Carbohydrates get a lot of bad press and blame for the obesity epidemic, but a new study suggests that this negative attention may not be deserved for pasta.

Unlike most 'refined' carbohydrates, which are rapidly absorbed into the bloodstream, pasta has a low glycemic index, meaning it causes smaller increases in blood sugar levels than those caused by eating foods with a high glycemic index.

Researchers at St. Michael's Hospital undertook a systematic review and meta-analysis of all of the available evidence from randomized controlled trials, the gold standard of research design. They identified 30 randomized control trials involving almost 2,500 people who ate pasta instead of other carbohydrates as part of a healthy low-glycemic index diet. Their results were published today in the journal BMJ Open.

"The study found that pasta didn't contribute to weight gain or increase in body fat," said lead author Dr. John Sievenpiper, a clinician scientist with the hospital's Clinical Nutrition and Risk Modification Centre. "In fact analysis actually showed a small weight loss. So contrary to concerns, perhaps pasta can be part of a healthy diet such as a low GI diet."

The people involved in the clinical trials on average ate 3.3 servings of pasta a week instead of other carbohydrates. One serving equals about one-half cup of cooked pasta. They lost about one-half kilogram over a median follow-up of 12 weeks.

The study authors stressed that these results are generalizable to pasta consumed along with other low-glycemic index foods as part of a low-glycemic index diet. They caution more work is needed to determine if the lack of weight gain will extend to pasta as part of other healthy diets.

"In weighing the evidence, we can now say with some confidence that pasta does not have an adverse effect on body weight outcomes when it is consumed as part of a healthy dietary pattern," said Dr. Sievenpiper.

This work received funding from the Canadian Institutes of Health Research through the Canada-wide Human Nutrition Trialists' Network; the Diet, Digestive Tract and Disease Centre, funded through the Canadian Foundation for Innovation, and the Ministry of Research and Innovation's Ontario Research Fund, among other non-industry sponsors.

Some of the authors have received prior research grants, in-kind donations of pasta for a randomized controlled trial, and travel support from the pasta maker Barilla.