The Health Benefits of Soy

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1997 Oldways Preservation & Exchange Trust

Grilled Chicken & Kiwi Salad
Caribbean Kiwi Salsa

Mention the word “soy” to Earl Mindell, a passionate advocate of soy foods and their benefits, and you’ll get an earful.

Mindell, a.k.a. “Dr. Soy” and author of Earl Mindell’s Soy Miracle (Simon & Schuster, 1995), has studied soy foods and their health-giving properties for more than thirty years. He laments that most Americans, in his view, eat poorly and are ignorant of soy foods’ potential value. Research indicates that soy foods may provide relief from many illnesses–from heart disease to osteoporosis.

“Wake up, America!” says Mindell, a registered pharmacologist with a doctorate in nutrition from Pacific Western University and author of twenty-eight books. “We have all these health problems, and much of these could be prevented by changing things in our diets.”

Why soy?

According to the Indiana Soybean Board, publisher of the U.S Soyfoods Directory, soybeans cannot be considered “a miracle food.” However, soy-rich foods may reduce the risk of certain diseases, and extensive research is under way to document the real effects of soy on health.

In recent years, scientists have isolated phytochemicals, or compounds found in plants, that may protect against disease. In Soy Miracle, Mindell reviews research that suggests that some of soy’s phytochemicals can lower cholesterol levels. Others, specifically antioxidants, can protect cells from unstable oxygen molecules that may damage normal cells. Some soy compounds may also deactivate cancer-causing substances and boost the immune system.

Mindell started visiting Japan more than twenty-five years ago because he was interested in the long life span of the Japanese people. “It was pretty obvious back then–they eat fish, rice, and soy,” he says. In his book, he says that the Japanese diet also tends to be lower in fat and higher in fiber than typical Western diets, but that many researchers believe that soy consumption is a primary factor in Japanese health and longevity.

Soy and estrogen

Soybeans, Mindell writes, also contain isoflavones, a form of plant estrogen found in soy and other legumes. Isoflavones are 500 to 1,000 times weaker than human estrogen, yet some research demonstrates they have beneficial effects on bone density and cholesterol metabolism. A trail of evidence also links these chemicals with a reduction of hot flashes experienced by meno­pausal women.

Isoflavones, particularly one unique to soy called genistein, may also help beat breast and prostate cancer; they appear to play a part in the low breast cancer rates among women in Southeast Asia, where soy protein is eaten regularly. A typical Asian consumes the equivalent of 30 mg to 50 mg of isoflavones; some Asians consume as much as 100 mg daily, according to Prevention magazine (August 1996). A typical American consumes ten to sixteen times less.

In 1996, a University of Illinois study suggested that isoflavones could be a substitute for hormone-replacement therapy (HRT). For the study, sixty-six women ate soy protein for six months as part of a low-fat, low-cholesterol diet. Researchers incorporated 40 g a day of isolated soy protein into the women’s baked goods and drinks–a diet that increased the women’s bone-mineral density, according to the researchers. Although the study was relatively short term, it suggests that some postmenopausal women could use soy products instead of HRT and that women at risk for breast cancer may tolerate soy protein better than other estrogens. John Erdman, Ph.D., director of the University of Illinois Division of Nutritional Sciences who was involved in the research, stresses that a much longer study–“a multi-site, two-year study”–is needed to reach definitive conclusions. As of the early part of this year, however, further study has yet to be financed and could cost millions of dollars, Erdman says.

Giving soy a try

Mindell recommends that individuals include 4 ounces to 6 ounces of soy in their daily diet. The typical Japanese person eats about 50 g to 80 g (2 ounces to 3 ounces) of soy daily. In contrast, the average American unknowingly eats only about 5 g of soy food daily, usually in the form of oil hidden in foods such as baked goods or salad dressings, he says. Although soy oil and soy sauce may be healthy choices for other reasons, they don’t contain significant amounts of isoflavones.

The U.S. Soyfoods Directory states that eating 25 g to 50 g of soy protein a day may be enough to lower cholesterol. Additionally, a recent study found that 40 g of soy protein a day increases bone density in the lumbar spine region of postmenopausal women, although more research is needed to substantiate this.

But how does one begin?

“To start eating soy foods, go into a Japanese restaurant–one that serves sushi–and get an order of soybeans,” Mindell says. “Soybeans and fish make a nice meal; your appetite will be satiated.”

Or fix the beans at home. “Take a pot, put water in it, boil the water, put beans in the water. It’s that easy,” Mindell says. “If you can boil water, you can make boiled soybeans.” Or for a snack, try roasted soybeans instead of eating peanuts. Another option is to replace cow’s milk with soy milk, he says. Make a blender drink of soy powder and soy milk, which comes in different flavors. With this drink, “you can get your 4 to 6 ounces a day easily,” Mindell says.

And then there’s tofu, which means “top bean” in ­Chinese. “You can stir-fry it, you can add anything to it,” he says. It takes on the flavor of other foods. In Chinese restaurants, it’s often listed as bean curd on the menus. Mindell is also a fan of tempeh, a traditional Indonesian food that is a kind of tender soybean cake. His favorite recipe is a sweet-and-sour tempeh, which comes in burger form.

All of these products are available at health-food stores or at larger grocery stores. Hundreds of recipes are available on the World Wide Web or in dozens of books. Mindell’s book alone includes seventy recipes. Mindell says it’s easy to incorporate soy foods into a daily diet. However, he adds, soy is only one food that should be included in a varied and well-balanced diet. “Let’s take care of ourselves as well as we take care of our dogs and cats and automobiles,” Mindell says. “We’re not eating food that is good for us.”

You can order a free copy of the 1998 U.S. Soyfoods Directory by calling (800) TALKSOY (825-5769).

Kiwi: a nutrition ­superstar

Kiwi may look plain on the outside, but this brown, fuzzy, egg-shaped fruit has a sweet, green pulp that tastes like a combination of melon and citrus. And, according to a recent study, it’s the most nutrient-dense of all the major fruits, offering a wide range of vitamins and minerals.

Nutrient density is a measurement used by dietitians and nutritionists to calculate a food’s nutritional value. Two “nutrient density” indexes were determined in the study: the daily value per 100 g and the calories per nutrient. Researchers measured various fruits’ ability to provide the suggested amounts of nine nutrients considered essential by the U.S. Food and Drug Administration (FDA).

The nutrient density study–conducted by Paul Lachance, director of the Nutraceuticals Institute at Rutgers University and published in the October 1997 American College of Nutrition Journal–ranks more than twenty-five fruits. Kiwi was found to be the most nutrient dense, followed by papaya, mango, and oranges. The findings also show that:

• Kiwi is an excellent source of dietary fiber, has twice as much vitamin E as an avocado, contains nearly twice as much vitamin C as an orange, and has as much potassium as a banana, but fewer calories. It has no cholesterol and is low in sodium.

• Kiwi is a formidable source of antioxidants, too. “Considering the high level of vitamin C, the presence of vitamin E, and some carotenoids, this makes kiwi higher than other fruits in antioxidant delivery,” Lachance says.

• Kiwi also offers a significant amount of folic acid, copper, and manganese–all of which are limited in American diets. Folic acid is critical for preventing birth defects and the formation of homocysteine, a risk factor for coronary heart disease; manganese and copper are important in thwarting osteoporosis, he says.

The study shows that kiwi has the highest concentration of magnesium, important for good cardiovascular health. Kiwi also has an unusually good complement of amino acids, the building blocks of protein. The average daily serving recommended for fruit by the U.S. Department of Agriculture is 140 g, Lachance says. “That would require two kiwis,” he says. “And that does not include the skin. Few people eat the skin, even though it provides fiber.” Lachance said there are no reported side effects from adding kiwi to one’s diet. However, he says, like many foods, kiwis may cause allergic reactions in a few people

Kiwi’s blood pressure benefits

By U.S. Food and Drug Administration standards, kiwi is a good source of potassium. According to the ­California Kiwi Commission, an average serving ­contains more than 10 percent of the recommended ­dietary intake. It has as much potassium as a banana but has fewer calories–61 per 100 grams compared with 92 calories per 100 grams for a banana. Potassium is important in the upkeep of muscles and the nervous system and for maintaining a healthy heart.

In a recent study, Frank Sacks, professor of nutrition at the Harvard School of Public Health, found that potassium lowers high blood pressure, a risk factor for strokes and heart attacks. The results of his findings were reported in 1998 in Hypertension: Journal of the American Heart Association.

For the study, Sacks divided 300 female nurses–with an average age of thirty-nine, an average weight of 140 pounds, and an average blood pressure of 116/73–into five groups. Each group received ­either potassium, magnesium, or calcium; a combination of the three; or a placebo. Researchers took blood pressure readings over a twenty-four hour period, with results indicating that blood pressure went down significantly with potassium, but not with magnesium or calcium.

Sacks recommends that people eat more potassium-rich fruits such as bananas, oranges, and green leafy vegetables to help prevent high blood pressure. Kiwis fit in here, too. He recommends potassium supplements only for hypertensives who do not like to eat fruits and vegetables. But first, he advises, they should check with their physicians.

Kiwi in the kitchen: fast and easy recipes

When choosing kiwi from the market, buy firm, unblemished fruit. The size of the fruit does not affect the taste. Press the outside of the fruit with your thumb. If it gives to slight pressure, it’s ripe; if you apply pressure and the fruit doesn’t give at all, it’s not ready to eat. Kiwi will keep for several days at room temperature and up to four weeks in your refrigerator. If your kiwi is a bit firm, put it in a vented plastic bag with an apple or a banana, and leave it out on the counter for a day or two. Try these recipes using kiwi: Grilled Chicken & Kiwi Salad and Caribbean Kiwi Salsa.

Experts question ­vitamin C study

Some researchers are criticizing a widely publicized study released in April that links vitamin C and DNA damage. Many people take vitamin C for its antioxidant benefits, which studies have shown may help ward off the common cold and fight cancer, heart disease, and cataracts. The April study, conducted by two chemical pathologists from the University of Leicester, appeared in the British journal Nature. Their results suggest that 500 mg of supplemental vitamin C acts as both an antioxidant and a pro-oxidant, meaning that it actually encourages cell damage.

The researchers gave thirty healthy men and women 500 mg of a placebo daily for six weeks, then a 500-mg vitamin C supplement every day for six weeks. Then they measured the oxidation of two DNA bases in lymphocytes and found that one base showed reduced oxidation and the other showed increased oxidation, which could in­dicate genetic damage, according to the authors. Many experts say, however, that the design of the study makes the ­results questionable. Mark Levine, M.D., disagrees with the findings. Based on his calculations, “vitamin C in the lymphocytes could not have been responsible for the damage reported,” he says.

Levine, chief of the molecular and clinical nutrition section and senior staff physician at the National Institutes of Health, has researched vitamin C for more than fifteen years. “In my opinion the science was not done properly,” he says. “It was a measurement error.” The method of DNA isolation also may have skewed the results, says Bruce Ames, a professor of biochemistry and molecular biology at the University of California at Berkeley.

A healthy body uses vitamin C to absorb iron and to block cellular and molecular damage from free radicals. The U.S. Recommended Daily Allowance is 60 mg, but many health-care practitioners recommend more, especially for smokers and pregnant women.
–Sarah Kelch

New guidelines for vegetarians

“Eat your vegetables! Or no dessert!”

Many Americans grew up hearing this admonition. But instead of rebelling, many people are turning to vegetarian diets–especially because research shows that these diets may be linked to lower rates of heart disease, some cancers, obesity, osteoporosis, and certain degenerative diseases found in the United States. Unlike meat-eaters, American vegetarians have had to do some guesswork to create a balanced diet because the U.S. Food Guide Pyramid combines animal and plant foods in a single group. Now there’s an alternative: the Vegetarian Diet Pyramid.

Researchers from Cornell and Harvard universities joined forces to assist a nonprofit food-issues foundation called Oldways Preservation & Exchange Trust in creating the pyramid. It features a wide base of foods that should be eaten at every meal; the middle band suggests food to be eaten daily, and at the top of the pyramid are foods that may be omitted, eaten occasionally, or eaten in moderate amounts. Exercise and drinking lots of water are also emphasized, and a moderate intake of wine, beer, and other alcohol is deemed optional, according to a press release, because of the heart-health benefits of alcohol for people who are not at risk of alcohol-related diseases or side effects.

“I don’t believe that there are any other diets that can supply the correct proportional amounts of various nutrients as well as the vegetarian diet,” says T. Colin Campbell, Ph.D., a nutritional biochemistry professor at Cornell who helped develop the pyramid.

Campbell, co-chairman of the World Cancer Research Fund and project director of the China-Oxford-Cornell Diet and Health Project, says he believes that the evidence “indicates quite persuasively that a vegetarian diet–minus dairy and eggs–is superior to the typical Western diet.” “However,” he said, “we don’t know who it best suits; thus, the more important question is whether a vegetarian diet hurts anyone. The answer is no, in my view.” Campbell says the Vegetarian Diet Pyramid is good for all, regardless of age. “From my perspective, I am confident that there are going to be continuing ­questions about the advisability of using dairy and eggs,” he says.

A Cornell press release notes that the pyramid is subject to revision as ­nutrition research continues.

Fatty acids build bone, study says

The benefits of omega-3 fats have been widely touted: Research shows that eating more omega-3 fatty acids may decrease coronary heart disease risk and the chances of getting some types of cancers. Now, Purdue University research suggests that these fatty acids also may help bones grow. The research by Purdue food science professor Bruce Watkins shows that bones of animals fed increased amounts of omega-3 fats demonstrated improved formation rates and were stronger when compared with bones of animals that were not given the extra omega-3s. Although studies in humans have not been done yet, Watkins says the work is encouraging.

“Our research in animals and cell cultures would strongly suggest that these fatty acids benefit bone and cartilage,” he says. “This is good news, but it is also consistent with the other health/nutrition rationale for consuming more omega-3 fatty acids.” Watkins says he is conducting more animal studies to determine which omega-3 fatty acids are the most effective for bone formation.

Omega-3 fatty acids can be found in flaxseed, soybean and canola oils, nuts, green vegetables, and fish such as salmon, sardines, and shellfish

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