Modest Dietary Changes

The recommendation for a low-fat diet took a big hit in February when JAMA published three articles from the large Women’s Health Initiative (WHI) randomized controlled trials, which reported that a “low-fat dietary pattern” did not help in preventing cardiovascular disease, breast cancer, or colon cancer (1, 2, 3). Lovers of French fries and cheesecake rejoiced that they could return to enjoying them without health consequences. Another staple of physician recommendations went by the wayside. What are people to believe from recommendations for good health?

The media spin on these studies may have done as much damage to the health of Americans as the opening of another chain of fast food restaurants. It seems that whenever new information comes out, all previous work is either forgotten or disregarded. What about the incredible angiographic data from the 1980s that atherosclerosis could actually be reversed by a very low-fat diet (4)? If only we would reconcile new research with the body of knowledge already accumulated. The JAMA editorial in the same issue did that, but unfortunately the attention of the media did not go that far.

What is actually learned from analyzing the WHI studies is that modest dietary changes accomplished by this large group of women were of little benefit in preventing heart disease and cancer. These postmenopausal women (read already existing atherosclerosis) were on a 39 percent fat diet at baseline — 9 percent more than even the most conservative recommendations. While they did pretty well the first year, after eight years the intervention group only achieved a 27 percent fat diet. Using “low fat” to describe this percentage is a travesty to the most important dietary recommendation. Moreover, the intervention group only reduced their saturated fat intake by 2–3 percent.

Robert Powell, a former, tenured UCSD professor, described the lunacy of these studies by comparing them with a smoker reducing from 39 to 27 cigarettes a day and expecting benefit, or an alcoholic reducing from 39 to 27 ounces of liquor a day and expecting benefit. To be fair, these studies were worth publishing, and learning that modest changes in dietary fat were of little if any benefit is worthwhile information. However, as a medical profession and as a society, the lessons here are that major changes in lifestyle, especially diet, are needed to improve health and that negative studies are often distorted by the media.

Another interpretation of the WHI dietary studies is that diet probably does not have a major role in breast or colon cancer. We have already learned that increasing dietary fiber did not prevent colon cancer. Cancer happens, and genes, along with some viruses, certainly play a role. With respect to heart disease, once the atherosclerotic process has begun, most physician experts will say use statins or other “miracles” of modern pharmacology to achieve benefit. While I will not argue with this perspective, I cannot let these studies go without defending the benefits of the real, low-fat diet.

Dean Ornish deservedly gets the most credit today for advocating the low-fat diet. His elegant studies in the 1980s demonstrated angiographically for the first time that atherosclerosis and active coronary artery disease could be reversed with a low-fat diet. He articulated two diets based on this work: a reversal and a prevention diet. To reverse heart disease, a 10 percent fat diet was necessary. To prevent the development or progression of atherosclerosis, a 20 percent-or-less diet was necessary (4). Credit should be given to Nathan Pritikin for starting this dietary alternative (5).

While these diets are challenging to maintain in our society, with food abundance and more people eating in restaurants, they are doable, and thousands of people have found success with them. I continue to offer these options to my patients and am pleasantly surprised by the number of patients who adopt them and stick with them — not the majority, but a substantial number — and when it comes to prevention and lifestyle change, that is good. It is a tragedy in my opinion that not all physicians offer this lifestyle alternative to their patients.

What have we learned in the last 16 years since Ornish became known for his findings? The main thing is that we know some fats are actually healthy and reduce cardiovascular risk. Taken in moderation, monosaturated and polyunsaturated fats improve the lipid profile (6). Ornish is famous for saying that all oils are 100 percent fat. This is true and worth keeping in mind the next time we are tempted to soak our bread in olive oil. Healthy oils in moderation while maintaining a healthy weight are now part of a modern dietary prescription.

One of the problems with evidence-based medicine is that it is constantly changing. This stands in contrast with the never-changing recommendations of antiquated information, such as in homeopathy. People want consistent information that they can believe in, and that sometimes leads patients away from ever-changing science. We in the scientific community should become more sensitive to the potential social impact of our new information. We should always put it in perspective with what is already known. If we continue to yo-yo with recommendations such as a healthy diet, we reduce the power of medicine to help society address the major epidemic of our time: excess dietary fat, which is resulting in overweight and obesity, and the potential for a reduced life expectancy for the first time in centuries. Eating right still means avoiding saturated fats.

References:

1. Prentice RL, Caan B, Chlebowski RT, Patterson R, Kuller LH, et al. Low-Fat Dietary Pattern and Risk of Invasive Breast Cancer. JAMA. 2006;295:629–642.
2. Beresford SAA, Johnson KC, Rittenbaugh, C, Lasser NL, Snetselaar LG, et al. Low-Fat Dietary Pattern and Risk of Colorectal Cancer. JAMA. 2006;295:643–654.
3. Howard BV, Van Horn L, Hsia J, Manson JE, Stefanick ML, et al. Low-Fat Dietary Pattern and Risk of Cardiovascular Disease. JAMA. 2006;295:655–666.
4. Ornish D. Dr. Dean Ornish’s Program for Reversing Heart Disease. New York: Random House, 1990.
5. Pritikin N. Pritikin Program for Diet and Exercise. New York: Grosset and Dunlap, 1979.
6. Willett W, Skerrett PJ, Giovannucci EL, Callahan M. Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. New York: Simon and Schuster, 2001.