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Authors have their theories

Acai berries, green tea, soy, olive oil and sweet potatoes have all been hyped for their life-prolonging potential. Diets rich in vegetables, fruits and grains, and low on meat may help prevent chronic disease. But so far there’s only one dietary approach shown to lengthen life span: eating less. Of course, a dearth of firm data hasn’t stopped doctors, scientists and nutritional dilettantes from penning anti-aging diet books. Here are a few of them.

The Longevity Factor

How Resveratrol and Red Wine Activate Genes for a Longer and Healthier Life

Joseph Maroon

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Atria, 2009

Dr. Maroon, professor of neurological surgery at the University of Pittsburgh and neurosurgeon to the Pittsburgh Steelers, says the key to living longer (or one such key) is resveratrol, a potent antioxidant in red wine.

Resveratrol is one of a class of compounds that Maroon refers to as xeno factors, chemicals that plants produce under stressful conditions, such as drought or harsh sun. In plants, xeno factors trigger survival genes that help fight infections and other hazards. Studies show that when lab animals consume plant xeno factors, the chemicals activate the animals’ own survival genes and enable them to live up to 50% longer than animals on normal diets. Scientists studying this hypothesis speculate that xeno factors may activate genes that delay aging in any life form.

Maroon cites many studies supporting the life-extending capabilities of the xeno factor resveratrol: fish fed resveratrol live 60% longer; worms and flies 30% longer; mice, 25% longer. Other lab studies suggest how resveratrol may do this: In rats and mice the chemical appears to help regulate blood sugar, prevent platelets from aggregating in blood vessels, slow the growth of cancer cells, reduce brain damage and decrease the death rate following heart attack. In many ways, the chemical’s effects mirror that of calorie restriction.

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Maroon does not recommend that people ingest resveratrol any way they can to lengthen life span. Instead, he advises eating foods and drinks with high levels of xeno factors -- red wine, green tea, grape juice, dark chocolate and apples -- as part of a heavily plant-based diet, rich in whole grains, low in saturated fats.

Maroon also strongly advocates resveratrol supplements and “resveratrol-like” prescription drugs (none of the latter is on the market yet). But his confident and enthusiastic endorsement of resveratrol is based on research conducted mostly on animals and in test tubes. Relatively little human research has been performed to date. Though existing research suggests the chemical may improve cardiovascular health, none has yet shown it helps prolong life in people.

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The Younger (Thinner) You Diet

How Understanding Your Brain Chemistry Can Help You Lose Weight, Reverse Aging, and Fight Disease

Eric Braverman

Rodale, 2009

The “Younger (Thinner) You Diet” is based on the premise that body weight and aging are tightly bound. “Your excess weight is your aging brain’s cry for help,” writes Dr. Braverman, who runs a private practice (the Place for Achieving Total Health, or PATH) in New York and is clinical professor of integrative medicine at Weill Cornell Medical College. The aging brain he describes is characterized by low levels of the key nerve cell-signaling chemicals dopamine, acetylcholine, GABA and serotonin, deficiencies he asserts can be remedied with the right foods.

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The book is packed with meal plans, shopping lists and recipes for boosting blood chemicals: acetylcholine-boosting frittata, dopamine-boosting scrambled eggs, GABA-boosting salad, serotonin-boosting tofu and total-brain-chemical-boosting lamb tagine. The dishes don’t include the chemicals themselves but the building blocks needed to make them, such as the amino acids phenylalanine and tyrosine, precursors to dopamine; and choline, the B vitamin from which acetylcholine is made.

Braverman also provides advice on how to reverse what he refers to as the “pauses,” the physiological changes associated with the aging of the body’s organs. To make an aging heart younger, he recommends low-sodium, high-fiber foods, complex carbohydrates and foods that provide omega-3 fats. For osteopause he advises foods rich in calcium; for menopause, foods high in vitamin D.

Overall, Braverman recommends a high-protein, high-fiber, low-fat diet packed with foods rich in vitamins, minerals and antioxidants. He prescribes tea, spices with every meal, yogurt and whole grains.

This is all fairly sound dietary advice, but the justifications are sometimes slim: He promotes nutmeg as an antidepressant, for example, although the only evidence for the claim comes from a single study in mice.

As for Braverman’s claims about brain chemistry, scientists in the 1970s and 1980s began to demonstrate a link between diet and brain neurotransmitter levels. Since then, researchers have, in fact, shown that levels of brain chemicals, such as dopamine, can become depleted with age; they’ve also linked obesity with deficiencies in certain brain chemicals. Braverman cites such studies, but for proof that his regimen works he points to the successes of his patients, whose cases are reported throughout the book. With supposedly brain-chemical-boosting dietary changes and exercise plans, the profiled patients reportedly shed pounds, gained energy and improved their life outlook. But these stories are case reports, not formal scientific studies. Whether people improved because of better brain chemistry, and whether they’ll live longer as a result, is any scientist’s guess.

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The Anti-Aging Zone

Barry Sears

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Regan Books, 1999

This decade-old book continues to attract followers. Sears first unveiled the Zone Diet -- a dietary approach to fighting heart disease and diabetes by optimizing hormone levels -- in his 1996 book “The Zone.” In “The Anti-Aging Zone,” Sears, a biochemist now widely known for his diet books, explains why the Zone Diet may be able to prolong life.

The diet is low in carbs and calories. Sears advises people to consume 40% fewer calories than normal: 1,200 a day for women and 1,500 for men. He says that the diet is calibrated to prevent hunger, malnutrition and declines in mental and physical performance. It’s high in protein, rich in vitamins and minerals, low on starches and grains, and stresses low-glycemic vegetables and mono-unsaturated fats.

In “The Anti-Aging Zone,” Sears attributes aging to excesses of insulin, blood glucose, free radicals and cortisol. The Zone Diet aims to keep levels of all four within a “zone”: not too high and not too low. He advocates small meals and snacks throughout the day to help control insulin and blood glucose; reducing calories to cut consumption of free radicals; and lifestyle changes to control the stress that can stimulate cortisol production.

On a typical day, a Zone Dieter may eat a vegetable cheese omelet for breakfast, steak and vegetables for lunch, chicken and vegetables for dinner, and snack on ham-wrapped apple slices, wine and cheese. Moderate exercise helps keep insulin and blood glucose low, and meditation helps balance cortisol. Stick with it, Sears writes, and blood sugar will normalize, blood lipid levels will fall, stress and depression will diminish, and sexual function will return.

Some of Sears’ claims are supported by clinical trials. When patients with Type 2 diabetes go on Zone-like diets, for example, their blood sugar and blood lipid levels have fallen. But a good fraction of the claims are theoretical. Nutrition experts have criticized Sears’ basic premise -- that diet can control such a broad spectrum of hormones. And some finer details don’t hold up to scientific scrutiny. There’s no proof, for example, that the Zone Diet can improve skin tone by promoting collagen synthesis. And though it’s true that consuming fewer calories can prolong life in various animals, the effect has yet to be demonstrated in people.

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Aging Fight It With the Blood Type Diet

Peter D’Adamo

Berkley Books, 2005

Naturopath Peter D’Adamo’s first bestseller, “Eat Right 4 Your Type” (1996) introduced the idea that a person’s blood type determines his or her dietary needs. In “Aging: Fight It with the Blood Type Diet,” D’Adamo tailors the diet for those who want to stay physically healthy and mentally sharp into their old age.

The blood-type diet is based on the notion that people with different blood types share physiological characteristics: People of type O are purportedly prone to inflammatory diseases, whereas people of type A are deemed prone to free radical damage. Diets are prescribed based on these supposed vulnerabilities.

But first and foremost, each type’s dietary recommendations are based on D’Adamo’s theory that people should eat foods containing proteins that match the shape of the antigens, or proteins, on their blood cells. The details of this theory aren’t replicated in the book (D’Adamo refers to his earlier works), but people with type O are advised to eat a high protein diet, those with type A to eat vegetarian, type Bs to avoid chicken and corn, and type ABs to eat a mix of meats and vegetables.

D’Adamo recommends four more approaches: consuming “brain foods” and probiotics, taking supplements and exercising -- all, again, based on blood type. Blood type B’s top “brain power super food” is lean, organic, grass-fed red meat; type A’s is the walnut. Aerobic exercise and weight lifting are recommended for type Os, yoga and tai chi for type As. The bulk of D’Adamo’s book consists of tables and charts listing foods, supplements and exercises for each type, and ones to avoid.

Conspicuously absent from the book is an equally exhaustive list of sources or references to buttress his theories. He cites a handful of studies to make the claim that diet, exercise and lifestyle can keep brain and body healthy. But as he moves into the chapters detailing plans for each type, scientific references are slim.

Some research has linked blood type to susceptibility to diseases such as cholera, smallpox and malaria. But to date, there’s no good evidence that tailoring diet to blood type can prevent disease, or prolong health into old age.

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health@latimes.com


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