Antioxidants, UVR: Orally administered carotenoids, vitamins provide photoprotection

Key Points

International report - Ultraviolet radiation (UVR) is a well-established causative factor in the aging of human skin. The overexposure to "harmful" UVA and UVB radiation induces "oxidative stress" in our bodies and accelerates this natural aging process.

According to one expert, orally administered antioxidant supplements can impart photoprotection by supporting the antioxidant defense systems in place in our bodies, and can complement the photoprotection provided by topical sunscreens.

"Accelerated skin aging, as well as the development of skin malignancies, is, in part, attributed to the negative effects of UVR exposure. Aside from protecting our skin from increasing harmful radiation exposure with topical sunscreens, taking antioxidant supplements can strengthen the photoprotective capabilities of the body and help slow down the inevitable skin aging process," says Salvador Gonzalez, M.D., Ph.D., department of dermatology, Memorial Sloan-Kettering Cancer Center, New York, and consultant at the Ramón y Cajal Hospital, Madrid, Spain.

"The major ROS are superoxide anion, hydrogen peroxide and hydroxyl radical. These ROS are derived from molecular oxygen and may be formed by endogenous and exogenous factors. The skin's antioxidant defense systems must try to keep the level of pro-oxidants below a critical level and regenerate a sufficient amount of antioxidants.

"Once the ROS overcome the endogenous cutaneous antioxidant defense systems, a state of antioxidant stress occurs which will very likely leads to skin damage," Dr. Gonzalez tells Dermatology Times.

The body may not be able to neutralize the onslaught of free radicals generated by the excessive UV exposure, necessitating the supplementation of antioxidant measures, both topical and systemic.

Topical measures of photoprotection are sunscreens, particularly those containing antioxidant properties, and are considered the gold standard in UVR protection.

Systemic measures include the combination of vitamins and their derivatives as well as plant extracts such as Polypodium leucotomos.

Carotenoid protection

According to Dr. Gonzalez, the carotenoids (beta carotene), vitamin E (alpha-tocopherol) and vitamin C (ascorbate) can act as oral antioxidants or oral photoprotective agents, especially when used in combination therapies. Beta carotene is a precursor of vitamin A and is known to be a powerful singlet oxygen quencher.

Research done with the oral administration of beta carotene has shown controversial results in humans; however, animal research has shown it to reduce the incidence of skin cancer.

"A combination of three carotenoids - beta carotene, lycopene and lutein, dosed at 8 mg each for 12 weeks - seems to provide a slight photoprotection. Furthermore, mouse models have shown that a diet supplementation with lutein can protect the skin against acute UVR," Dr. Gonzalez says.

He says vitamins E and C are both supplemental antioxidants. However, they are only really useful in protecting the skin against UVR when taken in combination therapies and for more than one week. Vitamin C seems to have a minimal effect on erythema response in the skin, but it is vital in the regeneration of vitamin E from its free radical form.

"Alpha-tocopherol is the most abundant antioxidant in the cell membranes, and it is essential in preventing lipid peroxidation. The oral supplementation of both vitamin C and E act synergistically, increasing the concentration of these antioxidants in the plasma, helping to combat ROS and keep the skin healthy," Dr. Gonzalez says.

Several research groups conducted studies, investigating the supplementation of a daily dose of 2 g of vitamin C combined with 1,200 IU of vitamin E for one week, and found that there was an increased basal protection of the skin against UVR, increasing the MED by 21 percent.

When this dose was continued for three months in the same study group, the MED increased by 41 percent and decreased the UV-induced CPD (cyclobutane pyrimidine dimers).

Polypodium leucotomos is a tropical fern plant indigenous in central and South America, and is composed of a mixture of polyphenols, flavonoids and polysaccharides. This naturally occurring antioxidant is the only one that, taken at single oral doses, is able to induce skin tolerance to sunlight in terms of photoprotection.

According to Dr. Gonzalez, a hydrophilic extract of Polypodium leucotomos at single oral doses has shown to protect the skin against the harmful effects of UVR by inhibiting UVB-induced GSH oxidation, modulating UVB-induced pro-inflammatory mediators (TNF-alpha) and reducing thymine dimer generation.

He says not only the tolerance of the skin is increased, but the immune system of the skin is also preserved.

"The key to maximizing the photoprotective benefits of these vitamins, their derivatives as well as plant extracts, is to administer them together. Administering them as a monotherapy does not seem useful; however, they seem to work synergistically to impart photoprotection and can complement the photoprotection provided by topical sunscreens," Dr. Gonzalez says.