Your Medical e-Magazine

Cancer may seem beyond your control. But not all cancers are.

Avoiding smoking reduces your risk of lung cancer. Shielding yourself from the sun lowers your chance for skin cancer. And based on National Cancer Institute (NCI) estimates, eating a healthful diet may prevent as many as one-third of all cancer deaths.

Diet’s relationship to cancer is complicated and involves interpretation of many different and often conflicting studies. Although the evidence isn’t solid, an increasing amount of information supports eating more of some foods and less of others to reduce your risk.

The big picture

Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells.

As many as 500,000 Americans die from cancer each year, making it the second leading cause of death in the United States after cardiovascular disease.

The specific causes of most cancers aren’t known. Research suggests your genetic makeup predisposes you to some cancers. However, most cancers likely develop from a complex interplay of diet, lifestyle and environmental factors.

 Lung, breast, prostate and colon and rectal cancers account for more than half of all cancer deaths. Diet may be involved in some aspects of these plus other less common cancers. Here’s what the evidence suggests:

• Fat–Dietary fats may promote cancer by stimulating abnormal cell division. Some fats are susceptible to production of free radicals, toxic molecules that damage cells. If free radical damage overwhelms your body’s natural defenses, damage may contribute to aging and certain diseases such as cancer.

The evidence appears to be stronger for a connection between dietary fat and colon cancer than other cancers. In most studies, the specific food most strongly associated with increased risk of colon cancer was red meat (beef, pork or lamb). Red meat is a major source of fat in the American diet. Evidence for fat’s role in other cancers, including prostate and breast, is inconsistent. Excess calories from fat can also lead to obesity. Being overweight is linked with an increased risk of cancers of the endometrium (lining of the uterus), colon and rectum and, possibly, breast.

• Alcohol–Two or more alcoholic drinks a day can raise your risk for cancers of the mouth, throat, esophagus and liver. Alcohol may also increase your risk of breast cancer. But some researchers believe other factors in the lifestyles of women who drink alcohol may be responsible for the association.

Whether alcohol directly causes cancer or promotes tumor growth by other cancer-causing substances is uncertain. Alcohol abuse may also indirectly lead to cancer by causing nutrient deficiencies.

• Fiber–The role fiber may play in cancer, particularly colon cancer, is not well understood.

Fiber increases the movement of digested food through your intestines. This may reduce the amount of time your colon is exposed to cancer-promoting substances formed during digestion. Yet it’s not clear whether fiber alone may protect against cancer. Diets high in fiber also tend to be low in fat and high in other nutrients. These characteristics may enhance protection.

• Fruits and vegetables–They offer the strongest and most consistent evidence for diet’s role in reducing your risk for most cancers.

Nutrients, fiber and other chemicals contained in fruits and vegetables may work together. Antioxidants, such as vitamins C and E and beta carotene, may help block cell damage caused by free radicals. The B vitamin folic acid may inhibit transformation of normal cells into malignant cells and strengthen your immune system. Fruits and vegetables also contain virtually no fat and most contain fiber. NCI is looking at whether fiber in fruits and vegetables can prevent the development of pre-cancerous growths (polyps) on the inside wall of the colon. In addition to nutrients and fiber, fruits, vegetables and grains contain phytochemicals, naturally occurring plant chemicals. In this newest and most promising area of research, phytochemicals appear to prevent some cancers and inhibit spread of malignant cells.

How to reduce your risk

More than 20 studies are testing a variety of substances that may protect against cancer, including vitamins C and E and beta carotene. Researchers also hope to learn more about how specific phytochemicals may inhibit cancer development.

 Until these studies are completed, eating a diet that’s low in fat and high in plant foods is the best you can do to reduce your risk of some cancers:

• Eat at least five servings of fruits and vegetables daily–Emphasize citrus fruits for vitamin C and deep-yellow and dark-green vegetables for beta carotene. Turnip greens provide folic acid. Cruciferous vegetables such as Brussels sprouts, broccoli and cabbage contain a variety of substances that may protect against cancer.

One serving is one-half cup of fruit, three-quarters cup juice, one-half cup cooked vegetable, one cup leafy vegetable or one-quarter cup dried fruit.

• Eat plenty of high-fiber foods–Aim for 20 to 30 grams of fiber daily. Fruits and vegetables, especially legumes such as peas, beans and lentils, contain up to four grams of fiber in one-half cup.
• Reduce fat–Limit all types of fat to less than 65 grams daily, based on a 2,000-calorie diet.
• Limit alcohol–If you drink alcohol, limit daily amounts to no more than three ounces of 80-proof liquor, eight ounces of wine or 24 ounces of beer.
• Maintain a healthy weight–In addition to eating a low-fat, high-fiber diet, exercise regularly.
• Choose a variety of foods–No one food offers all the nutrients you need. Foods provide a unique balance of nutrients that can’t be duplicated by supplements.

People commonly blame low blood sugar (hypoglycemia) between meals for a cluster of complaints–light-headedness, cold sweats, shakiness, headache and irritability.   

But true hypoglycemia, in which blood sugar levels approach 40 milligrams per deciliter (mg/dl), typically occurs only in people with diabetes or pancreatic disease. Why, then, do some healthy people have similar, yet less severe, symptoms after eating–despite blood sugar levels that remain within the normal range (60 to 110 mg/dl)?  

 A study suggests caffeine may be involved. Eight people consumed caffeine in an amount equal to two to three cups of drip-brewed coffee (400 milligrams). They then described “feeling hypoglycemic” at low, but still normal, blood sugar levels about an hour later.   Caffeine may increase your brain’s need for sugar (glucose). Caffeine also decreases the sugar available to your brain by reducing blood flow. Your brain, in turn, interprets the “demand” as an abnormal drop in blood sugar level and triggers symptoms.   

More research is needed. But if you feel “hypoglycemic” after drinking lots of coffee or cola, try cutting back.