Scientific Update

Fruits and Vegetables — How Are We Doing?

Adults in the United States have been encouraged to "Strive for 5," meaning "eat at least 5 servings of fruits and vegetables daily." A recent report suggests that we have taken the letter of this message to heart. A large study found that men and women eat an average of 3.6 servings of vegetables and 1.6 servings of fruits daily for a total of 5.2 servings of fruits and vegetables. Sounds good, right? It does until you look at the numbers more closely. The most commonly consumed fruits and vegetables are iceberg lettuce, tomatoes, French fried potatoes, bananas, and orange juice — not a wide variety supplying diverse nutrients. Where are the broccoli and other dark green and cruciferous vegetables like kale, collards, and Brussels sprouts? Where are the carrots, sweet potatoes, and other good sources of carotenoids? Where are citrus fruits? These foods have been linked to reduced cancer risk. French fries and iceberg lettuce have not. "Strive for 5" may not be enough. Broccoli or carrots, anyone?

Why Do Some People Dislike Vegetables?

Not everyone likes the taste of vegetables. There may be a reason for this. Plants contain compounds that give them a bitter flavor, possibly to provide a defense against predators by making the plant taste bad. Many of the substances that make plants taste bitter are substances that appear to be health-promoting phytochemicals like isoflavones. However, the food industry has, in some cases, selectively bred plant foods to reduce these substances so that the food will taste better, possibly reducing the levels of health-promoting phytochemicals. Plant varieties that have been bred to be less bitter tend to be more susceptible to being attacked by insects and other pests, thus requiring greater pesticide use. Perhaps a little bitterness is not such a bad thing.

Hallelujah Diet Associated with Poor Vitamin B12 Status

The Hallelujah Diet is a type of vegan diet that is based on raw vegetables, fruit, nuts, seeds, carrot juice, and a limited amount of cooked whole-grain products. The diet does not contain vitamin B12. After being on this diet for 1-2 years, the majority of people studied had low blood levels of vitamin B12 or other signs of poor vitamin B12 status. Vitamin B12 supplements and vitamin B12-fortified nutritional yeast were both effective in improving vitamin B12 status. These results strongly support the need for regular use of a reliable source of vitamin B12 for those following the Hallelujah Diet, other raw-food diets, and other diets that do not contain animal products.

Pregnant Vegetarians Have Favorable Folate Status

Women need to have adequate amounts of folate, a vitamin found in green leafy vegetables, enriched cereals and grain products, dried beans, and orange juice, before becoming pregnant, in order to reduce risk of having a child with spina bifida or other problems with the nervous system. It is also important to have enough folate during pregnancy. A recent study examined the folate status of pregnant women, 27 of whom followed a lacto-ovo vegetarian diet. They were compared to 43 women who were described as low meat eaters and 39 women who ate a standard Western diet. The vegetarians and low meat eaters ate more than 3 ounces of raw vegetables per day. Folate intake was highest in the vegetarians, intermediate in the low meat eaters, and lowest in those eating the Western diet. Similarly, blood levels of folate were highest in the vegetarians. The authors conclude that long-term high vegetable intake reduces the risk of developing a folate deficiency during pregnancy.

Diet and Bladder Cancer

Bladder cancer is the sixth most common cancer in the United States (other than skin cancer). While cigarette smoking appears to be an important risk factor for this disease, diet also appears to be important. Researchers from the University of California combined results of 38 studies on the relation between diet and bladder cancer. They found that diets that are high in fruits and vegetables and low in fat reduce risk of developing bladder cancer.

New Resource on Alternative and Complementary Medicine on the Internet

Are you interested in alternatives and complements to conventional medicine like herbs, homeopathy, and traditional oriental medicine? If so, you might check out the National Institute of Health’s database of citations of articles from medical and scientific journals related to complementary and alternative medicine. Currently, there are over 220,000 citations in the database dating from 1966 to the present. The number of citations is expected to increase, as this is a fast-growing area of research. Consumers, health care providers, students, researchers, and practitioners of complementary and alternative medicine can use the database. There is no charge for using this service. It can be accessed at <www.nlm.nih.gov/nccam/camonpubmed.html>. A search for "vegetarian" turned up more than 400 citations while "vegan" had close to 90 citations.

New Recommendations for Iron and Zinc

The Institute of Medicine recently released new recommendations (Recommended Dietary Allowances or RDAs) for a number of vitamins and minerals, including iron and zinc. These minerals are especially noteworthy because special mention was made of vegetarian needs for these nutrients. These recommendations take the place of the RDAs for these nutrients that were last updated in 1989.

While vegetarians often have iron intakes that are similar to non-vegetarians, less of the iron is absorbed from a vegetarian diet. This is because iron from plant foods is all in the form of non-heme iron that is not as well absorbed as heme iron, found in meat and fish. The amount of non-heme iron that is absorbed is increased by vitamin C and decreased by phytates (found in dried beans, rice, and grains), calcium, tea, and coffee. This lower absorption of iron from a vegetarian diet can lead to lower levels of ferritin in the blood. Blood ferritin is an indicator of iron stores, so low ferritin levels show that little iron is stored for use when need is greater or intake is less.

Based on the lower absorption of iron from a plant-based diet, the Institute of Medicine recommends that vegetarians (except those age birth to 1 year) get 1.8 times more iron than non-vegetarians, as indicated below:

Recommended Dietary Allowance for Iron for Vegetarians

Age	Iron (mg)
1-3 years	12.6
4-8 years	18
9-13 years	14.4
Boys, 14-18 years	19.8
Girls, 14 - 18 years	27*
Men, 19 - 30 years	19.8
Women, 19-50 years	32.4**
Women, 51 years and older	19.8
Pregnant Women	48.6
Breastfeeding Women	16.2 (18 mg if age 14-18 years)

While it is possible for many vegetarians to get this much iron from their diets, some vegetarians, namely, young children, teenage girls, women, and especially pregnant women, may need iron supplements. Good sources of iron for vegetarians include dried beans, soy products, vegetables like kale and turnip greens, and whole and enriched grains.

Zinc is also less well absorbed from plant-based diets, especially those based on whole grains and dried beans. Because of this, zinc requirements may be as much as 50 percent higher for some vegetarians, according to the Institute of Medicine. However, the committee that creates the RDAs did not feel there was enough evidence to make a separate RDA for vegetarians. Vegetarians should be aware of good sources of zinc like legumes, wheat germ, fortified cereals, nuts, and tofu.