Energy value (calories per serving): Low
Saturated fat: None Cholesterol: None Carbohydrates: Trace Fiber: Trace
Major vitamin contribution: None
Major mineral contribution: None
About the Nutrients in This Food
Coffee beans are roasted seeds from the fruit of the evergreen coffee 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 exceptions of caffeine, none of these nutrients is found in coffee.
Like spinach, rhubarb, and tea, 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 ner- vous system stimulant caffeine. How much caffeine you get in a cup of coffee depends on how the coffee was processed and brewed. Caffeine is
Caffeine Content/Coffee Servings Brewed coffee 60 mg/five-ounce cup Brewed/decaffeinated 5 mg/five-ounce cup
Espresso 64 mg/one-ounce serving
Instant 47 mg/rounded teaspoon
The Most Nutritious Way to Serve This Food
In moderation, with high-calcium foods. Like spinach, rhubarb, and tea, coffee has oxalic acid, which binds calcium into insoluble compounds. This will have no important effect as long as you keep your consumption moderate (two to four cups of coffee a day) and your calcium consumption high.
Diets That May Restrict or Exclude This Food
Diet for people with heart disease (regular coffee)
Buying This Food
Look for: Ground coffee and coffee beans in tightly sealed, air- and moisture-proof containers.
Avoid: Bulk coffees or coffee beans stored in open bins. When coffee is exposed to air, the volatile molecules that give it its distinctive flavor and richness escape, leaving the coffee flavorless and/or bitter.
Storing This Food
Store unopened vacuum-packed cans of ground coffee or coffee beans in a cool, dark cabinet—where they will stay fresh for six months to a year. They will lose some flavor in storage, though, because it is impossible to can coffee without trapping some flavor- destroying air inside the can.
Once the can or paper sack has been opened, the coffee or beans should be sealed as tight as possible and stored in the refrigerator. Tightly wrapped, refrigerated ground coffee will hold its freshness and flavor for about a week, whole beans for about three weeks. For longer storage, freeze the coffee or beans in an air- and moistureproof container. ( You can brew coffee directly from frozen ground coffee and you can grind frozen beans without thawing them.)
Preparing This Food
If you make your coffee with tap water, let the water run for a while to add oxygen. Soft water makes “cleaner”-tasting coffee than mineral-rich hard water. Coffee made with chlorinated water will taste better if you refrigerate the water overnight in a glass (not plastic) bottle so that the chlorine evaporates.
Never make coffee with hot tap water or water that has been boiled. Both lack oxygen, which means that your coffee will taste flat.
Always brew coffee in a scrupulously clean pot. Each time you make coffee, oils are left on the inside of the pot. If you don’t scrub them off, they will turn rancid and the next pot of coffee you brew will taste bitter. To clean a coffee pot, wash it with detergent, rinse it with water in which you have dissolved a few teaspoons of baking soda, then rinse one more time with boiling water.
What Happens When You Cook This Food
In making coffee, your aim is to extract flavorful solids (including coffee oils and sucrose and other sugars) from the ground beans without pulling bitter, astringent tannins along with them. How long you brew the coffee determines how much solid material you extract and how the coffee tastes. The longer the brewing time, the greater the amount of solids extracted. If you brew the coffee long enough to extract more than 30 percent of its solids, you will get bitter compounds along with the flavorful ones. (These will also develop by let- ting coffee sit for a long time after brewing it.)
Ordinarily, drip coffee tastes less bitter than percolator coffee because the water in a drip coffeemaker goes through the coffee only once, while the water in the percolator pot is circulated through the coffee several times. To make strong but not bitter coffee, increase the amount of coffee—not the brewing time.
How Other Kinds of Processing Affect This Food
Drying. Soluble coffees (freeze-dried, instant) are made by dehydrating concentrated brewed coffee. These coffees are often lower in caffeine than regular ground coffees because caffeine, which dissolves in water, is lost when the coffee is dehydrated.
Decaffeinating. Decaffeinated coffee is made with beans from which the caffeine has been extracted, either with an organic solvent (methylene chloride) or with water. How the coffee is decaffeinated has no effect on its taste, but many people prefer water-processed decaf- feinated coffee because it is not a chemically treated food. (Methylene chloride is an animal carcinogen, but the amounts that remain in coffees decaffeinated with methylene chloride are so small that the FDA does not consider them hazardous. The carcinogenic organic sol- vent trichloroethylene [TCE], a chemical that causes liver cancer in laboratory animals, is no longer used to decaffeinate coffee.)
Medical Uses and/or Benefits
As a stimulant and mood elevator. Caffeine is a stimulant. It increases alertness and concentra- tion, intensifies muscle responses, quickens heartbeat, and elevates mood. Its effects derive
from the fact that its molecular structure is similar to that of adenosine, a natural chemical by-product of normal cell activity. Adenosine is a regular chemical that keeps nerve cell activ- ity within safe limits. When caffeine molecules hook up to sites in the brain when adenosine molecules normally dock, nerve cells continue to fire indiscriminately, producing the jangly feeling sometimes associated with drinking coffee, tea, and other caffeine products.
As a rule, it takes five to six hours to metabolize and excrete caffeine from the body. During that time, its effects may vary widely from person to person. Some find its stimu- lation 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 imme- diately stimulating than those who drink it only once in a while.
Changes in blood vessels. 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, doc- tors often advise patients with heart disease to avoid caffeinated beverages entirely.
As a diuretic. Caffeine is a mild diuretic sometimes included in over-the-counter remedies for premenstrual tension or menstrual discomfort.
Adverse Effects Associated with This Food
Stimulation of acid secretion in the stomach. Both regular and decaffeinated coffees increase the secretion of stomach acid, which suggests that the culprit is the oil in coffee, not its caffeine.
Elevated blood levels of cholesterol and homocysteine. In the mid-1990s, several studies in the Netherlands and Norway suggested that drinking even moderate amounts of coffee (five cups a day or less) might raise blood levels of cholesterol and homocysteine (by-product of protein metabolism considered an independent risk factor for heart disease), thus increas- ing the risk of cardiovascular disease. Follow-up studies, however, showed the risk limited to drinking unfiltered coffees such as coffee made in a coffee press, or boiled coffees such as Greek, Turkish, or espresso coffee. The unfiltered coffees contain problematic amounts of cafestol and kahweol, two members of a chemical family called diterpenes, which are believed to affect cholesterol and homocysteine levels. Diterpenes are removed by filtering coffee, as in a drip-brew pot.
Possible increased risk of miscarriage. Two studies released in 2008 arrived at different conclusions regarding a link between coffee consumption and an increased risk of miscar- riage. The first, at Kaiser Permanente (California), found a higher risk of miscarriage among women consuming even two eight-ounce cups of coffee a day. The second, at Mt. Sinai School of Medicine (New York), found no such link. However, although the authors of the Kaiser Permanente study described it as a “prospective study” (a study in which the research- ers report results that occur after the study begins), in fact nearly two-thirds of the women who suffered a miscarriage miscarried before the study began, thus confusing the results.
Increased risk of heartburn /acid reflux. The natural oils in both regular and decaffeinated coffees loosen the lower esophageal sphincter (LES), a muscular valve between the esopha- gus and the stomach. When food is swallowed, the valve opens to let food into the stomach, then closes tightly to keep acidic stomach contents from refluxing (flowing backwards) into the esophagus. If the LES does not close efficiently, the stomach contents reflux and cause heartburn, a burning sensation. Repeated reflux is a risk factor for esophageal cancer.
Masking of sleep disorders. Sleep deprivation is a serious problem associated not only with automobile accidents but also with health conditions such as depression and high blood pres- sure. People who rely on the caffeine in a morning cup of coffee to compensate for lack of sleep may put themselves at risk for these disorders.
Withdrawal symptoms. Caffeine is a drug for which you develop a tolerance; the more often you use it, the more likely you are to require a larger dose to produce the same effects and the more likely you are to experience withdrawal symptoms (headache, irritation) if you stop using it. The symptoms of coffee-withdrawal can be relieved immediately by drinking a cup of coffee.
Drugs that make it harder to metabolize caffeine. Some medical drugs slow the body’s metabolism of caffeine, thus increasing its stimulating effect. The list of such drugs includes cimetidine (Tagamet), disulfiram (Antabuse), estrogens, fluoroquinolone antibiotics (e.g., ciprofloxacin, enoxacin, norfloxacin), fluconazole (Diflucan), fluvoxamine (Luvox), mexi- letine (Mexitil), riluzole (R ilutek), terbinafine (Lamisil), and verapamil (Calan). If you are taking one of these medicines, check with your doctor regarding your consumption of caf- feinated beverages.
Drugs whose adverse effects increase due to consumption of large amounts of caffeine.
This list includes such drugs as metaproterenol (Alupent), clozapine (Clozaril), ephedrine, epinephrine, monoamine oxidase inhibitors, phenylpropanolamine, and theophylline. In addition, suddenly decreasing your caffeine intake may increase blood levels of lithium, a drug used to control mood swings. If you are taking one of these medicines, check with your doctor regarding your consumption of caffeinated beverages.
Allopurinol. Coffee and other beverages containing methylxanthine stimulants (caffeine, theophylline, and theobromine) reduce the effectiveness of the antigout drug allopurinol, which is designed to inhibit xanthines.
Analgesics. Caffeine strengthens over-the-counter painkillers (acetaminophen, aspirin, and other nonsteroidal anti-inflammatories [NSAIDS] such as ibuprofen and naproxen). But it also makes it more likely that NSAIDS will irritate your stomach lining.
Antibiotics. Coffee increases stomach acidity, which reduces the rate at which ampicillin, erythromycin, griseofulvin, penicillin, and tetracyclines are absorbed when they are taken by mouth. (There is no effect when the drugs are administered by injection.)
Antiulcer medication. Coffee increases stomach acidity and reduces the effectiveness of nor- mal doses of cimetidine and other antiulcer medication.
False-positive test for pheochromocytoma. Pheochromocytoma, a tumor of the adrenal glands, secretes adrenalin, which is converted to VM A (vanillylmandelic acid) by the body and excreted in the urine. Until recently, the test for this tumor measured the levels of VM A in the patient’s urine and coffee, which contains VM A, was eliminated from patients’ diets lest it elevate the level of VM A in the urine, producing a false-positive test result. Today, more finely drawn tests make this unnecessary.
Iron supplements. Caffeine binds with iron to form insoluble compounds your body cannot absorb. Ideally, iron supplements and coffee should be taken at least two hours apart.
Birth control pills. Using oral contraceptives appears to double the time it takes to eliminate caffeine from the body. Instead of five to six hours, the stimulation of one cup of coffee may last as long as 12 hours.
Monoamine oxidase (MAO) inhibitors. Monoamine oxidase inhibitors are drugs used to treat depression. They inactivate naturally occurring enzymes in your body that metabolize tyra- mine, a substance found in many fermented or aged foods. Tyramine constricts blood vessels and increases blood pressure. Caffeine is a substance similar to tyramine. If you consume excessive amounts of a caffeinated beverage such as coffee while you are taking an M AO inhibitor, the result may be a hypertensive crisis.
Nonprescription drugs containing caffeine. The caffeine in coffee may add to the stimulant effects of the caffeine in over-the-counter cold remedies, diuretics, pain relievers, stimulants, and weight-control products containing caffeine. Some cold pills contain 30 mg caffeine, some pain relievers 130 mg, and some weight-control products as much as 280 mg caffeine. There are 110 –150 mg caffeine in a five-ounce cup of drip-brewed coffee.
Sedatives. The caffeine in coffee may counteract the drowsiness caused by sedative drugs; this may be a boon to people who get sleepy when they take antihistamines. Coffee will not, however, “sober up” people who are experiencing the inebriating effects of alcoholic beverages.
Theophylline. Caffeine relaxes the smooth muscle of the bronchi and may intensif y the effects (and/or increase the risk of side effects) of this antiasthmatic drug.