If you want to live longer -- avoid heart disease, Alzheimer's disease and cancer -- then pick and choose your foods with care to quiet down parts of your immune system.
That's the principle promoted by the founders and followers of anti-inflammatory diets, designed to reduce chronic inflammation in the body.
Dozens of books filled with diets and recipes have flooded the market in the last few years, including popular ones by dermatologist Dr. Nicholas Perricone and Zone Diet creator Barry Sears.
Those who frequent message boards that discuss arthritis or acne trade tips on which pro- or anti-inflammatory foods may help or trigger their symptoms -- urging co-sufferers to try cherries for their rheumatoid arthritis or avoid gluten for their psoriasis.
But proponents claim the benefits go far beyond that, fighting not just pain from inflamed joints or skin flare-ups but also life-threatening diseases.
"If your future currently looks bleak because of high levels of silent inflammation, don't worry, because you can change it within thirty days," Barry Sears promises in his book, "The Anti-Inflammation Zone."
There's still a lot of science to be done. And should you try such a diet, you probably shouldn't expect any 30-day miracles. But there may be something to eating in an anti-inflammatory way.
"[Chronic inflammation] is an emerging field," says Dr. David Heber, a UCLA professor of medicine and director of the university's Center for Human Nutrition. "It's a new concept for medicine."
The point of an anti-inflammation diet is not to lose weight, although it is not uncommon for its followers to shed pounds. The goal: to combat what proponents call "chronic silent inflammation" in the body, the result of an immune system that doesn't know when to shut off.
The theory goes that long after the invading bacteria or viruses from some infection are gone, the body's defenses remain active. The activated immune cells and hormones then turn on the body itself, damaging tissues. The process continues indefinitely, occurring at low enough levels that a person doesn't feel pain or realize anything is wrong. Years later, proponents say, the damage contributes to illnesses such as heart disease, neurological disorders like Alzheimer's disease or cancer.
In general terms, following an anti-inflammatory diet means increasing intake of foods that have anti-inflammatory and antioxidant properties. (Antioxidants reduce the activity of tissue-damaging free radicals at sites of inflammation.) The diet includes vegetables, whole grains, nuts, oily fish, protein sources, spices such as ginger and turmeric and brightly colored fruits such as blueberries, cherries and pomegranates.
Foods that promote inflammation -- saturated fats, trans fats, corn and soybean oil, refined carbohydrates, sugars, red meat and dairy -- are reduced or eliminated.
It would seem logical that a diet that could dampen an overactive immune system could help prevent or slow diseases that are caused or exacerbated by inflammation. And evidence is certainly mounting that such diseases include heart disease, cancer and Alzheimer's. (See related story online.)
Studies with animals suggest that the diet's followers may be on to something.
"If you feed rodents different diets, you can very strongly modulate inflammation," says Dr. Andrew Greenberg, the director of the Obesity and Metabolism Laboratory at the Human Nutrition Research Center on Aging at Tufts University in Boston. "Fish oil, for example, ameliorates inflammation in rodents."
Resveratrol, found in grape skin and red wine, has been shown to improve blood vessel function and slow aging in rats.
Pomegranate juice decreases atherosclerosis development in mice with high cholesterol. Garlic improves blood vessel functioning in the hearts of rats with high blood pressure.
And curcumin (an antioxidant chemical found in turmeric) improves ulcerative colitis, rheumatoid arthritis and pancreatitis in mice and has anti-cancer effects in the animals too.
Curcumin has also been shown to ease the symptoms of rheumatoid arthritis in people, reducing joint swelling, morning stiffness and walking time. In India, turmeric is used to promote wound healing and reduce inflammation. But though curcumin's effects are being tested in several clinical trials addressing various diseases, rigorous human results are lacking -- as is the case for most anti-inflammatory foods.
Large, careful human clinical trials are expensive and few have been designed to test dietary interventions. Small trials on individual supplements have been done, though. And scientists have learned a lot from studying populations -- chronicling the natural habits of people and seeing what diseases they get and which they don't.
The drug factor
It makes sense that anti-inflammatory diets might help the heart, says Dr. Robert H. Eckel, a past president of the American Heart Assn. and professor of physiology and biophysics at University of Colorado Denver's Health Sciences Center.