nutrition
May 18, 2024

"Smart people do not drink coke"

Professor Walter Willett is a graduate in medicine and nutrition and directs the Department of Nutritional Sciences at the Harvard School of Public Health in Boston

ChroniquesDuVasteMonde: For years we were told that eggs and fats are bad. Milk was considered healthy? Now everything is different again. Do we really need nutrition research when it is so often wrong?

PROF. WALTER WILLETT: Yes, even urgently! When I started researching in the late 1970's, I realized that there was no scientific evidence for many dietary recommendations. For example, in the eggs: No study showed that high egg consumption led to more heart attacks. Or fats: they have been generally demonized, with no scientific evidence that they are actually harmful. So, as we urgently needed research, we launched four major long-term studies at Harvard with more than 300,000 participants.

Since then we have collected many, many data over a period of 35 years. Although we have gained interesting insights, for example, that not all fats are harmful and dietary fiber reduces the risk of diabetes, but no evidence that eggs increase the risk of heart attack or that protects milk from osteoporosis. But, of course, it takes a while for the new findings to be in people's minds. We have to regain confidence.

So today we are struggling with the fact that your colleagues did not work properly?

Yes, exactly, and the public is rightly confused. Quite clear: making recommendations without evidence is harmful. That's exactly what happened then. The experts should now gather the findings, draw conclusions and formulate scientifically proven nutritional principles. At the Harvard School of Public Health, we did that and created a nutritional pyramid that, to our knowledge, is a trusted source for current nutrition research.

What do we know today about how food affects our health?

Trans fatty acids, ie industrially hydrogenated fats, which are mainly found in baked goods, fried foods and chips, are the biggest risk factor for cardiovascular diseases. Not quite as harmful, but nevertheless a risk factor are saturated fatty acids, which occur in red meat, sausage, butter and milk. On the other hand, unsaturated fatty acids found in vegetable oils, nuts, avocados and oily fish lower the risk of having a heart attack later on.

Dispensable: red meat, sausage, butter, white flour products, soft drinks, sugar, salt

"Ideal is the traditional Mediterranean diet"

The WHO has just classified sausage as carcinogenic and red meat as likely to cause cancer ...

In my opinion, the assessment is a reasonable summary of the scientific data. When deciding what to eat, should one also consider that red meat and processed meat products in particular increase the risk of cardiovascular disease and diabetes? compared to nuts, vegetables, fish and poultry as alternative protein sources. That does not mean that you have to go without red meat now, but it should not be on the table every day, but only on special occasions. And then, best of all, meat from species-appropriate animals.

The list of prohibitions is getting longer.

Any food that we call unhealthy is replaced by another. That's exactly what happened in the 1980s when people called for fat savings: instead of fat, people ate more refined carbohydrates, especially white flour and sugar. And became thereby ever thicker. Replacing the animal fats with vegetables and vegetable oils is much better for your health because it lowers bad blood cholesterol. So the key question is: how do I replace the saturated fats? Neither fats nor carbohydrates are basically bad, but there are both good and bad variants of both macronutrients. We need to pay more attention to the quality of food and focus on telling people what to eat instead of what not.

And? What should we eat?

Our knowledge today is that a diet with healthy unsaturated fats, whole grains, fruits and vegetables and proteins mainly from plant products reduces the risk of developing cardiovascular diseases, diabetes and some cancers. Ideal is the traditional Mediterranean diet: plenty of vegetables, fish, vegetable oils, nuts and whole grains.

What else can we eat with a clear conscience?

But can we really change much with our eating habits? or are not the genes ultimately crucial?

No, we can do a lot ourselves. Today, people are mainly dying from heart attacks, strokes and diabetes. One of our long-term studies found that reducing the risk of getting cardiovascular disease by 82 percent means not smoking, having a BMI in the normal range, exercising regularly, drinking little alcohol and being healthy malnourished. These are the factors that have a big impact on the length of life and a high quality of life in old age. The problem: Only three percent of respondents actually lived like this.

It is also very enjoyable!

Sure, food should taste. But we can not ignore the fact that chronic diseases such as diabetes and heart attacks are also increasing in younger people? and they are largely preventative preventable. Everyone has to decide for themselves how he lives, but a chronic illness also means that you feel bad. One should not forget that.

The bottom line is only fruits and vegetables that we can eat without hesitation, right?

Here, too, a differentiation is taking place. Fruit is not equal to fruits and vegetables are not equal to vegetables? Not all varieties are good for us. Studies show that, for example, blueberries, grapes, plums, apples and pears lower the risk of diabetes. Potatoes and corn, on the other hand, are not among the good vegetables because they contain far too much starch. Good for the heart are green leafy vegetables, red, orange, yellow vegetables and fruits and cooked tomatoes.

What about milk? That's just very controversial ...

So far, we have found no evidence in studies that high milk intake prevents bone fractures and osteoporosis. There are indications that too much milk could increase the colorectal cancer risk. How much we can drink, there is no agreement among experts. In my opinion, it is good to limit the consumption of milk. One glass per day is okay, with yoghurt and cheese in moderation. Soy milk and other milk substitutes such as rice milk or almond milk, which are very popular because many people wrongly believe that they suffer from cow's milk intolerances, usually contain too much sugar.

What's with butter?

Vegetable oils are generally better for blood lipid levels. Butter is not a poison, but not an optimal fat, so please? if any ? moderately.

And white flour?

The body quickly converts it to glucose, the reaction is similar to sugar. This can promote insulin resistance and diabetes, especially if you move a little.

"Smart people do not drink cola anymore"

There are studies showing that low-fat and low-carb diets lead to similar weight loss ...

When you reduce calories, are people losing weight? No matter which food you save. However, studies show that it is difficult to sustain a low-fat diet for a long time. The downside is that it costs a lot of energy and makes you dissatisfied with losing fat. Fat tastes and saturates better. We have to accept that, and that's fine if it's the right fat.

Transfats were banned in the US. The taxes on sweet soft drinks should be raised to deter people. Is compulsion the right way to a healthier diet?

Soft drinks increase the risk of developing type 2 diabetes and contribute to the overweight epidemic. Taxation is therefore a good step, but only if it is explained why the drinks are unhealthy and what is the best way to replace them? namely by water. If everyone changes to fruit juices, that is not much health wise. For the trans fat it can be said that the ban has helped in the US. The big corporations now do without it.

Eating habits are also culturally anchored. Can you change your habits at all?

Of course not overnight, but it works. I grew up on a farm, we often had red meat and potatoes. Nevertheless, I managed to eat differently. We are already seeing changes in the US. Take the fats: After being warned, the percentage of fat in the diet dropped from 42 to 33 percent. Consumption of soft drinks has fallen by 25 percent within twelve years. Smart people no longer drink coke. We can change, but not from one year to the next.

Is it best to start with small steps?

People who are very motivated can change their diet in one fell swoop. They will soon realize that they are feeling better, that they are losing weight, and that, in turn, increases their motivation to stay there. The problem with small changes is that you hardly notice them. The goal of not having a heart attack later on is abstract and far away. Therefore, I am in favor of a correct change in food habits.Incidentally, the changes that I mean are not particularly difficult to implement: instead of finely ground white flour, the whole grain variant instead of red meat more vegetable protein, fish and poultry, instead of potatoes and rice rather vegetables, instead of animal fats more unsaturated fats from liquid vegetable oils, nuts, Avocados and olives. And keep the consumption of sugar and salt as low as possible.

Will it be like smoking that people say, "Yuck, you're still eating beef!"?

Yes, that's the case with sweet drinks? at least in the higher income strata. Social norms are about to change.

"It's crucial how we feed our children"

In Germany too, nutrition is heavily dependent on income. What has to happen so that all healthy food can afford each other?

There is no simple solution. With a combination of education and policies, we need to make healthy eating affordable not only for the rich. Otherwise we will eventually get very different social problems.

They have been studying our dietary habits for 40 years now. How will we eat in 40 years?

Definitely healthier. Even if there is a great deal of confusion about food at the moment, the information we have today can be the basis for nutritional recommendations.

In which areas do we need more research?

We need to know more about how childhood nutrition affects later life. One of our studies with 10- to 14-year-olds showed that consuming red meat increases breast cancer risk. It is therefore crucial how we feed our children. And we also need to explore the effects of eating on neurogenic diseases like dementia.