Coffee, Wine or Tea?
These drinks offer several health benefits as well as some risks. Get the lowdown from Carol Ann Rinzler

Coffee
Coffee beans are roasted seeds from the fruit of the evergreen tree. Like other nuts and seeds, they are high in proteins (11 percent), sucrose and other sugars (8 percent), oils (10 to 15 percent, assorted organic acids (6 percent), B vitamins, iron, and the central nervous system stimulant caffeine (1 to 2 percent). With the exception of caffeine, none of these nutrients is found in coffee. Coffee contains oxalic acid (which binds calcium ions into insoluble compounds your body cannot absorb), but this is of no nutritional consequence as long as your diet contains adequate amounts of calcium-rich foods.

Coffee's best known constituent is the methylxanthine central nervous system stimulant caffeine. How much caffeine you get in a cup of coffee depends on how the coffee was processed and brewed. Caffeine is water-soluble. Instant, freeze-dried, and decaffeinated coffees all have less caffeine than plain ground roasted coffee.

Medical uses/benefits. Caffeine is a stimulant. It increases alertness and concentration, intensifies muscle responses, quickens heartbeat, and elevates mood. As a rule, it takes five to six hours to metabolise and excrete caffeine from the body. During that time, its effects may vary widely from person to person. Some find its stimulation pleasant, even relaxing, others experience restlessness, nervousness, hyperactivity, insomnia, flushing, and upset stomach after as little as one cup a day. It is possible to develop a tolerance for caffeine, so people who drink coffee every day are likely to find it less immediately stimulating than those who drink it only once in a while.

Caffeine's effects on blood vessels depend on site: It dilates coronary and gastrointestinal vessels but constricts blood vessels in your head and may relieve headache, such as migraine, which symptoms include swollen cranial blood vessels. It may also increase pain-free exercise time in patients with angina. However, because it speeds up heartbeat, doctors often advise patients with heart disease to avoid caffeinated beverages entirely.

Caffeine is also a mild diuretic sometimes included in over-the-counter remedies for premenstrual tension or menstrual discomfort.

Adverse effects. In 1994, researchers at the Agricultural University in the Netherlands identified two chemicals in coffee that may raise cholesterol levels. The chemicals, cafestol and kahweol, are members of a chemical family called diterpenes in coffee oils. The amount of diterpenes varies with the brewing method. Drip-brewed coffee, instant coffee, and percolated coffee contain only minimal amounts of diterpenes. Boiled coffees, such as Greek, Turkish, espresso, and those made in a French "press" coffeemaker, may have 6 to 12 mg diterpenes in a 5-ounce cup. The Dutch researchers estimate that drinking five cups of press-brewed coffee or 15 espressos a day might raise cholesterol levels 8 to 10 points.

A 1997 study found that even moderate coffee consumption (five or fewer cups a day) is linked to higher blood levels of homocysteine. This may explain the results of a 1995 study at Boston University School of Public Health, showing the risk of heart attack 2.5 times higher among women who drank 10 cups of coffee a day than among those who averaged less than one cup.

Caffeine slows the flow of blood to the placenta, makes the fetal heart beat faster, and lowers the level of estradiol in a pregnant woman's body. A number of epidemiological human studies suggest that consuming more than 300 mg caffeine a day, about the amount in three cups of coffee, may slightly increase the risk of spontaneous abortion or giving birth to a low birthweight infant or one with microcephaly (an abnormally small head and brain).

Wine
Wines contain carbohydrates, a trace of protein, and small amounts of vitamins and minerals but no fats. Unlike food, which has to be metabolised before your body can use it for energy, the alcohol in wine can be absorbed into the bloodstream directly from the gastrointestinal tract. Ethyl alcohol provides seven calories per gram.

Medical uses/benefits. Red wine contains the antioxidant flavonoid resveratrol, one of the naturally occurring plant chemicals in grape skin and stems associated with a lower risk of heart disease, lower cholesterol levels, and a lower risk of cancer.

One study shows that men who take one drink a day have a 21 percent lower risk of heart attack and a 22 percent lower risk of stroke than men who do not drink at all. Women who have up to one drink a day also reduce their risk of heart attack.

Beverage alcohol decreases the body's production and storage of low density lipoproteins (LDLs), the protein and fat particles that carry cholesterol into your arteries. As a result, people who drink moderately tend to have lower cholesterol levels and higher levels of high density lipoproteins (HDL), the fat and protein particles that carry cholesterol out of the body.

Alcohol beverages stimulate the production of saliva and gastric acids that cause the stomach contractions we call hunger pangs. Moderate amounts, which may help stimulate appetite, are often prescribed for geriatric patients, convalescents, and people who do not have ulcers or other chronic gastric problems.

Adverse effects. According to the American Cancer Society's Cancer Prevention 1 study, men and women who consume more than two drinks a day are at a higher risk of cancer of the mouth and throat. The risk increases if they smoke. The same study also showed an increased risk of breast cancer among women consuming more than three drinks a week.

Alcoholism is an addiction disease, the inability to control one's alcohol consumption. It is a potentially life-threatening condition, with a higher risk of death by accident, suicide, malnutrition, or acute alcohol poisoning, a toxic reaction that kills by paralysing body organs, including the heart.

Malnutrition is another possible adverse effect of alcohol. While moderate alcohol consumption stimulates appetite, alcohol abuses depresses it. In addition, an alcoholic may drink instead of eating. When an alcoholic does eat, excess alcohol in his/her body prevents absorption of nutrients and reduces the ability to synthesize new tissue.

When grapes are fermented, their long protein molecules are broken into smaller fragments. One of these fragments, tyramine, inhibits PST, the enzyme that deactivates phenols (alcohols). The resulting build-up of phenols on your bloodstream may trigger a headache. All wines have some tyramine, but the most serious offenders appear to be red wines, particularly chianti.

Tea
The tea plant is a good source of the B vitamin folate, and it is high in fluorides. It is not uncommon to find a tea plant with a fluoride concentration of 100 ppm (parts per million). By comparison, fluoridated water is generally 1 ppm fluoride. Tea leaves also contain antinutrient enzymes that can split the thiamine (vitamin B1) molecule so that it is no longer nutritionally useful. This is not generally considered a problem for healthy people who eat a balanced diet and consume normal amounts of tea, but it might trigger a thiamine deficiency if you drink a lot of tea and your diet is marginal in thiamine. The tannins in tea are also potential antinutrients that bind calcium and iron into insoluble compounds your body cannot absorb.

Medical uses/benefits. Tea drinkers have a lower risk of heart disease, perhaps because of the high concentration of antioxidant chemicals in tea leaves. Recent studies with laboratory hamsters show that animals fed green tea have lower cholesterol levels and lower incidence of blood clots, but there is no similar study for human beings.

Green tea's ability to fight tooth decay, once attributed to its natural fluoride content, may actually be due to its hexans---oily, flower-scented insoluble chemicals such as caryophyllene and indole that give tea its distinctive flavor.

Adverse effects. Drinking tea may increase severity of premenstrual syndrome (PMS). Beta-estradiol and progesterone, two hormones that rise and fall during the monthly menstrual cycle, directly affect brain levels of adenosine. Beta-estradiol (an estrogen), which rises just before ovulation, keeps adenosine from slowing down nerve cell activity, which may be why many women feel pleasantly energized at mid-cycle. Progesterone encourages adenosine; it's a soothing hormone. That may be why many women feel tense and irritable when progesterone levels fall just before menstrual bleeding begins. Because caffeine alters adenosine activity in the brain, drinking tea may make beta-estradiol's "highs" higher and progesterone's "lows" lower. Because tea contains less caffeine than coffee, its effects would be much weaker.

The tannins in tea may also be constipating.

Reprinted with permission from "The New Complete Book of Food: A Nutritional, Medical, and Culinary Guide by Carol Ann Rinzier. Copyright 1999 by the author. Published by Facts On File www.factsonfile.com, New York, NY10001-2006. All rights reserved.