Aug 2, 2017
Magic Beans
Susan Kundrat

According to the United Soybean Board, soybeans are now the country’s second largest crop in cash sales and the number-one value crop export. Due to its nutritional value and an expanding vegetarian market, the variety of soy foods available to consumers has skyrocketed in recent years. And with more and more athletes looking to maximize their nutritional intake, many are wondering how to make soybeans a positive addition to their diets.

Like most legumes, including dried peas and beans, soybeans are inexpensive and an excellent source of key nutrients. Soybeans, however, provide even more health benefits than other legumes thanks to some additional components in soy. Here’s a quick breakdown of what’s found in the soybean:

Protein: Soybeans are made up of 35 to 38 percent protein. That is higher than most other legumes, which generally contain 20 to 30 percent protein. Even more important is that the protein in soy is ranked as a high-biological value protein, receiving a rating of one (the best possible) from the FDA. That means it contains the protein equivalent of meat and milk. Soy is considered a “complete protein” because all the amino acids needed to form proteins are found in soybeans.

Fat: Soybeans are approximately 40 percent fat, significantly higher than other legumes. However, most of the fat in soybeans is polyunsaturated and monounsaturated fat. It’s a good source of linoleneic acid, an omega-3 fatty acid, which may help decrease inflammation.

Fiber: Soybeans are an excellent source of dietary fiber. Just one cup of green soybeans contains over 10 grams of fiber, which can equal one-third of a day’s goal. Soy foods that utilize the whole bean (such as tempeh, textured soy protein, and soy flour) are also high in fiber. About 30 percent of the fiber in soybeans is soluble fiber, which helps regulate blood sugars and manage lipids.

Calcium: Soybeans provide a good supply of calcium, containing 175 mg of calcium per cup of cooked soybeans. In addition, many soy foods are fortified with additional calcium.

Iron and zinc: Soybeans are a good source of iron and zinc, which are key nutrients for athletes. However, due to the fiber and phytates found in soybeans, these minerals are not well-absorbed.

Isoflavones: Soybeans are rich in isoflavones, plant-derived compounds with estrogenic and antioxidant properties.

One of the neat things about soy is that it can help athletes at both ends of the diet spectrum–those who consume little fat but need more protein, and those who get plenty of protein but from fatty products. Even those with a balanced diet can use soy to help improve the timing of their protein intake.

Athletes need 1.4 to 1.7 grams of protein per kilogram of body weight, or 0.6 to 0.8 grams of protein per pound of body weight. That means:

• For a 150-pound athlete (eating 100 grams of protein), soy would make up 15 to 20 percent of total protein intake for the day.

• For a 200-pound athlete (eating 140 grams of protein), soy would supply 11 to 14 percent of total protein.

• For a 250-pound athlete (eating 175 grams of protein), soy would comprise eight to 11 percent of total protein.

For athletes who are not getting enough protein, adding soy products to the diet can be a big boost. Vegetarian athletes often fit this description. Even vegetarian athletes who incorporate milk products and eggs in their diet may be low in overall protein. Adding soy-based foods can be an easy way to add the extra 15 to 20 grams of protein needed to reach recommended levels. I encourage my athletes to eat soybeans, soy nuts, soymilk, tofu, tempeh, and other natural sources of soy as first options for the greatest overall health benefit.

For athletes who are consuming sources of protein with high fat contents, such as fatty meats or high-fat dairy products, I recommend they switch to soy products. Similarly, I suggest soy products to athletes trying to lose bodyfat. Soy foods like soybeans, soy nuts, and tempeh (which contain both protein and fiber) are good options as they keep athletes satisfied longer and aid in keeping calories low, while supplying needed protein for maintaining muscle mass.

For athletes who have had stress fractures or are at risk for bone problems down the road based on genetics, adding soy may be critical since some studies show soy to have a bone-strengthening effect. Many soy foods (such as soymilk and soy yogurt) are also fortified with calcium and Vitamin D, providing an extra boost. As an added benefit, the calcium in soymilk is easily absorbed.

Another issue to consider is when the athlete eats protein. There’s no question that many athletes skip breakfast, grab a small lunch, and eat huge dinners after workouts. So developing a simple strategy for helping athletes balance out their protein intake is key. This is where soy can help. For example, a fruit smoothie made with soy or a bagel with soy butter can serve as breakfast, lunch, or a snack.

Post-workout protein is also important. The latest recommendations call for recovery fuel with one gram of carbohydrate per kilogram of body weight plus 15 to 20 grams of protein within 30 minutes of a hard workout. Athletes can experiment with both soy and whey protein in recovery shakes and recovery drinks, although I suggest they try whey first since some studies find it to be superior. In addition, they should be looking to get their soy in more natural sources.

If I had to sum up a simple recommendation to athletes on this topic it would be this: Be aware of your protein intake and consider using soy as a source. In reality, the most important message for most athletes is that they need to get enough (but not too much) quality protein in their diet while avoiding excess fat. If soy can help them in this goal, great!

Susan Kundrat, MS, RD, CSSD, LDN, is a Clinical Associate Professor of Kinesiology and the Nutritional Sciences Program Director at the University of Wisconsin-Milwaukee.

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