Indigestion and Antacids

Americans spend close to one billion dollars a year on nonprescription digestive remedies—mostly for hundreds of antacids, including syrupy liquids, fizzing powders, and chewable tablets. All these products attempt to do the same thing: neutralize stomach acid.

What is “stomach acid” and why does it need to be neutralized? The cells that line the stomach secrete hydrochloric acid continuously, with greatest production shortly after meals. The acid helps dissolve food and activate pepsin, an enzyme that breaks down protein. But at certain times and under certain conditions, the acid causes a burning sensation.

The burning usually takes place not in the stomach but in the esophagus, the tube that carries food and liquid from the mouth to the stomach. A special muscle, or sphincter, between the esophagus and stomach usually keeps the stomach’s caustic juices from “refluxing,” or backing up, into the esophagus. But sometimes refluxing does occur, bringing stomach juice into contact with the sensitive lining of the lower esophagus.

The resulting discomfort has gone by different names through the years. Until the 1970s, antacid makers claimed their products relieved such miseries as “the blahs,” “gassy-acid nausea,” and morning sickness. Since then, however, the U.S. Food and Drug Administration (FDA) has forced manufacturers to tone down those claims. Now, antacid labels are all basically the same: “For the relief of heartburn, sour stomach, or acid indigestion, and upset stomach associated with these symptoms.”

Actually, the terms heartburn, sour stomach, and acid indigestion all refer to the same basic symptom, with minor distinctions. Heartburn characteristically begins low in the front of the chest and may rise toward the throat. Acid indigestion and sour stomach are vaguer terms, but they often mean that stomach juice has entered the mouth, causing a burning sensation and taste. To simplify matters, most physicians use “heartburn” to describe all types of irritation caused by wayward stomach juice.

Many laypeople, however, lump these three terms, along with many other complaints, in the category of “upset stomach.” As a result, antacid manufacturers may claim relief for upset stomach on their labels—as long as they specify that it’s upset stomach associated with heartburn, acid indigestion, or sour stomach. That’s to indicate that antacids probably won’t help other types of stomach complaints, such as nausea, stomachache, abdominal cramps, and gas pains. Conversely, products that may help some of these other symptoms probably won’t help heartburn.

Understanding, Preventing, and Relieving Heartburn

About 10 percent of the population has heartburn every day; another 30 percent experiences it occasionally. Women are affected more often than men.

Heartburn can range from barely noticeable, seemingly “normal” irritation to severe pain inside the chest. The intensity of the pain depends mainly on the amount of stomach juice reaching the esophagus, how caustic it is, and how long it stays there. In more severe cases, the acid damages the esophageal lining and causes inflammation (esophagitis), intense pain, difficulty in swallowing, even ulceration and bleeding.

Heartburn results most commonly from overeating and tends to occur about an hour after a large meal. It is often associated with specific foods, though any food may provoke heartburn in any individual at any time. Anxiety and stress, by triggering increased stomach acid production, can also bring on heartburn.

Antacids are the mainstay of heartburn treatment. They can be taken when symptoms begin or, as a preventive, 30 to 60 minutes after a meal you suspect may cause heartburn. An antacid generally reduces symptoms within three to five minutes after you take it. The effect lasts only about an hour, however, and the symptoms can then recur. To break this cycle, it is important to prevent the refluxing of stomach juice that causes heartburn.

Several steps can help. Certain foods are known to affect the sphincter that closes off the esophagus. Fatty foods, alcohol, and chocolate tend to relax the sphincter, opening the gate for the caustic juices to reflux from below. Conversely, a high-protein, low-fat diet helps to increase sphincter tone. So-called acid foods—tomato products and citrus juice—are also implicated in heartburn. They may irritate the esophagus directly, particularly in people who already have heartburn, thus making the condition worse.

Cigarettes are notorious for causing heartburn by lowering sphincter tone, most probably because of the nicotine. The role of coffee (both with and without caffeine) in heartburn is contradictory. It appears to increase sphincter tone, which is good, and also to increase acid production, which is bad. On balance, the bad probably outweighs the good, so the usual recommendation is to forgo coffee if you have a tendency to heartburn.

Gravity helps keep the stomach contents away from the esophagus, which explains why many heartburn sufferers are afflicted when they go to bed too soon after eating. One effective measure is to elevate the head of the bed at least six inches; a wedged pillow also works, but not as well. Avoiding meals or snacks before bedtime helps reduce the amount of acid secreted that can reflux and cause trouble. Heartburn sufferers should also try to avoid lying down or even bending over soon after a meal.

Increased abdominal pressure can also force stomach juices upward and bring on heartburn, as many pregnant women can attest. To lower abdominal pressure, lose weight if you’re obese, do not engage in strenuous exercise, and avoid tight garments.

Related Problems: Ulcers and Gastritis

The bad effects of stomach acid are not limited to heartburn. Acid can damage the lining of the stomach or of the adjacent duodenum, the upper part of the small intestine. That can cause erosions (ulcers) or inflammation (gastritis or duodenitis). For many years, physicians have prescribed antacids for symptoms that arise from these problems. Studies have shown that antacids in high doses can help heal duodenal ulcers.

However, a new class of prescription drugs has emerged that can better treat many of these conditions. Known as histamine-2 blockers, or H2 blockers, these drugs—which include cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid), and nizatidine (Axid)—all interfere with the secretion of stomach acid from acid-producing cells. According to their FDA-approved indications (duodenal ulcer, benign gastric ulcer, pathological hypersecretory conditions), they are probably overused. But their popularity among physicians and patients attests to their relatively minor side effects—although the long-term effects of continuous blockade of stomach acid secretion remain to be seen.

Chronic antacid users may actually be trying to relieve one of these more serious problems rather than a persistent “upset stomach.” That can be dangerous. While an antacid may relieve ulcer pain, the ulcer may occasionally get worse without your knowing it. Stomach cancers may also be mistaken for repeatedly upset stomach; the use of antacids to relieve pain may delay their detection. Anyone with stomach pain that recurs for more than two weeks should stop self-medication and consult a physician.

One problem often confused with indigestion has nothing whatever to do with the gastrointestinal tract. The pain of a heart attack can mimic simple indigestion. Features that distinguish a heart attack include a sensation of chest pressure or tightness rather than burning, sometimes radiating to the arms, neck, jaw, or upper back. Anyone experiencing such symptoms—often accompanied by sweating and weakness—should seek medical attention immediately.

Judging Effectiveness

Are antacids effective against heartburn? The many people who have found relief by downing two tablets or a tablespoonful no doubt think so. Specialists consulted by CU agreed—but said that their belief is based only on informal clinical observations, not on hard scientific evidence. To CU’s knowledge, no well-controlled clinical trials with human subjects have been performed to determine whether antacids are more effective than placebos. One reason: The FDA review panel for antacid products never required that antacid manufacturers conduct such studies, but settled instead for a simple laboratory test.

The laboratory test required by the FDA resembles the familiar Rolaids commercial (“absorbs 47 times its weight in excess stomach acid”). Acid and antacid are mixed together in a glass beaker. For a product to qualify as an antacid, a standard dose must neutralize a certain amount of hydrochloric acid. For each brand, the total amount of acid neutralized is expressed as a number: the acid neutralizing capacity (ANC) per dose. Television ads often refer obliquely to the ANC: “Without its top layer, Di-Gel consumes as much heartburn-producing acid as plain antacids, like Rolaids”; “Compared to the leading tablet, Tempo is 75 percent stronger in acid-neutralizing power”; “Lo-Sal is twice as effective as the leading tablet.”

But will Di-Gel, Tempo, and Lo-Sal really work better against heartburn than, say, Rolaids, which has a lower ANC? A test in a glass beaker can’t determine the answer. The FDA recognizes the test’s limitations and won’t allow ANC values to appear on product labels. The agency fears that consumers might rely entirely on the numbers, when there’s no clinical evidence that higher numbers mean greater effectiveness.

We tend to disagree with the FDA’s judgment on antacid labeling and believe that ANC values should be available to consumers. They would provide one of the few ways to compare different antacid brands. But consumers would not rely on the numbers for efficacy, as this information would be useful only for comparing prices. Higher ANC values may not always be better in relieving symptoms than lower ones are; but of two brands that have the same ANC value, the one that costs less would be the better buy.

Tablets are more convenient to carry than a bottle, and more likely to be taken in the proper dosage. Suspensions, however, offer a compensating advantage. A teaspoon of the liquid generally has a higher acid neutralizing capacity than a tablet of the same brand.

The Ingredient Lineup

The hundreds of antacids on the shelves make choosing confusing. But there are basically just four active ingredients involved. Some products use one, others include two, and some even more. Unfortunately, the ingredients that are fastest-acting for occasional heartburn have drawbacks that often make them unsuitable for long-term use. These are the four:

Sodium Bicarbonate

Ordinary baking soda. A potent neutralizer that reacts rapidly with stomach acid, it’s probably the fastest-acting and cheapest antacid available. (Brands that currently contain sodium bicarbonate as their single active ingredient include Alka-Seltzer Effervescent Antacid, Bell-Ans, Citrocarbonate, and Soda Mint.)

Sodium bicarbonate is fine for occasional heartburn (defined as once a week or less). However, it is the least desirable antacid ingredient for frequent use, for one and possibly two reasons. It is highly alkaline and readily absorbed into the bloodstream; regular use may affect the body’s acid-base balance and may encourage urinary tract infections by making the urine more alkaline. And the sodium component rules out its use by people on sodium-restricted diets.

Alka-Seltzer Effervescent

Antacid contains citric acid, which buffers the sodium bicarbonate solution so that it’s not as strongly alkaline (and which also helps to create the fizz). You can modify ordinary baking soda the same way—and make it taste better than Alka-Seltzer—by dissolving half a teaspoon of baking soda in half a glass of “natural” citic acid: orange juice. However, this doesn’t reduce the high sodium content.

Calcium Carbonate

This ingredient—the main component of chalk—shares some of the assets of sodium bicarbonate: It’s inexpensive, reasonably fast-acting, and potent as an acid neutralizer. (Brands of calcium carbonate tablets include Alka-Mints, Amitone, Calcium Rich Rolaids, Chooz, Dicarbosil, Titralac, and Tums.)

These products are fine for occasional heartburn. In large doses over a prolonged period of time, however, they may raise calcium levels in the blood and urine, increasing the likelihood of kidney stones and impaired kidney function. This drawback prompted the FDA antacid panel to set a maximum recommended dose of eight grams of calcium carbonate daily (equal to 16 Turns tablets) for no more than two weeks. Unfortunately, many people exceed even that liberal recommendation. (For healthy people who have not experienced problems with kidney stones, an intake of one to 1% grams of calcium daily from food and calcium supplements is a reasonable measure to help prevent osteoporosis, an abnormal loss of bone that can occur with age.)

Research has shown that calcium carbonate can cause “acid rebound” by triggering increased amounts of stomach acid after its own antacid effect has subsided. Whether acid rebound actually impairs calcium carbonate’s overall clinical effectiveness as an antacid is not known. Constipation, which has traditionally been attributed to calcium carbonate, occurs only at high doses.

Magnesium Hydroxide

Milk of magnesia, the common name for magnesium hydroxide, is a nearly perfect antacid. First, it’s a good, fast-acting acid neutralizer. Second, frequent and long-term use is possible for most people. Those with kidney disease, however, are unable to eliminate magnesium adequately, allowing it to accumulate in the body and eventually cause serious problems.

Magnesium hydroxide’s main drawback is its well-known laxative effect. The antacid dose is only one to three teaspoons, while the laxative dose is usually six teaspoons or more. But even the smaller dose can cause diarrhea in susceptible individuals or if doses are taken throughout the day.

Aluminum Hydroxide

A few antacids have aluminum hydroxideslow-acting and weak as an acid neutralizer—as their only active ingredient. (Examples include ALternaGEL, Amphojel, and Basaljel) Such products are recommended only for people who are sensitive to magnesium’s laxative effect.

Aluminum hydroxide causes constipation. It’s used mainly in combination with magnesium hydroxide, to counteract the latter’s laxative effect. Some of the many brands based on this combination include Aludrox, Delcid, Gelusil, Kolantyl, Maalox, Mylanta, and WinGel. A related magnesium-aluminum compound called magaldrate forms the basis of Riopan.

The aluminum-hydroxide/magnesium-hydroxide combinations are the type that physicians most often recommend for long-term, frequent use. Ideally, the constipating and laxative components should balance each other out. But chronic users often experience one or the other problem, more commonly the laxative effect.

Until recently, it was thought that the aluminum in antacids passed harmlessly through the digestive tract without being absorbed into the bloodstream. It’s now known that some of the aluminum is absorbed. People with normal kidney function eliminate most of this absorbed aluminum in their urine, but those with impaired kidney function do not. Studies indicate that aluminum can accumulate in certain sites in the body, including the brain and the parathyroid glands. The aluminum-containing antacids constitute a major source of aluminum in the American diet. According to the Federation of American Societies for Experimental Biology, the average daily aluminum intake is about 20 milligrams, compared with the 100 milligrams contained in a single teaspoon of a typical aluminum-containing antacid. The available evidence suggests that elderly people (many of whom have decreased kidney function) and those with kidney disease should use these antacids only on a physician’s advice. It’s still too early to say whether the aluminum “load” from such antacids may pose a health risk for the general population. Despite frequent speculation, there is no persuasive evidence that intake of aluminum from food, antacids, use of aluminum cookware, or antiperspirants plays any role whatever in causing Alzheimer’s disease.

Gaviscon is an aluminum/magnesium product that takes a unique approach. According to the manufacturer, Marion Laboratories, Inc., the antacid ingredients do not neutralize stomach acid; rather, they form a foamy layer that floats atop the stomach contents. When the contents back up, the foamy layer precedes the acid into the esophagus, thus pro tecting the esophageal tissue from irritation. Several clinicians familiar with Gaviscon told CU that the product appears to be effective, though no more so than conventional antacids. And this product is considerably more expensive than the others.

The Simethicone

Simethicone, a so-called antigas ingredient, is added to certain liquid and tablet antacids, such as Gelusil, Mylanta II, and Silain-Gel. This is the “plus” in Maalox Plus and Riopan Plus. Simethicone is also available by itself, in tablets such as Gas-X and Mylicon-80. But monetary relief for drug makers may well be the only kind of relief that simethicone offers.

In 1973, the FDA advisory panel on antacids concluded there was “inadequate evidence” for simethicone’s effectiveness as an “antiflatulent” (antigas remedy). Several months later, the FDA overruled its panel and deemed simethicone effective. The agency’s decision was influenced partly by two clinical studies carried out and submitted by Plough, Inc., maker of Di-Gel. But that did not end the matter. A later FDA advisory panel, reviewing miscellaneous internal drugs, questioned the effectiveness of all antiflatulents, including simethicone. In its 1982 report, the panel said, in effect: “Let’s assume, although proof is scanty, that simethicone really does release bubbles trapped in the stomach or intestine. There’s no evidence that these small gas bubbles actually cause the bloating, fullness, and pressure that people attribute to them.” So far, the FDA has not acted on this panel’s conclusion.

None of CU’s medical consultants feel that simethicone does much good. They’re joined in this opinion by the two FDA advisory panels and by several authoritative medical publications, including The Medical Letter.

Neither simethicone nor any other ingredient is likely to help reduce gas. But certain measures can help prevent the gas from reaching the digestive system in the first place. The major, if not only, source of gas in the stomach is swallowed air. It may help to give up gum-chewing, smoking, and drinking carbonated beverages, to eat more slowly, and to not talk with your mouth full.


Antacids are made more palatable by such ingredients as sucrose, peppermint, wintergreen, mint, orange, and citrus flavor. Some brands still include saccharin, a proven animal carcinogen. The FDA tried to ban this additive, but congressional action allowed it to remain in use. Products that contain saccharin must display a warning on the label.

Sorbitol is also used as a sweetener in many antacids, as well as in some “sugar-free” products such as candy, gum, and dietetic foods. In large amounts-5 or 10 grams—sorbitol can cause intestinal problems, primarily diarrhea. Antacids whose sorbitol content might cause such problems (at high doses) include ALternaGEL and the liquid versions of Gaviscon, Gelusil, Mylanta, and Mylanta-II. With about 600 milligrams of sorbitol per teaspoon, routine amounts of these antacids probably won’t cause diarrhea. But one clinical study, using a high-dose regimen of Mylanta-II to treat ulcer patients, had to switch two-thirds of the patients to another antacid because of diarrhea. According to CU’s medical consultants, Mylanta-II’s sorbitol dose-28 grams per day in that study—may have been responsible.


Self-medication with antacids should be limited to treating occasional heartburn (no more than once a week). Obviously, many people take antacids far more often. Some keep a bottle of liquid antacid close by and rarely venture out without a roll of tablets. Unfortunately for them, persistent heartburn or upset stomach has become an accepted part of life. It’s easy to fall into the antacid habit. Turns and Rolaids, sweet and minty, are right there on the candy rack next to Lifesavers and Clorets. Turns tablets even come in different flavors. The antacid abuser, however, is merely sugarcoating the stomach problem, often for months or years.

Antacid abuse can aggravate some gastrointestinal problems and mask others that may be serious. For these reasons, persistent heartburn or upset stomach that lasts more than two weeks calls for evaluation by a physician. The cause, if it can be identified, can often be effectively treated.

It is really not possible to say that one brand of antacid will work better than another. Under the FDA’s definition of effectiveness, a standard dose of any brand of antacid should help relieve heartburn. Until someone actually compares antacids in a clinical study, the best advice to follow is: Buy the least expensive antacid with the active ingredient(s) you can tolerate and with the taste and form (tablet or liquid) that appeal to you.

Finally, follow these precautions:

  • Do not use any antacid regularly for more than two weeks, except with the advice and supervision of a physician.
  • Restrict sodium bicarbonate antacids to occasional use only.
  • Do not take calcium carbonate antacids for prolonged periods, except in low doses intended for prevention of osteoporosis.
  • Give preference to products with magnesium and possibly aluminum ingredients, particularly if antacids must be used for extended periods.
  • If you are on a sodium-restricted diet, stick to an antacid low in sodium.
  • If you have kidney problems, consult your physician before using any antacid.
  • Don’t take antacids containing aluminum, calcium, or magnesium at the same time you take a prescription antibiotic that contains tetracycline. Those three ingredients can interact with tetracycline and reduce its absorption into the bloodstream. In general, there should be at least an hour’s interval between taking antacids and any other medication.
  • If you take antacids in tablet form, be sure to chew them thoroughly for maximum effectiveness.
  • Rather than accepting antacid use as a way of life, try to eliminate the cause of your heartburn.
  • And most important, if repeated or painful episodes of indigestion occur, stop self-diagnosis and self-medication and consult your physician.


  1. A date last published or revised is necessary for citation of this as a viable source. It would be really helpful if I could actually use this in my research.

  2. Does an antacid take effect or takes effect faster if chewed? And how can we experiment this safely?

  3. Thanks, wanted to learn more about Baking Soda as use in an antacid and got some great information… thanks!

  4. Excellent advice and guidance!

  5. A very nice educative article!

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