A healthy diet includes extremely low consumption of meat. This was previously the consensus in nutritional medicine. But then suddenly many major newspapers and online portals headlined: You can eat more meat with peace of mind. Because according to a US meta-study that summarizes numerous other studies, there is no evidence that meat is unhealthy.
The publication caused a stir in early October 2019 because it challenges the findings of nutritional science. But experts criticize the alleged turnaround in nutritional medicine as irresponsible: Immediately after publication, numerous counter-statements from well-known scientists and institutions, including the World Cancer Research Fund and the Max Rubner Institute, appeared.
Why the Fleisch Study is Misleading
In their meta-study, the authors summarized large amounts of data from different studies:
- In the first three analyses, they evaluated more than 100 observational studies with a total of six million participants. These consistently show a positive effect on the risk of dying from cancer when people reduce their meat consumption just a little bit.
- The fourth analysis showed little or no effect of on cardiovascular disease and cancer. However, the study was dominated by a study with a large number of participants (Women’s Health Initiative, WHI), which does not examine meat reduction, but the importance of a low-fat diet.
- The fifth analysis only examines whether people like to eat meat – regardless of its health effects.
Three studies confirm that reduced meat consumption is healthier. The fourth showed a small effect and the fifth did not provide any useful data on the question. Thus, the authors should actually have recommended a reduction in meat consumption. Instead, they criticized that the available observational studies did not have the same validity as studies on the approval of new drugs.
Why nutrition studies are often problematic
The best standard for gaining certainty in medicine is so-called randomized controlled trials (RCTs). Whether a therapy works is determined by comparing a test group that is given a new drug, for example, with a control group.
Since it is not possible to study people for nutritional studies in a laboratory over decades and to randomly feed them sausage or a placebo sausage while the rest of the diet of the two groups does not differ, only observational studies can be carried out. Although these are methodologically weaker than randomized controlled trials, they are the best studies currently available.
Meta study commissioned by the agricultural lobby?
Experts also distrust the controversial meta-study for another reason. Because their authors are obviously not as independent as they claim. Some were financed by the US agricultural lobby, which, among other things, is committed to more cattle breeding in Texas.
The lead author Bradley C. Johnston had already attracted attention in 2016 with a study that downplayed the health consequences of sugar and was funded by the soft drink and fast food industry, among others.
In addition, the authors justify their surprising recommendations in part with studies that were not about health. The health consequences of a vegetarian or vegan diet were not examined.
Nutritional medicine recommendations
The US meta-study has not changed the recommendations for nutritional medicine in Germany. Accordingly, a healthy diet consists of
- lots of vegetables
- good oil
- enough dietary fiber
- as little sugar and meat as possible
Possible consequences of meat consumption
Not everyone who eats a lot of meat gets sick. But numerous diseases are caused or aggravated by high meat consumption:
- colon cancer
- Cardiovascular diseases, such as coronary artery disease (CHD)
- renal insufficiency
- chronic inflammation
Meat consumption affects the intestinal flora
Millions of bacteria live in the gut, the so-called microbiome. It is ascribed an essential role in the immune system. A person’s microbiome is as individual as their fingerprint – and it develops depending on how we live and what we eat. High meat consumption leads to potentially aggressive bacteria multiplying in the microbiome, which can cause inflammation and, in the long term, colon cancer.
Meat consumption increases the risk of cancer
Because there are people who are harmed by high meat consumption, the World Health Organization (WHO) already took action in 2015: It classified processed meat as definitely carcinogenic and red meat as probably carcinogenic. That means processed meat