Are eggs bad for you? The verdict is still outside.

Over the years, there has been a lot of confusion about what constitutes a healthy breakfast. In the 1970s, carbohydrates were present, fat was eliminated and the only omelette considered healthy was that made from egg whites and asparagus. In the 1990s, carbohydrates became the number one public enemy and, suddenly, a jamming with cheese-stuffed eggs was considered optimal for health and energy. Today, herbal diets are increasing and a healthy breakfast can simply avoid eggs to the benefit of an oatmeal bowl or a rich green smoothie. in nuts and seeds.

Eggs make one of the oldest and most controversial debates about nutrition, thanks to dietary cholesterol: a big yolk of egg contains 186 milligrams, making it one of the most rich in nutrients. In 1977, the government began recommending diets low in fat and cholesterol, as research showed that dietary cholesterol increased bad blood cholesterol (LDL). The eggs have been dubbed indulgent and unhealthy.

Then, in 2013, the American Heart Association announced that limiting dietary cholesterol did not lower a person's LDL, which would have changed his official position. The 2015-2020 US dietary guidelines followed, saying that dietary cholesterol was "not a worrying nutrient for overconsumption". A meta-analysis of 2018 in nutrients went further, explaining that saturated fats had always been responsible for elevated LDL cholesterol and an increased risk of heart disease. The eggs contain a little more than one gram of saturated fat and have thus found their place.

But in March 2019, a study in the Journal of the American Medical Association Flip-flop again, concluding that eating one egg a day is linked to a significantly higher risk of heart disease after all.

Each of these pivots was based on legitimate nutrition research, raising the question: How is it possible that nutrition experts – doctors, dieticians and researchers – so often disagree on the fundamentals of science? nutrition? How do they study the same questions without proposing such different answers? How can an ordinary person make sense of all this? Here is an overview of the ever-changing world of nutrition science and why you should take the essentials with a grain of salt.

Data collection is imperfect

For 2019 JAMA In this study, researchers analyzed data from six previous studies involving a total of 29,615 adults followed for an average of 17.5 years. All studies used self-reported data on the basic diet, which means that subjects recorded what they ate daily or weekly at the start of the study. The researchers then drew conclusions on the assumption that the subjects ate about this way every day during the rest of the study.

There are, of course, important issues here. It is an exaggeration to think that a person's eating habits will remain the same for many years (or even decades). Beyond that, people tend to misrepresent what they eat. "Self-reported diet data is flawed," says Connie Weaver, professor of nutrition at Purdue University. "People do not report what they eat accurately, because they do not remember, do not know how to judge the size of a serving, do not know the ingredients or do not want to admit the nibbling that they do. " And most nutrition studies rely on self-reported data.

In an ideal world, Weaver says, there would be controlled feeding studies where researchers prepare each meal and know exactly which topics are eating at any given time. These exist, but they are long and expensive. Realistically, they can only be used for short-term, shorter-term studies that do not assess the risk of long-term chronic disease and are too small to be applicable to the general population.

Food does not exist in a vacuum

When a study seeks to evaluate a single nutrient, such as dietary cholesterol, it is impossible to know for sure that cholesterol has an effect on itself. Nutrients do not act alone and the presence of one can affect the impact of another. "For example, calcium absorption is influenced by vitamin D status," Weaver explains. Similarly, eating a lot of fiber probably has a positive influence on the risk of heart disease, while eating a lot of saturated fat probably has a negative influence – so it would be difficult to study the effects of one or the other. the other of these nutrients in a person who is eating fiber. – rich in whole grains and vegetables every day but also regularly eat red meat saturated with fats.

Even though scientists could create nutrient-only foods, accurately measure and track the diet, research would still be complicated by the fact that diet is just one of the many factors that affect health. . "The biggest problem in the science of nutrition is that we can not reduce the effect we're looking at in a single component," says researcher and author Linda Bacon. Health at all sizes. "Exercise, relationships, sleep, stress and a long list of other factors will affect health beyond nutrition. And yet, when you do a nutrient study, you only consider nutrition. Maybe someone eats eggs at breakfast every day but also has a stressful job and never sleeps more than six hours. If this person has heart health problems in the end, it is impossible to say that eggs are the cause.

Researchers often consider factors such as race, socio-economic status and gender. It is widely believed that these factors can be stronger determinants of health than diet, says Bacon. But it's almost impossible to control other influencing factors, such as chronic mental health issues, food anxiety and genetics.

The needs of each are different

Every five years, the Food Policy Committee of the US Agriculture, Health and Human Services Departments reviews all existing research to determine how it is consumed. which promotes the most health for most people. This is what brings us closer to a consensus on a "perfect" diet. But these recommendations – which currently recommend limiting your sugar intake, eating lots of plants and consuming at least some of your protein intake in eggs – are a general advice for public health and will not necessarily work for all the world.

Our body reacts differently to various foods, including dietary cholesterol. "I would never tell anyone that lowering their dietary cholesterol would reduce their blood cholesterol without first knowing their medical history," he said. Kevin Klatt, a scientist in molecular nutrition. Individuals have varying tolerance to dietary cholesterol, based on genetics or chronic diseases such as diabetes. Blood tests are the only way to know how you could be touched individually. Overall, Klatt views eggs as a neutral food. He explains that dietary cholesterol is suitable for most people in moderate amounts – about one egg per day or even two.

A contradictory science of nutrition is not going anywhere. Neither the debates on eggs nor Twitter's endless discussions on low-fat and low-carb diets. But that does not mean that you should live according to the general advice on nutrition.

"Your body can give you a lot of great information," says Bacon. She uses fiber as an example: if you are not eating enough, you will probably feel slow and constipated. It is a signal to eat more fiber in the form of whole foods. The same goes for sugar. It's good to eat it, but all too often you may feel lethargic. Instead of trying to follow the evolution of nutrition science, pay close attention to how you feel, and you will probably find that you end up eating in a way that promotes health.

If you think that chronic health problems are related to diet, a more personalized approach to nutrition science could help you. Discuss your symptoms with a doctor or dietician (with blood tests, allergy tests, and other diagnostic tools) to determine if a specific dietary change might be right for you. Whatever you do, try to ignore the headlines.