Nutrition Science: What to Believe and What Not

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

Does meat cause cancer or not? Can adults drink milk or not? Low-fat foods - solid good or evil embodied? Research says one thing or the other. And so the scientists themselves told why such a mess is going on in nutrition science.

Once upon a time, the study of nutrition was a simple matter. In 1747, a Scottish doctor (James Lind) decided to find out why so many sailors suffer from scurvy, a disease that leads to wasting and anemia, bleeding gums and tooth loss. So Lind set up the first clinical trial of 12 patients with scurvy.

The sailors were divided into six groups, each with a different treatment. People who ate lemons and oranges eventually recovered. An irrefutable result that revealed the cause of the disease, that is, a lack of vitamin C.

Something like this was solved the problem of nutrition in the pre-industrial era. Many diseases, significant for that time, such as pellagra, scurvy, anemia, endemic goiter, appeared as a result of a lack of one or another element in food. Doctors put forward hypotheses and set up experiments until they experimentally found the missing piece of the puzzle in the diet.

Unfortunately, the study of nutritious nutrition is not so easy now. During the 20th century, medicine has learned to cope with most diseases caused by an unbalanced diet. In developed countries, this is no longer a problem for most residents.

Overeating has become the biggest problem today. People consume too many calories and low quality food, which leads to chronic diseases such as cancer, obesity, diabetes, or cardiovascular disease.

Unlike scurvy, these diseases are not so easy to deal with. They do not appear acutely overnight, but develop over the years. And buying a box of oranges cannot get rid of them. It is necessary to study the entire diet and lifestyle of the patient in order to weed out all risk factors leading to the disease.

This is how nutritional science became imprecise and confusing. A sea of conflicting studies has emerged, in which a host of inaccuracies and limitations are easily discovered. The confusion in this area makes nutritional advice confusing. Scientists cannot agree in any way, protect tomatoes from cancer or provoke it, red wine is useful or harmful, and so on. Therefore, journalists writing about nutrition often sit in a puddle, describing the next report.

To get an idea of how difficult it is to study nutrition, Julia Belluz interviewed eight researchers. And this is what they said.

There is no point in doing a randomized trial to find answers to common nutritional questions

The gold standard of evidence-based medicine is a randomized controlled trial. Scientists recruit test takers and then randomly assign them to two groups. One gets the medication, the other gets a placebo.

The implication is that, due to random sampling, the only significant difference between the groups is the drug intake. And if research results differ, it is concluded that the drug is the cause (which is how Lind calculated that fruits cured scurvy).

The point is, for most critical nutritional issues, this approach does not work. It is too difficult to assign different diets to several groups, which will be strictly followed for a long time, in order to determine which food affects which disease.

In an ideal world, I would take 1,000 newborn babies to study and divide them into two groups. To feed one group only fresh fruits and vegetables for the rest of their lives, and the other with bacon and fried chicken. And then I would measure in which group they were more likely to have cancer, heart disease, who would grow old and die earlier, who would be smarter, and so on. But I would have to keep them all in jail, because there is no other way to make 500 specific people not try anything other than fruits and vegetables.

Ben Goldacre physiologist and epidemiologist

It's wonderful that scientists cannot imprison people and force them on a diet. But that means existing clinical trials are cluttered and unreliable.

Take, for example, one of the most expensive and large-scale studies by Women’s Health Initiative magazine. The women were divided into two groups, one of which followed a regular diet and the other a low-fat diet. It was assumed that the subjects would eat in this way for several years.

What is the problem? When the researchers collected the data, it turned out that no one followed the recommendations. And both groups ended up eating the same.

Billions were wasted and the hypothesis was never tested.

Walter Willett physiologist, nutritionist at Harvard University

Rigorous, randomized, placebo-controlled trials can be performed within a short period of time. Some nutritional supplementation studies allow subjects to stay in the laboratory for days or weeks and monitor what they eat.

But such studies have nothing to say about the effects of long-term diets that can be followed for decades. All we can know is fluctuations in blood cholesterol levels, for example. Researchers only make assumptions that something will affect health in the long term.

Researchers have to rely on observational data full of unknown variables

Instead of randomized trials, scientists have to use data. They have been going on for years, a huge number of people participate in them, who already eat the way the researchers need. Checks are periodically carried out among them to detect, for example, the development of cancer or diseases of the cardiovascular system.

This is how scientists learn about the dangers of smoking or the benefits of exercise. But due to the lack of control, as in experiments, these studies lack precision.

Let's say you're going to compare people who have consumed a lot of red meat for decades versus people who prefer fish. The first snag is that the two groups can differ in other ways. Nobody even distributed them at random. Maybe fish lovers have a higher income or better education, maybe they take better care of themselves. And it is some of these factors that will influence the results. Or maybe meat lovers smoke more often.

Researchers may try to control these confounding factors, but it is impossible to track them all.

Many dietary studies rely on surveys

Many observational (and non-observational) studies rely on survey data. Scientists cannot stand behind each person's shoulder for decades and watch what he eats. I have to ask.

An obvious problem appears. Do you remember what you ate for lunch yesterday? Crumbled nuts into a salad? And then you had something to eat? And how many grams, in grams, did you eat this week?

Most likely, you will not be able to answer these questions with the required accuracy. But a huge amount of research uses this data: people themselves tell what they remember.

When the researchers decided to test these memory-based nutritional assessment methods for the magazine, they found the data "fundamentally wrong and hopelessly flawed." After reviewing a nearly 40-year national study of population health and nutrition, which was based on self-reported dietary reports, the researchers concluded that the reported calories reported by 67% of women could not physiologically match objective data on their body mass index.

Maybe this happened due to the fact that everyone lies and gives those answers that public opinion will approve. Or maybe the memory fails. Whatever the reason, it doesn't make it easier for researchers. I had to create protocols that take into account some errors.

I need a camera, gastric and intestinal implants, as well as a device in the toilet that will collect all your secretions, instantly process them and send information about their full composition.

Christopher Gardner

Christopher Gardner, a Stanford researcher, says that in some studies, he provides food for participants. Or it involves nutritionists who closely monitor the diet of the subjects, checking their weight and health status to confirm the purity of the experiment. He calculates an error that can be kept in mind when analyzing other results.

But researchers dream of better instruments, such as sensors that detect chewing and swallowing movements. Or trackers that will display the movement of the hand from the plate to the mouth.

All different. Both people and products

As if there were few problems with the accuracy of the data … Scientists have learned that different bodies react differently to the same food. This is another factor that makes it difficult to study the effects of diet on health.

In a recent study published in the journal, Israeli scientists monitored 800 participants for a week, constantly collecting blood sugar data to understand how the body responds to the same food. Each individual's response was individual, suggesting that universal dietary guidelines were of limited benefit.

It is clear that the impact of nutrition on health cannot be considered only in terms of what a person consumes. Much depends on how nutrients and other bioactive food components interact with the genes and gut microflora of each individual.

Rafael Perez-Escamilla Professor of Epidemiology and Public Health at Yale University

Let's complicate the problem. Foods that appear to be the same actually differ in nutrient composition. Local farm-grown carrots will contain more nutrients than the mass-produced carrots found on supermarket shelves. A diner burger will contain more fat and sugar than a homemade burger. Even if people will report what exactly they ate, the difference in the composition of the products will still affect the result.

There is also the problem of meal replacement. When you start consuming one product in large quantities, you have to limit the use of something else. So if a person chooses to eat a diet rich in legumes, for example, they are more likely to eat less red meat and poultry. The question is, what influenced the results more: beans or avoiding meat?

The latter problem is vividly illustrated by dietary fat. When scientists looked at a group of people who were on a low-fat diet, they found that a lot depends on what they substituted for the fatty foods. Those who instead of fat began to use sugar or simple carbohydrates, as a result, they suffered from obesity and other diseases in the same amount as people who ate a lot of fat.

Conflict of Interest - Nutrition Research Issue

There is one more complication. Today, nutritional science cannot count on government funding. This creates an extensive field for sponsorship by private companies. Simply put, food and beverage manufacturers pay for a huge amount of research - sometimes the results are dubious. And the legislative sphere of nutrition is not as tightly regulated as medicine.

There is so much research by manufacturers that professionals and consumers alike may question even the basic principles of healthy eating.

Marion Nestle

Sponsored research yields results that benefit sponsors. For example, out of 76 sponsored studies conducted between March and October 2015, 70 did what the product makers needed.

"Mostly independent studies find a link between sugary drinks and poor health, but those that the soda makers paid to do are not," Nestlé writes.

No matter what, nutritional science is alive

The complexities of studying nutrition create the feeling that it is generally unrealistic to find out something unambiguous about the effect of diet on health. But this is not the case. Researchers have used all of these imperfect tools for years. A slow and careful approach pays off.

Without these studies, we would never have known that a lack of folate during pregnancy leads to the development of fetal malformations. We would not know that trans fats have a negative effect on the heart. We wouldn't know that soda in large quantities increases the risk of diabetes and fatty liver disease.

Frank B. Hu Professor of Public Health and Nutrition, Harvard University

The researchers discussed how they determine which data to trust. In their opinion, it is necessary to evaluate all available studies on one issue, and not isolated reports.

They also recommend looking at different types of research that focus on the same subject: clinical research, observational data, laboratory research. Different work with different introductory, different methods, leading to the same results, is an objectively good indicator that there is a connection between diet and changes in the body.

You need to pay attention to the source of research funding. Independents are funded by state and public funds and are more credible, in particular because the research plan has fewer constraints.

Good researchers never say they've found a superfood, or advise them to completely skip a particular product, or make bold claims about the effects of eating a particular fruit or type of meat, limiting themselves to the assumption that a particular diet might be beneficial.

These tips reflect the general consensus of researchers who have recently discussed nutrition and health issues. Here are the conclusions of their meeting:

A healthy diet consists of lots of vegetables, fruits, whole grains, seafood, legumes, nuts, and low fat; you also need to be moderate in your consumption of alcohol, red meat, and processed meats. And there is also less sugar and processed grains. You don't have to completely cut out any food group or stick to a strict diet to get the best results. You can combine foods in many ways to create a balanced diet. The diet should take into account individual needs, preferences and cultural traditions.

Claims that cabbage or gluten, for example, are killing humanity are not the voice of science. Because, as we understood, science simply cannot prove anything like that.