Soy May Not Lower Blood Pressure

A new study suggests that soy supplementation may not reduce blood pressure in menopausal women.

Soy contains protein, isoflavones and fiber, all thought to provide health benefits. Soy is an excellent source of dietary protein, including all essential amino acids. Soy is also a source of lecithin or phospholipid. Soy isoflavones and lecithin have been studied scientifically for numerous health conditions. Isoflavones such as genistein are believed to have estrogen-like effects in the body, and as a result are sometimes called "phytoestrogens."

There is limited human research on the effects of dietary soy on blood pressure. Some research suggests that substituting soy nuts for non-soy protein may help improve blood pressure. Further research is needed before a firm conclusion can be made.

In a new study, researchers randomly assigned 24 menopausal women with high normal blood pressure to receive 80 milligrams of soy isoflavones or placebo daily for six weeks. Changes in blood pressure and nitric oxide metabolism were evaluated as the main outcome measures through several methods, including forearm blood flow and 24-hour blood pressure monitoring.

After the six weeks of treatment, the researchers found that soy supplementation had no significant effects on blood pressure or nitric oxide metabolism when compared to the control group.

Larger-scale, well-designed clinical trials are needed to further evaluate these findings.

In addition to soy, many other integrative therapies have been studied for their effects on blood pressure. Numerous human studies report that garlic may lower blood pressure. Multiple human trials have also reported small reductions in blood pressure with intake of omega-3 fatty acids. Additionally, preliminary research suggests that CoQ10 causes small decreases in blood pressure (systolic and possibly diastolic). Low blood levels of CoQ10 have been found in people with hypertension, although it is not clear if CoQ10 "deficiency" is a cause of high blood pressure. Well-designed long-term research is needed.

For more information about integrative therapies for high blood pressure, please visit Natural Standard's Comparative Effectiveness Database.

For more information about soy, please visit Natural Standard's Foods, Herbs & Supplements Database.

 

Comments

[nb]

In terms of maintaining a healthful diet, moderation is key. I think that it would be good to incorporate soy into one's diet as it is a phytonutrient and has health benefits, but it may not agree with someone who decides to incorporate a lot of soy products into one's diet all of the sudden. Overall, maintaing a diet low in sodium and high in fruits and vegetables will be important, perhaps more so than antihypertensive medications.

[Charles]

While soy may not help lower blood pressure, there is strong evidence that both garlic and omega-3 can aid in treating high blood pressure. These two supplements are really easy to incorporate into one's diet, so keeping high blood pressure at bay might not be as hard a task as one might imagine. As always, it is best to consult a physician or pharmacist before trying any supplements.

[CHD]

According the Natural Standard Comparative Effectiveness database, there are other good alternative choices for controlling high blood pressure. Garlic and yoga both have a grade A rating, meaning that there is strong scientific evidence to recommend use. There are also other options which good evidence (grade B) and are tasty like green coffee, extracts of hibiscus, and stevia. It's great that there are so many options.

[CC]

In response to the above post by KO, I am able to answer one of your questions. Is there a reason why studies involving soy tend to include more women? Soy can have “estrogen like effects” in the body. Menopause is a result of a decrease in estrogen, which explains why soy can help with some of the symptoms traditionally associated with menopause. Therefore, I assume it’s studied in women because it has the opportunity to provide a benefit to all women as they age. In terms of use in women of all ages, I believe it is a little controversial. The reason for the controversy probably has to do its role in breast cancer. Patients have to be careful with soy consumption if they have an estrogen hormone driven breast cancer, it could make the breast cancer worse.

[EM]

Another potential option for patients with high blood pressure is yoga. Yoga is given a grade A evidence distinction for use in this disease state, along with the garlic and fish oil mentioned in the post. Could be a good recommendation for patients!

[Tim Cober]

According to the Natural Standard monograph on soy, soy is also evidence grade A in moderately decreasing blood levels of total cholesterol and low-density lipoproteins (bad cholesterol). It also mentions that small decreases in triglyceride levels can occur as well.

[UP]

I’ve heard about soy being used for menopausal symptoms such as hot flashes; however, I didn’t know that it was used as an antihypertensive. While this study shows that it may not to be useful for blood pressure, more long-term studies using soy as an antihypertensive needs to be conducted.

[GDC]

I do know the possible decrease in blood pressure for humans consuming large quantities of soy compared to the consumption of cow milk. This is base on small clinical trials published in some nutrition journals. What I cannot understand is how the results differ in menopausal women as far as lowering blood pressure. Could soy isoflavone supplementation causing the stimulation of nitric oxide production be less significant in menopausal women?

[SM]

Although based on this study soy may not be effective in lowering blood pressure, its important to keep in mind that it may have other benefits. For example, looking through the Natural Standard database, soy has indications as a source of protein as well as for lipid lowering therapy, both rated as evidence grade A.

[KO]

Since soy has long been used for menopausal symptoms such as hot flashes, it is interesting that this study looked at the effects of soy on blood pressure in menopausal women. Has research been done to test the effects of soy on premenopausal women? Also, I wonder how the effects of soy differ for men vs. women. Is there a reason why studies involving soy tend to include more women?

[MN]

To add to the previous comment, soy also may be beneficial in cholesterol reduction. Along with high cholesterol, high blood pressure contributes to a risk of developing metabolic syndrome, which is becoming highly prevalent in the United States. Those with metabolic syndrome have an increased risk for developing heart disease and type 2 diabetes. So even if there isn't an indication for soy with hypertension, it still might be an option for those with other metabolic syndrome risk factors.

[MW]

It is great that we continue to learn more and more information on CAM therapy. For many years the medical community did limited research on CAM therapy, choosing instead to focus on prescription drugs. But patients have been taking CAM therapies for years, it's nice to see research finally being done in these areas. While Soy may not help with blood pressure at least medical professionals can now make this recommendation. The Natural Standard regular shows updates of new studies it is good to check out the website once in a while to keep up to date.

[Charles]

Soy might not lower blood pressure, but this little bean may still be helpful. According to Natural Standard's monograph, soy has lipid lowering effects, notably on cholesterol and triglycerides. Natural Standard has some good recipes involving soy so one may be able to get a tasty meal and health benefits all in one sitting.

[WL]

It is too bad that there is so much conflicting information in the news about what is healthy and what isn’t. With all of these different results the public can get very confused and frustrated that the medical community can’t “make up its mind”. While we understand that interpreting results from clinical trials and determining how a therapy works is not that easy, most people must be overwhelmed with all of the conflicting news articles.

[TC]

I wasn't aware of the possible blood pressure lowering effect soy may (or may not) have, although I have heard of women using it mainly for menopausal symptoms.

[EM]

I'm so glad CAM therapies are getting this research attention. Soy has been linked to so many varied conditions like diabetes, Crohn's disease, and, of course, hypertension. I was just reading a different article this morning, actually, that was giving light to the controvery regarding soy and breast cancer. I look forward to reading future research about this therapy.

[Emily]

Although lower blood pressure did not result in the treatment group, the Natural Standard monograph on soy indicates that it is a great source of protein as a substitute for other protein sources, like meat. Although this is not a scientific correlation, the opportunity cost of consuming soy is consuming another form of protein that may be more linked with increasing blood pressure, such as red meat and unhealthily processed lean meat.