High Protein Diet May Increase Risk of Alzheimer’s Disease

High protein diets have been popular off and on since the 1960s, and are once again grabbing the attention of millions of people desperate to lose weight. But before you jump on the bandwagon, there are some things you might want to consider. High protein diets can produce a rapid initial weight loss, but most of this loss can be water rather than fat. Additionally, many high protein diets are high in saturated fat and low in fiber, a combination that can increase cholesterol levels and raise the risk of heart disease and stroke. High protein diets have also been shown to cause higher than normal calcium excretion through the urine, which over a prolonged period of time can increase the risk of osteoporosis and kidney stones. And a recent study suggests that a high protein diet may actually cause brain shrinkage and an increased “susceptibility to or progression of Alzheimer’s disease.”

The discovery was an unexpected one, found while studying the effects of different diets on mice bred to develop Alzheimer’s disease (AD). The mice were fed either a regular diet, high fat/low carb custom diet, high protein/low carb version or a high carb/low fat option. When the researchers looked at the brain and body weight of the mice, as well as plaque build-up and differences in the structure of several brain regions involved in the memory defect underlying AD, they were surprised to find that the brains of the mice fed a high protein/low carb diet were 5 percent lighter than all the others and the regions of their hippocampus were less developed.

The researchers theorize that the high protein diet may leave neurons more vulnerable to AD plaque. “High protein diets are used for weight control, and those diets sometimes combine high fat and high protein, which may be doubly damaging, if the high fat increases the accumulation of plaques and the high protein sensitizes nerve cells to the poison released by plaques,” said lead author Sam Gandy, a professor at The Mount Sinai School of Medicine and a neurologist at the James J. Peters Veterans Affairs Medical Center in New York. “Given the previously reported association of high-protein diet with aging-related neurotoxicity, one wonders whether particular diets, if ingested at particular ages, might increase susceptibility to incidence or progression of Alzheimer’s disease.”

Gandy believes the only way to know for sure if these findings have implications for the human brain is to perform prospective randomized double blind clinical diet trials. “This would be a challenging undertaking but potentially worthwhile. If there is a real chance that the ravages of Alzheimer’s disease might be slowed or avoided through healthy eating,” he said. “Such trials will be required if scientists are ever to make specific recommendations about dietary risks for Alzheimer’s disease.” Previous research has shown a Mediterranean-style low-calorie, low-fat diet rich in vegetables, fruits, and fish might delay the onset or slow the progression of AD.

AD is the most common type of dementia, affecting as many as 5.3 million Americans. Brain lesions, called amyloid plaques and tangles, accumulate, destroying brain cells, causing memory loss and problems with thinking and behavior severe enough to affect work, social life and even the ability to cope with everyday life. Over time, AD gets worse and is fatal. Currently, there is no cure for AD, but researchers around the world continue to search for better ways to treat the disease, delay its onset, or prevent it from developing.

The study is published in the journal Molecular Neurodegeneration.