Eat Your Fruits and Vegetables Part 5

Fruits, Vegetables, and Gastrointestinal Health

One of the wonderful components of fruits and vegetables is their indigestible fiber. As fiber passes through the digestive system, it sops up water like a sponge and expands. This can calm the irritable bowel and, by triggering regular bowel movements, can relieve or prevent constipation.

The bulking and softening action of insoluble fiber also decrease pressure inside the intestinal tract and so may help prevent diverticulosis (the development of tiny, easily irritated pouches inside the colon) and diverticulitis (the often painful inflammation of these pouches).

Source: HARVARD SCHOOL OF PUBLIC HEALTH
©2005 President and Fellows of Harvard College.

Eat Your Fruits and Vegetables Part 4

Fruits, Vegetables, and Cancer

Numerous early studies revealed what appeared to be a strong link between eating fruits and vegetables and protection against cancer. But because many of these were case control studies, it is possible that the results may have been skewed by problems inherent in these types of studies, such as recall bias and selection bias. Data from cohort studies that follow large groups of initially healthy individuals for years have not consistently shown that a diet rich in fruits and vegetables prevents cancer in general.

Data from the Nurses' Health Study and Health Professionals Follow-up Study support this finding. Over a 14-year period, men and women with the highest intake of fruits and vegetables (8+ servings a day) were just as likely to have developed cancer as those who ate the fewest daily servings (under 1.5).

A more likely possibility is that fruits and vegetables may protect against certain cancers. The International Agency for Research on Cancer, which is part of the World Health Organization, recently completed a monumental review of the best research on fruits, vegetables, and cancer.

Here's what this 387-page tome concludes about studies in humans: "There is limited evidence for a cancer-preventive effect of consumption of fruit and of vegetables for cancers of the mouth and pharynx, esophagus, stomach, colon-rectum, larynx, lung, ovary (vegetables only), bladder (fruit only), and kidney. There is inadequate evidence for a cancer-preventive effect of consumption of fruit and of vegetables for all other sites." However, considering all evidence from human epidemiological, animal, and other types of studies, it appears that eating more fruit "probably lowers the risk of cancers of the esophagus, stomach and lung" and "possibly reduces the risk of cancers of the mouth, pharynx, colon-rectum, larynx, kidney, and urinary bladder." Eating more vegetables "probably lowers the risk of cancers of the esophagus and colon-rectum" and "possibly reduces the risk of cancers of the mouth, pharynx, stomach, larynx, lung, ovary and kidney."

Keep in mind that this is for total fruit and total vegetable consumption and that, as pointed out by the International Agency for Research on Cancer, specific fruits and vegetables may protect against specific types of cancer. For example, a line of research stemming from a finding from the Health Professionals Follow-up Study suggest that tomatoes may help protect men against prostate cancer, especially aggressive forms of it. One of the pigments that give tomatoes their red hue - lycopene - could be involved in this protective effect. Although several studies other than the Health Professionals' study have also demonstrated a link between tomatoes or lycopene and prostate cancer, others have not or have found only a weak connection.

Taken as a whole, however, these studies suggest that increased consumption of tomato-based products (especially cooked tomato products) and other lycopene-containing foods may reduce the occurrence or progression of prostate cancer. But more research is needed before we know the exact relationship between fruits and vegetables, carotenoids, and prostate cancer

Source: HARVARD SCHOOL OF PUBLIC HEALTH
©2005 President and Fellows of Harvard College.

Eat Your Fruits and Vegetables Part 3

Fruits and Vegetables, Blood Pressure, and Cholesterol

High blood pressure is a primary risk factor for heart disease and stroke. As such, it's a condition that is very important to control. Diet can be a very effective tool for lowering blood pressure.

One of the most convincing associations between diet and blood pressure was found in the Dietary Approaches to Stop Hypertension (DASH) study. This trial examined the effect on blood pressure of a diet that was rich in fruits, vegetables, and low-fat dairy products and that restricted the amount of saturated and total fat. The researchers found that people with high blood pressure who followed this diet reduced their systolic blood pressure (the upper number of a blood pressure reading) by about 11 mm Hg and their diastolic blood pressure (the lower number) by almost 6 mm Hg - as much as medications can achieve.

Eating more fruits and vegetables can also help lower cholesterol. In the National Heart, Lung, and Blood Institute's Family Heart Study, the 4466 subjects consumed on average a shade over 3 servings of fruits and vegetables a day. Men and women with the highest daily consumption (more than 4 servings a day) had significantly lower levels of LDL (bad) cholesterol than those with lower consumption.

How fruits and vegetables lower cholesterol is still something of a mystery. It is possible that eating more fruits and vegetables means eating less meat and dairy products, and thus less cholesterol-boosting saturated fat. Soluble fiber in fruits and vegetables may also block the absorption of cholesterol from food.

Source: HARVARD SCHOOL OF PUBLIC HEALTH
©2005 President and Fellows of Harvard College.