Have you ever been confused by the news headlines that tell us conflicting information about what foods are “good” and what foods are “bad” based on a recent scientific study? For years, we were told that butter, eggs, and coffee were “bad,” and now the news headlines tell us that we should be putting butter in our coffee and eating egg yolks for their valuable nutrition. This information is all based on scientific studies, of course. Were scientists of the 80’s just totally wrong about everything and scientists of today finally on the right track because of better technology? Is dietary carbohydrate the real villain that has caused 3 out of every 4 Americans to become overweight?A randomized, 3-period, crossover feeding study conducted between April 2003 and June 2005, called the OmniHeart Randomized Trial, sought to find out whether a diet higher in carbohydrates, protein, or fat would be the most beneficial for reducing risk factors for heart disease in patients with early hypertension. Study participants were randomly assigned to 1 of 3 different diets for a period of six weeks and all meals were provided. Each six week diet period was followed by a 2 – 4 week “washout” period in which participants went back to their usual diet. They were then assigned to another diet for 6 weeks, followed by another washout period, until each study participant had tried all 3 diets for 6 weeks each.
So what were the study findings? All 3 diets reduced heart disease risk factors for the 159 participants who made it through all 3 legs of the study. However, the study authors concluded that replacing dietary carbohydrate with protein or fat was healthier than a high carbohydrate diet. Indeed, the high fat diet lowered blood pressure and cholesterol more than the high protein diet, and the high protein diet lowered blood pressure and cholesterol more than the high carbohydrate diet.
But before you replace your baked potato with a handful of nuts, allow me to explain why this conclusion is intentionally misleading. You see, news journalists rarely look beyond a study’s summary and conclusions, either because of a lack of time or a lack of know-how on how to investigate a study’s methodology and vested interests.
When I read about the OmniHeart study, I was most interested in what food the participants were actually eating on the 3 different diets. Since heart disease risk factors improved on all 3 diets, we can conclude that the food was at least somewhat healthier than what the participants had been feeding themselves prior to the study. When we dive deep to find out what the macronutrient ratios of the 3 different diets were, we find that they didn’t vary all that much. The so-called high carbohydrate diet was 58% carbohydrate, 27% fat, and 15% protein. This is not really a high carbohydrate diet, which I consider to be at least 70% carbohydrate and no more than 15% fat. The high protein diet was 48% carbohydrate, 27% fat, and 25% protein. And the so-called high fat diet was 48% carbohydrate, 37% fat, and 15% protein. This “high fat diet” most closely resembles the macronutrient ratio of the Standard American Diet, though this is the one that actually produced the most superior results.
The food itself for each of the 3 diets was nothing like what I would recommend. It was basically cereal and milk for breakfast, sandwiches for lunch, and a meat-based dinner with a side salad and oil. The “high carbohydrate” diet included more fruit juice and low-fat desserts (such as peppermint patties), the “high protein” diet included larger portions of meat, and the “high fat” diet included more nuts and olive oil. None of the diets were high in vegetables, and processed foods appeared at every meal. Participants likely saw improvements on the diets because (1) they were not eating restaurant fare and sodas during each 6 week period, and (2) their calorie intake was controlled to prevent them from gaining weight. The diet that was slightly higher in carbohydrates most likely fared the worst because those extra carbohydrates came from fruit juice and desserts with added sugars. Neither of these food categories contain fiber, which is a nutrient that lowers cholesterol. Fruit sugar (fructose) elevates triglycerides and blood pressure, though to a lesser degree than corn sugar (high fructose corn syrup found in soft drinks and a variety of processed foods). The “high fat” diet most definitely fared the best because it contained the most dietary fiber of the 3 diets. Instead of fruit juice or meat, the higher fat diets featured nuts. The former two contain no fiber, while the latter contains a significant amount of fiber and a variety of other nutrients known to lower blood pressure.
Finally, when we look to see who funded the study and if there were any parties involved who may have had a vested interest in the study outcome, we find some very interesting information. Though the study was funded by grants from the National Institutes of Health, food was donated by The Almond Board, International Tree Nut Council, Olivio Premium Products Inc (an olive oil company), and The Peanut Institute. The study authors may have been pressured to arrive at a conclusion that would financially benefit the study’s donors. The high carbohydrate diet was specifically designed to produce inferior results by adding fruit juices and desserts as the extra carbohydrate source instead of fiber-rich starchy carbohydrates such as potatoes, legumes, and brown rice. If the study authors were to continue getting paid to do research, they would need to design a study that would put money into the pockets of the businesses that were paying for the study by providing food. How could anyone overlook this fact?
The key message here is that you should always look behind the news headlines that claim that “a study shows” such and such food or herb or therapy is good or bad. When somebody says a study shows this or that, you’ve got to read the actual study and find out whether the conclusion is truly valid or not. If the conclusion appears to be valid, seek out whether the study findings have been replicated. Although its impossible to remove all possible biases from study outcomes, always be skeptical of studies funded by a particular company that “discover” that you should eat more of their product for better health (like this one funded by the Avocado Board).
Want to learn more science-based information about optimal nutrition for preventing and reversing disease? Check out my latest book, Plant-Powered Paleo. This book is not full of fluff and it wasn’t written as a sales tool for corporate food products and the supplement industry.