Soy, what's new?
by Vicki Koenig, MS, RD, CDN

In case you haven't noticed, soy is popping up everywhere! Today, in addition to the traditional items like tofu, soy milk, soy cheese, soy nuts, soy yogurt and soy burgers, you'll also find new items like soy energy bars, pasta, powder for smoothies, dips and soups, pizza, crackers, chips, hot dogs, tempeh, miso, tamari soy sauce, edamame (whole soybeans), etc.. These varied sources of soy make it easier than ever to add a healthy ingredient to your diet.

Here's the latest rundown of all
the potential benefits of soy:

Reduced Risk of Heart Disease. There is significant research to substantiate the fairly well known effects of soy
on blood lipids like cholesterol, triglycerides and LDL-cholesterol (the bad cholesterol). The FDA now allows food companies to make the following claim:

Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day reduce the risk of heart disease.

The amount of soy protein provided in one serving of the packaged food must accompany the claim. This claim is based on an analysis of 38 soy protein studies published in 1995 in the New England Journal of Medicine. In individuals with cholesterol over 220 mg/dl, cholesterol, triglycerides and LDL-cholesterol were reduced significantly with an intake of 25 grams of soy protein. Higher amounts of soy protein may lower blood lipids that aren't considered high or lower blood lipids even more significantly. Additionally, the isoflavones, the phytonutrient or plant nutrient in soy may also reduce oxidation of LDL-cholesterol while increasing the flexibility of the arteries. The oxidation of LDL cholesterol is recognized as the initiation of plaque formation and atherosclerosis. These are other indicators of the positive heart effects suggested by the soy research.

Reduced Symptoms of Menopause. New studies have begun to demonstrate the positive effect of eating soy on the reduction of hot flashes and night sweats associated with menopause. To see if this could work for you, simply try adding 2 to 3 servings of soy foods per day for three to four weeks. If it is effective in reducing your symptoms, integrate soy foods into your regular diet.

Bone Health and Prevention of Osteoporosis. Several studies have suggested the positive effect of soy isoflavones on bone mineral density. Additionally, soy protein causes the body to excrete less calcium in the urine than animal protein. Soy also contains calcium that has a similar absorption to dairy calcium. These are all good things as far as bones are concerned. More long-term studies are necessary to define soy's effects on bone health, however. A new study funded by the USDA, named OPUS (Osteoporosis Prevention Using Soy), will determine the benefits, safety and correct dosages of soy isoflavone supplements. The project will enroll 400 postmenopausal women at three sites across the country and follow them for two years. This study will also be able to follow up on potential benefits of soy on menopausal symptoms.

Reduced Risk of Certain Types of Cancer.

Prostate: Current research studies of soy continue to suggest that soy reduces the risk of prostate cancer. Several studies have advised that soy isoflavones may be useful in stabilizing prostate cancer where the PSA levels are increasing. Increasing PSA levels indicates an active cancer or one that is out of control. When fed soy isoflavones, PSA levels stabilized or decreased. Other recent research indicates that as little as 1 to 2 servings of soy protein per day may be effective in reducing prostate cancer.

Breast Cancer: While concerns have been raised about soy actually stimulating estrogen-dependent breast cancer, more recent and long-term studies seem to alleviate this fear. One year-long study found that isoflavone supplements, (76 mg/day) had no effect on breast tissue density in premenopausal women. Another yearlong study with menopausal women supplemented with 40 mg/day isoflavone supplements found no increase in breast density. In fact there was a significant decrease in density in women aged 56-65. Breast density is an excellent marker of breast cancer risk. Agents known to increase breast density and cancer risk are HRTs. An agent known to decrease density and cancer risk is the drug tamoxifen. Additionally, there are two recent rat studies that show a greater reduction in breast tumors when tamoxifen was given with soy than when taken separately. The correlation to humans is not known. While all of these studies suggest a benefit of eating soy, women at risk for breast cancer, those receiving treatment for breast cancer and breast cancer survivors should consult their doctor for individualized recommendations until the data is even more definitive.

Improved Kidney Function: Soy foods seem to help in the prevention of kidney disease largely because they replace animal proteins, which can stress the kidneys. As many as 1/3 of all diabetics develop kidney disease. Two recent studies suggest that regular consumption of soy may lower incidence of diabetic kidney disease and may delay the onset of end stage renal disease, (requiring dialysis).

Excellent Source of Protein. Trying to increase protein to help with weight loss? Soy is an excellent example of a good quality lean protein to include. Not only does it have the beneficial satiating effect of protein, but it also could be said to have "more bang for the buck." Soy provides protein with all of its other benefits like lowering cholesterol and building bone, contrary to animal protein.

How much Soy Do You Need? Some of the research information looks at levels of isoflavones and some give recommendations for grams of protein. Dr. Mark Messina, a leading expert on soy devotes his time primarily to studying the health effects of soyfoods and soybean constituents, especially the isoflavones (phytoestrogens) found in soy. Based on what Asians have been eating for thousands of years, clinical and epidemiological findings, safety data, and practical considerations, he recommends 15 grams of protein and 50 mg of isoflavones per day. This amount of soy protein and isoflavones is found in approximately two servings of soyfoods. An example of a serving of soy is 1-cup soymilk, 1/2-cup soy yogurt (cultured soy) or 1/2-cup tofu. Including 3 to 4 servings of soy in a varied and diverse diet can provide even more significant effects.

At this point in what we know about soy, I still recommend eating soy versus taking an isoflavone supplement. It should be stressed that more is not always better. Isoflavones are pharmacologically active compounds. It's best to leave the research to the researchers who are conducting the studies unless recommended by a health professional. It also seems that the effects of soy on health conditions are a combination of the soy protein and the isoflavones together.

Soy, what's new? It's an ever-evolving relationship with a food that's highly adaptable in many forms. You can bet that more will be written on it in this column as we identify the benefits and have more specific recommendations for exact amounts to eat.

Reference:

Soy and Heart Health
http://www.soyfoods.com/Anderson.html Soy and Heart health. A discussion of Dr. Anderson's research on the lipid-lowering effect of soy.

http://www.webdietitian.com/document/CVTopic/topic/pencvsoyprotein Lipid-lowering effects of soy are discussed in detail. This article includes a table with soy protein and isoflavone content of common soy foods.

Breast Cancer and Women's health
http://www.cancerrd.com/FAQs.htm#Brea This is a website written by a Registered Dietitian who is a Breast Cancer survivor. It is well researched and very personal.

General Discussions of the Benefits of Soy on Health
http://www.talksoy.com/SoyConnection/default.htm This is an excellent resource for well-written discussions on soy-related topics. It is a very credible newsletter edited by Mark Messina, PhD. Through this link you may read specific newsletters on:

• Soy Connection Volume 10, Number 1:
  Special Report on Highlights of Symposium on Role of Soy
  in Preventing and Treating Chronic Disease
  
• Soy Connection Volume 9, Number 2:
  Soy and Thyroid Function, Research Updates on Bone Health, Hot Flashes and Breast Cancer
• Soy Connection Volume 9, Number 1:
  New Evidence on the Relationship of Soy and Human Health, Research Awards Program, New Soyfoods
  
• Soy Connection Volume 8, Number 3:
  Soy Safety Issues: Breast Cancer & Cognitive Function

Soy and Osteoporosis
http://www.fcs.uga.edu/fdn/research/lewis/opus2.html This describes the suggested relationship of soy on bone health and the upcoming research study.

http://www.bcm.tmc.edu/cnrc/consumer/nyc/vol3_02/soy.htm Soy benefits bone health.