Vitamin C-rich Foods
While topical skincare is still valuable, Dr. Rajani emphasizes that lifestyle factors—including diet, sleep, and exercise—play a far larger role in maintaining youthful skin. “Food is just way less exciting than fancy skincare serums. Sleep is the real key to great skin. Think of it this way: skincare is just the finishing touch, but your lifestyle is what really matters.”
Vitamin C is particularly crucial because most over-the-counter forms are water-soluble and struggle to penetrate the skin barrier. “...It turns out your body is pretty great at delivering vitamin C to your skin from the inside,” he explains.
The study Dr. Rajani references, published in the Journal of Investigative Dermatology and conducted by the University of Otago, tracked both blood and skin vitamin C levels in healthy adults. Researchers found a clear correlation: higher vitamin C in the blood meant higher levels in the skin, especially in the epidermis—the outer layer responsible for visible signs of aging.
In a dietary intervention, participants with below-average vitamin C intake consumed two kiwifruits daily (about 250 mg of vitamin C) for eight weeks. The results were compelling: not only did vitamin C levels rise in both plasma and skin, but skin density and cell turnover also improved. Measurements showed epidermal cell growth increased, indicating that the skin was renewing itself more efficiently—a key factor in a youthful appearance.
Dr. Rajani stresses that these effects were measurable, not just subjective. “The increase of vitamin C in the plasma was linked to a noticeable rise in skin density. Signs of skin layer renewal are increasing, which means your skin cells are multiplying faster, producing new skin cells more efficiently.”
As for products, he highlights the importance of the type of vitamin C used. Oil-soluble forms like THD ascorbate (tetraheyl ascorbate) penetrate deeper, work faster, and are less irritating than water-soluble forms. “Being oil-soluble means it penetrates deeper. It works faster and more effectively. Most importantly, it has a higher pH, so it doesn’t irritate your skin. That’s what makes all your active products—and everything you put on your skin—actually work.”
The bottom line
Ultimately, Dr. Rajani emphasizes the synergy between diet, exercise, and sleep. “Your lifestyle is like a mirror. Food provides the raw materials, and exercise is how you deliver them. Sleep is when your repair team kicks in, rebuilding your skin. So, you need food, exercise, and sleep. If your nutrient levels are low, your skincare routine is like putting lipstick on a tired chicken.”
The takeaway? Incorporating vitamin C-rich foods like kiwifruit, citrus, and bell peppers daily can support skin health from the inside out, helping you look younger without overcomplicating your routine.