Nutritionists and vegetarians have claimed for years that soy provides a wide range of health benefits, such as lowering rates of heart attack, reducing blood cholesterol levels, relieving menopausal symptoms in postmenopausal women, and in the general enhancement of the immune system. In fact, in 1999, the Food and Drug Administration even permitted food manufacturers to put label on products with high soy protein contents, with the indication that the corresponding food product may be able to reduce heart disease risks (Henkel 2000). Consequently, ever since these claims were announced, attention and examination of the impact of soy on human health has been risen rapidly, as scientists and the public health community became more focused on the chemical components of soy (for instance, the soy isoflavone genistein and daidzein). Soybeans also contain a complete protein profile, which means that they provide all the essential amino acids that cannot be synthesized by the human body. Hence, soy protein products can be used to replace animal-based products, which are generally associated with unhealthy substances, such as saturated fats (Henkel 2000).
However, in addition to these well-known benefits, some previous publications reveal that soy extracts can even enhance cosmetic attributes. This includes healthier-looking skin and nails (Revival 1998, Kim et al. 2004) as well as the reduction of hair loss, in particular, male and female pattern baldness (Adams 2004). Therefore, this paper will intend to look more closely at this hair loss claim.
According to some conservative estimates, 60 million Americans are affected by hair loss, in which two-thirds are males (Hair Transplant Center, Inc.). Also, men above the age of 50 have a 50% chance to experience some type of hair loss, and such process can often start as early as the age of 20 (Bauman 2003). Typical male pattern baldness begins as a recession of the hairline with thinning at the top of the head; as the process progresses, the so-called “monk’s ring” of hair will result (Bauman 2003).
For females, the first sign of hair loss usually begins in their late 40’s to 50’s (Bauman 2003). In general, their pattern of baldness does not involve a receding hairline; rather, some women may experience thinning only on the top of the head, while others may have hair that thins out over broader regions or possibly even the entire scalp (Bauman 2003).
Before looking more closely at what contributes to hair senescence, it is important to recognize what does not cause hair loss. There are many misconceptions that the general public has about hair loss, including: poor scalp circulation; microscopic scalp mites; poor choices of shampoo and other hair-care products; and/or wearing hats or helmets. Indeed, in all of these cases, such considerations will only affect the quality, manageability, or potential breakage of hair (Bauman 2003). Real causes of male and female pattern baldness involve medications, diseases, poor nutrition, hormonal changes, stress, and genetics.
Among these causes, genetics appears to be at the forefront, and in fact, accounts for 95% of hair loss cases (Yap 2005). This implies that it is the inherited DNA from either of the parents that will determine hair loss in the individual. And this inheritance of common baldness appears to be related to the actions of androgens, such as the male circulating hormone dihydrotestosterone (DHT) (Kuster and Happle 1984). Here, this genetic disease is often known as “androgenic alopecia” (Kuster and Happle 1984) – essentially, when a diseased individual ages, his/her hair follicles on the scalp begin to miniaturize and the follicles will continue to shrink until they no longer produce hair (Yap 2005). Although the exact mechanisms are still unclear, DHT is has been shown to influence the hair growth cycle, which usually consists of hair expansion, falling out, and new expansion. Studies have shown that as the level of DHT increases, the expansion phase shortens, and the rate of hair senescence will elevate (Yap 2005). Eventually, the ability of follicles to produce hair will cease, and microscopic scarring will result (Bauman 2003).
Hair transplant, and medications such as Provillus, are some of the current treatments for hair loss, although often not without significant side effects. Alternative solutions can be focused on changing lifestyle or adopting an appropriate diet habit. This includes the potential use of soybean in ones diet.
In essence, soy proteins have been indicated to play a role in hair growth in many previous studies. Soy contains isoflavones, which belong to a class phytoestrogens known as flavonoids (Lund et al. 2004). Phytoestrogens are essentially plant compounds capable of acting like estrogen. Among all the isoflavones, genistein and daidzein carry the most estrogenic properties and functions (Lund et al. 2004). Although soy products are not composed of high levels of genistein and daidzein, they do have high amounts of their precursor forms (genistin and daidzin respectively) (Lund et al. 2004). After the conversion, daidzein is further metabolized in the intestine to equol (Lund et al. 2004). Equol acts as an anti-androgen, but does so in a very specific and unique manner. It does not actually bind the androgen receptor (AR), but rather binds DHT with high affinity, which prevents the latter from binding the AR (Lund et al. 2004). Thus, the biological activity and physiological process of DHT can be modified.
Moreover, it has been shown that in the soy extract, the isoflavone genistein can stimulate the production of hyaluronic acid (HA) in the epidermis and dermis (Miyazaki 2003). HA is a carbohydrate, and occurs naturally in the human body (Hyalogic 2001). When not binding with other molecules, HA binds with water readily, which contributes to its viscous gel property. HA has been found in many movable parts of the body, and acts as a lubricant (Hyalogic 2001). Since HA is one of the most hydrophilic molecules in nature, it is often referred to as “nature’s moisturizer” (Hyalogic 2001), which is why it is applied in many skin-care products (Hylogic 2001).
HA is present abundantly in the scalp tissue, and its function is (by holding water) to form a gelatinous fluid in tandem with the connective tissue in the dermal layer. This results in providing support, nourishment, and hydration to the deep layers of scalp, which in turn facilitates the good health of the hair follicles locating in the dermal layer (Miyazaki et al. 2002). In fact, HA powder has been shown to facilitate the turnover and regeneration of hair follicle keratinocytes (Annely 2006), and to enhance hair colour restoration (HairSite 2002). Furthermore, HA forms a gel-like shield directly on the hair follicles (HairSite 2002 which can protect them from the harmful effects of DHT (HairSite 2002).
Finally, soy extracts have also been shown to reduce another disease-causing baldness, called alopecia areata (AA) (McElwee et al. 2003). AA is an autoimmune disease, manifest of focal inflammation in hair follicles that ultimately leads to hair loss (Asaleh et al. 1995). AA is also genetic in nature, as many studies have been reported where monozygotic twins show similar onset and hair loss patterns of AA (Scerri and Pace 1992), as well as multiple generations within the same family being affected by the affliction (Van der Steen et al. 1992). Research has shown that the intake of soy oil content modifies the susceptibility of AA. The data showed that mice being fed soy oil developed a resistance to AA induction by skin grafting in a dose-dependent manner (McElwee et al. 2003). Further studies reveal that the injection of isoflavone genistein into mice reduced the occurence of AA (McElwee et al. 2003). Based on this data, the researchers proposed that since genistein is a tyrosine protein kinase inhibitor (tyrosine phosphorylation is an importance part of the immune response) and has been shown to suppress inflammatory cells in many tissues, the presence of the protein inhibits autoimmunity and inflammation in the affected areas (McElwee et al. 2003).
Taken together, soy seems to be a putative treatment to prevent hair loss, and is less expensive while arguably much safer and healthier than prescription drugs and surgery. However, despite being aware of all the health benefits from consuming soy products, the majority of North Americans and Western Europeans detain to include soy foods as one of their dietary staples. Even so, soy products are inadvertently being consumed in a large variety of food products in supermarkets. For instance, 79% of the edible fats are composed of soybean oil (Henkel 2000). Also, many brands of commercial mayonnaises, margarines or salad dressings have soybean oil (Henkel 2000). Although taking soy contents may not stop hair loss outright, having this food source in diets is always a healthy and nutritional strategy for both men and women.
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