Soy Benefits FAQs

Soy foods are cholesterol free, low in saturated fat, high in fiber and are an excellent source of protein. Soy is one of the few plant foods that contain the proper balance of the eight essential amino acids.

The FDA concluded in 1999 that daily diets containing 25 grams of soy protein, low saturated fat, can decrease cholesterol and help prevent heart disease. Other benefits believed to be found in soy foods are: the prevention of breast, colon, lung, and prostate cancer, osteoporosis, and kidney disease. Soy foods also contain antioxidant compounds, amino acids that boost the immune system, and phytoestrogen, which provides relief from the effects of menopause.

Possibly! Soy is the only source of genistein, a natural estrogenic compound which has shown promise in significantly decreasing levels of LDL cholesterol (the bad cholesterol) while increasing levels of HDL cholesteral (the good cholesterol) in numerous studies. Combined with a healthy diet and regular exercise, eating soy-based foods may help lower your cholesterol.

Many people believe soy foods can help decrease the risk of cancer because they contain antioxidants (compounds that protect cells from damage caused by unstable oxygen molecules called “free radicals”) “Free radicals” are believed to be responsible for initating many forms of cancer as well as premature aging. Certainly, there are many variables that factor into decreasing an individual's cancer risk. But it's important to note that there are encouraging studies that have highlighted the beneficial role of soy foods. One such major study in Singapore (carried out by scientists from Cancer Research UK, National University of Singapore and the U.S. National Cancer Institute), women who ate soy were much less likely to develop breast cancer than those who didn’t. Researchers noted that women whose diets were high in soy products developed less of the “dense” tissue associated with breast cancer. Additionally, a direct correlation between tofu consumption and lowered rates of prostate cancer was discovered in a major study of Japanese men in Hawaii. Studies of soy compounds have shown that they can inhibit prostate cancer cell growth in laboratory cultures.

The genistein found in soy does appear to reduce the severity of menopausal “hot flashes.” Japanese women, who traditionally eat a diet high in soy, rarely complain of “hot flashes.” Additional studies of this phenomenon are necessary to provide further proof of the benefits of genistein.

A Closer Look at Bone
Structure:
Bone is a metabolically active organ providing the structural material for the body’s framework, or skeleton. Inside the bone is a fatty tissue or bone marrow in which cells busily produce red and white blood cells and other blood components. Bone contains calcium and phosphorus which makes the outer-layer hard and rigid while specific bone fiber makes it resilient.

Growth:
The growth of bone is an orchestrated balance of bone turnover. This refers to a cycle of bone breakdown by osteoclasts and then bone re-building by the osteoblasts. Osteoclasts are continually breaking down bone in areas where it is not needed. Low dietary calcium intake increases the action of osteoclasts, drawing calcium from the bone to increase blood calcium levels. A supply of calcium is vital to all cells in the body, not just bone. Osteoblast cells release a collagen protein mixture which forms the support structure of the bone. It then encourages the deposition of the mineral calcium phosphate into bone which strengthens the bone. Before new bone can be built, the old bone in that particular area must be partially broken down. The actions of the osteoblast and osteoclast cells are controlled by a variety of hormones including the adrenal hormones, parathyroid and thyroid hormones, sex hormones estrogen and testosterone and growth hormone. These hormones also work to maintain normal calcium levels in the blood.

Bone Mass/Density
Bone mass throughout life is determined by a variety of genetic and environmental factors including body height and weight, physical activity, smoking, alcohol use, and age of menopause. Dietary measures such as intake of calcium, vitamin D, phosphorus and trace minerals play a large role in bone mass development and maintenance. For several years after longitudinal growth has stopped, bones continue to increase in mass, reaching a peak during the third or fourth decade of life (1).

Bone Loss
Both men and women have bone loss. Men lose bone at a fairly constant rate (.5-2%) between the ages of 20 and 90 years. Women have some bone loss from the spine and hip (approximately 10% between ages 20 and 40 years) and radius (wrist area) before menopause. However, an increased rate of bone loss of the hip occurs around the time of menopause (2) and loss at the spine (approximately 3 – 6% annually) has been reported during the first 5 years after cessation of menses, with a reduction in the rate thereafter (3,4).

Defining Osteoporosis in the United States
Osteoporosis is a disease defined by a decrease in bone mineral density (BMD), causing bones to weaken and increase the risk of fracture. According to the Center for Disease Control and Prevention (CDC), bone strength is determined by the amount of bone mass or bone mineral density (BMD) and its quality and microarchitecture. The World Health Organization (WHO) has developed diagnostic criteria for reduced bone density and osteoporosis in caucasian women. Osteopenia is defined as a mild reduction in BMD, and osteoporosis, as a more severe reduction. Results of the third National Health and Nutrition Examination Study (NHANES III, 1988-94) (5), 56 % of women 50 years of age and older had a reduction in bone density; 40 % of these had osteopenia and 16 percent had osteoporosis. Among men of the same age, 18 % had reduced bone density; 16 percent of these had osteopenia (the more mild type), and only 2 percent had osteoporosis. The prevalence of bone loss or reduced bone density does rise considerably with age. Women 80 years and over show a 10 fold risk over women age 50-59 years of age. Non-Hispanic white women have the highest risk of reduced bone density, and non-Hispanic black women have the lowest risk (6).

Osteoporosis: Nutritional Risk Factors & Interventions
Bone is composed of calcium, phosphorus and other trace minerals. It is expected that nutritional status of these nutrients and other nutrients that affect their absorption may pose as risk factors for low bone density and osteoporosis. Calcium and vitamin D play the largest nutritional role in bone health and maintenance. The active form of vitamin D hormone, calcitriol, stimulates intestinal calcium and phosphorus absorption, reduces kidney elimination of calcium, and helps regulate the deposition of calcium in the bones. Vitamin D and calcium absorption levels are frequently lower in patients with osteoporosis when compared with age-related controls (7,8).

Calcium intake during different stages of life may affect bone loss. Inadequate calcium intake has been implicated as a contributor to osteoporosis at the peak of bone formation and during the various stages of menopause. Increased calcium intake, in peri-menopause, appears to slow the rate of bone loss in some skeletal areas. However, in later stages of menopause, some bone loss is unresponsive to higher calcium intake (9).
Dietary modifications alone have not proven effective in individuals with established osteoporosis. Therapeutic agents such as estrogen replacement therapy, calcitonin, diphosphonates and other drugs may provide the most promising treatments for individuals diagnosed with osteoporosis.

The Role of Soy and Bone Health
Estrogen increases the synthesis of calcitriol, (the active form of vitamin D), which in turn, increases calcium absorption. Estrogen receptors have been identified in normal human osteoblastic-like (bone building) bone cells (10). This discovery shows the strong influence that estrogen plays in bone metabolism. Therefore, a decrease in the hormone estrogen is a major risk factor for osteoporosis in post menopausal women (11). Hormone replacement therapy (HRT) effectively alleviates post-menopausal symptoms and lowers the risk for coronary heart disease and osteoporosis (12). However, a considerable number of eligible women (80%) are unwilling to be placed on this type of therapy because of fear of increased risk of certain types of cancer or other contraindications (13). In fact, one large study revealed that 55 % of post-menopausal women had never taken estrogen therapy, 27 % had previously taken estrogen but had stopped, and only about 17 % were currently taking estrogen (14). Promising research has been conducted using natural bioactive food components. This may provide alternative treatments for post-menopausal women who are more willing to use natural remedies to reduce their risk for disease such as osteoporosis.

Soy Phytoestrogens (Naturally Occurring Plant Chemicals)
Phytoestrogens are defined as naturally occurring, non-steroidal, plant compounds classified as isoflavones, coumestrans and lignans, that are structurally and functionally similar to human estrogen, 17 beta-estrodial (15). Plant foods rich in these compounds include soybeans, flaxseed, various fruits and vegetables, grains and nuts. The most researched phytoestrogens are isoflavones. Isoflavones are primarily found in soybeans and foods made from soy. Medications called selective estrogen receptor modulators (SERMS) are defined as compounds that seem able to mimic or counter the effects of estrogen (16). Some researchers have found that phytoestrogens may behave as a “natural SERM” (17). These findings may help provide insight to alternative therapies for those women not able or willing to use hormone replacement therapy.

A high dietary intake of phytoestrogens was first noted to be associated with a decreased risk of disease associated with the Western diet. Asian women have lower rates of osteoporosis than American women, in spite of the fact that they consume lower levels of calcium and use less hormone replacement therapy; 4 % versus 30% in postmenopausal women(18). Many researchers propose that the high dietary intake of soy foods may explain this fact (19, 20). However, soy’s estrogenic effect may only be one mechanism in which it may protect against bone loss. Soy and soy foods are naturally a good source of protein. It is also suggested that a diet high in soy protein may prevent the urinary calcium loss seen with a high animal protein diet (21). Various short-term animal and human studies demonstrate phytoestrogenic soy isoflavones favorably impact bone health (22). However, although it appears that naturally-occurring isoflavones are responsible for bone protective effects, other bioactive components of soy, such as phytic acid, saponins and trypsin inhibitors cannot be ruled out.

In conclusion, as yet, there is no conclusive evidence on the efficacy of phytoestrogens and soy in the prevention of osteoporosis (23). Although hormone replacement therapy is currently seen as the best “non-dietary” preventative for bone maintenance, it is not full-proof. In fact, some researchers indicate that osteoporosis and fractures are common in older women who used estrogen therapy continuously since menopause (24). More long-term research is needed in the area of bone health, soy consumption and estrogen therapy.



References:

1. Shils M, Olson J, Shike M. Modern Nutrition in Health and Disease, 8th edition: 1560, 1994.
2. Mazess RB, Barden HS, Ehinger M, et al.: Bone Min., 2: 211-219, 1987.
3. Krolner B, Pors Nielson S. Clinical Sci., 62: 329-336, 1982.
4. Gallagher JC, Goldgar P, Moy A. J Bone Min Res., 2: 491-496, 1987.
5. Center for Disease Control and Prevention, National Health and Examination Survey III (1988-94), Osteoporosis: www.cdc.gov/nchs/nhanes.htm
6. Center for Disease Control and Prevention, National Health and Examination Survey III (1988-94), Osteoporosis: www.cdc.gov/nchs/nhanes.htm
7. Gallagher JC, Riggs BL, Eisman J, et al.: J. Clin. Invest., 64: 729-736.
8. Lips P, van Ginkel FC, Jongen M, et al.: Am. J. Clin. Nutr., 46: 1005-1010, 1987.
9. Dawson-Hughes B, Dallal G, Drall E, et al.: N. Engl. J. Med., 323:878-883, 1990.
10. Erickson EF, Covrd DS, Berg NJ, et al.: Science, 241:84-86, 1988.
11. Dempster DW, Lindsay R: Pathogenesis of osteoporosis. Lance 341:797-801, 1996.
12. Armandi B. The Role of Phytoestrogens in the Prevention and Treatment of Osteoporosis in Ovarian Hormone Deficiency. J. Amer. Coll. Nutr., 20:398S-402S, 2001.
13. Johannes CB, Crawford SL, Posner JG, McKinlay SM. Longitudinal patterns and correlates of hormone replacement therapy use in middle-aged women. Am J Epidemiol., 140: 439-452, 1994.
14. Salamone LM, Pressman AR, Seeley DG, Cauley JA. Estrogen replacement therapy. A survey of older women’s attitudes. Arch Intern Med., 156(12):1293-1297, 1996.
15. Mackey R, Eden J. Phytoestrogens and the menopause. Climacteric, 1(4):302-8, 1998.
16. Cosman F, Lindsay R. Selective estrogen receptor modulators: clinical spectrum. Endocr Rev 20: 418-434, 1999.
17. Brzezinski A, Debi A. Phytoestrogens: the “natural” selective estrogen receptor modulators. Eu J Obstet Gynecol Rep Biol., 85:47-51, 1999.
18. NIH Consensus Development Panel on Optimal Calcium Intake. JAMA 272(24); 1942-1948, 1994.
19. Horivchi T, Onouchi T, Takahashi M, Ito H, Orimo H. Effect of soy protein on bone metabolism in postmenopausal Japanese women. Osteoporosis Int., 11(8):721-4, 2000.
20. Adelercreutz H, Mazur W. Phyto-oestrogens and Western diseases. Ann Med., 29(2):95-120, 1997.
21. Kurzer M, Xu X. Dietary Phytoestrogens. Annu Rev Nutr., 17:353-38, 1997.
22. Brynin R. Soy and its isoflavones: a review of their effects on bone density. Altern Med Rev., 7(4):317-27, 2002.
23. Nitsan-Kaluski D, Stern F, Kachel J, Leventhal A. Soy and phytoestrogen consumption and health policy hesitation or certitude. Harefuah, 14(1):61-66, 2002.
24. Nelson HD, Rizzo J, Harris E, Cauley J, Ensrud K, Bauer DC, Orwoll E; Study of osteoporotic fractures research group. Osteoporosis and fractures in postmenopausal women using estrogen. Arch Intern Med., 162(20):2278-84, 2002.

Obesity in the United States: A Call for Action
The prevalence of obesity continues to be on the rise in the United States for both adults and children. According to the National Institute of Health (NIH), approximately 65% of American adults are either overweight (Body Mass Index > 25.0) or obese (Body Mass Index equal to or > 30). Over 25% of children and adolescents combined are currently overweight, and this number has been increasing rapidly (NIH, 2000).

The Health Cost of Obesity
The economic cost of obesity in the United States was estimated at $117 billion in 2000 (U.S. Surgeon General's Call to Action, 2001). Obese individuals suffer from numerous adverse health consequences including increased risk for cardiovascular disease, some types of cancers, stroke, diabetes, osteoarthritis, gallbladder disease, sleep apnea and higher mortality rates from all causes than those of normal weight (NHLBI and NIDDK, 1998). Experts say that the medical costs associated with treating these diseases will strain the healthcare system and economy in the years to come (Hellmich, 2003).

Factors that Increase the Risk of Obesity
It is well known that obesity is a complex condition resulting from a variety of factors. These include a combination of family history (genetics), behavioral and environmental factors. Various studies of obesity clearly find that genetic factors predispose specific individuals to develop obesity and its related adverse health risks. Jeffrey Friedman, a scientist at the Howard Hughes Medical Institute at Rockefeller University, says basic differences in an individual's genetics may partly explain why some remain lean in the current environment of fast food and huge portions, while others are hundreds of pounds overweight (Hellmich, 2003). Behavioral and environmental factors that increase the risk for obesity include; an increased sedentary lifestyle, a decrease in physical activity, availability of inexpensive and convenient calorie-dense foods and cultural factors (Hill and Peter, 1998). Other contributing factors may include stage of life, economic status, specific drug initiation (corticosteroids), cigarette smoking cessation and family history of obesity. Some indicate that the large consumption of animal protein in the typical Western diet may be the origin of obesity in the U.S. (McCarthy, 2000).

Weight Loss Trends and Statistics
According to the Calorie Control Council National Surveys, fewer Americans are on diets. Their survey shows that only 24% of U.S. adults (51 million people) are currently dieting compared to 37% in 1986. Although 47% (124 million people) are reported to be making a conscious effort to control their weight, waistlines continue to grow.

The number one reason in the survey given for weight loss failure is a lack of exercise (50% of respondents). Other top reasons include frequent splurging on favorite foods (36% of respondents), too much snacking (33% of respondents), and respondents claiming that they eat too many high-fat foods and eat for emotional reasons (28%).(Calorie Control Council, 2003).

Americans may be getting the message that short-term diet measures just don't work. This is evident in that approximately two thirds of dieters have lost at least ten pounds in recent months, according to the study. "Pills, fad diets and cutting out certain food groups just aren't working and consumers are finally realizing this. To loose pounds, you've basically got to lighten up and also get moving", said Lynn O'Brien Nabors, Executive Vice President of the Calorie Control Council.

Weight Reduction: The Controversy of Dietary Composition
There are a multitude of diets proclaiming the benefits or risks of carbohydrates (CHO) versus protein or fat for weight loss. However, the ideal ratio of CHO to protein for weight management and adult health is inconclusive. Additionally, the optimal balance of all macronutrients (CHO, fat and protein) for controlling obesity is at the center of debate (Laymen et al, 2003)

Changes in body composition and weight require changes in energy intake (calories consumed) and energy expenditure (calories burned). Acceptable Macronutrient Distribution Ranges (AMDRs) for adults are 20 - 35% fat, 45 - 65% carbohydrates and 10 - 35% protein. (Institutes of Medicine, 2002).

Diets high in some carbohydrates (simple and refined) can cause a rapid rise in blood sugar leading to a period of hypoglycemia (low blood sugar) and increased hunger. Diets high in protein, namely animal protein, have been termed ¡°atherogenic¡± or increasing the risk of heart disease. This is due to their higher levels of fat, saturated fat and cholesterol than the typical high CHO diet. Although not any one diet works for everyone, recent studies suggest that changes in the ratio of protein (animal) to carbohydrates toward a higher protein diet can improve body composition and blood lipids during weight loss in adult women ( Laymen et al, 2003 ).


The Role of Soy Protein and Weight Reduction
Soy Protein: High Quality Protein
Calorie-restricted diets require adequate, high quality protein for muscle repair and synthesis and lean muscle tissue maintenance. Various findings show that well processed soy protein isolates and concentrates can serve as the major or even sole source of protein intake and that their protein values are essentially equivalent to that of foods of animal protein (Young, 1991).

Soybeans are the only vegetable that contains complete protein. Soybean protein provides all eight essential amino acids in the amounts needed for human health. Additionally, the amino acid profile of soy protein is essentially equivalent in protein quality to that of milk, meat and egg protein.


Soy Protein and Weight Loss
Soy protein contains all eight essential amino acids. It is also higher in non-essential amino acids than the majority of animal proteins. Some researchers feel that proteins higher in non-essential amino acids should preferentially favor glucagon production (fat burning) and decrease insulin secretion (McCarthy, 1999). Moreover, protein from legumes (soy and others) may be more slowly absorbed, as compared to animal protein. (McCarthy, 2000). In single meal tests, protein exhibited a greater thermogenic (heat producing) and satiating effect than carbohydrate (Mikkelsen et al., 2000). This means that soy protein produces a larger calorie expenditure than carbohydrate. In fact, substitution of carbohydrate with 17-18% of energy as either pork-meat or soy protein produced a 3% higher 24- hour energy expenditure, which may serve as a preventative measure in the treatment of obesity (Mikkelsen et al.,2000).

Isolated soy protein provokes a greater release of the hormone glucagon. Glucagon is responsible for the obstruction of fat storing enzymes and increasing fat metabolism (fat burning). It is also responsible for decreasing cholesterol synthesis (production). Thus, diets featuring vegan (plant) proteins can be expected to lower elevated serum lipid levels (triglycerides and cholesterol), and promote weight loss. Bosello et al, (1988), Jenkins et al (1989), McCarthy (1999).

Weight loss, especially when seen from very low calorie diets, promotes fat and lean muscle tissue loss. Researchers have reported increases in lean body mass in peri-menopausal (before menopause) women when soy protein and not animal protein was used as the dietary source of protein. (Moeller et al, 2000). Animal studies have also shown the beneficial effects of soy protein on weight reduction. (Arjmandi et al., 1996).

In another animal study by Aoyama et al (2000), weight and body fat reduction in rats and mice subjects was more dramatic when fed a diet of soy protein isolate compared to those fed a casein-based diet. It was concluded that these results indicate that soy protein isolate is a suitable protein source in an energy-restricted diet for treating obesity.

Soy Protein: Improved Glucose Control
Soy protein and its many bioactive components may play a beneficial role in obesity and diabetes. Small, short-term human and animal studies with obese, diabetic and non-diabetic subjects have shown positive effects on weight loss, and reduction in blood lipids, insulin and insulin resistance (Bhathena et al, 2002). In a study by Aoyama et al (2000), rats fed a diet of soy protein had lower plasma glucose levels than those fed the casein diets. It is not clear which component of soy is responsible for these effects. However, it appears that soy and its bioactive components may help to regulate insulin secretion.



References

1. Aoyama T, Fukui K, Takamatsu K, Hashimoto Y, Yamamoto T. Soy protein isolate and its hydrolysate reduce body fat of dietary obese rats and genetically obese mice (yellow KK). Nutrition 2000;16(5):349-54.
2. Arjmandi BH, Alekel L, Hollis BW, et al. Dietary soybean protein prevents bone loss in an ovariectomized rat model of osteoporosis. J Nutr 1996;126:161-67.
3. Bhathena S, Velasquez M. Beneficial role of dietary phytoestrogens in obesity and diabetes. American Journal of Clinical Nutrition 2002; 76(6):1191-1201.
4. Bosello O, Cominacini L, Zocca I, et al. Short-and long-term effect of hypocaloric diets containing proteins of different sources on plasma lipids and apoproteins of obese subjects. Ann Nutr Metab 1988;32:206-14.
5. Calorie Control Council. Calorie Control National Surveys. www.caloriecontrol.org 2002.
6. Hellmich N. Obesity rate could reach nearly 40% in five years. USA Today; February 7, 2003(4A).
7. Hill Jo, Peters JC. Environmental contributions to the obesity epidemic. Science 1998;280:1371-74.
8. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids (Macronutrients), 2002.
9. Jenkins DJA, Wolever TMS, Spiller G, et al. Hypocholesterolemic effect of vegetable protein in a hypocaloric diet. Athersclerosis 1989;78:99-107.
10. Layman D, Boileau R, Erickson D, Painter J, Shiue H, Sather C, Christou D. A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J Nutr 2003;133:411-417.
11. McCarthy MF. Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagons activity. Med Hypotheses 1999;53(6);459-85.
12. McCarthy MF. The origins of western obesity: a role for animal protein? Med Hypotheses 2000;54(3):488-94.
13. Mikkelsen, B, Toubro S, Astrup A. Effect of fat-reduced diets on 24-h energy expenditure: comparisons between animal protein, vegetable protein, and carbohydrate. American Journal of Clinical Nutrition 2000; 72(5):1135-1141.
14. Moeller LE, Peterson CT, Hanson KB, et al. Isoflavone-rich soy favorably affects regional fat and lean tissue in menopausal women. FASEB 2000;348.4 A487.
15. NIH, NHLBI, NAASO. The Practical Guide; Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. October 2000.
16. Young VR. Soy protein in relation to human protein and amino acid nutrition. J Am Diet Assoc. 1991;91(7):828-35.

The Prevalence of Cancer in the United States

Cancer is the second leading cause of death among Americans (1,2). According to the American Cancer Society, one of every four deaths is due to cancer. The national Institute of Health (NIH) estimates that, in 2002, indirect and direct medical costs of cancer will be about $171.6 billion (3). Although cancer death rates in all age groups are declining, it is anticipated that the number of Americans diagnosed with cancer will double each year for the next 50 years (4). The expected growth and aging of the U.S. population are being blamed for the anticipated increase in cancer diagnoses and treatments (4).


Cancer-Causing Agents: Carcinogens
A person's susceptibility to cancer is determined by his/her inherited genetic background. There are a variety of agents that initiate cancerous changes in susceptible individuals. Some of these include chemical and environmental factors such as cigarette smoking and alcohol consumption, and viral and dietary factors. It is estimated that natural food constituents represent the largest cancer-causing agents (35%) next to tar in tobacco smoke (30%). Occupational hazards represent (4%); alcohol (3%) and food additives (1%). Dietary factors such as food preparation (charcoal grilling, smoking and deep-fat frying, etc.), high dietary fat and red meat intake are some of the leading dietary cancer-causing agents.


Causes of Cancer
Most cancers are a feature of aging. Cancer is initiated when the genes, located inside a cell, responsible for controlling normal growth and manipulation (oncogenes), are altered by cancer-causing agents or carcinogens. The change in the cell's oncogenes is now passed on to all offspring cells. This establishes a small group of abnormal cells which divide more rapidly than the normal surrounding cells. These groups of abnormal cells no longer perform the specialized task of the cells of the host tissue, but act as parasites, where they continue to consume nutrients and grow. Abnormal or cancer cells may spread (metastasis) from their original site to another part of the body where a new cluster of cancer cells may continue to grow and spread again. The rate of cancer growth varies according to the tissue origination. Some types of cancers may take years before cell growth is large enough to cause symptoms. Timely, preventative screening and interventions will increase an individual's cure and survival rate.


The Role of Soy in Cancer Prevention
As stated previously, some types of cancer may take years before being diagnosed. Once diagnosed, surgery, radiation, chemotherapy or drugs may offer the most promising therapy. Dietary factors may represent the largest group of carcinogens. This fact implies that diet plays an important role in cancer prevention and development. A variety of natural bioactive food components have shown positive results in both animal and human research. Asians who consume a diet rich in soy products, exhibit relatively low rates of cancer, particularly breast and prostate, compared to Americans. Breast cancer is the most common cancer site among American women and prostate cancer is the leading cancer diagnosed among men in the U.S. (5). Interestingly, Asians who immigrate to the United States and adopt a Western-style diet have shown a higher risk of breast and prostate cancers (6). There are many factors that may contribute to epidemiological differences between Asian and U.S. countries is the higher intake of soy and soy products in the traditional Asian diet. The average daily Asian intake of soy products exceeds 7 times that of a typical American (6). Extensive research has been conducted with soy protein and its various bioactive components. Isoflavones are a sub class of natural plant substances known as phyto "fito" estrogens. The isoflavones in soy protein are genistein, daidzein and a small amount of glycitein. Phytoestrogens may have anticarcinogenic potential (7), however, the protective effect may be dependent on the timing and exposure to soy (7,8). Some studies indicate that the risk of breast cancer is inversely associated with soy intake during adolescence and adult life (7-10). One Asian-American study (Asians who have immigrated and now live in the U.S.) showed a statistically significant reduced risk of breast cancer for those who reported soy intake of at least once per week during adolescence. The lowest risk was for those women who consumed high levels of soy during both adolescence and adult life (9).

There has been growing evidence that soy contains a variety of bioactive components. Some researchers have indicated that certain compounds in soy, such as protease inhibitors, phytic acid, and/or b-sitosterol may have active anticancer properties (11), while most current research indicates that isoflavones provide the protective action against cancer. Genistein, one of the predominant soy isoflavones, has exhibited protective effects in cancer prevention. In animal and in-vitro (cell culture) studies, genistein provides protection from breast and prostate cancer (9, 10, 12, 13). Genistein has shown to help prevent cancer initiation, reduce promotion, and obstruct cancer progression (14, 15, 16).

In summary, epidemiologic, animal and cell culture studies suggest a link between soy consumption and the reduction in cancer risk. There is growing opinion among researchers that soy's anticancer effects may not be solely from one component but rather a synergistic combination of compounds. Human studies are currently underway to determine the role of isolated soy protein and its bioactive components in the prevention and/or treatment of cancer.



References

1. American Cancer Society. Cancer Facts and Figures 2002. Atlanta (GA): American Cancer Society; 2002. Also available from URL: http:/www.cancer.org[accessed 2002, June 17].
2. Centers for Disease Control and Prevention (CDC). The Burden of Chronic Diseases and Their Risk Factors: National and State Perspectives Atlanta (GA): CDC; 2002.
3. National Heart, Lung, and Blood Institute (NHLBI). Fact Book, Fiscal Year 2001. Bethesda (MD): NHLBI; 2001.
4. Edwards BK, Howe HL, Rier LAG, Thun MJ, Rosenberg HM, Yancik R, wingo PA, Jemal A, Feigal EG. Annual report to the nation on the status of cancer, 1973-1999: featuring implications of age and aging on U.S. cancer burden. Cancer 2002; 94: 2766-2792.
5. Department of Health and Human Services. The United States Cancer Statistics 1999 Incidence, 2002. http:/www.cancer.gov.
6. Sarkar FH, Li Y. Mechanics of Cancer. Chemoprevention by soy isoflavone genisten. Cancer Metastasis Rev. 21(3-4): 265-80, 2002.
7. Peter PH, Keinan-Boker L, vander Schouw YT, Grobbee DE. Phytoestrogen and breast cancer risk. Review of the epidemiological evidence. Breast Cancer Res Treat. 77(2): 171-83, 2003.
8. Lamartiniere CA. Timing of exposure and mammary cancer risk. J Mammary Gland Biol Neoplasia. 7(1): 67-76, 2002.
9. Wu AH, Wan P, Hankin J, Tseng CC, Yu MC, Pike MC. Adolescent and adult soy intake and risk of breast cancer in Asian-Americans. Carcinogenesis. 23(9): 1491-6, 2002.
10. Adlercreutz H. Phytoestrogens and breast cancer. J Steroid Biochem Mol Biol. 83(1-5): 113-8, 2002.
11. Adlercreutz H, Mazur W. Phyto-oestrogens and Western diseases. Ann Med. 29:95-120, 1997.
12. Katz AE. Flavonoi and botanical approaches to prostate health. J Altern Complement Med. 8(6):813-21,2002.
13. Gaynor ML. Isoflavones and the prevention and treatment of prostate disease: is there a role? Cleve Clin J Med. 70(3):203-4, 206, 208-9 passim, 2003.
14. Arliss RM, Biermann CA. Do soy isoflavones lower cholesterol, inhibit atherosclerosis, and play a role in cancer prevention? Holost Nurs Pract. 16(5):40-8.
15. Potter S. Soy-new health benefits associated with an ancient food. Nutrition Today. 35(2):53-9, 2000.
16. Li Y, Sarkar FH. Gene expression profiles of genistein-treated PC3 prostate cancer cells. J Nutr. 132(12):3623-31, 2002.

The Role of Antioxidants
Antioxidants are compounds that help protect healthy cells from substances called “reactive oxygen species”, or simply “free radicals”. Free radicals are natural bi-products of such things as breathing, vigorous physical activity, sun exposure, infection, x-rays, cigarette smoke and dietary carcinogens (nitrites, cured meats, charcoal broiled or foods fried at high temperatures). Although they are a necessary part of cell metabolism, they can cause a series of destructive cell and tissue damage if they are not contained. These unstable, short-lived compounds are in search of something that they are lacking; an electron. In fact, free radicals can pull needed electrons from cell membranes or its genetic coding material (DNA). These events may lead to an increased risk for certain diseases or speed the aging process. Antioxidants are notable electron and hydrogen donors. When present, these compounds can donate the required electrons or hydrogen to the electron-seeking free radical, thus neutralizing its damaging affects. Antioxidants aid in retarding the aging process, decrease risk of heart disease and stroke, reduce the risk of cancer, help the body detoxify cancerous food agents, protect the eyes against loss of vision, protect against conditions of the lungs and help protect the body from environmental pollution.


Origins of Antioxidants

Antioxidants Inside the Body
Antioxidants are found both inside the human body and in our diet. Inside the human body is an enzyme-based antioxidant system. Some of the more popular internal antioxidants are superoxide dismutase (SOD), glutathione and lipoic acid. These enzymes are responsible for removing free radicals and boosting the immune system. As we age, production of these antioxidants starts to decline. Therefore, it is important to consume an adequate amount of dietary antioxidants.

Antioxidants in the Diet
Fruits and vegetables are noted for their contribution of nutrients including vitamins, minerals, fiber and antioxidants. Health officials recommend consuming 5-9 servings of fruits and vegetables each day to help prevent a variety of diseases. Phytochemicals are natural chemical substances found in plants. These substances act as a plant’s immune system and give fruits, vegetables, grains and legumes their color, flavor, and protection against disease. A brief summary of plant antioxidants are as follows:

• Isoflavones
  Compounds of soybeans and other legumes called isoflavones exhibit antioxidant qualities. The best known isoflavones are genistein and daidzein and are most abundant is soy products. These plant nutrients help protect the growth and development of cancer, lower cholesterol and show promising results in decreasing osteoporosis, symptoms of menopause, diabetes and kidney disease, and aiding in weight reduction.



• Vitamins
  The most well-known vitamins that act as antioxidants are vitamins C, E, A. Vitamin C is the antioxidant warrior. This water-soluble antioxidant protects other antioxidants in the body, may inhibit the production of cancer-causing agents, and aids in the reduction of heart disease. Vitamin C also helps recharge vitamin E, another powerful antioxidant. Vitamin E is a fat-soluble antioxidant that has shown positive effects in protecting blood vessels from free radical damage. Vitamin A, particularly its precursor’s beta- and alpha-carotene, may help to protect against certain cancers and protect eyes from free radical damage.



• Carotenoids
  Carotenoids (plant-derivatives of vitamin A) are the fat-soluble pigments found in orange, yellow, red and green fruits and vegetables that protect them from constant exposure to the sun’s ultraviolet rays and many other environmental cancer-causing agents. There are over 600 known carotenoids. The most popular carotenoids are lycopene (may decrease risk of cancer), lutein (protects eyes against macular degeneration), alpha- and beta-carotene (protects eyes against cataracts, may protect against heart disease and cancer) and zeaxanthin (protects eyes against macular degeneration).



• Minerals
  The major free-radical mineral scavengers are selenium and zinc. The body does not manufacture minerals; therefore, all minerals must be acquired from dietary sources. Vitamins need the assistance of minerals for absorption and to function in the body. Selenium works together with vitamin E to increase their effectiveness. It may help to boost the immune system and protect against heart disease and cancer. Zinc helps increase the level of infection-fighting cells and may offer protection against loss of vision and prostate cancer.



• Flavanoids
  Flavonoids are another class of phytochemicals. Examples of flavonoids include catechins, reserveratrol, proanthocyanidins and anthocyanidins (OPC’s). These compounds may help protect the body against the build up of fatty deposits on blood vessel walls. They may also help decrease the risk of heart disease and stroke and promote good circulation by strengthening the body’s collagen protein.

Soy and Exercise Performance

Antioxidants and Bi-products of Exercise
Very strenuous exercise is the most stressful condition that the normal circulatory system faces (1). In fact, physical exercise may be associated with a 20-fold increase in blood flow to the muscles and a 10 to 20-fold increase in whole body oxygen uptake (2). This increase in oxygen elevates reactive oxygen species (ROS) or free radicals to a level that overwhelms the internal antioxidant defense system. This condition is referred to as exercise-induced oxidative stress. A growing body of evidence suggests that free radicals play a large role as mediators of skeletal muscle damage and inflammation after strenuous exercise (3). Physical activity provides a variety of health benefits; however, it does create oxidative stress. Oxidative stress contributes to muscle soreness, inflammation and fatigue. Very strenuous exercise may increase the risk of cancer and certain diseases in the case of ultra endurance athletes or those who train hard, but sporadically (3). The magnitude of oxidative muscle tissue damage is determined by the strength of the antioxidant defense system. Physical fitness, performed on a continual basis, has been shown to increase the strength of the internal antioxidant system. However, the “weekend athlete” may not have the augmented antioxidant defense system such as produced through continuous training (3, 4). Despite the augmentation of internal antioxidant defenses, skeletal muscle still appears to be susceptible to oxidative injury. Dietary antioxidants are crucial in that they assistant internal antioxidant enzymes to neutralize or detoxify free radicals produced during exercise and therefore may prevent muscle damage or fatigue.

Soy Protein versus Animal Protein and Exercise Performance
Soy protein contains isoflavones that exhibit antioxidant activity. The two main soy isoflavones are genistein and daidzein. “Soy protein consumption can consistently produce antioxidant effects in humans” according to Robert DiSilvestro, Ph.D., professor of Human Nutrition & Food Management at Ohio State University. Strenuous aerobic exercise produces oxidative stress and increases levels of specific enzymes in the body. These enzymes are markers for muscle damage, soreness and fatigue. Human and animal studies have compared the effects of soy protein verses whey protein on exercise performance and recovery. Results of these studies have indicated that soy protein but not whey protein, consumed after a strenuous bout of exercise restricted an exercise-induced increase in enzymes creatine kinase and myeloperoxidase, indicators of muscle damage and inflammation (3, 6). In fact, “the degree of increase in creatine kinase actually went up after participants consumed whey protein”, says DiSilvestro, Ph.D., professor of Human Nutrition & Food Management at Ohio State University.

Additional Performance Benefits of Soy Protein
Many individuals that engage in rigorous aerobic, endurance sports or strength training consume a diet high in protein content to enhance performance. Historically, concern has been raised regarding high dietary protein intake and kidney function. “Studies in both humans and animals indicate that consuming soy protein versus animal protein promotes a decrease in glomerular filtration rate, reducing the workload of the kidneys”, says Belinda Jenks, Ph.D., Solae® Company’s director, Novel Health Benefits. Soy protein contains a higher level of amino acids arginine, glutamine and the branch chain amino acids than many animal proteins. Branch chain amino acids are an important energy source for muscles during exercise. Arginine is noted as playing a key role in muscle formation, maintenance of a strong immune system, blood vessel health, and reduction in muscle damage. Glutamine is essential in maintenance of cellular hydration and helps decrease lactic acid build-up that occurs during exercise of anaerobic nature such as strength training or high intensity aerobic exercise. Lactic acid is responsible for muscle soreness and fatigue.

Effects of Soy Protein and Elite Athletes
Research studies have evaluated the effects of soy protein, particularly Solae® Company’s SUPRO® brand isolated soy protein, and athletic performance. One particular study was conducted with the Romanian Olympic Rowing Team. The group that was supplemented with an additional 1.5g/kg of body weight with Supro® isolated soy protein displayed enhanced physiological gains and post exercise performance. Results showed that this group, after two months of soy protein consumption, increased lean muscle mass, strength indexes, blood proteins hemoglobin and total calcium, and displayed decreases in muscle damage and fatigue after training sessions, especially when compared to the non-supplemented group (7).


References

1. A Guyton. Human Physiology and Mechanisms of Disease, 5th edition, 1992.
2. Senck. Antioxidants in exercise nutrition. Sports Medicine. 31(13):891-908, 2001.
3. DiSilvestro, R. Supro®Soy protein beverage produces antioxidant effects in athletes and weekend warriors; whey protein did not. Journal of Nutraceuticals, Functional and Medical Foods. Vol. 3, 2000.
4. Clarkson PM. Antioxidants and physical performance. Crit Rev Food Sci Nutr. 35(1-2):131-41, 1995.
5. Dekker JC, van doormen LJ, Kemper HC. The role of antioxidant vitamins and enzymes in the prevention of exercise-induced muscle damage. Sports Medicine. 21(3):213-38, 1996.
6. Nikawa T, Ikemotom, Sakai T, Kano M, Kitano T, Kawahara T, Teshima S, Rokutan K, Kishi K. Effects of a soy protein diet on exercise-induced muscle protein catabolism in rats. Nutrition. 18(6):490-5, 2002.
7. Dragan I, Stroescu V, Stoian I, Georgescu E, Baloescu R. Studies regarding the efficiency of Supro isolated soy protein in Olympic athletes. Rev Roum Physiol. 29(3-4):63-70.

There certainly are! It seems that in the past decade there has been much discussion surrounding potential health benefits relating to women’s health issues. However, more men may start to consider adding soy to their diet as they become aware of its potentially healthy benefits. The Food and Drug Administration (FDA) has approved a soy health claim. This claim states that consuming 25 grams of soy protein each day in combination with a diet low in saturated fat and cholesterol may help decrease the risk for heart disease. Soy assists in this process by naturally helping the body lower its bad cholesterol (LDL) and triglycerides, maintaining or increasing good cholesterol (HDL). Recently, soy protein has shown promising results in the prevention of prostate cancer in men. In fact, the American Cancer Society has included consumption of soy foods as one of their seven steps to reducing risk of prostate cancer. Special compounds called isoflavones in soy may be responsible for the decrease of cancer risk in men. Soy protein may also protect men from bone loss. It has been found that around the age of 65, men start losing bone as severely as women following menopause. According to a recent study at Oklahoma State University, soy protein, not milk protein, improved bone formation and reduced bone loss in men. More research needs to be conducted regarding how soy affects prostate cancer and bone health in men, however, the initial studies look promising. Incorporating soy foods into your diet is easier than you think. Visit the “25 Grams of Soy a Day the Veggie Patch Way” section on the Veggie Patch website for meal planning ideas and eat for the “health of it”!