Supermarkets, pharmacies, health-food stores and the Internet offer a confusing array of digestive-support products that promise relief from bloating, gas, abdominal discomfort…and more. 

The fact is, many of these don’t work as claimed—and might contribute to other health problems. In spite of rave reviews, scientific evidence does not back the claims of many digestive supplements. Dietary supplements do not need Food and Drug Administration (FDA) approval that they are safe, nor do supplement makers need to test their products to prove marketing claims. 

To help ensure that you get the digestive support you need, here’s a quick primer on products that really can help…

Magnesium—for constipation. This essential mineral plays a critical role in maintaining nerve and muscle function…regulating blood pressure and blood sugar levels…and may help prevent migraines and stroke. Doses of 350 mg or more stimulate bowel movements by drawing water into the gastrointestinal tract. 

Use any form of magnesium (citrate, sulfate, oxide, hydroxide). Typically, 400 mg taken at night with a full glass of water (with or without food) produces an easy, cramp-free bowel movement the next morning. If it doesn’t, increase the dose by 200 mg/night up to 1,000 mg. If 1,000 mg isn’t helpful, talk to your doctor about other options. 

Good product to try: Phillips’ Milk of Magnesia (500 mg magnesium per liquid or caplet dose). 

Lactose-digesting enzyme (lactase)—for lactose intolerance. Digestion of the milk sugar lactose requires lactase, an enzyme that is deficient in about 65% of adults worldwide. Lactase supplements allow people who are deficient in lactase to still enjoy dairy foods. Key: Consume enough lactase with the first bite of dairy-­containing food to handle the full amount of lactose in the dairy meal/snack. Lactase products on the market typically recommend 9,000 acid lactase units (ALU) per dose, which should be sufficient for most dairy-containing meals. 

Good product to try: One that does not contain the gas-producing sugar alcohols sorbitol or mannitol, such as Puritan’s Pride–brand lactase.

Alpha-galactosidase—for gas, bloating and abdominal discomfort from eating certain foods. In order to digest the highly fermentable fibers in certain healthy foods, including legumes (chickpeas, beans), cabbage, broccoli and brussels sprouts, you need to have enough of the enzyme alpha-galactosidase.If these foods cause you excess gas, bloating and abdominal distress, you may be able to comfortably eat them if you also consume alpha-galactosidase, the active ingredient in Bean-zyme and Beano. Note: This enzyme may reduce the effectiveness of the diabetes medication acarbose (Precose).

Research finding: In a small study from University of Pavia in Italy, participants who consumed alpha-­galactosidase while eating a meal that contained about two cups of beans produced significantly less gas afterward, compared with those who received a placebo with their beans. 

A serving size of Beano (two capsules) or Bean-zyme (one capsule) contains 300 alpha-galactosidase units (GalU). Participants in the study who got the most intestinal relief consumed 1,200 GalU—but they also ate a lot more beans than you’re likely to eat in one meal. How much to take varies by individual. Try 300 GalU with your first bite of a problem food. I often recommend two Bean-zyme pills per half cup of beans, adjusting as needed. 

Note: Look for alpha-galactosidase supplements that do not contain sugar alcohols, such as mannitol (or other ingredients that end in ol). As noted earlier, these can cause gas.