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Introduction
The intersection of nutrition, dermatology, and skin health is an area of growing interest, yet one that remains riddled with misinformation and oversimplified claims.
The influence of dietary patterns, specific nutrients, and lifestyle factors on conditions such as acne, eczema, psoriasis, and skin aging has been widely debated, with varying levels of evidence supporting different interventions.
While some nutritional strategies may play a role in optimizing skin health, the challenge lies in distinguishing practical, evidence-based approaches from overstated or anecdotal claims.
A significant issue in this space is the naturalistic fallacy—the belief that diet alone can replace medical treatments, or that conventional dermatological interventions should be avoided in favor of “natural” approaches. This has led to widespread vilification of certain foods, such as dairy, gluten, and sugar, despite a lack of strong supporting data.
Similarly, supplements and probiotics are often promoted with broad claims, while their actual efficacy is highly context-dependent—varying based on individual nutrient status, disease severity, and baseline dietary intake.
In this episode, Dr. Thivi Maruthappu, a consultant dermatologist and researcher in nutritional dermatology, joins Danny Lennon to explore the current state of evidence in this field.
Related resources
- Join the Sigma newsletter for free
- Subscribe to Sigma Nutrition Premium
- Enroll in the next cohort of our Applied Nutrition Literacy course
- Dr. Maruthappu’s website
- [02:52]Start of interview
- [03:37]Dr. Maruthappu’s background and expertise
- [05:57]Sunscreen and skin health: myths and facts
- [12:15]Effective skincare ingredients
- [16:07]The role of nutrition in skin health
- [20:25]Dairy and skin conditions
- [24:10]Collagen supplements: do they work?
- [27:45]Probiotics for skin health
- [31:35]Research outcomes and challenges
- [35:20]Practical applications in clinical practice
- [43:05]Key ideas segment (premium-only)
Guest Information
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As the UK’s first and only dual-qualified dermatologist and nutritionist, her pioneering expertise bridges the gap between diet and skin health. Dr Thivi continues to work in the NHS and has her own practice based at London’s renowned Cleveland Clinic.
Dr Thivi studied Medicine at Oxford University and completed Dermatology training in London. She undertook a PhD to understand the links between our skin and internal health and this research featured in top tier scientific journals. She is one of a handful of dermatologists to have completed training in severe eczema and psoriasis during a fellowship at St John’s Institute of Dermatology, London and achieved a Certificate in Nutrition Science from Stanford Medical School, USA.
Danny Lennon has a master’s degree (MSc.) in Nutritional Sciences from University College Cork, and he is the founder of Sigma Nutrition.
Danny is currently a member of the Advisory Board of the Sports Nutrition Association, the global regulatory body responsible for the standardisation of best practice in the sports nutrition profession.
Introduction to this Episode
The intersection of nutrition, dermatology, and skin health is an area of growing interest, yet one that remains riddled with misinformation and oversimplified claims.
The influence of dietary patterns, specific nutrients, and lifestyle factors on conditions such as acne, eczema, psoriasis, and skin aging has been widely debated, with varying levels of evidence supporting different interventions.
While some nutritional strategies may play a role in optimizing skin health, the challenge lies in distinguishing practical, evidence-based approaches from overstated or anecdotal claims.
A significant issue in this space is the naturalistic fallacy—the belief that diet alone can replace medical treatments, or that conventional dermatological interventions should be avoided in favor of “natural” approaches. This has led to widespread vilification of certain foods, such as dairy, gluten, and sugar, despite a lack of strong supporting data.
Similarly, supplements and probiotics are often promoted with broad claims, while their actual efficacy is highly context-dependent—varying based on individual nutrient status, disease severity, and baseline dietary intake.
In this episode, Dr. Thivi Maruthappu, a consultant dermatologist and researcher in nutritional dermatology, joins Danny Lennon to explore the current state of evidence in this field.
About The Guest
Dr Thivi Maruthappu MA PhD FRCP ANutr is a consultant dermatologist, nutritionist and leading researcher. Dr Thivi continues to work in the NHS and has her own practice based at Londonʼs renowned Cleveland Clinic.
Dr Thivi studied Medicine at Oxford University and completed Dermatology training in London. She undertook a PhD to understand the links between our skin and internal health. She is one of a handful of dermatologists to have completed training in severe eczema and psoriasis during a fellowship at St Johnʼs Institute of Dermatology, London and achieved a
Certificate in Nutrition Science from Stanford Medical School, USA.
Useful Terminology for this Episode
- Naturalistic Fallacy: In health contexts, this refers to the flawed belief that “natural” means better or safer. In the episode, it describes the tendency of some to favor natural diet-based remedies over proven medical interventions (like medications or sunscreen) without scientific justification.
- Skin Barrier: The outermost layer of the skin (primarily the epidermis, especially the stratum corneum) which acts as a protective barrier. A healthy skin barrier prevents water loss and blocks entry of irritants/microbes. Compromised barrier function (as in eczema or very dry skin) leads to irritation, dryness, and increased susceptibility to inflammation.
- SPF (Sun Protection Factor): A measure of how well a sunscreen protects the skin from UVB rays (the chief cause of sunburn and contributor to skin cancer). For example, SPF 30 means it would take 30 times longer for protected skin to burn compared to unprotected skin. Higher SPF and broad-spectrum sunscreens guard against both UVB and UVA, helping prevent skin cancer and premature aging.
- Retinol: A derivative of Vitamin A, used in skincare for acne, pigmentation, and anti-aging.
- Isotretinoin (Roaccutane): A powerful oral retinoid (vitamin A derivative) medication used for severe cystic acne. It dramatically reduces sebum production and can lead to long-term remission of acne, but has significant side effects (e.g., dry skin, lips, eyes; risk of birth defects), so its use is closely monitored by dermatologists.
- Probiotics: Live beneficial microorganisms (often bacteria like Lactobacillus or Bifidobacterium) that, when ingested, can alter the gut microbiome in ways that may benefit health. In dermatology, probiotics are being studied for their potential to modulate inflammation and immunity – for instance, preventing eczema in infants or reducing acne severity by influencing the “gut-skin axis.”
- Lactobacillus rhamnosus GG: A probiotic strain studied for its role in preventing eczema.
- Polycystic Ovary Syndrome (PCOS): An endocrine disorder in women characterized by ovarian cysts, hormonal imbalances, insulin resistance, and symptoms like irregular periods, infertility, acne, and excess hair growth. PCOS-related acne is common due to high androgen levels; treatments can include lifestyle changes, medications, and supplements like inositol to improve insulin sensitivity and hormone balance.