By Elena Voropay

Probably no other food has been the subject of so many contradictory claims than soy. As an ancient and new food, it came a long way to help celebrate the female power of reproduction. Indeed, lifetime hormonal changes all women experience don't always bring satisfactory feelings. And soy has been found to have natural magical powers to help fight top killer diseases and improve overall health.

Some research have shown that soy may prevent against cancer, balance hormones, slow down the aging body's declining hormone levels and thus relieve menopausal symptoms, decrease the risk of heart disease and osteoporosis, and even assist in weight loss. But instead of making soy a nutritional staple, investigators found just as many negative effects of soy labelling it as a 'danger' food. An analysis of close to 200 soy studies conducted over the past two decades showed only limited evidence of specific health benefits associated with eating soy products or taking soy supplements. Some unfavourable claims state that prolonged ingestion of soy may contribute to an increased risk of cancer, osteoporosis, fibromyalgia, metabolic and hormonal imbalances. Find out whether these claims hold any water and if you should add soy to your diet.

Menopause

Pros

Menopause is a natural stage of life all women experience at around age of 40 as a result of declining oestrogen levels. Monthly periods cease, and fluctuations in hormones make you feel worse than you felt during your teenage years. When oestrogen decides that your body is too old and outdated for reproduction, your body reacts in many unpleasant ways giving you hot flashes, night sweats, mood swings, fatigue, reduced bone mineral density and elevated cholesterol. Clinical trials have demonstrated that soy can help reduce these symptoms due to the hormone-like effect of phytoestrogens.

Found in a variety of plants, including flax seeds, soybeans, pumpkin seeds, rye and broccoli, phytoestrogens are plant chemicals that mimic the effects of hormone oestrogen in the body. Their chemical structure is very similar to that of our own oestrogen and so they hook onto the same spots of the receptor cells where the natural hormone attaches. If there is little oestrogen in the body, such as after menopause, phytoestogens may replace the missing link. However, when there is plenty of this hormone in the body, these plant chemicals are thought to reduce the effects of oestrogen overabundance by taking up the its place on the attachment sites. Soy is loaded with one type of phytoestrogens, particularly one type known as isoflavones, which may help you combat the negative consequences of menopause, help balance your hormones, and protect against breast cancer [1-4].

Cons

Whether or not soy helps to ease menopausal symptoms for the average women remains unclear. Some studies have shown soy's benefits, others have demonstrated similar results with a placebo. Isoflavones may certainly alter hormonal levels, but whether or not it will be a positive change for everybody is unknown. If you wanted an oestrogen-boosting effect but have found that soy supplementation actually lowers your oestrogen levels, you could worsen the symptoms you are trying to eliminate. After examining 21 studies of soy effects on menopause, researches concluded that most studies were of poor quality representing a very wide latitude of soy dosages and changes in the frequency of hot flashes. With supplementation ranging from 17.5 to 100 milligrams of soy a reduction of hot flashes varied from seven to 40 per cent with unknown effects on other symptoms and conditions [5].

Weight Loss

Pros

Adding soy to your diet may help you lose weight for several reasons. Soy is a potent plant source of complete protein containing all essential amino acids needed for reconstructing all tissues, fighting infections, handling stress, supporting metabolism and staying healthy. While other plant foods contain some amino acids, they are usually missing one or more amino acids which makes the protein in these foods not complete. Animal proteins from meat and dairy provide all amino acids, just like soy. But plant proteins are easier for the body to digest and use than meat proteins. Besides, many people may not tolerate milk products, eggs, or some meats because the structure of each form of protein is slightly different, and some may trigger an allergic response. For this reason, vegetarians may greatly benefit from eating soy on a regular basis, or they can eat grains and legumes at the same time as an excellent protein source. Additionally, soy contains very little fat and practically all of it comes from healthy unsaturated fatty acids. Small amounts of low-glycemic carbohydrates accompanied by high fibre content position soy on the list of best low GI (glycemic index) foods. Compared to most fatty meats and high-carb grains and legumes, soy are the only source of highly concentrated easily digestible vegetable protein that contributes to the feeling of satiety immediately after a meal and keeps hunger at bay for longer. This will help you lose weight as you are less likely to overeat or to snack between meals [6,7,8,9].

Cons

Soy's isoflavones may hinder thyroid function due to the presence of goitrogens, potent anti-thyroid agents. Thyroid hormones regulate all metabolic functions, particularly how your body uses available energy and burns calories. Isoflavones act as inhibitors of thyroid peroxidase which makes hormones T3 and T4 involved in metabolism. When these hormones are produced inefficiently, thyroid stimulating hormone tries to increase synthesis of T3 and T4 and also causes the thyroid gland to grow in size as a type of compensation. As a result, thyroid abnormalities including goiter (enlarged thyroid gland) and autoimmune thyroiditis can be expected. Besides soy's effect on your metabolic regulator, the thyroid gland, there are other mechanisms involved in weight loss. Frequent eating of small meals that contain less total calories than you use will show a noticeable weight loss. Also, a high-fibre low-fat diet with sufficient protein from natural grains, legumes, vegetables, fruit and lean meats and fish will also help to reduce appetite and increase satiety [10].

Cholesterol

Pros

To protect the heart and improve heath, we should aim to increase our HDL (high density lipoprotein) and decrease LDL (low density lipoprotein). And soy may assist in that process. Studies show that supplementation with soy lowers total cholesterol, the “bad” LDL cholesterol, triglycerides, and may even raise good HDL cholesterol levels. Soy isoflavones are the active ingredients that may inhibit the growth of cells that form artery clogging plaque which can lead to a heart attack. In particular the isoflavone genistein stops the blood plates from attaching to the wall of the blood vessels. And like all plant foods, soy is a great source of antioxidants important in prevention of hear disease [11-13].

Cons

Even though soy supplementation have shown to improve blood lipid profile, this reduction is relatively small. From 63 studies reviewed, LDL-cholesterol levels were lowered by only 3 percent without any changes in HDL-cholesterol. What's more, the subjects in the study eat larger quantity of soy than most people would, corresponding up to half a kilo of tofu. Nobody knows for sure whether you can lower your cholesterol levels and the risk of heart disease by eating less soy. If you want to fight heart disease, genetics and other lifestyle factors [5].

Bone Health

Pros

Weaker bones is another side effect of aging. Our bones are continuously rebuilding themselves by breaking down old and constructing new cells. With aging, the creation process slows down and more bone is destroyed than regenerated causing osteoporosis, the degeneration of bone mineral density and bone strength. Both men and women may develop porous bones, but women are especially vulnerable due to the loss of oestrogen during menopause. This hormonal change slows down the remodelling cycle even more and causes to excrete more calcium from the bones. In the 5 years following menopause, women can lose up to 20 percent of their bone mass. Soy's one important isoflavone, called daidzein, acts as a bone-guard. It stimulates the growth of new bone cells and decreases calcium loss. Regular soy and calcium intake together with weight-bearing exercise will support a healthy skeletal system [14, 15].

Cons

In order to see the possible benefits of soy on bone strength long-term daily use of soy active ingredients is important. Additionally, there are other factors involved in fighting osteoporosis, such as diet and regular exercise. You need to get sufficient amounts of calcium and magnesium, vitamin D and C in order to keep the mineral balance of bones. Soy, on the other hand, contains phytic acid, a naturally occurring plant fibre which impairs absorption of all minerals and may cause calcium to be stripped from the body. This further aggravates osteoporosis and may lead to other nutrient deficiencies.

Bottom Line

Soy has definitely shown to improve many health related conditions, but it has also shown to have just as many side effects. Researchers don't know yet what long-term consequences this new food may have and what are the precise amounts considered safe. For now, individual choices and careful observations may help you decide. And, like with all other foods, remember to practice moderation.

Soy's Nutritional Profile

http://www.nutritiondata.com/facts-001-02s020t.html

Power Up With Soy

To get the most benefits of soy, try this legume in its most natural state such as soy beans, nuts, tofu and tempeh. Other good sources include newly created vegetarian versions of hot dogs, burgers, cheeses, pasta, chips, milk or cereals made with soy protein, but check out other ingredients added to these products such as starches, sugars and artificial flavourings. These may cause unwanted reactions and not provide the very best nutrition. If you want to experience the soy's magic power from the original source, the highest amounts of isoflavones can be found in fresh soy beans, soy nuts, unflavoured tofu and tempeh.

• Puree silken tofu and use instead of sour cream and ricotta cheese in lasagna. Try adding herbs and spices to the puree

• Add small pieces of tempeh to your favourite salad, stew, stir fry, soup or any dish in place of meat. Toast tempeh cubes in the oven – this adds flavour and preserves the form.

• Blend tofu with orange juice and frozen banana or avocado for a power smoothie.

• Sprinkle toasted sesame seeds on steamed soy beans for a great low-fat low-carb crunchy snack (you can also buy soy nuts from the supermarket, but I find them too dry).

Elena Voropay is a journalist specializing in health and fitness writing. She is a Certified Personal Trainer and Certified Nutritionist. For a wealth of information about health, fitness, fat loss, muscle building and more, visit her website at www.AustralianFitness.com

References

1. Obstetrics & Gynecology 1998 Jan;91(1):6-11. The effect of dietary soy supplementation on hot flushes. Albertazzi P, et al.
2. Soy Isoflavones Decrease Hot-Flash Frequency: A Meta-Analysis of Studies Examining Soy Protein, Soyfood, and Soy Isoflavones. M. Kurzer, et al. 5th International Symposium on the Role of Soy in Preventing and Treating Chronic Disease, Sept. 21-24th, 2003. Orlando, FL.
3. Menopause 2000 Mar-Apr;7(2):105-11. Clinical effects of a standardized soy extract in postmenopausal women: a pilot study. Scambia G, et al.
4. Menopause 2002 Sep-Oct;9(5):329-34. Effects of a standardized soy extract on hot flushes: a multicenter, double-blind, randomized, placebo-controlled study. Faure ED, et al.

5. Balk, E. "Effects of Soy on Health Outcomes." Ethan Balk, MD, medical researcher, Tufts-New England Medical Center Evidence-based Practice Center, Boston. Carolyn M. Clancy, MD, director, Agency for Healthcare Research and Quality.

6. Eisenstein J, Roberts SB, Dallal G, Saltzman E. High-protein weight-loss diets: are they safe and do they work? A review of the experimental and epidemiologic data. Nutr Rev 2002, 60:189-200.
7. Nishi T, Hara H, Tomita F. Soybean ß-conglycinin peptone suppresses food intake and gastric emptying by increasing plasma cholecystokinin levels in rats. J Nutr 2003, 133:352-7.
8. Ludwig DS. The glycemic index: physiological mechanisms relating to obesity, diabetes and cardiovascular disease. JAMA 2002;287:2414-23.
9. Sydney University's Glycaemic Index Research Service. The glycaemic and insulin index values of six soy-based foods. The Glycaemic Index Report, July 2004.

10. Divi RL; Chang HC; Doerge DR, National Center for Toxicological Research, Jefferson, AR 72079, USA, Biochem Pharmacol, 1997 Nov, 54:10, 1087-96).

11.Circulation. 2000 Nov 14;102(20):2555-9. AHA Science Advisory: Soy protein and cardiovascular disease: A statement for healthcare professionals from the Nutrition Committee of the AHA. Erdman JW Jr.
12. Anderson JW, Johnstone, BM, and Cook-Newell ME. Meta-analysis of the effects of soy protein intake on serum lipids. New England Journal of Medicine. 1995. Aug 3;333(5):276-82.
13. Washburn S, Burke GL, Morgan T, Anthony M. Menopause 1999 Spring;6(1):7-13. Effect of soy protein supplementation on serum lipoproteins, blood pressure, and menopausal symptoms in perimenopausal women.

14. Chen YM et al. Soy isoflavones have a favorable effect on bone loss in Chinese postmenopausal women with lower bone mass.J Clin Endocrinol Metab. 2003 Oct;88(10):4740-7.

15.Atkinson C et al. The effects of phytoestrogen isoflavones on bone density in women.Am J Clin Nutr. 2004 Feb;79(2):326-33.