Dietary Guidelines Aim to Reduce Alzheimer's Risk

July 25, 2013

New dietary guidelines for the prevention of Alzheimer's disease have been developed by the Physicians Committee for Responsible Medicine (PCRM).

PCRM is a nonprofit organization that advocates preventive medicine, especially good nutrition; conducts clinical research; and advocates for higher ethical standards in research, according to their Web site. The new guidelines were released last week at the International Conference on Nutrition and the Brain held in Washington, DC, sponsored jointly by PCRM and George Washington University School of Medicine.

PCRM president and lead author of the guidelines, Neal Barnard, MD, said, "The current generation of clinicians is in a battle over food — especially Alzheimer's-promoting foods, such as those which contain saturated and trans fats. We potentially have the capabilities to prevent a disease that is poised to affect 100 million people worldwide by 2050. Why wait?"

The guidelines are very similar to the habits that prevent heart disease in that they recommends avoiding saturated and trans fats, grounding the diet in plant-based foods, and adding sources of vitamin E and B. "Combining this diet with physical exercise and avoiding excess metals, such as iron and copper in multivitamins, can maximize protection for the brain," Dr. Barnard claimed.

The 547 healthcare providers who attended the conference sampled the dietary recommendations themselves by eating meals such as roasted broccoli salad, spiced chickpea curry, baby bok choy, and blueberry sorbet.

Several Alzheimer's experts asked to comment on the guidelines for Medscape Medical News all had similar opinions: that the recommendations were for a healthy diet and exercise, which was always good general advice, but that high levels of evidence that following these guidelines would definitively reduce Alzheimer's risk are lacking.

The 7 Dietary Principles to Reduce Alzheimer's Risk

1. Minimize saturated fats and trans fats.
2. Vegetables, legumes (beans, peas, and lentils), fruits, and whole grains should be the primary staples of the diet.
3. One ounce of nuts or seeds (one small handful) daily provides a healthful source of vitamin E.
4. A reliable source of vitamin B12, such as fortified foods or a supplement providing at least 2.4 μg per day for adults) should be part of the daily diet.
5. Choose multivitamins without iron and copper, and consume iron supplements only when directed by your physician.
6. Avoid the use of cookware, antacids, baking powder, or other products that contribute dietary aluminium.
7. Engage in aerobic exercise equivalent to 40 minutes of brisk walking 3 times per week.


The Evidence

Dr. Barnard cited several studies that supported these guidelines. For example, in the Chicago Health and Aging Project, individuals who consumed the most saturated fat (around 25 g each day) were 2 to 3 times more likely to develop Alzheimer's disease than those who consumed only half that amount. He acknowledged that not all studies agree.

For example, a Dutch study found no protective effect of avoiding saturated fats, although the population was somewhat younger than that in the Chicago study. He suggested that high-fat foods and/or the increases in cholesterol they may cause can contribute to the production of β-amyloid plaques in the brain. High-fat foods also increase the risk for obesity and type 2 diabetes, common risk factors for Alzheimer's disease, he added.

A large study of Kaiser Permanente patients showed that participants with total cholesterol levels above 250 mg/dL in midlife had a 50% higher risk for Alzheimer's disease 3 decades later compared with participants with cholesterol levels below 200 mg/dL, Dr. Barnard reported. And he noted that the APOE ε4 allele, which is strongly linked to Alzheimer's risk, produces a protein that plays a key role in cholesterol transport.

On the recommendation for vegetables, legumes, fruits, and whole grains, Dr. Barnard pointed out that these foods are rich in vitamins, such as folate and vitamin B6, that play protective roles for brain health. Studies of Mediterranean-style diets and vegetable-rich diets, such as the Chicago Health and Aging Project, have shown reduced risk for cognitive problems compared with other dietary patterns.

Dr. Barnard cited an Oxford University study of older people with elevated homocysteine levels and memory problems, in which supplementation with B vitamins improved memory and reduced brain atrophy.

On potentially harmful metals, he noted that excessive iron and copper have been linked to cognitive problems. And while the role of aluminium in Alzheimer's disease remains controversial, he pointed out that aluminum has been demonstrated in the brains of individuals with Alzheimer's disease, and studies in the United Kingdom and France have found increased Alzheimer's prevalence in areas where tap water contained higher aluminium concentrations.

He added that several studies have found a correlation between exercise and a reduced risk for Alzheimer's.

Experts Cautious

Commenting on the guidelines for Medscape Medical News, Heather Snyder, PhD, director of scientific operations at the Alzheimer's Association, said, "There is evidence supporting the idea that physical activity reduces risk of Alzheimer's. And it is always good advice to keep to a healthy diet and stay active. So we would endorse those views. But there is really not enough evidence to support some of the other specific aspects in these guidelines to the level of prescription given."

She added that some positive studies suggest benefits with certain foods/vitamins, but there were also others that show completely opposite results. "So it is difficult to reach a consensus on individual foods."

She noted that benefits have been suggested with some foods, such as dark leafy vegetables (eg, spinach, which is low in saturated fat and has antioxidant effects), but these are not definitive.

Malaz Boustani, MD, Indiana University Center for Aging Research, Indianapolis, had broadly similar views.

"Unfortunately there is no high level evidence to support these guidelines," he commented. "But the adverse effects of following such a diet would be minimal. It is a very healthy diet that they are recommending so there would be no harm in it. But whether it provides value in reducing risks of Alzheimer's is not known. Yes, there are some observational studies suggesting that some of these guidelines may be beneficial. But there is no hard evidence from randomized trials."

Dr. Boustani pointed out that recently, the National Institute on Aging reviewed the literature and did not find any strong evidence to support issuing these type of guidelines and that in a randomized controlled trial vitamin E did not slow Alzheimer's disease or the underlying pathology.

"I would say the major caveat would be whether people can afford to pay for the supplements recommended. If you can afford it then there is no harm in trying it. It is always good to eat a diet low in saturated fat and trans fat and do physical exercise every day. We should all do that anyway," he added.

Samuel Gandy, MD, Mount Sinai Center for Cognitive Health, New York, said, "The diet recommendations makes good sense but must be subjected to one or more randomized clinical trials before one can say that they truly modify the risk for Alzheimer's."

"The new dietary guidelines are mainly based on findings from observational studies and seem reasonable," added Joe Verghese, MBBS, Albert Einstein College of Medicine, New York. "However, there is a paucity of proof from well-conducted clinical trials that supplementation prevents Alzheimer's disease in elders without nutritional deficiencies."

The full guidelines document is available at the PCRM Web site.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as: