Scientific Update

Copper and Vegetarians

Copper, an essential mineral for humans, is found in many vegetarian foods like whole grains, cocoa, nuts, and seeds, as well in non-vegetarian foods like organ meats and seafood. Researchers at the USDA set out to answer whether or not copper absorption would also be lower on a vegetarian diet.

They had 18 young women eat a lacto-ovo vegetarian diet for eight weeks and a non-vegetarian diet for eight weeks. The women’s copper absorption and the levels of copper in their blood were measured while they were on each diet. The women did absorb somewhat less copper from the vegetarian diet (about one-third of copper was absorbed compared to 42% on the non-vegetarian diet). However, because the vegetarian diet was considerably higher in copper than the non-vegetarian diet, the total amount of copper absorbed was higher on the vegetarian diet. Blood levels of copper were not affected by either diet. We don’t have to eat meat or seafood to get enough copper; foods like whole grains, legumes, nuts, and seeds can be used to meet the copper requirement.

Dairy Products and Calcium Seem to Increase Risk of Prostate Cancer

Prostate cancer is the most common cancer in men in the United States and is the third most common cause of death from cancer in men. Vegetarian and Japanese men have the lowest rates of prostate cancer. Diets high in meat and fat and lower in tomato products, selenium, and vitamin E have all been linked to a higher risk of developing prostate cancer. A recent study examined the association between dairy products and risk of prostate cancer. More than 20,000 male physicians were studied for 11 years. About 1,000 of them developed prostate cancer during the study period. Men who used the most dairy products (more than 2.5 servings per day) and whose intakes of calcium were highest had about a 30% greater risk of developing prostate cancer than did those men with the lowest intakes of dairy products (one-half serving or less daily) and calcium. Generous amounts of dietary or supplemental calcium could lead to reduced production of the active form of vitamin D (the form activated by the body, as opposed to the inactive form in cow’s milk, sunlight, and dietary supplements). The activated form of vitamin D is believed to protect against prostate cancer; if its production were reduced, risk of prostate cancer could increase. Vegetarian men may be at lower risk for prostate cancer already because their diets do not contain meat and may be lower in fat. There may be some added benefit to a diet that contains little or no dairy products.

Caffeine and Bone Loss

There have been many studies of caffeine and bone health, some showing that caffeine increases the risk of hip fracture and some showing that it has no effect. Many factors affect bone health, so these conflicting findings are not surprising. It is known that caffeine does increase the amount of calcium lost in urine. It also appears that high caffeine intakes are mainly a problem for women with low calcium intakes. A new study of women aged 65 to 77 years suggests that it is only caffeine intakes of more than 300 milligrams per day that are problematic. This amount of caffeine would be found in 16 ounces of brewed coffee, 32 ounces of brewed tea, or 72 ounces of most caffeinated soft drinks. Some women are more likely to be affected by caffeine than others due to genetic factors; however, it seems prudent to recommend that all older women have adequate dietary calcium, and limit caffeine intake to no more than 300 milligrams per day.

Animal-Based Nutrients Associated with Greater Risk of Some Types of Cancer

A recent study examined dietary factors that could increase risk of developing cancer of the esophagus or stomach. Dietary factors may be important because both the esophagus and the stomach are exposed to the food we eat. Nearly 500 people with cancer of the esophagus, 600 people with stomach cancer, and almost 700 healthy people were studied. Each person was questioned about his or her eating habits three to five years earlier (before those with cancer had cancer). The groups were then compared. Those with cancer of the esophagus or stomach had higher intakes of cholesterol, animal protein, and vitamin B12, suggesting that their diets were higher in animal products. Those without cancer had higher intakes of fiber, beta-carotene, and folate, suggesting that their diets were higher in plant-based foods. These results are especially pertinent for people with gastroesophageal reflux disease (also called reflux esophagitis), who are more likely to develop cancer of the esophagus. The results of this study suggest that diets rich in fruits, vegetables, and fiber, and low in animal protein and fat, could be especially useful for those with gastroesophageal reflux disease to reduce their risk of developing cancer of the esophagus.

Should Women with Breast Cancer Use Soy Products?

Substances found in soy products called isoflavones can act like estrogen, a hormone that may play a role in breast cancer. Concerns have been raised over the use of soy by women with breast cancer. A recent review article looks at whether or not women with breast cancer should use soy products. The reviewers conclude, “The data are not impressive that the adult consumption of soy affects the risk of developing breast cancer or that soy consumption affects the survival of breast cancer patients.” They go on to say that if women with breast cancer enjoy soy products, they should continue to use moderate amounts.

Food for Thought

Nutrition plays a role in how well our brains work. As we age, it is not uncommon to experience a decrease in memory. Can diet influence this loss? Apparently so. Canadian researchers studied 22 healthy elderly men and women. The subjects received either a drink containing pure protein, pure fat, or pure carbohydrate, or a drink with no protein, fat, or carbohydrate (and thus, no calories). They were tested 15 minutes and 60 minutes after drinking the beverages. Compared with the drink without protein, fat, or carbohydrate, the other drinks tended to improve performance on tests of memory. Apparently food, whether high in protein, fat, or carbohydrate, improves memory. These results may be important for older people who do not eat well. Perhaps in someone with mild memory impairment, adequate food intake can help to slow memory loss. It’s something to think about.

Beans Protect Against Heart Disease

Vegetarians tend to have lower rates of heart disease than do non-vegetarians. Many factors have been hypothesized to lead to this reduced risk. A recent study suggests that vegetarians’ use of beans may be one factor leading to their lower risk of heart disease. This study followed more than 9,600 men and women over approximately a 19-year period to determine what dietary factors increased their risk of developing heart disease. Eating beans four or more times a week reduced the risk of developing heart disease by 22%, as compared with eating beans fewer than once a week. Bean burrito, anyone?