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Zoe Diana Draelos, M.D., is a consulting professor of dermatology, Duke University School of Medicine, Durham, N.C. She is investigator, Dermatology Consulting Services, High Point, N.C., and a Dermatology Times Editorial Advisor and co-medical editor.
In this month's Cosmetic Conundrums column, Dr. Draelos addresses why fatty acids are essential in skin health, how best to treat estrogen deficient skin and she asks, "What is the skin natural moisturizing factor?"
Q. What is the skin natural moisturizing factor?
For years, cosmetic chemists have searched for the perfect moisturizer formulation that will maintain the optimal skin water content. Since normal skin does not require external moisturizer application to maintain water balance, there must be some substance in the skin that confers this quality.
Before our increased understanding of stratum corneum physiology, this substance was named the natural moisturizing factor and abbreviated NMF. NMF is a mixture of amino acids, derivatives of amino acids, and salts. Cosmeceutical formulations that contain synthetic NMF are based on amino acids, pyrrolidone carboxylic acid, lactate, urea, ammonia, uric acid, glucosamine, creatinine, citrate, sodium, potassium, calcium, magnesium, phosphate, chlorine, sugar, organic acids and peptides. 10% of the dry weight of the stratum corneum cells is composed of NMF, which is derived from fillagrin.
Some higher end cosmeceutical moisturizers are based on NMF formulations. The question is whether these individual ingredients can function like naturally derived NMF. The analogy I use to explain the difference between individual ingredients and final formulation is cake baking. In order to make a cake, the flour, sugar, oil, baking powder, eggs, and flavorings must be put a bowl, mixed and placed in the oven. When the concoction comes out of the oven, it looks like a cake, but the eggs, flour, sugar, etc., can no longer be distinguished. The baked cake is its own unique formulation. This same concept applies to skin NMF. The individual ingredients can be put on the skin, but their organization must be exact to insure functionality.
Q Why are fatty acids essential in skin health?
Another essential part of skin health is the presence of essential fatty acids (EFAs), sometimes referred to as vitamin F. EFAs are composed of unsaturated linoleic, linolenic, and arachidonic acid. These fatty acids are termed essential since they cannot be synthesized by the body, requiring oral ingestion. EFAs are important in barrier function maintenance. Linoleic acid is found in high concentration in ceramides, which are a major component of the intercellular lipids filling the spaces between the corneocytes. It is a burst a ceramide production that initiates the sequence leading to barrier repair.
It might seem that topical linoleic acid would be desirable, since external application might promote ceramide synthesis. This is not the case. Linoleic acid is a strong cutaneous irritant and highly unstable when exposed to oxygen. Cosmeceutical formulations that advertise EFA on their labels usually contain vitamin E linoleate.
Q. What can be done for estrogen deficient skin?
Estrogen deficiency is one of the key factors in postmenopausal skin thinning. Many postmenopausal women no longer wish to take oral estrogens due to their association with increased heart disease, breast cancer, uterine cancer, and ovarian cancer. This has led to increased interest in plant-derived phytoestrogens. One excellent source of plant estrogens is flaxseed. Flaxseed can be consumed as the roasted seeds on cereal or yogurt, but the ends of the seeds are sharp and the ground seeds are gritty. An easy way to consume flaxseed phytoestrogens is to take organic flaxseed oil in gel capsules daily, which are inexpensive and easy to swallow. While there are no well controlled studies on the cutaneous benefits of flaxseed oil, this is a healthy dietary suggestion the dermatologists can offer. Flaxseed is also rich in essential fatty acids, previously discussed.