Dr. Mark Messina
Apr 04, 2011
To answer your questions about Soy and its benefits for women's health, the Wellness Advisor sat down with Dr. Mark Messina, a leading expert on soy. Dr. Messina received a Masters degree in nutrition from the University of Michigan and a Ph.D. in nutrition from Michigan State University. From 1987 to 1992, he was a program director in the Diet and Cancer Branch at the National Cancer Institute (NCI). He is currently the president of Nutrition Matters, Inc., and an adjunct associate professor in the Department of Nutrition at Loma Linda University.
Dr. Messina devotes his time primarily to studying the health effects of soyfoods and soybean constituents, especially the isoflavones (phytoestrogens) found in soy. He is the chairperson of the editorial advisory board of, and writes a regular column for, The Soy Connection, a quarterly newsletter that reaches over 100,000 dietitians and other health professionals. Dr. Messina organized and chaired all four international symposia on the role of soy in preventing and treating chronic disease and has co-authored several books, including The Simple Soybean and Your Health.
When was soy first found to be beneficial specifically for women's health?
Dr. Mark Messina: Soy foods have been a dietary staple in Asia for centuries. The soybean has long been viewed as a versatile bean from which a wide variety of foods can be produced. Interestingly, Asian women used to bathe in soymilk because of the reported benefits of soy for skin health. Of course this practice predates the current interest in soy for this purpose as evidenced by the many skin care products that advertise that they contain soy. There is some scientific support for the benefits of soy in this regard although the benefits come from topical application. Nutritionally, until recently the soybean was recognized only as a good source of high quality protein and essential fatty acids. Of course, there is much more to soy than this.
Why is soy beneficial for women's health? What effect does it have on the body?
Dr. Messina: There are two components of soy thought to be primarily responsible for the hypothesized health benefits, the protein and the isoflavones. Encouraging data indicate that early soy consumption increases long-term breast health later in life. This is likely because soy is a unique dietary source of isoflavones. Isoflavones may also benefit the bones and coronary vessels. Isoflavones are considered to be selective estrogen receptor modulators (SERMs). SERMs have a helpful effect in some tissues but either no effects or anti-estrogenic effects in other tissues.
How can soy help with the symptoms of menopause?
Dr. Messina: Several short-term clinical studies indicate that isoflavone-rich soy protein helps maintain bone health in perimenopausal and postmenopausal women, although effects have been observed primarily at the spine. In any event, longer term studies are needed before firm conclusions can be drawn. In addition to the effect of isoflavones, the protein itself, when substituted for animal protein, will reduce urinary calcium excretion. Since that calcium comes from the bones, all other things being equal, substituting soy protein for animal protein should improve bone health. Isoflavones have also been shown to make the arteries more flexible. Artery health can lead to better heart health. Whether soy or isoflavones eliminate hot flashes is unclear as clinical studies have produced conflicting findings. Certainly, Asian women have fewer hot flashes than Western women. But whether this is due to soy has not been definitively established. Overall, a review of the research shows that isoflavones can reduce hot flash frequency by 20% and severity by 30% more than placebo. Finally, three clinical studies have found isoflavones improve some aspects of cognitive function.
How much soy should be consumed to receive these benefits? Where can soy be found in foods? Is it realistic to digest that amount in your diet, or are supplements helpful?
Dr. Messina: On the basis of Asian intake, clinical and epidemiologic findings, safety data, and practical considerations, the daily recommended soy protein and isoflavone intake is 15 g and 50 mg, respectively. This amount of soy protein and isoflavones is found in approximately two servings of soyfoods. A serving is for example 1 cup soymilk or 1/2 cup tofu. For people who don`t eat two servings per day, I recommend consuming an isoflavone supplement to bring the total amount of isoflavones up to the recommended amount of 50 mg per day. The supplements won`t be as beneficial as the foods because the protein itself, which is not found in isoflavone supplements, has its own benefits. However, studies have found that isolated isoflavones are beneficial and I think isoflavones are primarily why there is so much interest in soy, especially in relation to women`s health. So, soyfoods first, and soy isoflavone supplements secondarily as a means of getting sufficient isoflavones when insufficient amounts of isoflavones are consumed via foods.
Does soy help protect women's breast health?
Dr. Messina: Scientists have struggled to identify dietary factors that affect breast health. Unfortunately, much of the data on this subject is conflicting and equivocal. This may be because early life events have a particularly profound impact on later risks of breast health and studies usually focus on adult lifestyle habits. Certainly though, being obese as a postmenopausal women increases risk.
Based on animal data and a recent epidemiologic study, I think that eating soy (1-2 servings per day) when young (teenage years) may markedly improve breast health in adulthood.