essential fatty acid intake. She describes "keto rash" from consuming under 30 grams of carbs daily. On dairy, survey data shows it is commonly restricted, but evidence linking it to acne is weak and specific to low-fat milk due to IGF-1. For collagen supplements, she explains the proposed mechanism where peptides may signal skin injury, prompting collagen production, though most data comes from supplement companies. Probiotic research shows promise for preventing childhood eczema with *Lactobacillus rhamnosus* GG, but benefits in adults are less clear. A surprising insight is that the top layer of skin lacks its own blood supply and relies entirely on nutrients from the diet delivered via the dermis. Dr. Maruthappu notes that despite popular belief, cutting out dairy products like butter or cheese often lacks a mechanistic basis for acne. She personally observed faster nail growth while taking collagen supplements. The discussion reveals that in rosacea, antibiotics are used for their anti-inflammatory properties, not to treat infection, raising questions about their effect on the gut microbiome. Clinical outcomes for skin studies combine objective measures like lesion counts with quality-of-life indexes, emphasizing the condition's psychological impact. The tone is educational and conversational, with the host posing practical questions and the guest providing clear, evidence-informed clinical perspectives. The style is interview-based, focusing on translating research and clinical experience into actionable advice. This episode is ideal for listeners seeking to navigate skincare and nutrition claims with a critical, evidence-based lens. Those looking for definitive, simple answers or endorsements of popular wellness trends might find it too nuanced.

As heard by us

A careful, clinically grounded look at skin claims without the usual certainty theater.

Sigma Nutrition Radio treats skin health as a question of evidence, not slogans, bringing on consultant dermatologist, researcher, and qualified nutritionist Dr. Thiby Marathupu to sort through what diet can and cannot realistically do for the skin.

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Why you'd press play

Want the evidence, clinic reality, and online noise sorted on skin health?

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