Diet and disease

Definition
This article provides descriptions of nutritional and dietary elements that have proven relationships to certain diseases or conditions. For additional information on FDA-approved health claims, refer to nutrition labeling.

Information

This article addresses the following:

  1. Calcium and osteoporosis.
  2. Fiber and cancer.
  3. Fruits, vegetables, and cancer.
  4. Fiber and coronary heart disease.
  5. Fat and cancer.
  6. Saturated fat, cholesterol, and coronary heart disease.
  7. Sodium and hypertension.
  8. Alcohol.
  9. Nitrates and cancer.

1. CALCIUM AND OSTEOPOROSIS:
Calcium is one of the most important minerals for human life. It is essential for the formation and maintenance of healthy bones and teeth. Calcium also plays a vital role in nerve conduction, muscle contraction, and blood coagulation.

Osteoporosis is a disease in which the calcium content of bones has been depleted. In this disease, calcium and phosphorus, which are normally present in the bones, become reabsorbed back into the body. This process results in brittle, fragile bones that are easily fractured.

Adequate calcium intake throughout childhood and puberty is one key to preventing osteoporosis. Lack of a calcium-rich diet during these years keeps individuals from reaching their peak bone mass. A low-calcium diet later in life also increases the risk of osteoporosis.

The recommended dietary allowances (RDA) for calcium reflect the varying needs of individuals based on age, gender, and hormonal factors. Many foods, such as some vegetables, contain calcium, but milk and dairy products are some of the most readily accessible sources. Calcium can also be obtained by taking supplements.

2. FIBER AND CANCER:
Dietary fiber is found in plant foods, where it occurs in two forms: soluble and insoluble. Soluble fiber attracts water and turns to gel during digestion. This process slows digestion and the rate of nutrient absorption from the stomach and intestine. Soluble fiber is found in oat bran, barley, nuts, seeds, dried beans and legumes, lentils, peas, and some fruits and vegetables. Insoluble fiber also adds bulk to the stool. It is found in wheat bran, vegetables, and whole grains.

A diet high in fiber has been thought to reduce the risk of cancers of the rectum and colon.

3. FRUITS, VEGETABLES, AND CANCER:
Eating more fruits and vegetables helps provide a good supply of fiber, Vitamin A, Vitamin C, beta carotene, other carotenoids and vitamins, and other valuable substances called phytochemicals. Studies have indicated that a diet high in these nutrients and fiber can reduce the risk of developing several kinds of cancer, including stomach, colorectal, esophagus, larynx, and lung cancer.

Vitamin C and beta carotene, which forms Vitamin A, are antioxidants. As such, they protect body cells from oxidation, a process that can lead to cell damage and may play a role in cancer. In addition to nutrients that are needed for normal metabolism, plant foods also contain phytochemicals, plant chemicals that may affect human health. There are hundreds of phytochemicals, and their exact role in promoting health is still uncertain. However, a growing body of evidence indicates that phytochemicals may help protect against cancer.

To reap these benefits, eat more fruits and vegetables that contain Vitamins A and C and beta carotene, including dark-green leafy vegetables, such as spinach, kale, collards, and turnip greens; citrus fruits, such as oranges, grapefruit, and tangerines; other red, yellow, and orange fruits and vegetables; and juices made from any of these. Note: Juicing removes the fiber.

4. FIBER AND CORONARY HEART DISEASE:
Some fiber, especially soluble fiber, binds to lipids such as cholesterol. The fiber then carries the lipids out of the body through the stool. This lowers the concentration of lipids in the blood and may reduce the risk of coronary heart disease.

5. FAT AND CANCER:
A diet high in fat has been shown to increase the risk of cancers of the breast, colon, and prostate. A high-fat diet does not necessarily cause cancer. Rather, it may promote the development of cancer in people who are exposed to cancer-causing agents. A diet that is high in fat may promote cancer by causing the body to secrete more of certain hormones that create a favorable environment for certain types of cancer, such as breast cancer. It also may change the characteristics of the cells so that they are more susceptible to cancer-causing agents.

To reduce fat in the diet, choose lean cuts of beef, lamb, and pork as well as skinless poultry and fish. Baking, broiling, poaching, and steaming are recommended cooking methods. Choose skim or low-fat milk and dairy products as well as low-fat salad dressings.

6. SATURATED FAT, CHOLESTEROL, AND CORONARY HEART DISEASE:
Eating too much saturated fat is one of the major risk factors for heart disease. A diet high in saturated fat causes cholesterol, a soft, waxy substance, to build up in the arteries. Eventually, the arteries harden and narrow. The result is an increased pressure in the arteries as well as strain on the heart to maintain adequate blood flow throughout the body.

Because of its high calorie content, too much dietary fat also increases the risk of heart disease in that it increases the likelihood that a person will become obese, which is another risk factor for heart disease.

7. SODIUM AND HYPERTENSION:
Sodium is a mineral that helps the body regulate blood pressure. It also plays a role in the proper functioning of cell membranes, muscles, and nerves. Sodium concentration in the body is controlled by the kidneys, adrenal glands, pituitary gland, and other glands.

The balance between dietary intake and renal (kidney) excretion through urine determines the amount of sodium in the body. Only a small amount of sodium is lost through the stool or sweat. This balance is maintained primarily by the steroid hormone aldosterone, which controls the amount of sodium in urine. Water and sodium are also related. Retention of more sodium is followed by retention of more fluid, and vice versa.

Sodium-sensitive individuals may experience high blood pressure from excess amounts of sodium in the diet. The American Heart Association has developed specific guidelines for sodium intake. Dietary changes may be beneficial. Sodium intake may have little effect in persons without high blood pressure, but it may have a profound effect in sodium-sensitive individuals.

8. ALCOHOL:
Alcohol use increases the risk of liver cancer. When combined with smoking, alcohol intake also increases the risk of cancers of the mouth, throat, larynx, and esophagus. In addition, alcohol intake is associated with an increased risk of breast cancer in women.

The liver metabolizes alcohol. Continued and excessive use of alcohol can damage the liver in various ways, including the development of a fatty liver. A fatty liver can progress to cirrhosis of the liver.

Alcohol can damage the lining of the small intestine and stomach, where most nutrients are digested. As a result, alcohol can impair the absorption of essential nutrients. Alcohol also increases the body’s requirements for some nutrients, while interfering with the absorption and storage of other nutrients.

Continued and excessive use of alcohol can result in an increase in blood pressure. Chronic heavy drinking also can cause damage to the heart muscle (cardiomyopathy). In addition, stroke is associated with both chronic heavy drinking and binge drinking.

If a person chooses to drink alcohol, moderation is recommended - not more than two drinks per day for men and one per day for women.

9. NITRATES AND CANCER:
Countries in which people eat a lot of salt-cured, smoked, and nitrite-cured foods have a high prevalence of cancer of the stomach and esophagus. Examples of such foods include bacon, ham, hot dogs, and salt-cured fish.

If salted, smoked, and cured foods are part of the usual diet, they should be restricted to occasional consumption.

Johns Hopkins patient information

Last revised: December 6, 2012
by Simon D. Mitin, M.D.

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