Researchers go fishing for answers to Alzheimer's
by Craig Weatherby
On November 25, 1901, Dr. Alois Alzheimer began seeing a new patient known as Auguste D. (shown in photo). At only 51, she couldn't remember her entire name, or how long she had been in the hospital. Dr. Alzheimer asked her to write her name. She failed several times before she looked up, exasperated, and declared, "I have lost myself"—an apt description of the fate that had befallen her. After Auguste D.'s death, the pioneering German physician discovered plaques and tangles covering her brain, and the term "Alzheimer's disease" entered the medical lexicon.
November was Alzheimer's Month, so it’s a good time to revisit the role of diet in this devastating disease. New research puts fish at the forefront of efforts to understand and prevent this and other forms of senile dementia.
According to a recent report in “USA Today,” “Fish is becoming to Alzheimer's candidates what the aspirin-a-day regimen is to many heart patients.” And, as the article went on to say, there's fresh evidence that fish is potent, brain-saving food: “Population studies already indicate that people who frequently eat fish may protect themselves from Alzheimer's.”
Of mice and mental function
The USA Today story highlighted a study by medical researchers at the University of California, who say that DHA—one of the two omega-3 fatty acids in fish—showed dramatic memory-protective effects in mice. Better yet, the UCLA study also revealed some of the mechanisms by which DHA slows and even reverses the physiological and behavioral signs of dementia conditions such as Alzheimer's Disease.
The UCLA team studied mice with genetic mutations that produce an Alzheimer's-like condition. One group ate a diet without adequate DHA, and a second group received DHA-enriched food. After five months, they put the mice to a memory test, which the high-DHA group mice passed most of the time, and the low-DHA mice flunked consistently. These low-DHA mice also showed signs of the brain damage seen in people with advanced Alzheimer’s.
The low-DHA mice suffered a loss of key brain communication chemicals, and increased levels of oxidative damage to brain tissues. These negative effects vanished when low-DHA mice were given more DHA: a dietary change that also promoted a biochemical process (phosphorylation) that protects against brain cell death. As the researchers concluded, “…these findings have implications for neurodegenerative diseases… especially AD [Alzheimer's Disease].
American diet poses heart and dementia dangers
Researchers put much of the blame for the current epidemics of Alzheimer’s, heart disease, and diabetes on the standard American diet, and its preponderance of processed foods high in refined carbohydrates (sugars and starches) and hydrogenated fats, which are high in harmful trans fats. This is because these bad dietary actors promote three key causes of all three diseases: insulin resistance, oxidation of blood lipids, and silent, systemic inflammation.
Current research indicates that the very high fat and refined carbohydrate intake characteristic of the standard American diet is unhealthful—in part because this excess translates into a high calorie intake, and promotes insulin resistance: two major risk factors for diabetes and heart disease. (Gram for gram, fat contains more than double the calories—nine per gram versus four per gram—contained in carbohydrates or protein.) In addition, the relative proportions of fats in the standard American diet are imbalanced: most Americans eat too much omega-6 unsaturated fat, too little omega-3 unsaturated fat, and too much hydrogenated (artificially saturated) fat.
This is not to say that the saturated fats that occur naturally in meats and dairy foods promote cardiovascular disease and Alzheimer’s. Instead, it’s a matter of moderation.
Help stop senility: eat fish everyday for protective DHA
Two recent literature reviews summarized the implications of research into the links between dietary fats and the risk of cardiovascular—and Alzheimer’s—disease (my notes are in brackets):
Rates of Alzheimer's are far lower in countries where most people’s diets are both low in fat—compared with the very high amounts in the American diet—and high in fish. In other words, their diets offer moderate amounts of fat, and a higher ratio of omega-3 fats to omega-6 fats and saturated fats.
- “The available evidence suggests that IRS [insulin resistance], and therefore diabetes and cardiovascular disease [and Alzheimer’s], can be prevented by a high fiber/low glycemic index diet [i.e., one low in refined carbohydrates] containing dairy products and a higher amount of unsaturated fats than currently recommended.”
- “…a diet low in saturated and trans-fatty acids, with adequate amounts of monounsaturated and polyunsaturated fatty acids, especially long-chain omega-3 fatty acids, would be recommended to reduce the risk of developing CHD [and Alzheimer’s].”
Scientists trace the protective powers of fish to omega-3 fatty acids, which are most abundant oily fish such as salmon, sardines, herring, tuna or mackerel. Fish is the richest food source of DHA, the omega-3 most closely associated with learning, memory and overall brain cell function, but most American’s diets are low in DHA. As Dr. Sally Frautschy of the UCLA research team told USA Today: "Unless you're eating fish every day, you're not getting enough DHA."
A DHA deficit is no joke for the millions of aging baby boomers. Results of the Framingham Dementia Study found that people with the highest blood levels of DHA enjoy only half the risk of developing all forms of dementia, including Alzheimer's. Only people who ate fish two to three times a week enjoyed high levels of DHA and low rates of Alzheimer's.
Fruits, veggies, and fish: healthy foods discourage dementia
It’s not hard to decrease the risk of senile dementia: the group of degenerative brain conditions that range from Age-Related Cognitive Decline to Alzheimer’s. In fact, it’s easy to kill three birds with one dietary stone, since the same foods and lifestyle factors can reduce the risk of heart disease, diabetes, and dementia. Like the heart, the brain needs good nutrition, as well as physical and mental exercise.
One long-term study found that adults who are obese in middle age are twice as likely to develop dementia, while those who also had high cholesterol and high blood pressure suffered six times the risk of dementia. Studies have also shown that high intake of saturated fat and LDL (“bad”) cholesterol—both concentrated in dairy foods and red meats—tends to clog arteries and raise the risk of Alzheimer’s.
As the Alzheimer's Association says, “Cold water fish contain beneficial omega-3 fatty acids: halibut, mackerel, salmon, trout and tuna” (Note: Our new Vital Choice sablefish has even more omega-3s than salmon).
The Alzheimer's Association also recommends high-antioxidant, high-fiber plant foods, which are known to protect against oxidation and hardening of the arteries—the two processes most closely associated with dementia, cardiovascular disease, and diabetes:
Nuts (especially walnuts) contain substantial amounts of omega-3 fatty acids—albeit in a less beneficial “short-chain” form—and some (especially cashews) are a good source of vitamin E, which is a potent antioxidant.
- Protective vegetables include onions, garlic, kale, spinach, Brussels sprouts, beans, red cabbage, alfalfa sprouts, broccoli, beets, chilies, and red-orange-yellow bell peppers.
- Protective fruits include blueberries, strawberries, raspberries, blackberries, cranberries, pomegranates, red grapes, and cherries. (Note: Prunes, plums, and raisins are high in antioxidants, but they’re also extraordinarily high in sugar, which is pro-inflammatory and promotes aging. Berries offer a preferable ratio of antioxidants to sugar, and blueberries were recently ranked as the highest in antioxidant capacity among all common fruits.)
- Calon F, Lim GP, Yang F, Morihara T, Teter B, Ubeda O, Rostaing P, Triller A, Salem N Jr, Ashe KH, Frautschy SA, Cole GM. Docosahexaenoic acid protects from dendritic pathology in an Alzheimer's disease mouse model. Neuron. 2004 Sep 2;43(5):633-45.
- Fackelmann K. “Fishing for answers to Alzheimer's.” USA TODAY, http://www.usatoday.com/news/health/2004-11-16-fish-alzheimers_x.htm. Accessed 11/16/04.
- Lichtenstein AH. Dietary fat and cardiovascular disease risk: quantity or quality? J Womens Health (Larchmt). 2003 Mar;12(2):109-14. Review.
- Ludwig DS. Diet and development of the insulin resistance syndrome. Asia Pac J Clin Nutr. 2003;12 Suppl:S4.
- Morris MC, Evans DA, Bienias JL, Tangney CC, Bennett DA, Wilson RS, Aggarwal N, Schneider J. Consumption of fish and n-3 fatty acids and risk of incident Alzheimer disease. Arch Neurol. 2003 Jul;60(7):940-6.
- Schaefer EJ, et al.Plasma Phosphatidylcholine (PC) Docosahexaenoic Acid (DHA), Fish Intake and Risk of Dementia. American Heart Association Scientific Sessions 2003. November 9-12 2003, Orlando Florida. Moderated Poster Sessions, APS.94.4M. Novel Environmental, Personal and Pharmacologic Risk Factors.
- Wijendran V, Hayes KC. Dietary n-6 and n-3 fatty acid balance and cardiovascular health. Annu Rev Nutr. 2004;24:597-615. Review.