April 22nd, 2011
Diet and Cardiovascular Health: What’s the Bottom Line?
CardioExchange welcomes Dr. Eric Rimm, Sc.D., the director of the Program in Cardiovascular Epidemiology at Harvard School of Public Health and a member of the USDA’s 2010 Dietary Guidelines Advisory Committee. Dr. Rimm answers Associate Editor Susan Cheng’s questions about the DGAC’s 2010 report. We welcome you to offer your own questions and opinions.
Background: The 2010 USDA guidelines take a strong position on reducing overall calorie consumption and increasing physical activity as the foundation of ensuring optimal nutrition in a population with a majority of overweight and obese adults and a rapidly growing proportion of overweight and obese children. Specific dietary recommendations for achieving these goals focus on increasing consumption of vegetables, fruits, whole grains, fat-free and low-fat dairy products, and seafood; and on reducing consumption of sodium, saturated and trans fats, added sugars, and refined grains.
Cheng: What would you highlight as the key take-home message(s) from the new USDA guidelines that clinicians should communicate to their patients?
Rimm: As you know, the 13-member scientific committee was just an advisory committee: The USDA and HHS wrote the final guidelines. However, many of the points in our advisory report were carried through to the final guidelines. We wanted them to be focused as much as possible on the total diet and not overly focused on one specific aspect such as the fat content or the potassium content (as examples). It is clear that this country is gaining too much weight, which is due to an imbalance between calories in and calories out; so a healthy diet is important, but there is no question that regular exercise is a crucial component, too.
In general, a complete diet should have plenty of fruits and vegetables, whole grains, healthy sources of protein such as fish, poultry, legumes, and low or nonfat sources of dairy. The data are quite clear that individuals should not focus on the total fat content of their diets but, rather, aim for diets low in saturated fat and refined grains.
Cheng: The salt restriction recommended in the guidelines generated some controversy. Was it difficult for the group to reach consensus on this topic? How should physicians counsel patients around salt in particular?
Rimm: Interestingly, among the scientific advisors around the table, there was quite a clear consensus that the target should be 1500 mg/day. However, the final government report was more forgiving and had a cutoff of 2300 mg for some people and 1500 mg for high-risk individuals (aged >50, African Americans, or with existing health conditions). Many reasons were given for the difference, but in general more leniency was reported because of concern that the food industry would not be able to produce processed foods lower in sodium. Docs should counsel all patients to lower sodium and to be wary (read the labels) of processed foods, store-baked foods, and especially ready-made meals in the freezer and deli section and at restaurants. Most of the sodium we get every day has nothing to do with how much salt is added at the table and much more to do with how much is stealthily put into prepared/processed foods.
Cheng: There has been a lot of recent interest in the lay media about detrimental health effects of sugar consumption. To what extent do you think this is backed up by evidence?
Rimm: The evidence continues to mount on the adverse health effects of added sugar. It is true that sugar is just a carbohydrate source that, like others, is readily absorbed and converted into fat for storage. Unfortunately, added sugars like high-fructose corn syrup are so cheap that the food industry can put it into everything; so, even when consuming small amounts, we all get more calories than we need. Just one added 12-oz soda a day (145 kcals) can lead to substantial weight gain over a year if it is not burned, or if other aspects of the diet are not reduced. Since many of these types of foods (e.g., soda) are consumed quickly and do not affect satiety, the evidence shows that they lead to weight gain and increase risk for diabetes.