Dallas, TX - The American Heart Association (AHA) has released an update to its 2000 dietary recommendations, this time expanding its scope to include "lifestyle changes" that go beyond diet to embrace such factors as tobacco exposure, socioeconomic status, and environment [1]. Several aspects of the new guidelines offer a glimpse into the progress of nutritional science, but at least one expert believes the approach ignores recent data that challenge the supremacy of the conventional low-fat diet.

In a statement to the media, the writing group from the AHA's Nutrition Committee highlighted the sweeping scope of the new document. "The previous recommendations stressed a healthy dietary pattern; the new ones broaden that concept to include the importance of a healthy lifestyle pattern. The two go together—they should be inseparable," committee chair Dr Alice Lichtenstein (Tufts University, Boston, MA) commented.

While the 2000 guidelines [2] made reference to "lifestyle practices," actual recommendations were limited to achieving and maintaining a healthy body weight, engaging in regular physical activity, and reducing alcohol consumption. In the 2006 recommendations, the writing group has included these components but also adds avoiding use of and exposure to tobacco and advice for eating outside the home.

"The key message of the recommendations is to focus on long-term, permanent changes in how we eat and live," Lichtenstein noted in the statement. "The best way to lower cardiovascular risk is to combine physical activity with heart-healthy eating habits, coupled with weight control and avoiding tobacco products."

As in the 2000 revision by the AHA's Nutrition Committee, the new recommendations emphasize the importance of a diet rich in fruit and vegetables, whole grains, oily fish, low-fat dairy products, and lean meats. Some notable differences, however, appear in the form of specific food recommendations in the 2006 document. Of note, in the 2000 recommendations, saturated fats and trans fats were both deemed "cholesterol-raising fats" and maximum intake for the two, in any combination, was set at 10% of daily energy requirements. By contrast, the 2006 recommendations state that saturated fat intake should be less than 7% while trans fat consumption should be less than 1% of daily calories. In a nod to the soaring consumption of empty calories in the form of cola drinks and sugary juices, the new recommendations—but not the old—suggest minimizing consumption of drinks with added sugars.

Other recommendations pertaining to reducing salt intake and achieving optimal blood pressure and lipid goals are more or less unchanged between the two documents; however, the 2006 recommendations also include the advice to aim for a normal fasting glucose level, defined as <100 mg/dL in nondiabetics.

Both sets of guidelines include sections on unproven strategies and strategies requiring further study and, side by side, speak to the steady march of scientific understanding. The section on antioxidants in the 2000 recommendations, for example, is five paragraphs long and tentatively discourages use of vitamin E; the same section in the new recommendations is only one paragraph long and firmly rejects a role for antioxidant supplements. Similarly, soy proteins are broadly recommended in the 2000 guidelines, reflecting the FDA's 1999 decision to permit food packaging to claim that heart disease risk is reduced with relatively high levels of soy consumption and that these benefits would be especially pronounced in people with elevated LDL- and total-cholesterol levels. By contrast, the 2006 guidelines explicitly state, "Although earlier research has suggested that soy protein has clinically important favorable effects on LDL-cholesterol levels and other CVD risk factors, studies reported during the past five years have not confirmed those results."

Specific groups singled out for special attention in both sets of recommendations include children, older adults, and people with kidney disease; however, the 2006 recommendations drop the section on "Diabetes Mellitus and Insulin Resistance" and replace it with "Persons with Metabolic Syndrome" and also have a new section on socioeconomic groups at high risk of CVD. Also reflecting the more comprehensive scope of the new guidelines, the writing group included a section addressing environmental influences on CVD, such as " cultural forces, societal norms, and commercial interests."

Low-carb expert looks at the AHA guidelines Commenting on the new recommendations to heartwire, Dr Eric Westman (Duke University, Durham, NC) said that he was impressed by what he saw as a new flexibility in the Nutrition Committee's outlook. "I think they're getting away from the one-size-fits-all approach, which is good," he observed. "Specifically, they've started making accommodations for the idea that there might be multiple dietary patterns that are effective and healthy, although they do restrict these to the time-honored low-saturated fat, DASH-diet-type examples." A conspicuous omission, he says, is the low-carbohydrate-diet approach that has been the focus of a growing number of rigorously conducted clinical trials over the past five years. "Low-carb diets aren't mentioned at all in these recommendations, not a whisper," Westman points out. This, despite the fact most of these studies compared a low-carbohydrate approach with an AHA-recommended diet. I think we just need better science to say that saturated fat is bad. "It's unfortunate they didn't reference the six or seven randomized trials of a low-carb diet that showed the triglyceride-lowering and the HDL-raising effects of the low-carb dietary patterns," he noted. The omission seems particularly surprising, given the fact that several participants in the 2006 writing group are currently involved in studies examining low-carbohydrate approaches, he added. "It could be that they're just waiting for longer-term studies, but you could at least say that over a six-month period, the HDL-raising effects of low-carb diets look promising. Certainly if these were the effects of a drug, not a diet, they would be mentioned that way." Westman acknowledged that popular enthusiasm for low-carbohydrate diets appears to have ebbed in the past year but argues this is not so much a reflection of disappointing study results as it is dwindling support from celebrities and food-product manufacturers. He points to several positive studies presented at the American Diabetes Association meeting earlier this month, one by his own group at Duke. "Low-carb businesses have gone up and down, but the research has stayed steady, if not increased." Westman also took issue with the lack of hard outcomes data to support the recommendations for reducing saturated fat and cholesterol intake. "In all the other sections, there are data that link the problem and the recommendations to good data, but this section is particularly weak," Westman argued. In the data cited, saturated- and trans-fat intake is linked to LDL-cholesterol changes, he noted. "Show me a study where these recommendations [for reducing saturated-fat intake] have led to improved outcomes: there isn't one. . . . In the drug world, you can't rely on intermediate outcome measures anymore, so that makes me wonder about saturated fats. This is pretty controversial to say, but I think we just need better science to say that saturated fat is bad." Overall, however, Westman says he approves of many things in the new recommendations. "I like that they've included smoking cessation, weight loss, blood pressure, and diet, so it's a comprehensive approach rather than just focusing on diet."