Alzheimer's Disease: Nutritional Considerations

Several epidemiological studies have examined associations between diet and Alzheimer's disease risk.¹⁸ The following factors are under study for a possible role in reducing risk:

Low Plasma Cholesterol

Elevated cholesterol levels are associated with increased risk for Alzheimer's disease, even after controlling for the presence of the apo E e4 allele.¹⁹ Use of lipid-lowering agents has been found in several epidemiological studies to be associated with a lower risk of dementia,^20,21 although clinical trials have not yet supported this conclusion. It is not clear whether the lipid-lowering effect of statin drugs or some other neuroprotective effect of these medications may be responsible.

Reduced Saturated and Trans Fatty Acids

High intake of saturated fats and trans fats, which come mainly from animal products, are associated with risk of Alzheimer's disease.^22-24 In contrast, limited evidence suggests that diets high in omega-3 fatty acids may reduce Alzheimer's disease risk.²⁵

Adherence to a Mediterranean diet is associated with reduced Alzheimer's risk.²⁶ Some have suggested that the regular consumption of fatty fish intake (ie, more than twice per week) may be associated with lower risk for AD in individuals without the e4 allele.²⁷ However a systematic review by the Agency for Healthcare Research and Quality (AHRQ) concluded that data are inadequate to justify conclusions.²⁸

Maintaining Healthy Weight

Avoidance of overeating and maintenance of ideal weight may lower risk for Alzheimer's. Reduced energy intake may reduce the risk for Alzheimer's, especially in people carrying the apo E e4 allele.²⁹ An 18-year follow-up study found that women diagnosed with dementia had higher average body mass index than non-demented individuals.⁷

Antioxidants

Antioxidant supplements and nutrients may offer a measure of protection against Alzheimer's disease. Some evidence indicates that a combination of vitamins C and E is associated with an 80% lower risk for Alzheimer's disease,³⁰ and two prospective studies found that greater intakes of foods high in either vitamin E31 or vitamin C32 may lower the risk for Alzheimer's disease. One study suggested benefits from pharmacologic dosages of vitamin E in treating Alzheimer's disease that were similar to those from selegiline.³³ Recent studies have suggested that the specific, diet-derived forms of vitamin E may be important to any protective effect.³⁴ Not all studies have supported these findings, however, andcontrolled clinical studies are required to assess the possible benefits of vitamin E and vitamin C.

Good sources of vitamin C include citrus fruits, kiwi, melons, and many vegetables. Good sources of vitamin E include wheat germ, peanuts, and sunflower seeds.

B Vitamins

An adequate intake of folate, B₆, and B₁₂ may reduce risk of Alzheimer's disease. Inadequate intakes of these B vitamins can cause a rise in plasma homocysteine, which in turn is a strong and independent risk factor for the development of Alzheimer's disease.^9,35 Findings suggest that low folate or B₁₂ status may precede the onset of Alzheimer's disease.^18,36

Avoiding Aluminum

Some evidence suggests that avoiding dietary or environmental exposure to aluminum may reduce the risk for Alzheimer's disease. Although aluminum is not yet established as a direct cause of Alzheimer's disease in humans,^37,38 epidemiological studies have found statistically significant relationships between aluminum in drinking water and Alzheimer's disease,³⁹ and some evidence exists that patients with Alzheimer's disease have increased absorption of aluminum even when they are on normal diets.⁴⁰ Aluminum has caused neurotoxic effects in individuals who have been exposed to the metal occupationally, by dialysis, or through the use of aluminum-containing medications.^37,41

Avoiding Excess Iron

Excess iron intake may contribute to Alzheimer's risk. Iron accumulates in the brain with aging, and evidence suggests that iron contributes to the beta-amyloid deposition, amyloid precursor protein, free radicals, and neurofibrillary tangles that characterize this disease. In addition, the brains of Alzheimer's patients appear to exhibit numerous defects in iron storage, binding, and mobilization not seen in the brains of healthy control participants.⁴² Evidence of the role of these ions in Alzheimer's disease is partly confirmed by previous studies^43,44 and more recent investigations⁴⁵ revealed improvement in Alzheimer's patients treated with chelating agents that remove excess aluminum, iron, and copper.

Moderate Alcohol Consumption

Although alcohol intake as low as 20 grams per day (1.25 servings) is a known risk factor for certain cancers, hypertension, and several other diseases,⁴⁶ recent studies show that people who consume 1 to 3 drinks per day have a lower risk for Alzheimer's disease, compared with teetotalers.⁴⁷ In most of these studies, risk reduction was associated with wine and not alcohol per se,¹⁸ and a cause-and-effect relationship has not been established. Benefits of moderate alcohol consumption, if any, are thought to derive from alterations in blood lipids, platelet aggregation, and antioxidant flavonoids present in red wine.

Orders

See Basic Diet Orders.

Physical and occupational therapy consultation for home safety evaluation and needs assessment.

What to Tell the Family

Although no cure for Alzheimer's disease is known, drug treatment may slow progression. Additionally, behavioral changes that include mental and physical exercise may help slow the disease process. A diet low in saturated fat, cholesterol, and trans fatty acids will help prevent other age-related debilitating diseases in the patient. This diet is also ideal for the general health of the whole family, and may help prevent the occurrence of Alzheimer's in family members. Safety precautions for Alzheimer's patients are important at all times. Connection with social services or a support group may also help ease the burden of care for a person with Alzheimer's disease. Family members may desire to be tested for the presence of the apo E e4 allele; at minimum, they should be encouraged to mitigate their future risk of Alzheimer's by noting the above recommendations.