Vegetarian diet may help with insulin resistance

Experts disagree about the mechanism

A vegetarian diet can produce dramatic results for diabetics having a tough time getting control of glucose levels, says one researcher, while another has her doubts about the underlying causes of diabetes cases that are difficult to control.

Steve Provonsha, MD, MPH, director of preventive medicine at Kaiser-Permanente Medical Center in Riverside, CA, ties the reductions in fasting blood glucose in numerous patients to the elimination of glucagon and cortisol in animal tissue from their diets.

He theorizes in articles in Medical Hypotheses in November 1998 and Vegetarian Nutrition in March 1998 that glucagon from animal tissue aggravates insulin resistance.

Provonsha cites results on five patients who reduced sugars and reduced or even eliminated medications in a very short time after beginning vegetarian diets.

He says one patient, a 50-year-old white male, weighing 284 pounds with average blood glucose of 298 mg/dL, dropped his blood glucose 119 mg/dL over a 30-day period. He lost 38 pounds, and his HbA1c was 6.9%. The patient was able to discontinue his 55 units of insulin, and his left foot was saved because his severe osteomyelitis was alleviated.

Provonsha says he is uncertain of the exact cause of the response, but theorizes it is glucagon and cortisol in consumed animal tissue that trigger the catabolic injury response.

"It appears that there is something about dietary muscle protein that activates a catabolic response similar to starvation or injury. Since meat is muscle and fat — the two substances utilized for fuel in the fasting state — it seems necessary to verify that its digestion and absorption is not supplying too many of the redundant substances that create the chemical profile of starvation in the bloodstream," Provonsha wrote in Vegetarian Nutrition.

He also notes that glucagon promotes central obesity, a risk factor for diabetes, and cortisol makes the liver less sensitive to insulin and reduces insulin receptors on skeletal muscle. In addition, Provonsha says, high-protein diets are associated with insulin resistance.

Hard-pressed for scientific proof?

A vegetarian diet may have its merits in terms of lower calories, lower fat, and higher fiber intake, says Marion Franz, MS, RD, CDE, director of nutrition and professional education at the International Diabetes Center in Minneapolis. But there is no proof that insulin problems are a result of the body receiving mixed signals from eating meat.

"There is evidence of a relationship between fat content and insulin resistance," she says. "But I think we’d be hard-pressed for evidence that glucagon in animal tissue causes the insulin resistance. [Provonsha is] making a lot of statements without much scientific evidence."

If glucagon is ingested from meat, Franz says, "The effect shouldn’t last for more than a couple of hours."

In her experience, Franz says, "Vegetarian diabetics have no real unique problems. I can’t say they do better or worse."

She says most of her patients in Minnesota tend to be older adults who have followed a fairly traditional Midwestern meat-and-potatoes diet, so vegetarianism would be quite a stretch for them.

[Steve Provonsha can be reached at (909) 352-7039. Contact Marion Franz at (612) 993-3393.]