Trying to keep your blood pressure in check?
Eating soy-based foods, such as tofu, soybeans, soy milk and soybean chips, may help, according to a recent study from Columbia University's College of Physicians and Surgeons. The isoflavones that are found in large quantities in most soy products (and in smaller quantities in a few other foods, such as split peas, peanuts and kidney beans) help relax the blood vessels.
But loading up on soy isn't without its own risks-soy is estrogenic, meaning it mimics the effect of the hormone estrogen in the body. And the concern is that consuming it in excess might raise the risk for estrogen-sensitive diseases such as certain types of breast cancer and prostate cancer.
So exactly how little soy can you consume and still get help with your blood pressure?
You don't have to eat much
We spoke with Safiya Richardson, MD, the lead researcher and a resident at North Shore LIJ Health System in Manhasset, New York. She and her colleagues compared a teeny-tiny intake of isoflavones (less than 0.33 milligrams per day or about one-fifth of a tablespoon of soy milk) to relatively larger intakes of isoflavones.
The results? The more isoflavones that people ate, the lower their systolic blood pressure was.
Those who ate the most (2.5 mg or more per day) had, on average, 5.5 points lower systolic pressure, compared with those who ate the least (less than 0.33 mg per day). Even those who ate between 0.33 mg and 2.5 mg per day had blood pressure that was, on average, 2 to 3.5 points lower, compared with those who ate the least.
So this study suggests that if you're trying to keep your blood pressure under control but you're concerned about eating large amounts of soy to get large amounts of isoflavones, even eating as little as just 0.33 mg of isoflavones per day may help (but, of course, this study showed only an association-not cause and effect).
Easy to sneak in
Lots of different foods made from soy contain isoflavones (although soybean oil and soy sauce do not-the isoflavones get processed out). If you want to consume more isoflavones, keep reading for a list of isoflavone packed soy foods.
What about overdoing it? "Soy has estrogenic properties, but I don't know of any studies that have proven that eating soy has harmful effects," said Dr. Richardson. She doesn't see a reason to hold back, but the issue is controversial. Some doctors advise certain people to either limit soy intake or avoid soy altogether-these people include those who have been diagnosed with (or are at high risk for) hormone-sensitive conditions, such as breast, ovarian, prostate or uterine cancer or endometriosis... women who are on hormone therapy... pregnant women... and people with thyroid or kidney problems. If you fall into one of those categories...if eating soy causes any side effects (such as stomach problems or migraines)...or if you're simply worried about consuming too much, consult your doctor before changing your diet.
If you take blood pressure medication and you add some soy to your diet, you might be able to reduce your need for the medication, said Dr. Richardson, so ask your doctor. As for isoflavone supplements, hold off. Dr. Richardson doesn't know what their effect on blood pressure would be.
One challenge to eating more foods that contain isoflavones is that isoflavone content is not listed on packaging, but here are some estimates from the USDA of the isoflavone content in particular soy products. As you'll see, eating just one serving of each of the following foods each day will provide your body with plenty of isoflavones-so if you are concerned about overdoing it on soy and are focused on eating the minimum amount of isoflavones (just 0.33 mg per day), you need to eat only a tiny fraction of a portion of any of the following foods...
• 100 grams (3.5 ounces) of soy flour, defatted = 151 mg isoflavone
• 3.5 ounces (about~ cup) of soybeans= 49 mg (raw), 18 mg (boiled)
• 3.5 ounces (about seven pieces) of fried tofu = 35 mg isoflavones
• One 8-ounce glass of soy milk = 25 mg isoflavones
• one 1.3-ounce bag of soybean chips= 20 mg isoflavones
It's also possible to consume extremely tiny amounts of isoflavones from nonsoy foods, such as split peas, peanuts and kidney beans. But to consume at least 0.33 mg or more isoflavones per day, stick with soy foods.