Want more iVillage? Sign up for our
Newsletters
Soy Protein for Sports & Fitness
Soy
Why Do Athletes Use It?*
Some athletes say that soy protein provides a source of low-fat, cholesterol-free protein.
What Do the Advocates Say?*
Protein is necessary for rebuilding tissue, which is especially important for bodybuilders. All types of protein provide the body with amino acids.
From an athletic point of view, soy is just another type of protein. Choosing soy protein over other types of protein adds variety to the protein choices available. However, because soy lowers cholesterol, it is an excellent choice for those also trying to lower their cholesterol levels.
Soy is a common ingredient in many meal replacements that are designed to provide a large amount of nutrients in a minimal amount of calories.
*Athletes and fitness advocates may claim benefits for this supplement based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles.
Also indexed as:
- fitness,
- physical fitness,
- soy protein
About this treatment
Soy
How Much Is Usually Taken by Athletes?
Adding protein to carbohydrate intake immediately after exercise may be helpful for improving recovery of glycogen (carbohydrate) stores after exercise, according to some, though not all, controlled studies. Preliminary studies have suggested that protein supplements may have biological effects that could improve muscle growth resulting from strength training, especially if liquid supplements (typically containing at least 10 grams of protein in addition to varying amounts of carbohydrate) are taken immediately after exercise. However, controlled studies have found no advantage of protein supplementation (up to about 100 grams per day or about 14 grams immediately following exercise) for improving strength or body composition as long as the diet already supplies typical amounts of protein and calories. In one preliminary study, elderly men participating in a 12-week strength training program took a liquid supplement containing 10 grams of protein (part of which was soy protein), 7 grams of carbohydrate and 3 grams of fat either immediately following exercise or two hours later. Men taking the supplement immediately following exercise experienced significantly greater gains in muscle growth and lean body mass than those supplementing two hours later, but strength gains were no different between the two groups. A controlled study of female gymnasts found that adding 0.45 grams of soy protein to a diet that was adequate in protein during an 8-week training program did not improve lean body mass compared to a placebo. No research has compared different sources of protein to see whether one source, such as soy protein, has a better or more consistent effect on exercise recovery or the results of strength training.
Side Effects
Soy products and cooked soybeans are safe at a wide range of intakes. However, a small percentage of people have allergies to soybeans and thus should avoid soy products.
Soy isoflavones have been reported to reduce thyroid function in some people. A preliminary trial of soy supplementation among healthy Japanese, found that 30 grams (about one ounce) per day of soybeans for three months, led to a slight reduction in the hormone that stimulates the thyroid gland. Some participants complained of malaise, constipation, sleepiness, and even goiter. These symptoms resolved within a month of discontinuing soy supplements. However, a variety of soy products have been shown to either cause an increase in thyroid function or produce no change in thyroid function. The clinical importance of interactions between soy and thyroid function remains unclear. However, in infants with congenital hypothyroidism, soy formula must not be added, nor removed from the diet, without consultation with a physician, because ingestion of soy may interfere with the absorption of thyroid medication.
Most research, including animal studies, report anticancer effects of soy extracts, though occasional animal studies have reported cancer-enhancing effects. The findings of several recent studies suggest that consuming soy might, under some circumstances, increase the risk of breast cancer. When ovaries have been removed from animals—a situation related to the condition of women who have had a total hysterectomy—dietary genistein has been reported to increase the proliferation of breast cancer cells. When pregnant rats were given genistein injections, their female offspring were reported to be at greater risk of breast cancer. Although premenopausal women have shown decreases in estrogen levels in response to soy, pro-estrogenic effects have also been reported. When pre-menopausal women were given soy isoflavones, an increase in breast secretions resulted—an effect thought to elevate the risk of breast cancer. In yet another trial, healthy breast cells from women previously given soy supplements containing isoflavones showed an increase in proliferation rates—an effect that might also increase the risk of breast cancer.
Of 154 healthy postmenopausal women who received 150 mg of soy isoflavones per day for five years, 3.9% developed an abnormal proliferation of the tissue that lines the uterus (endometrial hyperplasia). In contrast, none of 144 women who received a placebo developed uterine hyperplasia. Although no case of uterine cancer was diagnosed during the study, endometrial hyperplasia is a potential forerunner of uterine cancer. The amount of isoflavones used in this study is two to three times as much as that used in many other studies. Nevertheless, the possibility exists that long-term use of isoflavones could cause uterine hyperplasia, and women taking isoflavones should be monitored appropriately by their doctor.
Some postmenopausal women taking the soy isoflavone genistein have experienced gastrointestinal side effects (abdominal pain, epigastric pain, dyspepsia, vomiting, or constipation).
Interactions with Supplements, Foods, & Other Compounds
Soy contains a compound called phytic acid, which can interfere with mineral absorption.
Interactions with Medicines
Certain medicines interact with this supplement.
 | Some medicines may increase the need for this supplement. |
|---|---|
 | Some medicines interact with this supplement, so they should not be taken together. |
 | Some interactions between this supplement and certain medicines require more explanation. Click the link to see details. |
Note: The following list only includes the generic or class name of a medicine. To find a specific brand name, use the Medicines Index.
| Dessicated Thyroid |
|---|---|
| Levothyroxine |
| Liothyronine |
| Liotrix |
| Ipratropium Bromide |
| Theophylline |
| Warfarin |
Last Review: 05-11-2011
Copyright © 2011 Aisle7. All rights reserved. www.Aisle7.net
Learn more about Aisle7, the company.
The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2011.
© 1995-2011 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.
Welcome to Care Circle, an exclusive tool to help you take care of yourself and your loved ones. Here's how it works:
- Create profiles for yourself and your loved ones.
- Select the topics and conditions that interest each of you.
- Get customized news updates, original content, tools, and expert advice for each Care Circle member delivered directly to your personalized homepage.
The information you input is strictly private; you choose who has access to your Care Circle.
How do I add myself or someone else to my care circle?
Click on "Add someone." Fill out the short profile. Choose an avatar. Select the topics and conditions that interest this person from the pulldown menu. You can select as many as you want, but you must choose at least one. Click on "Add Someone" again. You should start getting updates immediately.
How do I save content to my Care Circle?
Click on "Manage My Care Circle." Select the tab of the person for whom you're saving content. Put your cursor over the piece of content that you want to save; a disk icon will appear in the righthand corner. Click on the disk and the piece of content will be moved to a save folder.
How do I add additional topics and conditions for someone in my Care Circle?
Click on "Manage My Care Circle." Select the tab for the person whose preferences you'd like to update. Under "Add More to Follow," select additional topics and conditions.
How do I delete topics and conditions for someone in my Care Circle?
Click on "Manage My Care Circle." Select the tab for the person whose preferences you'd like to update. Under "Follows," scroll over the topic or condition you want to delete. An "X" should appear on the righthand side. Click on the "X" and the topic or condition will be deleted from the list.
To manage your Care Circle, Please
Sign In.
