Last week I heard Dr. Roger Clemens speak at the California Dietetic Association meeting in Pasadena. Dr. Clemens is a member of the 2010 Dietary Guidelines scientific advisory committee.
I am grateful for the candid discussion. I would never know the limitations of the 2010 USDA Dietary Guidelines if I only read materials printed by the USDA. Dr. Clemens spoke with honesty and humility. We really don’t know much about human nutrition. We only think we do.
NUTRITION IS A YOUNG SCIENCE
Nutrition is a young science, studied for a bit over 100 years as a specific scientific entity. Vitamins were discovered in the early 19th century. We didn’t appreciate the role of fiber until the 1970’s.
We are still debating how carbohydrate, protein and fat influence metabolism and energy utilization. We want to believe calories count, but maybe not as much as the hormones and other regulators that determine what we do with those calories.
During Dr. Clemens talk, five key messages resonated with me.
1. The 2010 Dietary Guidelines are not prescriptive. The guidelines are developed as a public health policy tool. It is a recommendation for the population, but not necessarily for individuals. This means there is plenty of range for people to figure out what balance of carbohydrate, protein and fat works for them. We do not all need to be on a lower fat diet.
2. Calories count, but no one is looking at hunger and satiety. There is not enough data to tell us which diet is better. Research shows that if you restrict calories, every diet works well to help people lose weight.
The problem is that no one is asking the dieters what they think and how they feel. We really don’t know more than calories count. Knowledge is not the same as behavior. It is time we look at what behavior science can tell us.
3. Too much refined sugar and starch is a problem, but the research that was considered didn’t find any distinctions between the impact of high fructose corn syrup, sucrose in white table sugar or any other sweetener. This is a situation where the time lag is glaring.
The dietary guidelines were drawn from research that is about 5-10 years old. The guidelines are always looking backwards at what we know, not what we are finding out. The onerous time lag makes it very difficult for me as a practicing dietitian to support the static position of the guidelines–especially since the current ones will be around for another five years.
4. The 2010 Guidelines continue to tell us to eat less fat, less saturated fat and cholesterol even as more current research tells us that fat is not the problem .
This is exactly the kind of rear view mirror thinking that is inherently a part of public policy that relies on research that takes decades and longer to plan, fund, conduct, and then publish results. It takes even longer to understand. No one study is significant by itself, so we need additional research for corroboration.
One saturated fat, stearic acid, is already vindicated. Stearic acid is naturally found in ruminant animals (cattle, goats, sheep, bison), along with milk and milk products from the same animals. It is also found in cocoa and chocolate. Stearic acid is not associated with increased risk of cardiovascular disease.
Milk, cheese, and red meat have been vilified for decades–and now we know better. In his talk, Dr. Clemens remarked that if you subtract the stearic acid component of saturated fat from beef and cows milk, there would no longer be enough saturated fat to be a problem, even by the old standards.
Interestingly, 8 of the top 16 sources of stearic acid in the American diet are high carbohydrate foods like grain desserts, mixed Mexican dishes, pizza, and candy. I’ve often wondered if it is the refined sugar and starch with added fats that are more of the problem, not the fat itself.
5. Sodium intake may be high, but it is not always a problem. It seems only people already predisposed to elevated blood pressure benefit from reduced sodium intake. In addition, whether someone actually develops hypertension due to the sodium in the diet depends on many other elements. Hypertension is not a single nutrient disease.
Total calorie intake, specifically overeating, is the biggest source of excessive sodium intake. If people started to eat just the energy they needed, sodium intake will drop right along with the excess poundage.
Highly processed and pre-prepared foods contribute 77% of all sodium in our diets. These foods are a major source of all sodium intake.
Just about 10% of our sodium comes from cooking and another 7-10% from the salt shaker. We don’t have to eat food that is less tasty or well prepared to reduce sodium content.
The best way to reduce sodium in the diet is to stop overeating. It is also helpful to purchase less highly processed and prepared foods. Lastly, we can learn how to season food for full flavor, not just to taste salty. By eating more fresh foods prepared at home, sodium intake will plummet even if we use the salt shaker.
GRATEFUL FOR A FLAWED BUT USEFUL TOOL
I am grateful for the impressive efforts of all the scientists, researchers, clinicians and academics who contribute to these Dietary Goals. They provide a framework for us to think about food, nutrition and health.
It is valuable to have the Dietary Goals as a reference, but it is equally important to remember the Dietary Guidelines are limited. We are still learning. The Guidelines can only tell us what was understood before 2010.