A major study was just published in the Annals of Internal Medicine from Harvard. In approximately 85,000 women who were followed for 26 years and 45,000 men who were followed for 20 years, researchers found that all-cause mortality rates were increased in both men and women who were eating a low-carbohydrate Atkins diet based on animal protein.

However, all-cause mortality rates as well as cardiovascular mortality rates were decreased in those eating a plant-based diet low in animal protein and low in refined carbohydrates. Although this plant-based diet was called an "Eco-Atkins" diet, it's essentially the same diet that I have been recommending and studying for more than 30 years.

In many debates with Dr. Atkins before he died, I always made the point that it's important to look at actual measures of disease, including mortality, not just risk factors such as HDL cholesterol. This is the first study that examined mortality rates in those consuming an Atkins diet, and it confirms what I've been saying all along: an Atkins diet is not healthful and may shorten your lifespan.

Dr. Atkins and I agreed that the American diet is too high in refined carbohydrates such as sugar, white flour and concentrated sweeteners) which promote a variety of chronic diseases. That's why people often lose weight on an Atkins diet when they restrict their intake of refined carbohydrates.

However, the answer is not to replace refined carbohydrates with animal protein such as beef, pork rinds, bacon and sausage, which Dr. Atkins claimed were good for your heart. I'd like to be able to say that they're good for your heart, but they are not. It's much more healthful to replace refined carbohydrates ("bad carbs") with healthy carbs instead.

It's not low-fat vs. low-carb. An optimal diet is high in healthy carbs such as fruits and vegetables and whole grains (including whole wheat, brown rice), legumes, soy products, nonfat dairy and egg whites in their natural forms and some good fats such as the omega 3 fatty acids found in fish oil and salmon. It's low in unhealthy carbs such as sugar, white flour, white rice, white flour pasta and low in saturated fats and animal protein.

The message that many studies -- including one in the Annals last month -- have been giving the public and health professionals is that the Atkins diet is no worse for your heart than a plant-based diet, but all these studies examined only risk factors such as HDL, not measures of disease or mortality. That's why this new study is so important. (The Annals recently published my letter to the editor that expressed these concerns, which I appreciate.)

A recent study reviewed in The New England Journal of Medicine found that an Atkins-type diet "promotes atherosclerosis (heart disease) through mechanisms that do not modify the classic cardiovascular risk factors" such as HDL. Other studies also showed this.

Your body makes HDL to remove excessive cholesterol from your body. Eating a stick of butter will raise HDL, but butter is not good for your heart. Pfizer discontinued a study of its drug, torcetrapib, which raised HDL but actually increased risk of heart attacks.

Conversely, a whole foods plant-based diet that's also low in refined carbohydrates may reverse coronary heart disease and beneficially affect the progression of prostate cancer and even improve gene expression despite reductions in HDL.

Finally, what's good for you is also good for our planet. Livestock consumption causes more global warming than all forms of transportation combined. It takes 10 times more energy to produce animal-based protein than plant-based protein.

It's not all or nothing. You have a spectrum of choices. What matters most is your overall way of eating and living. If you indulge yourself one day, eat healthier the next. To the degree that you move in a whole foods, plant-based direction, the better you're likely to feel and the healthier you're likely to become.

Dean Ornish, M.D.

Medical Editor, The Huffington Post

Founder and President, Preventive Medicine Research Institute

Clinical Professor of Medicine, University of California, San Francisco

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www.pmri.org