October 1, 2004
Nutrition Expert Discusses New Dietary Guidelines
The Department of Health and Human Services (HHS) and the Department of Agriculture (USDA) are updating the Dietary Guidelines for Americans. The guidelines, which are updated every 5 years, are intended to help individuals choose diets that will promote optimal health and reduce risk of chronic disease. They are an indispensable tool to guide all government nutrition programs, including research, education, food assistance, labeling and nutrition promotion.
The updated guidelines, scheduled for release in early 2005, will be based on the report of the 13-member Dietary Guidelines Advisory Committee. Benjamin Caballero, PhD, MD, director of the Center for Human Nutrition at the Johns Hopkins Bloomberg School of Public Health, and Lawrence Appel, MD, MPH, professor with the Bloomberg School’s Department of International Health, served on the scientific panel. The committee’s report was released in August. It will be translated into a new food guide pyramid and other accessible messages relating to nutrition and health after public comment and an internal review.
To sort out some of the key changes in dietary advice that will appear in the 2005 Dietary Guidelines for Americans, Kelly Blake, communications and publications coordinator for the Center for Human Nutrition, spoke with Dr. Caballero, who was a member of the Dietary Guidelines Advisory Committee and the Institute of Medicine’s Panel on Dietary Reference Intakes for Macronutrients.
KB: What was different about the development of the new Dietary Guidelines from previous years?
BC: This was the first dietary guidelines report created using an evidence-based process to look at research data. While every expert panel obviously aims to base their recommendations on solid scientific evidence, “evidence-based” is a name defining a specific process for selecting, ranking and sumarizing research data. It is a useful process, although it can be used in two ways. It can enhance the objectivity of the review process, but it can also be used to minimize the relevance of solid but not definitive evidence, as was done in the past regarding the health effects of tobacco and the impact of global warming.
For our report, we first agreed upon what research questions should be addressed. The HHS and USDA staff then did comprehensive literature searches, talked to experts, and found every study related to each research question. The results were then ranked and sorted according to the rules of evidence-based reviews. These rules prioritize data based on a series of criteria that consider experimental design, sample size, randomization, and control groups.
KB: Can you describe the political process involved with creating the guidelines? Did food industry groups play an active role in trying to influence the content of the report?
BC: It was an open process. Anybody could submit comments either in writing or during one of the oral comment periods. The food industry takes full advantage of this, and I think this is a legitimate process. In some cases, we received extensive documentation from industry scientists that criticized key scientific papers, while others offered valuable points of view. Regardless of whether we agreed or disagreed, they raised useful points.
We received reminders from HHS and the USDA about issues that were potentially controversial, but we never received the pressure to go one way or the other. We just had to make sure that any statement we made had a scientific basis. Some staff members in the departments were concerned with the issue of television and obesity. They worried that we would say that TV, separate from any other sedentary activity, is bad for you. I think that the report is stronger because we anticipated many questions and criticisms.
KB: Among the notable changes to the Guidelines are the recommendations about consuming no more than 1 percent of calories from trans fat and the recommendation of consuming no more than 2300 mg of sodium per day. How far off are most American diets from this standard?
BC: American diets are very far from the targets in these areas. Most people consume about 5 or 6 grams of salt a day and the recommendation is about 1.5 to 2 grams. Likewise, Americans consume about 2-3 percent of calories from trans fat when we are telling people to consume less than 1 percent. So we are way over.
KB: Does the food industry share any responsibility to change its ingredients or processing techniques to help Americans get there?
Most trans fat comes from processed food. It’s an element largely created by the food industry by the hydrogenation of vegetable oils—so it could be easily be removed. Most of the industry is moving in that direction now that trans fat labeling is required, so most products will be low or free of trans fat in the future. There is some natural trans fat that comes from animal sources, but it’s probably 1 percent or less of our total fat consumption. I see trans fat as mostly an industry issue and a regulation issue. That’s why I did not agree with the report’s recommendation to reduce your consumption of trans fat, because I think telling the consumer to reduce consumption of something that the industry puts in is misleading. There are some elements of a healthy diet that fall squarely in the hands of the industry. Trans fats were eliminated in Europe years ago, and with the labeling requirement, they should be dropped in the United States.
Salt is a similar issue. Industry is responsible for about 75 percent of the sodium consumed. The other 25 percent is salt that we add to our food. The consumer can do a little bit to reduce sodium intake, but unless products change in terms of sodium content, you won’t see any significant difference.
Industry groups claim that every time they introduce a low salt product in the market, it flops. When people see ‘low-salt,’ they think it is for sick people. There are many products that would qualify for the low salt label, but they don’t use it. The Salt Institute has been aggressive in opposing the suggestion to reduce salt intake, but there’s no question that the scientific evidence for this is there.
KB: Another notable change was the omission of an explicit recommendation about sugar intake. This is the first Dietary Guidelines report that doesn’t have a key guideline relating to sugar. Why?
BC: This is a sensitive issue for two reasons. The previous guidelines in 2000 told consumers to moderate their intake of sugar. We didn’t say this in our report, because the previous recommendation had no scientific basis. The other issue is over sugary drinks, which has been in the media for several years and generates understandable, angry responses from parents, teachers and nutritionists. I too am angry that soft drink companies have been pushing soda in schools—essentially bribing them to put their machines in. This is unacceptable. Unfortunately, this anger doesn’t make scientific evidence appear. Soft drinks should not be allowed in schools, because they are not a healthy food. They provide no vitamins or minerals and they add to the caloric load without adding to the nutrient intake.
Also, there is no question that scientific evidence shows that the more sugary drinks people consume, that the more calories they will consume. But, there is no solid evidence that consumption of sugary drinks is correlated with obesity or gains in Body Mass Index (BMI). There are only a couple of studies that associate soda consumption with weight gain and the results have been questioned. There may be a link, but the link is not easy to prove.
A statement like 'Choose your carbohydrates carefully' may seem like a meek, vague, unhelpful thing to say, but the issue of food choices is more complex than one or two foods. I wouldn’t want to mislead people and tell them to just reduce your sugar and you will be okay. A person can like sugar and consume a certain amount and have a perfectly healthy diet. I am sensitive to individual choices and flexibility as long as the scientific evidence supports it.
KB: Can you explain another new addition to the guidelines – the notion of “discretionary calories?”
BC: It’s a great concept because it’s the first time that I’ve seen something that addresses the two reasons that we eat—to maintain our body weight, and to fulfill our need for essential nutrients. The amount of calories you need for each is not the same. It depends upon the quality of the diet. The more essential nutrients a food has, the fewer calories you need to meet your nutritional needs. These two have never been associated before in this way. The danger is in how this message is translated to the public. The communication will have to be figured out very carefully.
You can’t tell people that after you eat all you need, then you have extra room to eat some extra junk. People have to understand first that the average American has no discretionary calories available, because we already eat too many calories and are burning too few. However, we can tell people that if they are active and they eat high-quality food then they may have more flexibility. But we don’t need to use our discretionary calories to eat ice cream. The relationship between reduction in cancer risk and intake of fresh fruits and vegetables is linear, so if you can get more in your diet, why not do that?
KB: How does this report differ from the previous recommendations on physical activity? Why does the report suggest 30 minutes of physical activity for adults when the Dietary Reference Intake report on macronutrients and energy urged 60 minutes?
BC: It was a compromise to recommend 30 minutes, because there is not a lot of evidence to set up a fixed level. Most epidemiological studies that link physical activity with risk of disease show a continuum. If a sedentary person starts doing 15-20 minutes of exercise a day, they lower their risk over someone that’s sedentary, and so on as you increase activity. The peak of benefit occurs in some studies beyond 60 minutes. Others show there is no increased benefit beyond 40-50 minutes.
The 1995 recommendation of 30 minutes of moderate physical activity on most days was a consensus recommendation. At that time, walking was promoted because people were very sedentary and they wanted to promote something people were more likely to do than gym workouts. When the Institute of Medicine published the Dietary Reference Intake in 2002, that committee came up with a totally different approach by looking at data on energy expenditure. We found that 60 minutes per day is the level of activity needed to achieve energy balance for most people. Some studies show that those who have lost weight need 90 minutes to maintain their weight.
Keep in mind that brisk walking is not the same as more vigorous exercise in terms of disease prevention. You can burn the same amount of calories if you walk long enough, but for disease prevention, there is a difference between fitness and burning calories. The new guidelines mention the need for vigorous exercise, which should be done a few times a week. To reduce osteoporosis risk, you need weight bearing exercise. Not all exercise is equal in terms of health risk.--Kelly Blakekblake@jhsph.edu.Public Affairs media contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Lowe at 410-955-6878 or firstname.lastname@example.org.