Soyfoods Strengthen Diet

Eating soyfoods may be one easy way to help build strong bones and to lower risk of osteoporosis. Osteoporosis is most often seen in older people since bones become thinner, weaker and brittle with aging. The United States has one of the world's highest rates of osteoporosis. Between 15 and 20 million Americans suffer from this disease. Women are more likely than men to have poor bone health. One out of every five American women over the age of 65 has fractured one or more bones.

The good news is that diet and lifestyle changes can greatly reduce the risk of osteoporosis. As many as 50 different factors affect bone health. For example, exercise is very important for developing strong bones and for keeping bones from getting thin. Physical activity can slow the loss of bone matter that occurs with aging. In fact, exercise not only slows bone loss in the elderly, it actually leads to an increase in bone density. A healthy diet is also important for strong bones. Some dietary factors, like caffine, sodium and protein, may speed bone loss. Nutrients, like calcium and vitamin D, help promote bone health. Adding soybeans and soyfoods to the diet may also help reduce risk of osteoporosis. Soyfoods may work in three ways to protect the health of bones:

• Many soyfoods are rich in calcium.
• Soy protein helps conserve calcium in the body.
• Compounds in soybeans may protect the strength of bones.

Soyfoods Provide Calcium

The best protection against osteoporosis in later life is having strong, dense bones early in life. Adequate calcium intake is crucial for this.

Although most people think of milk first as a source of calcium, many foods are rich in this nutrient. Legumes, such as soybeans, are naturally good sources of calcium. One cup of cooked soybeans contains about 12 percent of the adult calcium recommended daily allowance. Some brands of tofu are especially rich in calcium because they are made with a calcium salt. The calcium in soyfoods is very well absorbed by the body.

Calcium in Soyfoods

Soyfood Calcium in mg Soybeans 80 (mature, 1/2 cup) Soybeans 130 (green, 1/2 cup) Tempeh 77 (1/2 cup) Tofu 130* (1/2 cup) Textured soy protein 85 (1/2 cup prepared) Soy milk 80 (1 cup) Soy milk 250-300 *Depending on how it is processed, 1/2 cup tofu can provide between 80 and 435 mg calcium. The recommended daily allowance for calcium for adults is 800 milligrams.

Soy Protein Helps Conserve Calcium

The bones are very dynamic as they constantly break down and rebuild. Some calcium is lost from the body every day and a new supply of calcium must come from the diet. As important as adequate calcium intake is, it is equally, or perhaps more, important to reduce the amount of calcium being lost from the body. A high intake of dietary protein can increase the loss of calcium and this may raise risk of osteoporosis. But all protein isn't equal in this regard. Studies show that soy protein does not have the same calcium-wasting effect. When people eat soyfoods in place of animal proteins, they excrete far less calcium in their urine.

Compounds in Soybeans Protect Bone Health

Soybeans are a unique source of a group of compounds called isoflavones. Soybeans are the only food that contain these compounds in significant amounts. One type of isoflavone called daidzein is very similar to a drug widely used in Asia and Europe to treat osteoporosis. This drug prevents bone from breaking down. When the drug is metabolized in the body, it produces daidzein - the same compound found in soybeans. This suggests that eating soyfoods - natural sources of daidzein - could help reduce the risk of osteoporosis. But another isoflavone in soyfoods, genistein, may help. In one recent animal study, genstein was shown to inhibit breakdown of bone.

A Bone-Healthy Lifestyle

Many factors affect bone health. A lifestyle that promotes healthy bones includes the following:

• Exercise. Weight bearing exercise, such as walking and running, is one of the most important factors affecting bone health.
• Adequate intake of calcium. Choose calcium-rich foods often. They include dark green leafy vegetables, broccoli, Chinese cabbage, many legumes (especially black beans, chickpeas and baked beans), almonds, figs, fortified orange juice, dairy products and soyfoods such as tofu made with calcium salts, fortified soy milk, tempeh, textured vegetable protein and cooked soybeans.
• Moderate protein intake. Avoid excessive animal protein by eating more grains, beans, fruits and vegetables and by limiting meat and other animal foods.
• Limited sodium intake. Most sodium comes from processed foods.
• Add soyfoods to diet. Because many soyfoods provide calcium, are rich in the type of protein that does not induce calcium loss and are a source of isoflavones, they provide a unique way to improve bone health.

This information was prepared by Mark Messina, PhD, and Virginia Messina, MPH, RD, authors of The Simple Soybean and Your Health.