Help Restore the Glow of Youth

Rejuvenate Your Skin
With Alpha-Hydroxy Acids

These natural, food-based compounds do
much more than just remove dead skin cells
I'm tired of all this nonsense about beauty being only skin-deep.
That's deep enough. What do you want - an adorable pancreas?
-- Jean Kerr, American author and playwright

ave you taken a bath in sour milk lately? No? Why not? Don't you know what's good for you - for your skin, anyway? Perhaps you've heard that in times past, women of the idle rich class used to take such beauty baths for the sake of their complexions - their all-over complexions. What a life. Not being up on modern chemistry, however, they didn't know that what they had to thank for the benefits of such baths was a class of compounds called alpha-hydroxy acids.

If bathing in acid doesn't sound too appealing, bear in mind that we're talking about organic acids, which are typically very weak compared with the strong inorganic acids, such as nitric and sulfuric acids. Most alpha-hydroxy acids* are derived from foods, and those that are found in fruits are called fruit acids. Malic acid, e.g., comes from apples, and citric acid is found in citrus fruits. On the other hand, lactic acid is found in sour milk, and tartaric acid is a constituent of wine.

*The term alpha-hydroxy refers to a certain feature of the molecular structure of these compounds: all of them have a hydroxyl group (-OH) attached to the carbon atom to which the carboxylic acid group (-COOH) is attached - the alpha carbon. The next carbon in the chain is the beta carbon, and there are also beta-hydroxy acids, and so forth.

Lotions containing alpha-hydroxy
acids can be used safely by
anyone who desires a smoother,
fresher, younger-looking skin.

Although these acids are not corrosive in the way that inorganic acids are, they are nonetheless strong enough - at high concentrations - to be used for chemically "peeling" the human skin. In this process, the outermost layer of dead skin cells, the stratum corneum, is removed, exposing the fresh, pink, tender, living cells of the underlying basal cell layer. Together, these two layers of cells constitute the skin's epidermis.

The Epidermis Is Constantly Regenerating Itself

The epidermis is about 0.07-0.12 mm (0.003-0.005 in.) thick, except on the palms of our hands and the soles of our feet, where it's about ten times thicker. The overall thickness of our skin, including the dermis - the much thicker layer of cells below the epidermis - is about 1-2 mm (0.04-0.08 in.), on average.

Clinical studies have shown that
skin treated with alpha-hydroxy
acids really is more youthful and
healthy - the treatment increases
epidermal thickness and the
synthesis of compounds that are
beneficial for the skin.

Normally the epidermis regenerates itself every three to four weeks. As the hard, tough cells of the stratum corneum (corneum means "horny," a term that has a double meaning when it comes to skin) continuously slough off through washing and the wear and tear of daily life, living cells at the top of the basal cell layer die off and replace them. While this is occurring, new basal cells are being formed in the dermis, and they migrate into the epidermis to keep the whole process in balance.

Alpha-Hydroxy Acids Cause Exfoliation

Chemical peeling of the stratum corneum is a tricky procedure that should be done only by professionals. Lotions containing alpha-hydroxy acids in lower concentrations are available over the counter, however, and they can be used safely by anyone who desires a smoother, fresher, younger-looking skin. In these product formulations, the alpha-hydroxy acids stimulate a process called exfoliation, in which the cohesion between the tough cells of the stratum corneum is reduced, causing some of them to slough off. This makes the stratum corneum thinner and more flexible. At the same time, the acids act as skin moisturizers, and they stimulate the proliferation of new, living cells in the basal cell layer.

The net result, after several months of regular use of such exfoliants, is a reduction in fine lines in the skin and an overall improvement in skin tone and texture: the skin looks smoother and more youthful.1,2,3 And who among us is immune to the desire to look as good as we can, even if it takes a little help from nature's storehouse of chemicals? There's nothing wrong with fighting back against the ravages of time.*

*Be aware, however, that using exfoliants makes the skin more sensitive to sunlight - which is hardly surprising when you think about it. It is then all the more important to make use of antioxidants and to use a suitable sunscreen to protect the newly sensitized skin from the sun's harsh rays. After all, you don't want to undo with one hand what you've done with the other.

Can Skin Aging Be Reversed?

As your skin ages, there is a gradual breakdown of the structural proteins - primarily collagen and elastin - that made it so firm and supple when you were younger. At the same time, the fat cells at the base of your skin, which formerly created the pleasing contours of your face and body, tend to shrink, and the skin itself becomes thinner and less elastic. Under the relentless tug of gravity, it starts to sag and wrinkle, and you start to look older. (See the sidebar "What's to Blame for Aging Skin?")

What's to Blame for Aging Skin?

The sun - giver of all life but giver also of nearly all skin cancers - is to blame for up to 90% of wrinkles. Did you ever notice that the skin on your behind has no wrinkles? That's because it has probably never seen the sun. There is a strong correlation between exposure to the sun and skin damage. We have a word for that kind of damage: photoaging. It is the dominant factor in skin aging and the development of skin cancer.

Solar ultraviolet (UV) radiation causes damage to cell membranes and to the DNA molecules inside the cells. It also causes the breakdown of collagen and elastin, proteins that are vitally important for maintaining the skin's structural integrity. Prolonged exposure to the sun causes a thickening of the epidermis that can produce a tough, leathery look and unsightly changes in skin pigmentation. You've heard it before, and it's true: if you want to keep youthful-looking skin, stay out of the sun. And when you do go out in the sun, use a broad-spectrum sunscreen lotion (preferably with an SPF rating of at least 15* ) - it will help prevent further wrinkling and will also protect against skin cancer.

*Too high an SPF, however, such as 25 or higher, can actually be undesirable (except in cases of very long or intense exposure), because a little solar UV radiation can be beneficial.

While the sun ages your skin from the outside, smoking attacks it from the inside. It constricts the blood vessels in your skin, thereby decreasing blood flow and depriving your skin cells of some of the oxygen they need to stay healthy (your skin needs about 7% of all the oxygen you take in, by the way). It also deposits toxins in the cells and greatly increases the production of destructive free radicals, which accelerate aging by damaging cell membranes and many of the molecules inside. If you value your health, please don't smoke!

Poor nutrition can damage your skin, as can inadequate physical exercise, which is vital for maintaining proper blood flow to your skin and every other part of your body. Without an adequate blood supply, your skin will be oxygen-deficient. As for nutrition, a well-balanced diet should be supplemented not only with vitamins and minerals, but also with antioxidants, which help keep free radicals in check (vitamins A, C, and E are antioxidants, by the way).

Another culprit in skin aging is excessive alcohol consumption, which dehydrates the skin, making it drier and older-looking. Showers that are too hot or too long can have the same effect: prolonged exposure to hot water strips the skin of its natural oils and replaces them with water. The water then evaporates, leaving dry skin.

Finally, too much stress in your daily life can cause a host of physiological responses that can harm your skin as well as many other parts of your body. And inadequate sleep robs your body of the "downtime" it needs to regenerate collagen, and it can dull your complexion. They don't call it "beauty sleep" for nothing.

So to keep your skin looking its best for as long as possible, stay out of the sun, don't smoke, eat sensibly, take your supplements, exercise regularly, don't drink too much, take short showers, minimize stress, and get adequate sleep. (Whew!) And if you do all that, your skin will barely be able to contain all the other health benefits you will surely reap.

But when it comes to skin, do looks deceive, or is skin treated with alpha-hydroxy acids really more youthful and healthy? Clinical studies have demonstrated that the latter is true, in the sense that the treatment increases epidermal thickness and increases the synthesis of compounds called glycosaminoglycans (GAGs), which are beneficial for the skin.4 These effects may be only skin-deep, but in this case, that's just right.

Citric Acid Rejuvenates Sun-Damaged Skin

In one study, American researchers investigated the effects of a 20% citric acid lotion on skin thickness and GAG content in sun-damaged skin.5 They recruited six female volunteers (aged 70-83) who had clinical evidence of sun damage, including fine wrinkling and alterations in pigmentation, on their forearms. Using a randomized, placebo-controlled, double-blind protocol, the women's forearms were treated with lotion that either did or did not contain the citric acid. The lotion was applied twice daily for three months, after which biopsy specimens were taken from the center of the treated area and analyzed.

In the citric acid-treated skin,
there was a dramatic increase
(41%) in viable epidermal
thickness. At the same time,
there was a significant increase
(16%) in overall skin thickness.

In the citric acid-treated skin, there was a dramatic increase (41%) in viable epidermal thickness, i.e., the thickness of the basal cell layer of living cells. At the same time, there was a significant increase (16%) in overall skin thickness. In the dermis, there were also major increases in the levels of two specific types of GAG: hyaluronic acid (up 57%) and chondroitin sulfate (up 66%). GAGs constitute only about 0.1-0.3% of the dry weight of normal dermis, but they have the remarkable property of being able to bind up to 1000 times their own weight in water. Thus, even a relatively small change in the amount of GAGs in the dermis can result in a large increase in its hydration (water content), and this may account for the observed increase in the thickness of the dermis.

Alpha-Hydroxy Acids Work Deep Down

In another intriguing study on the effects of alpha-hydroxy acids on sun-damaged skin, researchers have found that the thickening of the epidermis (despite the thinning of its outer layer, the stratum corneum) is accompanied by increased synthesis of GAGs and of collagen, one of the proteins that are so vital to the skin's structural integrity.6

What Your Skin Does for You

We don't usually think of our skin as an organ (let alone our body's largest organ), because it doesn't really do much except hold our innards together and keep us from leaking all over the carpet, right?

Not right. The skin performs a number of vital organ functions, including the control of body temperature, in part through perspiration (the evaporation of which has a cooling effect), and the synthesis of vitamin D as the result of solar radiation (sunlight). Skin also produces sensations of pain and pleasure, and it acts as a semipermeable barrier protecting us from assault by environmental pollutants, chemical toxins, biological pathogens such as bacteria, viruses, and fungi, and just plain dirt.

Did you catch that word "semipermeable"? There's the rub - semipermeable means that the skin is not an absolute barrier, but one that allows some things through, in one direction or the other. We know, for example, that it lets perspiration and oils out, and it lets various organic substances, including some pharmaceutical preparations, in.

Our sweat, by the way, provides nutrients for several hundred million bacteria and fungi that live on our skin throughout our entire lives. These beneficial microorganisms produce acidic waste products, such as lactic acid (an alpha-hydroxy acid), creating a surface environment that invading, harmful microorganisms find inhospitable. Thus, our sweat nourishes our tiny skin critters, and their waste products protect us from harm. Neat!

It is thus becoming increasingly apparent that alpha-hydroxy acids do more than just exfoliate the epidermis and stimulate the growth of new cells in its basal layer - they work deep down in the dermis to counteract some of the effects of aging.

Recapture the Youthful Glow of Your Skin

It's time to end this article - and we haven't even discussed the vital importance of antioxidants in protecting our skin from the damaging effects of free radicals, thereby helping to keep it healthier and more youthful-looking. That will be the subject of another article, coming soon. Meanwhile, it's gratifying to know that it really is possible, with natural chemical agents such as the alpha-hydroxy acids, to restore some of the glow of youth to our aging skin.


  1. Ridge JM, Siegle RJ, Zuckerman J. Use of •-hydroxy acid in therapy for "photoaged" skin. J Am Acad Dermatol 1990;23:932.
  2. Vide DG, Bergfeld WF. Cosmetic use of alpha-hydroxy acids. Cleve Clin J Med 1997;64:327-9.
  3. Thibault PK, Wlodarczyk J, Wenck A. A double-blind randomized clinical trial on the effectiveness of a daily glycolic acid formulation in the treatment of photoaging. Dermatol Surg 1998;24:573-7.
  4. Lavker RM, Kaidbey K, Leyden JJ. Effects of topical ammonium lactate on cutaneous atrophy from a potent topical corticosteroid. J Am Acad Dermatol 1992;26:535-44.
  5. Bernstein EF, Underhill CB, Lakkakorpi J, Ditre CM, Uitto J, Yu RJ, Van Scott E. Citric acid increases viable epidermal thickness and glycosaminoglycan content of sun-damaged skin. Dermatol Surg 1997;23:689-94.
  6. Ditre CM, Griffin TD, Murphy GF, Sueki H, Telegan B, Johnson WC, Yu RJ, Van Scott EJ. Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrastructural study. J Am Acad Dermatol 1996 Feb;34(2 Pt 1):187-95.

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