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While the biggest successes in terms of research and efficacy have been seen with vitamin A, other vitamins also offer varying degrees of benefits, but documentation of such benefits in topical uses still leaves much to be desired.
Las Vegas - In the journey from the test tube to a dermatological benefit, topical vitamins face more than a few obstacles, and many need to be overcome - and clinically documented - before topical vitamins' use can be fully realized, says Elizabeth Briden, M.D.
Dr. Briden, an adjunct associate clinical professor of dermatology at the University of Minnesota, spoke at the American Society of Cosmetic Dermatology and Aesthetic Surgery, here.
"There is, unfortunately, minimal documentation of most vitamins' topical effects because vitamins are considered foods and are already sold over the counter (OTC)," she tells Dermatology Times. "Many makers therefore don't want to conduct any clinical studies or make any claims, because then they would be regulated."
Numerous challenges are in store for those who do venture down the road of testing efficacy in topical vitamin formulations. The main obstacle is that the vitamins need to be delivered to the skin in sufficient quantities to reach therapeutic levels. Factors that need to be worked out to allow the formulations to penetrate the skin include the size of the molecule, its polarity and whether it is hydrophilic or lipophilic.
Another big issue in efficacy is the active ingredient and whether it is present in the formula or can it be activated once it is absorbed into the skin.
If the active ingredient is in the formula, then the formula must be stable, lest the ingredient may not make it out of the tube intact. Problems that could compromise stability include the active ingredient's interactions with other ingredients in the formulation or physical factors, such as exposure to light, heat or oxygen. Potentially, these factors can cause the active ingredient to disassociate itself from the formulation or become inactive and disabled.
So with all of the potential hurdles in topical applications, wouldn't it just be better to take the vitamins orally? Not necessarily, Dr. Briden says.
"Often, the doses that would be needed to achieve therapeutic levels in the skin would be toxic. With vitamin A, for instance, oral doses that would be high enough for benefits could cause hepatoxicity."
Only about 1 percent of oral vitamin intake is actually deposited in the skin, and factors such as the vitamin's water solubility can create problems. With vitamin C, for instance, by the time enough is taken to reach therapeutic levels, the body has excreted much of the vitamin.
The transport mechanism can also be troublesome, with factors in the blood and gastrointestinal system limiting transport of the vitamin in the system in some cases. Vitamin E, however, does well in this regard, Dr. Briden says.
"With vitamin E, there is some active secretion in the sebaceous gland, which, in fact, makes oral vitamin E a good option for increasing skin levels."
Topical uses nevertheless hold much promise, as has been evidenced by vitamin A, and the fact that clinical studies have documented benefits from topical formulations of the vitamin for everything from acne to photoaging.
While there are more than 2,500 preparations of various OTC formulations using vitamin-A derivative retinol, the greatest benefits have been attributed to prescription strength formulations with retinoic acid, with drawbacks including the potential for irritation and problems with stability, such as formulas being sensitive to light, oxygen and heat.
Vitamin B has been shown to be an ideal cosmetic ingredient due to its stability and vitamin B-5 (panthenol) is used as a humectant and is highly popular in moisturizers, shampoos and hair conditioners, offering barrier conditioning effects on the skin. There are no reports, however, of its usefulness on its own in terms of improving photoaging or skin renewal.
"In general, the B vitamins are not good stand-alone agents, but work ideally with other formulations because they are compatible, stable and readily penetrate the stratum corneum," Dr. Briden explains.