Apple cider vinegar: What the experts say

— Apple cider vinegar is one of the most popular natural health products around, with claims for everything from sanitizing toothbrushes to whittling waistlines.

But how much of its popularity is based on hype? Could you be wasting your time or -- even worse -- harming your health?

Here are 10 of the top ways people are using apple cider vinegar and what the science says.

Diabetes

What's the most popular use for apple cider vinegar? If a simple internet search is any measure, it involves diabetes.

Dietitian Carol Johnston has been studying the effects of the main component of any vinegar, acetic acid, on diabetic blood glucose levels since 2004. She's conducted 10 small randomly controlled studies and published six papers on the subject.

Her studies indicate vinegar can help lower blood sugar in people with type 2 diabetes; in those who are prediabetic, also called insulin-resistant; and even in healthy control subjects. The improvement was slight for all but those at risk for diabetes, she says.

"In pre-diabetics, it was too good to be true," says Johnston, who is also associate director of the University of Arizona's School of Nutrition and Health. "It fell a good bit and stayed that way. It may be this is the group that could benefit the most."

But this antiglycemic response can be induced by any sort of vinegar, she says: red and white wine vinegars, pomegranate vinegar or even white distilled vinegar. She suggests adding it to salads, as in the Mediterranean diet, or diluting it in water and drinking it before a meal.

"Basically, what acetic acid is doing is blocking the absorption of starch," Johnston says. "If my study subjects eat a starch and add vinegar, glucose will go down. But if they drink sugar water and add vinegar, nothing happens. So if you're having bacon and eggs, don't bother. It only helps if you are consuming a starch."

If you choose to use apple cider vinegar, be sure to tell your doctor, says nutritionist Lisa Drayer.

"If you're taking a diabetes drug, the vinegar could amplify the effects of your meds," she warns, "and your doctor might want to adjust your dosage."

Most important, if you're expecting vinegar to significantly alter or prevent diabetes, science suggests you reconsider.

Johnston notes that there is no evidence, in her studies or others, to establish that connection.

"I simply determine if your glucose level goes up and down," she says. "If I was to show that vinegar slows progression to diabetes, then I would need hundreds of people and millions of dollars to do the studies, because diabetes has a lot of causes, including genetics."

Weight loss

Weight loss, or dieting, is another popular use for apple cider vinegar and there is some evidence that it can help.

The most cited study was done with 175 heavy but otherwise healthy Japanese subjects. The 12-week treatment produced lower body weight, body mass index, visceral fat, waist measurements and triglyceride levels. Sounds great, right?