Stuart Bradford

Stomach acid has long been blamed for acid reflux, heartburn and other ills. But now some experts are starting to think that the problems may lie not just in the acid coming up from the stomach but in the food going down.

The idea has been getting a lot of attention lately, notably in popular books like “Crazy Sexy Diet” and “The Acid Alkaline Food Guide” — which claim that readers can improve their health by focusing on the balance of acid and alkaline in the diet, mostly by eating more vegetables and certain fruits and fewer meats and processed foods.

While the science behind such claims is not definitive, some research does suggest a benefit to low-acid eating. A handful of recent studies have shown a link between bone health and a low-acid diet, while some reports suggest that the acidity of the Western diet increases the risk of diabetes and heart disease.

This year, a small study found that restricting dietary acid could relieve reflux symptoms like coughing and hoarseness in patients who had not been helped by drug therapy, according to the journal Annals of Otology, Rhinology & Laryngology.

In the study, 12 men and 8 women with reflux symptoms who hadn’t responded to medication were put on a low-acid diet for two weeks, eliminating all foods and beverages with a pH lower than 5. The lower the pH, the higher the acidity; highly acidic foods and beverages include diet sodas (2.9 to 3.7), strawberries (3.5) and barbecue sauce (3.7). According to the study, 19 out of 20 patients improved on the low-acid diet, and 3 became completely asymptomatic.

The author, Dr. Jamie Koufman, who specializes in voice disorders and laryngopharyngeal reflux (the kind associated with hoarseness), advocates a low-acid diet in her new book, “Dropping Acid: The Reflux Diet Cookbook & Cure.” (You can see some of the recipes in Well’s Vegetarian Thanksgiving.)

Reflux drugs focus on neutralizing or reducing acid produced in the stomach. But while stomach acid is a factor, Dr. Koufman says, the real culprit for many patients is pepsin, a digestive enzyme that can exist in the esophagus. In these patients, she says, it’s not enough to quell the acid sloshing up from the stomach.

“Once you have pepsin in the tissue, acid from above is equally damaging,” she said. “When you drink a soda and you have chest pain, sometimes it may be because acid came from below or sometimes because acid came from above.”

Low-acid eating rebalances the diet: fewer high-acid foods and more high-alkaline ones. The pH scale runs from 0 to 14; distilled water has a pH of about 7 and is considered neutral, and acidity increases by 10 times with each decrease in a whole pH number. A food with a pH of 4 is 10 times as acidic as one with a pH of 5. (The pH of stomach acid is 1 to 4.)

Processed and bottled foods are particularly acidic because of federal rules requiring high acidity as a preservative, Dr. Koufman says. And she notes that the rise in consumption of such foods coincides with a staggering increase in esophageal cancer caused by chronic acid reflux.

To relieve heartburn and reflux symptoms, Dr. Koufman suggests a strict two-week “induction” diet with nothing below pH 5 — no fruit except melons and bananas, no tomatoes or onions but plenty of other vegetables, whole grains, and fish or skinless poultry. High-alkaline foods include bananas (5.6), broccoli (6.2) and oatmeal (7.2).

Some foods must be eliminated for reasons other than acidity. Regardless of pH levels, high-fat meats, dairy products, caffeine, chocolate, carbonated beverages, fried foods, alcohol and mints are known to aggravate reflux symptoms. Certain other foods, including garlic, nuts, cucumbers and highly spiced dishes, may also touch off reflux in some patients.

For people who don’t have severe reflux, Dr. Koufman suggests a “maintenance” diet of foods with a pH no lower than 4, which allows items like apples, raspberries and yogurt.

She notes that the diet is hardly radical, and is consistent with recommendations from various medical groups to eat a diet rich in vegetables and whole grains and to cut back on meats and fatty foods. Still, many people with a relatively healthy diet may be eating too many high-acid foods, like diet soda or citrus juice. She says that once people learn the basics of low-acid eating as well as their own trigger foods, it’s a relatively simple diet to follow.

“This is a trial-and-error process,” Dr. Koufman said. “Grains are good, and almost all the vegetables. It also means nothing from a bottle or can except water. And close the kitchen at 8 p.m.”