Proponents of the Paleo diet, which focuses on lean meat, fruits, vegetables and nuts, promote it as a way to avoid many of the chronic diseases present now that were absent in hunter-gatherers of olden times.
They may be right, say researchers from the City of Hope National Medical Center. They reviewed 13 studies on the diet, including 4 that looked at people with type 2 diabetes, and call it promising for reducing chronic disease risk and for weight loss and other health improvements.1
"The studies so far showed promising results with declines mainly in weight, and some studies showing a decline in fasting glucose and hemoglobin A1c," says Maximiliano Hyon, DO, MPH, senior endocrine fellow at City of Hope National Medical Center. He presented the findings at ENDO 2017, the annual meeting of the Endocrine Society, in Orlando Apr. 3.
He stops short of recommending it at this time, however. "These are small studies with short study duration, so we need to have larger and more robust data before we can truly make a recommendation regarding the Paleo diet for people with type 2 diabetes."
The studies each included only 10 to 30 people each, he says. Researchers compared the Paleo diet to a variety of other diets. Hyon and his colleagues evaluated the effects of the diet on the potential to prevent type 2 diabetes, heart disease and cancer risks.1
Results weren't consistent across all studies, Dr. Hyon tells Endocrine Web. Nor did all studies look at the same outcomes.
"The mean weight loss in most of the studies was between 5 and 20.5 pounds," he says. This was over a brief study period, usually three months.
"In terms of blood glucose and hemoglobin A1C [a three-month look back at blood sugar levels], not all the studies showed a significant decline," he says. In those that did find a decline that was significant from a statistics point of few, there was a .3 to .4% decline in the A1C, which Dr. Hyon calls modest.
In two studies, researchers found a decline of up to 30 milligrams/deciliter in fasting blood glucose, which Dr. Hyon views as moderate.
The studies also showed a beneficial effect in reducing deaths from all causes and from cancer and heart disease. "Most notable was cardiovascular disease and cancer," says study researcher Raynald Samoa, MD, an endocrinologist and assistant professor of medicine at City of Hope. "There was also some improvement in diabetes control."1
As to why the diet may help? Dr. Samoa says the diet may improve insulin resistance, and the improvement may confer more benefits beyond control of diabetes, also helping to reduce cancer and heart disease risk.
The findings don't surprise Lynda Frassetto, MD, professor of medicine and nephrology at the University of California San Francisco, who has also published her research on the diet.
"All of our studies showed pretty much the same thing [as the current review]," she tells EndocrineWeb. Proponents have a good argument for the diet helping reduce heart disease risk, she says. "It fixes the known risk factors for cardiovascular disease," she says, such as high blood pressure, high cholesterol and diabetes.
She views the current data on cancer as more investigational, she says. The studies on heart disease are short term, she adds, so longer studies would help clarify the benefits. In a recent study, she compared 14 who ate the Paleo diet with 10 who ate diets based on the American Diabetes Association, which focuses on low-fat dairy, whole grains, legumes and moderate salt intake.2
After 14 days on the test diet, both groups had improvements in measures such as blood sugar, but the Paleo group had greater improvements in blood sugar control and blood cholesterol. Those who had the most insulin resistance improved on the Paleo diet but not on the ADA diet, she found.
Some people should be especially careful to talk to their doctors before trying Paleo, Dr. Frassetto says. That includes anyone with kidney issues or digestion problems. The diet can include high amounts of potassium, which can be a problem for someone with kidney problems.3 High amounts of fiber in the diet may spell trouble for those with intestinal issues.
The diet cuts out dairy, so dietary calcium intake may become too low, Dr. Hyon says. He advises taking a multivitamin. Another potential concern, if those on Paleo do not eat enough seafood, is a low iodine intake, he says.