A new study recently published in the Annals of Internal Medicine raised some uncomfortable questions about dietary advice and nutritional research. NutriRECS researchers published their findings concluding that there was only “low- or very low-certainty” evidence existed to show that this meat causes any kind of disease. Not cancer, not heart disease, not Type 2 diabetes. They concluded that contrary to current dietary recommendations for reducing red meat consumption, there is insufficient evidence to advocate for more or less.
Even before publication of the papers, heavyweights in the field of nutrition science signed a letter demanding a preemptive “retraction” of the review. All the signers were members of a group called the True Health Initiative that advocates for a plant-based diet. The findings and the study have been widely criticised by nutrition researchers for being irresponsible and unethical, while others have defended the findings, saying they are based on strong science unlike prior dietary advice.
After publication of the controversial red meat review the Washington Post was revealed that while the NutriRECS researcher had formed a partnership with an arm of Texas A & M University that is partially funded by the beef industry. The non-disclosure of funding – however small – has further clouded the findings of the study.
Defending the Annals review, executive director of US NGO Nutrition Coalition Nina Teicholz said data from the US Government shows that despite a 28% reduction in red-meat consumption in the US since the 1970s, 60% of Americans still suffer from at least one chronic disease where diet is a major risk factor.
The larger issue concerns nutritional science itself and what it is possible to conclude from epidemiological studies about the effect of just one component of the diet. To conduct research in the form of randomised clinical trials – dubbed as the gold standard for medical evidence – is nearly impossible. It would require randomising and then feeding a sample of people meat/no meat for decades. Nutritional guidelines are therefore mostly based on epidemiological studies that follow a large group of people over time and asking them to self-report what they’ve eaten and then observing eventual health outcomes. While these studies can establish association, they rarely establish causation. In addition, people forget – or even lie about – what they eat. Red meat can be particularly problematic because high consumption is often a marker for lower concerns about nutrition and health.
While newspapers and consumers want simple take-home messages, according to epidemiologist Gideon Meyerowitz nutrition science is “fiendishly complicated, and we’ll probably never know whether red meat is good or bad for your health”.
With conflicts on both sides and differences in findings more about interpretation rather than definitive evidence either way, this latest study will only add to consumer confusion. It calls into question the broader conduct and interpretation of nutritional science based on epidemiological studies, spiced up by arguments about funding or ideological biases – will only add to consumer mistrust.