Everyone has so-called "senior moments." As people age, it's normal for them to forget a phrase or the names of people they seldom see; however, problems recalling the names of good friends and family members signal a serious problem. Alzheimer's disease—a progressive brain disease and the most common form of dementia, accounting for 50 percent to 70 percent of cases1—starts with seemingly harmless memory slips. As the condition progresses, sufferers have trouble learning new tasks, and their behavior and personality change. As daily living becomes increasingly difficult, Alzheimer's patients become dependent on others for care, which makes them prone to additional health complications, such as pneumonia, infections and falls.2,3
The Alzheimer's Foundation estimates that 5.1 million Americans have Alzheimer's disease, and an estimated 11 million to 16 million will be affected by 2050.4 The causes of Alzheimer's are poorly understood—age, genes and lifestyle all play a role.3 Stress may hasten the condition.5
The end result in all cases is damaged or dead neurons, perhaps in the form of tangles, which form inside dying neurons, or as plaques, made when tiny proteins called beta-amyloids overproduce and build up between neurons.2,3,4 Often, the brain tissue of Alzheimer's patients is inflamed and shows signs of oxidative stress.4
Research shows that once diagnosed, people with Alzheimer's survive about half as long as those of similar age in the U.S. population (for example, a 70-year-old woman recently diagnosed with Alzheimer's is expected to live eight more years, while a 70-year-old woman without Alzheimer's may live 15.7 more years).
A study of 521 men and women, age 60 years and older, investigated the effects of 11 variables on life expectancy after Alzheimer's diagnosis. Researchers found that gender, age when diagnosed, severity of symptoms when diagnosed, presence of gait disturbance, wandering, diabetes and history of congestive heart failure all were significant in determining life expectancy after diagnosis. In addition, women with Alzheimer's were found to live significantly longer after diagnosis than men with Alzheimer's.6
Because Alzheimer's symptoms progress slowly and may be dismissed in the earliest stages, diagnosis often comes late.2 Because Alzheimer's is still incurable3, prevention may be the best defense. Although research is ongoing and not altogether conclusive, a number of foods, herbs and supplements show promise for fending off the condition. A word of caution, however: Many of the studies are observational, rather than controlled experiments, so their results must be interpreted carefully.
The traditional Mediterranean diet—loaded with fruits, vegetables and legumes with a bit of fish, olive oil and wine—has long been studied for its heart-protective attributes.7,8,9 Now it's being studied as a helpful dietary pattern for Alzheimer's prevention and treatment.
The Mediterranean diet first earned Alzheimer's-prevention acclaim in a 2006 study of 2,258 New Yorkers. Those who adhered most closely to a Mediterranean diet during a four-year period reduced their risk for Alzheimer's disease.10 To confirm these findings, Columbia University researchers repeated the trial on 1,984 New Yorkers who had Alzheimer's or were at risk for the disease. The average age of participants was 76, and about one in 10 had an Alzheimer's diagnosis. Similar to the previous study, eating a Mediterranean diet was associated with a 42 percent to 68 percent lower risk for Alzheimer's disease.11 Mounting evidence suggests that because oxidative damage could lead to Alzheimer's,12,13 the antioxidants found in many Mediterranean diet foods—olive oil, fruits and vegetables, and wine—may explain the diet's anti-Alzheimer's effect.11
Additionally, scientists are finding that the Mediterranean diet may increase survival rates among Alzheimer's patients. A study published last year followed 192 Alzheimer's patients for 4.5 years. During that time, 85 of the participants died. Researchers found that participants who most conformed to a Mediterranean diet were 76 percent less likely to die during the study period.14 However, more research is needed to determine if the Mediterranean diet also enhances quality of life for Alzheimer's patients.
Vitamins E and C. One observational study evaluated the diets of 5,395 nondemented people age 55 or older. After six years, researchers discovered that higher intakes of vitamins E and C were associated with a lower risk of Alzheimer's disease; however, only a small number of participants reported supplements use, and dosages were unknown. 20
A four-year study of 980 nondemented subjects, age 65 or older, revealed that neither dietary nor supplemental intake of vitamins C and E decreased Alzheimer's risk.23 But the finding could have been the result of an imprecise food-frequency questionnaire. The questionnaire, used to assess vitamin C and E intake for one year, didn't account for day-to-day variation or longer-term intakes.23
In an observational study, from 1995 to 1997, researchers asked 4,740 Cache County, Utah, residents age 65 or older about their supplements use, and followed up from 1998 to 2000. Researchers concluded that a combination of vitamins E and C reduced the prevalence of Alzheimer's disease by 78 percent and its incidence by 64 percent.24 Incidence refers to the rate at which people develop new cases of a disease in a given time frame. Prevalence is the number of people who already have the disease. No effect was found with vitamin E alone, with vitamin C alone, with multivitamins or with B-complex supplements.24
Food sources of vitamin E may still have a place in Alzheimer's prevention. A prospective study of 815 nondemented people 65 years or older, conducted from 1993 to 2000, found that vitamin E from food (but not other antioxidants) was associated with reduced Alzheimer's risk. The preventive effect only appeared among participants who didn't have APOE epsilon 4 allele—one of the major lipid-transport proteins in the brain that has been associated with increased Alzheimer's risk among white study participants, though not among blacks. Study authors theorized that vitamin E may not be able to overcome the deleterious effects of APOE. 25
When supplementing with vitamin E alone, starting early may determine whether treatment is successful. In an animal study, researchers found that when they gave vitamin E to young mice without telltale plaques, the mice's levels of amyloid proteins decreased by half compared with older mice also given vitamin E.26
Green tea. Research on green tea is promising, but more studies are needed. In one study, mice treated with epigallocatechin-3-gallate, the main polyphenol in green tea, had reduced amyloid plaques.27
An observational study of 1,003 Japanese subjects age 70 or older showed that the more green tea they drank, the lower the prevalence of cognitive impairment.28 Black or oolong tea and coffee had little effect on cognitive function in this study,28 but other in vivo research found black tea almost as effective as green at stopping chemicals known to create Alzheimer's plaques and tangles.29 Green tea blocked all three chemicals—acetylcholinesterase, butyrylcholinesterase and beta-secretase—whereas black tea blocked only the first two.29
Omega-3 fatty acids
Omega-3 fatty acids are crucial for healthy brain growth and development. Studies have linked dietary intake of fish, which has high levels of omega-3s, to Alzheimer's prevention. In 1997, researchers evaluated the food intakes of 5,386 nondemented participants, age 55 and older. After 2.1 years, researchers screened participants for dementia and found that fish consumption was inversely related to dementia onset, but that total fat, saturated fat and cholesterol consumption increased dementia risk.15
A later study followed 1,674 French men and women age 68 and older without dementia. After seven years, those who ate fish or seafood at least once a week had a lower risk of developing many forms of dementia, including Alzheimer's.16 In another study that occurred from 1993 to 2000, scientists observed 815 people, age 65 to 94, who initially didn't have Alzheimer's. Participants who consumed fish at least once a week decreased their risk for Alzheimer's by 60 percent.17
Other scientists are also exploring how fish consumption prevents dementia. The theory is that fatty acids in fish—in particular DHA and, to a lesser extent, EPA—can reduce brain inflammation and slow the accumulation of proteins that lead to the brain-clogging plaques and tangles.16,18 In a 2007 study, mice fed diets rich in DHA for three months had less accumulation of beta-amyloid and tau proteins associated with brain cell decline and death.19 Now, human clinical studies are needed to determine if and how omega-3 fatty acids ward off Alzheimer's disease.
Other studies suggest omega-3s may not only prevent, but may also treat, very mild Alzheimer's. In a randomized, double-blind, placebo-controlled clinical trial that involved 174 Alzheimer's patients, half of the participants took omega-3 fatty acid supplements (1.7 g of DHA and 0.6 g of EPA), and the other half took placebos for six months. At the end of those six months, all participants took omega-3 supplements for six more months. Results showed no difference in the rate of mental decline between the treatment and control groups; however, a subgroup with very mild Alzheimer's lost fewer cognitive skills (as measured by the Mini-Mental State Examination and the cognitive portion of the Alzheimer Disease Assessment Scale) when they took the omega-3 fatty acid supplements.18 Studies on mice show similar results for Alzheimer's treatment.19,20,21
Vitamin B (folic acid and B-12)
People with Alzheimer's may have decreased levels of folic acid (B-9) and vitamin B-12, but it's unknown whether supplementation with these nutrients helps prevent or treat the disease. Researchers speculate that folate and B-12 may play a role in Alzheimer's because both nutrients help clear homocysteine—an amino acid correlated with heart disease, but which may also contribute to Alzheimer's—from the blood.30 Several studies measured folate and B-12 blood levels in humans and found that people with lower levels of these nutrients had an increased risk of developing Alzheimer's disease.31,32,33,34 However, other researchers found the converse to be true. They measured actual dietary intakes of folate and B-12 in 1,041 people age 65 and older who didn't have Alzheimer's at the start of the study. About four years later, the incidence of Alzheimer's was no lower in those who took the vitamins. Clinical trials are needed to determine whether B vitamins have any merit in Alzheimer's prevention or treatment.
Ginkgo (Ginkgo biloba)
Ginkgo is one of the best-researched and perhaps most controversial dementia treatments. It is widely used in Europe because of its ability to improve blood flow to the brain and its antioxidant properties.36 Clinical studies detailing its effect on dementia, however, are inconsistent.
One of the first large-scale clinical trials (double-blind, randomized, placebo- controlled) that tested the efficacy of ginkgo on the cognitive function of older adults was published in 2002. The study involved 262 male and female participants 60 years or older who had no history of dementia. Participants received either Ginkgo biloba extract EGb 761 (180 mg a day) or a placebo for six weeks. Using a battery of neuropsychological tests, researchers found that the ginkgo-takers had improved memory, though results were statistically significant on only three of 13 tests.37
Another six-week randomized, double- blind, placebo-controlled ginkgo study showed no effect on cognition. Among 203 participants older than 60, those who took 40 mg of ginkgo three times a day did no better on neuropsychological tests of learning, memory, attention and concentration, or naming and verbal fluency, than did the placebo group.38 Later, other researchers criticized this study for design flaws.39
A longer study (24 weeks) of 123 elderly participants with dementia showed similar results. Ginkgo (either 240 mg per day or 160 mg per day) did not significantly affect memory impairment.40 A later trial of 513 Alzheimer's outpatients who took either 120 mg per day or 240 mg per day of ginkgo or a placebo also did not detect a treatment effect.41
The future of Alzheimer's
Alzheimer's disease remains a mysterious condition; it lacks an irrefutable cause, let alone treatment. Both human and animal studies have begun to shed light on the potential of foods, supplements and herbs for Alzheimer's prevention and treatment, but more clinical trials are needed to back them up. In the meantime, consumers can eat foods and take supplements that defend against heart disease and cancer; so far, these seem the most helpful for preventing and treating Alzheimer's disease as well.
Pamela Bond is an Eldorado Springs, Colo.-based freelance writer.
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