Why Was The Mediterranean Diet Study Controversial?
The Mediterranean diet is one rich in fruits, vegetables, whole grains, moderate amounts of healthy fats like olive oil and avocados and a strict limit on red meat. It is believed that people living in some Mediterranean countries who follow this diet have lower instances of heart disease and cancer. In 2013, the New England Journal of Medicine published a study for this diet; The goal of the study was to determine the role of healthy fats, specifically extra virgin olive oil and mixed nuts in one’s diet, and whether or not they contributed to a decreased risk of cardiovascular disease. The Mediterranean diet study consisted of three different groups of participants – the first group consumed at least four tablespoons of extra virgin olive oil a day, the second group was to consume the same diet with an additional ounce of mixed nuts and the third group, the control group, was put on a traditional low-fat diet1. The study concluded that “[a] Mediterranean diet can cut the risk of heart attacks and strokes by about 30 percent in those at high risk.1” The study took place in Spain over the course of five years and consisted of 7,447 randomized participants between the ages of 55 to 80 years old.
The Mediterranean Diet Had Some Significant Flaws
However, a few years later the legitimacy of the study and whether or not it was accurately conducted came into question. There were flaws in the study affecting about 10 percent of its participants – it turns out that the randomly chosen participants were not so random. For example, if a wife in a household was assigned the diet with four tablespoons of extra virgin olive oil a day, the researcher also assigned that same diet to the husband. That action impacted the final results of the study because it is possible that a husband and wife both have similar lifestyles and daily habits – therefore, you cannot attribute their results to diet alone. In response to this conclusion, a reanalysis of the study was ordered and a statistical adjustment was made to more than 652 of the participants in the trial. Despite all these adjustments, some experts still voiced their skepticism towards the legitimacy of the study1. This is because the underlying problem of the study was not solved – the Mediterranean Diet Study cannot be classified as a randomized trial because there are too many outside factors to account for. Moreover, there are many different types of "Mediterranean" diets depending on what region you're in. Randomized diet studies are difficult to execute to begin with and assigning families and even entire villages the same diet has a significant impact on the overall results1. The bottom line is that the "conclusions" from the Mediterranean diet should be taken with a grain of salt (preferably sea salt!)
The reanalysis of the Mediterranean diet is a great lesson – we should look at studies with a lot of skepticism before accepting their results. Science and nutrition recommendations are continuously evolving as new research and data come out. Not too long ago, people were convinced that a low to no fat diet was the way to go, as they were under the false impression that all fats were bad. Luckily, we now know that is not the case and that not all fats are created equal – these studies on saturated fat being one great example as to why we should incorporate fats into our diet. One fat that is still under the radar and being heavily debated is saturated fat. Most dietary guidelines are based off of the hypothesis that saturated fat raises LDL cholesterol (bad cholesterol) in the blood and inadvertently causes heart disease. However, this hypothesis is not supported by any conclusive data. Eating fat does not necessarily make you fat. In fact, a number of recent studies have shown that there is no link between saturated fat consumption and heart disease (see the link above). Therefore, for the average individual it is safe to consume moderate amounts of saturated fat in combination with a healthy and balanced diet2.
Some of the most popular studies linking fat consumption and heart disease were funded by the sugar industry
When listening to specific health recommendations, it is important to understand the “why” behind it and where exactly that recommendation is coming from. Unfortunately, it is easy for big corporations to influence scientific studies and to sway the results in their favor. For example, back in the 1960s the sugar industry paid scientists to down play the link between sugar and heart disease and to instead make it look like saturated fats were the culprit. The Sugar Association funded studies specifically relating to sugar, fat and heart disease and paid scientists to draw conclusions in favor of the sugar industry. As a result this downplayed all the harmful effects that sugar has on the body and pointed the blame towards fats3. Because of this, it caused consumers to increase their consumption of low-fat, high sugar foods. Some believe that this is one of the major contributors to America’s obesity epidemic. The debate about fats and sugar is still prevalent in today’s society and is one that is sure to continue for the foreseeable future. However, today we know that excess sugar consumption can lead to a multitude of health complications, including heart disease3.
So then, what should you do when you come across a study? Next time, ask these following questions:
- What is the sample size of the study and how many people did they test?
- How long was the study carried out for?
- What method was used throughout the study – was it observational or experimental?
- Who was the study funded by and is it possible there could have been a conflict of interest?
Asking and answering these questions will help you to determine just how well a study is executed. If a study as popular and well-known as the Mediterranean diet study was flawed, you can see how easily and common it is for others to be flawed as well – the studies on saturated fats and sugar being perfect examples. So, when the next big scientific study comes out offering nutrition advice, be sure to dig a little deeper to determine just how well the study was executed before deciding to switch your whole diet around.
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