October 2001

Soy Foods: Should You Eat Them?
Lynda Zimmerman, zimmermanl@missouri.edu

Soy appears to be the current food in vogue.  Granted, the legume has a lot to boast about: it’s an excellent source of dietary fiber and high quality protein, low in saturated fat, and cholesterol-free.  Not to mention it provides many key nutrients such as iron, folic acid and vitamin B6. 

But these aren’t the only reasons we’re hearing to eat soy foods.  It seems every day there is another news story about its health benefits.  But is it the “miracle” food some make it out to be?  Here is a brief summary of the research regarding a few of these health claims.    

Soy and Heart Disease
Soy's cholesterol-lowering qualities are well documented.  Studies have consistently shown that people with elevated cholesterol levels who incorporated soy protein in their meals reduced their total cholesterol, thereby decreasing their risk for heart disease.  Most importantly, it's the LDL (“bad”) cholesterol that declined.  Soy also has been shown to raise HDL (“good”) cholesterol and decrease blood tryglicerides.  About 25 grams of soy protein a day is needed for these benefits.

Eating soy, however, cannot make up for poor food choices.  Soy protein should replace animal protein that is eaten and be combined with fruits, vegetables, and other high-fiber, low-fat, low-cholesterol foods.  In other words, drinking soy milk with a hamburger and fries is not what health experts have in mind when they advise you to eat more soy.  

Soy and Cancer
Studies indicate that people who eat at least two servings of soy products per day -- for example, a 3-ounce portion of tofu and 8 ounces of soy milk -- have less risk for cancers of the breast, colon, and prostate.

How do soy foods help fight cancer?  Studies suggest that it can be attributed to soy’s isoflavones, compounds which are similar in structure to the hormone estrogen which is naturally made in the body.

Some researchers caution that because isoflavones are similar to estrogen, soy foods may actually promote breast cancer in some women.  For this reason, women who have had breast cancer or a family history of breast cancer are often advised to check with their physician before eating soy (particularly if they are not accustomed to eating these foods).  Other researchers argue that the opposite is true: because soy's phytoestrogens bind to the same receptor site, they block estrogen from attaching to those cells, thus decreasing their potential to turn cancerous.

Mark Messina, a nationally known expert in soy, offers this advice: If a woman who has had breast cancer likes soy foods, he sees no convincing evidence that using them in reasonable amounts would cause problems.  Messina believes that moderate consumption of soy -- for example, 25 grams soy protein per day -- is safe for everyone, although he cautions against eating exceptionally large amounts of soy foods or taking soy supplements because we simply don’t have enough research to know what the health effects might be.  Of course it is always wise to discuss any concerns you may have with your physician. 

Soy and Menopause
Soy’s estrogen-like isoflavones also have been touted for treatment of menopause symptoms such as hot flashes, night sweats, and dryness.  But so far the research is contradictory.  In some studies, women experienced no change in symptoms with high intakes of soy; in others, women had modest relief.

Introduce Soy Foods Gradually
If you’re not currently eating soy foods, it may be a challenge to eat 25 grams of soy protein each day.  The best approach is to start slowly and gradually add more soy foods until you reach the goal.  Check the “Nutrition Facts” label on foods to find the grams of soy protein contained per serving. 

For more information and recipes using soyfoods, visit these websites:

• Soyfoods Association of North America - http://www.soyfoods.org/

• United Soybean Board and Soy Protein Partners - http://www.soybean.org/