Our body constantly produces free radicals. This includes our skin where they are produced due to the effects of UV, visible and infrared light rays. To protect itself, our skin has its own defensive antioxidant mechanisms: Vitamins (A, C, E, D), carotenoids (β carotene, lycopene and luteine) and various enzymes. Lycopene is the most powerful antioxidant of all the carotenoids. Since most cannot be synthesized, carotenoids must come from a diet rich in fruits, vegetables, cocoa, tea… When free radical production exceeds antioxidant capacities, they can destroy cells and trigger premature skin aging. Currently, we know how to turn back the clock. 

Many studies have shown that carotenoids represent a good marker for skin antioxidant potential. Several non invasive techniques (resonance spectroscopy) allow us today to measure in vivo the skin carotenoids concentrations. Fruits and vegetables are natural sources of antioxidants. Supplementation studies with individual antioxidants at high doses have not been conclusive, in terms of protection against cancer in particular.

Today we know that the most efficient protection involves a mix of antioxidants at physiological doses rather than one compound at high doses.

We know how to measure carotenoids concentrations in the skin

Various non-invasive methods have been developed to measure in vivo carotenoid concentrations in human skin.

Reflection spectroscopy consists of irradiating the skin with light at various wavelengths. The amount of light absorbed by skin carotenoids is a reflection of their concentrations. This method is limited by numerous artefacts linked to the skin’s optical properties and does not provide precise information.

A second method, Resonance Raman Spectroscopy is more precise. It uses an argon laser that emits two wavelengths: λ1 = 488 nm, absorbed by β carotene and lycopene and λ2 = 514 nm, mainly absorbed by lycopene. Thus the skin concentration of both carotenoids can be quantified.

How do carotenoids accumulate in skin?

Numerous studies using Resonance Raman Spectroscopy have shown that carotenoids found in foods – especially in fruits and vegetables – or dietary supplements, accumulate in skin. Their skin concentrations increase from the day after antioxidant-rich products are eaten. On the other hand, decrease is slower and can take a few days after stopping supplementation. This delay varies according to the initial amount ingested and patient lifestyle.

In addition, epidermal carotenoid distribution is heterogeneous. Carotenoid concentrations are maximal at the skin’s surface since sweat carries them toward the superficial epidermal layers. On the contrary, when carotenoids are topically applied (skin cream), again sweat carries them from the skin’s surface into the epidermis. Thus, cutaneous carotenoid concentrations are greater in areas where sweat glands abound such as the palms of the hands and feet and the forehead.

Amount ingested and ripeness: 2 important conditions

Experiments with volunteers have shown that non smokers who eat a lot of a fruits and vegetables have higher skin carotenoid concentrations than smokers who eat fewer fruits and vegetables. Seasonal increases of skin carotenoid concentrations (1.26 times) have been noted in summer and fall. Greater fruit and vegetable consumptions in summer and fall with respect to winter and spring are not the only explanation. Some people eat them year round. However, fruits come from local producers in summer and fall, whereas in winter and spring they are more likely to be imported and harvested before they are ripe. Thus, the fruits and vegetables are less rich in carotenoids. Hence, ingested amounts and produce ripeness represent two important factors that modulate skin carotenoid accumulation. On the contrary, situations such as stress, sun exposure, alcohol consumption or lack of sleep reduce skin carotenoid concentrations. Therefore, skin carotenoid accumulation reflects lifestyle.

Harmful UV effects

The impact of ultraviolet (UV) light on human skin has been widely studied. Following exposure to UV light, skin carotenoid concentrations diminish by roughly 35%. Lycopene concentrations rapidly drop between 0 and 30 minutes after exposure to reach trough concentrations after 1.5 to 3 hours. β carotene concentrations remain stable 30 to 90 minutes after exposure before dropping. It takes between two and four days for concentrations to return to normal. Do these phenomena have an impact on skin aging? Yes. Studies including hundreds of volunteers have clearly shown that subjects with higher carotenoid skin concentrations look younger than their age. Measurements of fine line and wrinkle density and depth showed they were less evident and skin was smoother. Measures were clearly correlated with skin carotenoid concentrations.

Unsurprisingly, UV light is a major cause of premature skin aging. Free radicals destroy collagen and elastin fibers. High local concentrations of antioxidants neutralize free radicals before they can cause any damage.

Of course, ladies, local cream applications can smooth rough skin and is helpful. However, above all, regular consumption of fruits and vegetables represents the best strategy in the fight against skin aging.

Just published :
“You Are What You Eat: Within-Subject Increases in Fruit and Vegetable Consumption Confer Beneficial Skin-Color Changes”
Whitehead RD, Re D, Xiao D, Ozakinci G, Perrett DI (2012)
PLoS ONE 7(3): e32988. doi:10.1371/journal.pone.0032988