Why Skin Is a Readout, Not a Target

Julie Russak, MD, FAAD, founder of Russak Dermatology Clinic and assistant clinical professor at Mount Sinai, opened her session at The Outlook on Women's Wellness conference with a reframing exercise. "I'm going to ask you to start thinking about skin not as the surface, and start thinking about it as a dashboard," she told attendees. "Everything that shows up on a woman's face— wrinkles, dryness, pigment, loss of firmness—is all reported on something that is happening inside your body: the ovary, the gut, the kidney, the muscles, the mitochondria. Those are the input signals. The skin is an output."

That framing, repeated throughout her presentation, anchored a session that moved between market data, evidence grading, and a detailed walk-through of which nutricosmetic ingredients currently hold up under randomized, placebo-controlled trials, and which do not.

What's Driving the Disconnect Between Nutricosmetics Sales and Consumer Trust?

Russak opened with market sizing, citing two independent research firms that arrived at similar projections: the global nutricosmetics market was valued at approximately $8.1 billion in 2026 and is projected to reach $18 billion by 2036, a compound annual growth rate of roughly 8.3%.¹ European hair, skin, and nail supplement launches grew 24% between 2020 and 2025, according to Innova Market Insights data cited in her presentation.

But Russak argued the evidence base has not kept pace with that growth. Of more than 50 commercially available nutricosmetic ingredients evaluated in a 2025 review published in the journal Nutraceuticals, only 17 carry placebo-controlled, double-blind, randomized controlled trial evidence specifically for skin outcomes.² "The market right now is running ahead of the science, and this gap is either a liability or an opportunity, depending entirely on how you approach it," she said. She cited commentary from Mallory Huron, director of beauty and wellness at Future Snoops, who described the category's current state at an April 2026 industry panel as defined by "a lot of hype and a lot of confusion."

What Is the "Iceberg Model" of Skin Aging and Why Does It Matter for Formulation?

Central to Russak's clinical framework is what she calls the iceberg model: visible signs of aging (wrinkles, dryness, pigmentation) represent only about 10% of what is actually happening, while the remaining 90% occurs at the molecular level, encompassing cellular senescence, collagen degradation, microbiome dysbiosis, estrogen receptor silencing, and mitochondrial dysfunction, among other hallmarks identified in foundational aging biology literature.³ A 2025 paper in Frontiers in Aging was, according to Russak, the first peer-reviewed work to apply that hallmarks-of-aging framework specifically to skin longevity.⁴

She described 4 organ-skin axes through which systemic health influences visible skin aging: a brain-skin axis mediated by cortisol, where chronic stress drives collagen breakdown and microbiome disruption; a gut-skin axis operating through short-chain fatty acids; a muscle-skin axis involving the exercise-induced molecule irisin; and a kidney-skin axis tied to the longevity biomarker klotho. "Those are the input signals," she said. "And each one, and that matters to you, is a place a supplement can actually intervene."

Why Does Dr. Russak Argue That Women's Skin Aging Cannot Be Modeled on Male Longevity Data?

Russak emphasized that estrogen decline, not chronological age alone, is the primary driver of skin aging in women, and that this decline begins meaningfully in a woman's 30s rather than at menopause. Citing 2025 research published in Dermatology and Therapy, she walked through the trajectory: collagen and elastin loss begins in the 30s, fibroblast activity slows by the mid-30s, and by menopause, typically around age 51, women lose approximately 30% of skin collagen within the first 5 years.⁵ "Estrogen loss, the primary driver of skin aging, begins in the 30s, not the 50s," she said. "By the time a woman hits menopause in her 50s, she has been losing collagen for two decades."

She also referenced a 2026 Global Wellness Summit report noting that longevity science has historically been built on male physiological data, arguing that products formulated without accounting for the female hormonal arc are, in her words, "formulating for the patient that doesn't really exist."

What Does the Evidence Actually Show About Collagen Supplementation?

Russak devoted significant attention to collagen, calling it simultaneously the most cited, most sold, and most scientifically contested ingredient in her evidence review. While earlier industry-funded trials showed consistent improvements in skin elasticity, hydration, and wrinkle depth, she cited a more recent meta-analysis pooling 23 trials that separated results by funding source: industry-funded trials showed benefit, while independently funded and higher-quality trials did not.⁶

"The author's conclusion was that there is currently no clinical evidence that collagen prevents or treats skin aging," she said, while noting that effective doses studied range from 1.65 to 10 grams daily, with 2.5 grams most frequently cited, though that figure was never derived from a dose-comparison study. She also noted that marine collagen's claimed bioavailability advantage over bovine or porcine sources lacks supporting human comparison trials, despite legitimate sustainability and sourcing rationale.

References

1. Future Market Insights. Nutricosmetics market outlook 2026–2036. Published January 2026.

2. Streker M, et al. Evidence-based evaluation of commercially available nutraceuticals for skin health. Nutraceuticals. 2025.

3. López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. Hallmarks of aging: an expanding universe. Cell. 2023;186(2):243-278. doi:10.1016/j.cell.2022.11.001

4. Klinngam W, et al. A geroscience framework for longevity-focused skin biology. Front Aging. 2025.

5. Lephart ED. Estrogen and skin aging: mechanisms and therapeutic considerations. Dermatol Ther (Heidelb). 2025.

6. Streker M, et al. Funding source and outcome heterogeneity in collagen supplementation trials for skin aging: a meta-analysis. Am J Med. 2026.