Nutrition and Disease

An improper or inadequate diet can lead to a number of diseases. On the other hand, good nutritional habits can help prevent certain diseases.

Heart disease in its most common form is called coronary artery disease (CAD). CAD narrows the coronary arteries and so reduces the blood supply to the heart. It can lead to crippling attacks of chest pain and, eventually, to life-threatening heart attacks. High blood pressure and high levels of blood cholesterol are two of the major risk factors for CAD. Each of these risk factors can often be lessened by following good nutritional practices.

Many people with mild high blood pressure can reduce it by limiting their intake of salt and calories. Similarly, many people can lower their blood cholesterol level by reducing the amount of fat--particularly saturated fat--cholesterol, and calories in their diet. They can do so by avoiding such foods as butter, cakes, cookies, egg yolks, fatty meats, tropical oils, and whole-fat dairy products.

Cancer. Scientists do not know exactly why cancer develops. But they have found that heredity, environment, and lifestyle all play a role in causing the disease. They have also learned that good nutrition can help prevent certain kinds of cancer in laboratory animals. Large doses of vitamins A and C have been proved to prevent some cancers in animals. Many scientists believe that certain foods contain substances that may help prevent some cancers in people. Such foods include broccoli, cabbage, carrots, cauliflower, fruits, spinach, whole-grain breads and cereals, and some seafoods. Lessening intake of fats and increasing the intake of fiber may also help prevent some cancers from forming.

Deficiency Diseases. Many diseases result from the deficiency (lack) of certain nutrients in the diet. When the missing nutrient is provided, the disease usually can be eliminated. Deficiency diseases are most widespread in developing countries, where people often lack access to adequate food supplies. The availability of a variety of foods the year around, along with vitamin and mineral fortification of many foods, have made deficiency diseases less common in most developed countries.

Protein-calorie malnutrition, also called protein-energy malnutrition, occurs when the diet is low in both proteins and calories. If the diet is especially low in proteins, the condition is called kwashiorkor. Signs of kwashiorkor include changes in the color and texture of the hair and skin, swelling of the body, and damage to the intestines, liver, and pancreas. The disease, which is common in some developing nations, usually attacks children who are suffering from an infectious disease. Kwashiorkor is fatal unless the patient is given protein along with food providing calories. If the diet is especially low in calories, the condition is called marasmus. Marasmus usually attacks infants and young children, and it causes extreme underweight and weakness.

Vitamin deficiencies. The signs and symptoms of vitamin deficiencies vary according to the missing vitamin. Vitamin C deficiency, also called scurvy, causes sore and bleeding gums, slow repair of wounds, and painful joints. Vitamin D deficiency, also called rickets, causes an abnormal development of the bones. A deficiency of niacin and the amino acid tryptophan, found in protein, causes pellagra. The early symptoms of pellagra include weakness, lack of appetite, diarrhea, and indigestion.

Mineral deficiencies. The most common mineral deficiency disease is iron-deficiency anemia, which results from a lack of iron. In a person with this disease, the blood does not have enough healthy red blood cells and cannot supply the tissues with sufficient oxygen. Thus, the person feels weak or tired. Other symptoms include dizziness, headaches, rapid heartbeat, and shortness of breath. A lack of iodine can cause goiter, a disease in which the thyroid gland becomes enlarged.

Other diseases may result from poor nutritional habits. For example, the excessive intake of alcohol causes some forms of liver disease. Obesity increases the risk of gall bladder disease and of diabetes in adults. The risk of osteoporosis (loss of bone tissue) is higher for women whose intake of calcium and level of physical activity are low. To prevent osteoporosis, physicians recommend a lifelong combination of regular exercise and a diet with adequate calcium.