Rule of thumb: Strive for pH balance
Kilgour is satisfied with the anecdotal evidence she collects from clients who report boosted energy, improved sleep and healthy weight loss when they eat a more pH-balanced diet.

A good balance generally consists of 75 percent alkaline foods and 25 percent acid foods, she adds. "It varies a little individually, but the point is that you want a balance. Eating only alkaline foods is just as unhealthy as eating too many acidic foods."

Whether you subscribe to the theory of the alkaline diet or not, it favours healthy staples such as leafy greens and fruit and discourages excessive consumption of processed foods, alcohol and red meats. So if you're mindful of your diet now, you're probably already on the right track.

The acid test
If you're interested in eating for pH, consider testing your urine before, then five to six days after, making a dietary change (pH paper designed to test urine is available at health-food stores), says Kilgour. Aim for a neutral reading of 6.2 to 7.4; anything lower is acidic and anything higher is alkaline.

Acidic foods and your teeth
Everyone agrees that foods with high acidity before digestion are bad for us in at least one way: if you drink or eat too much of them too often, tooth-enamel erosion may occur, says Benoit Soucy, a dentist and the director of clinical and scientific affairs at the Canadian Dental Association in Ottawa. "Enamel erosion is a very real concern," he says, "and we're seeing more and more of it, especially in teenagers."

Most cases of enamel erosion can be attributed to eating foods and drinks that have high acidity before they're digested, such as sports and soft drinks and citrus fruit. He explains that, after enamel has been eroded, it exposes the weaker underlying layer, called dentine, which is connected to the pulp, resulting in increased tooth sensitivity -- a sure sign you've got erosion.

Since the effect of erosion isn't reversible, Soucy recommends rinsing your mouth with water after eating or drinking any acidic foods and to avoid or eat less of those with little nutritional value.

"It's really not a problem for people who eat a healthy diet and maintain healthy oral hygiene," he says. "It's when you overdo those acidic foods and drinks that you increase your risk." Use a common-sense approach: don't cut out citrus, but do ditch the pop and sports drinks.

Did you know?
A 2006 review published in Archives of Internal Medicine found there's insufficient evidence to prove that cutting out certain typically highly acidic foods and drinks has an impact on heartburn. What did work was losing weight and falling asleep with your head positioned upright.