Another diet study, another controversy, and the public are wondering what to make of it. This is a series of studies in the Annals of Internal Medicine by an international research group showing that human consumption of red and processed meat does not have to be reduced.
One study after another has revealed that red and processed meat is so harmful to health that the World Health Organization lists red meat as a likely carcinogen and processed meat as such .
This new study does not dispute the finding of a possible increased risk of heart disease, cancer and early death due to meat consumption. However, the panel of international nutritionists concluded that the risk is so low and the studies of too low quality to justify a recommendation.
What does the new research really say?
The authors conducted a study on studies. This happens when the results of one or two researches may not be final. Or the effect of something is so small that you need to group smaller studies into one larger one. The authors said that reducing the intake of unprocessed red meat by three servings per week is associated with about eight percent less lifetime risk of heart disease, cancer and premature death.
are not surprising. However, this is a much smaller change in health than stopping smoking, eliminating high blood pressure or starting physical activity.
Read more: Yes, we still have to cut back on red and processed meat
The authors differed from earlier studies in that they considered both research as also assessed the benefits of reducing meat consumption to make their recommendations. They used a standard practice in medicine to evaluate the quality of the studies and determined that they were bad. In addition, they assessed the benefit of reducing unprocessed red meat (about eight percent lower lifetime risk) than low. They have collectively advised against the need to reduce meat consumption.
This has upset nutrition and health scientists. Serious Concerns .
Studies identify association, not causation
Food science is chaotic. Most of our guidelines are based on observational studies where scientists ask people what and how much they have eaten in a given time period (usually the previous year), and then follow them for years to see how many people are sick or die ,
Often the diet is evaluated only once, but we know that people's diet changes over time. Stronger studies are asking people to report their diets several times. This can take changes into account. However, it is known that self-reported nutritional data is poor . People may know what they have eaten, but they do not know how much and how it was prepared. All of this can affect the nutritional value of a food.
These studies also identify associations only and not causes. This does not mean that causality is not possible, only the design of the study can not show this. When a series of observational studies show similar results, our confidence in a causal effect tends to increase. But in the end this is still weak evidence.
Sticking to diets is a challenge.
The gold standard in medicine is the randomized controlled trial in which people are randomly assigned to different groups, with the best known being a new drug versus placebo. Some say we should not use the same nutritional standard because it is difficult to do so. Keeping diets is a major challenge, which is why it is difficult to carry out a study until it has an impact on the disease, not to mention the associated costs.
In addition, the diet is complex. It's not like smoking, where the goal is not to smoke at all. We have to eat to live. So if we stop eating one thing, we'll probably replace it with another. Which food we choose as a substitute may be as important to our overall health as what food was stopped.
There are numerous cases where observational studies have shown that the protective effect of a nutrient is refuted only in randomized trials. Observational studies have suggested that vitamins C, D and E, folic acid and beta-carotene preparations prevent disease. These claims remained unproven in randomized trials.
Beta-carotene supplementation, for example, has been shown to increase the risk of lung cancer . By not equating nutrition science with other medical sciences, we can do more harm than good to the public.
Weak evidence leads to poor guidelines.
From a public health point of view, a small individual change throughout the EU has repeated population can lead to major changes at the societal level. This could lead to changes in the average age of onset or the mortality rate, which in turn could lead to lower healthcare costs. That's why guidelines are required, but if we have bad evidence, we come up against bad guidelines.
Life expectancy has increased noticeably in recent centuries throughout the world. Although there are many reasons for this, advances in nutritional science are central. This knowledge has led to the elimination of nutrient deficiencies. Nowadays, most people in North America are not too worried about rickets, goiters or scurvy.
In the future, however, additional nutritional research will lead to less notable gains in quality and longevity, measured in days, not years.
As the war of words among scientists and public health officials continues, the real drawback to the general public is that leadership awaits. Over time, this ongoing inflamed rhetoric turns into white noise that is ignored at best and diminishes confidence in nutrition science.
One might wonder if we should stop nutrition research altogether until we can do it right.
] Scott Lear writes the weekly blog Scott Lear .
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This article was originally published under The Conversation. The article contributed to Live Science's Expert Voices: Op-Ed & Insights .