One recent study teaches us by its mistakes. A heart healthy diet is much more than being low in fat - it is high in fruit, vegetables, whole grains and beans.
A recent study by Dr. Dreon and others in the American Journal of Clinical Nutrition provides us, in a round about way, with a few lessons about eating for a healthy heart. Dr. Dreon found adverse changes in her subject’s blood lipids on a very-high-carbohydrate (CHO) diet and concluded this meant a very high-CHO diet may increase the risk of heart disease.
There are three flaws in the study design that explain the poor results of her high-CHO diet compared with her higher fat diet. The design of this study provides an opportunity to show why not all high-CHO diets are beneficial. And also why it is dangerous to generalize too much from the results of a single study. The three major problems with the high-carbohydrate diet in her study are the lack of fiber, amount of animal protein and cholesterol and amount of calories.
Dr. Dreon’s higher fat diet contained 50% more fiber than her high-CHO diet.
Since dietary fiber improves blood lipids and most high-fat foods have no fiber while many high-CHO foods have a lot, it seems odd that her higher fat diet had much more fiber than her high-CHO diet. These researchers used a high-CHO diet with 50% sugar. The first lesson here is that a heart-healthy diet depends on the type of CHO as well as the type of fat. It is wrong to assume all high-CHO foods (or all high-fat foods) have the same impact on blood lipids and the risk of CVD.
Just as olive oil or canola oil are preferable to butter in their impact on blood lipids, high-fiber, high-CHO foods, like beans and whole grains are preferable to sugar, fat-free cookies and white bread. Eating plenty of vegetables, fruit, whole grains and beans is far more preferable than processed, refined foods with little fiber, e.g. baked goods, crackers, white bread, sweetened cereal, cookies and candy.
Cholesterol and Animal Protein
The subjects in this study ate the same amount of cholesterol and animal protein on the high-CHO diet as on the higher fat diet. Those who advocate a very-low-fat diet to treat and prevent heart disease recommend a much higher fiber intake and a big reduction in dietary cholesterol and animal protein. Most high-CHO foods have no cholesterol. In the real world, a very-high-CHO diet usually would have more fiber and also less animal protein and cholesterol than a higher fat diet.
A heart-healthy, high-CHO diet is more than just eating more fat-free desserts and snacks and lowering your diet’s % fat calories. A heart healthy high-CHO diet means eating more vegetables, fruit, beans and whole grains.
Too Many Calories
Subjects on the high-CHO diet in this study consumed more calories than on the high-fat diet. The researchers wanted to keep the body weight of their subjects constant, but they had the people on the low-fat diet consume 370 more calories per day than on their usual routine. In the real world, people eat until they feel satisfied or full.
So the final lesson about eating to keep your heart healthy is that how many calories you eat is often as important as what you eat. One of the most important ways a high fiber, low-fat diet works is by helping you feel full on fewer calories so you will loss excess body fat. This is perhaps the most important lesson. It has already been shown that most of the adverse metabolic effects on blood lipids associated with very high-CHO diets disappear when people eat until they are full rather being required to eat a set amount of calories (often equal to what they eat willingly on a higher fat diet).
The Dreon study shows that a very low-fat, calorie-dense, low-fiber diet, consisting largely of refined sugars and white flour, without a reduction in animal protein and cholesterol is of questionable value for improving blood lipids and reducing the risk of heart disease.
If you look in the September 1999 issue of the American Journal of Clinical Nutrition, you will see my letter to the editor explaining the points I just made here. In Dr. Dreon’s reply to my letter, she stated that her research group planned to do further tests with higher fiber, high-CHO diets and have their subjects’ appetites (rather than the researchers’ protocol) determine how many calories are consumed.
Dr. James J. Kenney, PhD, RD, FACN, is the Nutrition Research Specialist for the Pritikin Longevity Centers. He is on the Board of Directors for the National Council for Reliable Health Information and is Board Certified as a Specialist in Human Nutrition by the American Board of Nutrition.
This article is the second of a series of articles on diet and heart disease and will be part of an 8 hour CPE program for dietitians. Next month we will look at how a high monounsaturated fat diet may actually promote atherosclerosis and increase the risk of blood clots (which can trigger a fatal heart attack or stroke).
Judy’s passion for cooking began with helping her grandmother make raisin oatmeal for breakfast. From there she earned her first food service job at 15, was accepted to the world famous Culinary Institute of America at 18 (where she graduated second in her class), and went on to the Fachschule Richemont in Switzerland where she focused on pastry arts and baking. But after learning that the quality of a croissant directly varies with how much butter it has, Judy sought to challenge herself by coming up with recipes that were as healthy as they were tasty.
Judy received The Culinary Institute of America’s Pro Chef II certification, the American Culinary Federation Bronze Medal, Gold Medal, and ACF Chef of the Year. Her enthusiasm for eating nutritiously and deliciously leads her to constantly innovate and use the latest in nutritional science to guide her creativity, from putting new twists on fajitas to adapting Italian brownies to include ingredients like toasted nuts and cooked honey. Judy’s publishing company, Food and Health Communications, is dedicated to her vision that everyone can make food that tastes as good as it is for you.