Analysis

Dietary guidelines and health—is nutrition science up to the task?

BMJ 2018; 360 doi: https://doi.org/10.1136/bmj.k822 (Published 16 March 2018) Cite this as: BMJ 2018;360:k822
  1. Dariush Mozaffarian, Jean Mayer professor of nutrition and medicine1,
  2. Nita G Forouhi, professor of population health and nutrition2
  1. 1Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA, USA
  2. 2MRC Epidemiology Unit, University of Cambridge, Cambridge, UK
  1. Correspondence to: D Mozaffarian dariush.mozaffarian{at}tufts.edu

Despite criticism and controversy, nutrition science can be relied on to improve our understanding of food and health, argue Dariush Mozaffarian and Nita Forouhi

Nutrition science has been much criticised. Two concerns stand out. The first is that it relies too much on observational studies susceptible to confounding and errors in self reported dietary assessments and on small short term interventions with questionable relevance to the real world. The second is that the conclusions are ever changing: a given nutrient or food is said to be harmful one moment, then healthy, then harmful again.

Is nutrition science methodologically inferior to other fields? Is nutrition knowledge insufficiently stable to be useful? Is it even causing harm? To examine these questions, we consider the evolution of modern nutrition science and the reliability of nutrition evidence compared with other disciplines.

History of modern nutrition science

A reasonable birthdate for modern nutrition science is 1932, when vitamin C was first isolated and proved to cure scurvy. Other single nutrient deficiencies were identified in the following decades, including vitamin A and night blindness, vitamin D and rickets, thiamine and beriberi, niacin and pellagra. At the same time, the Great Depression and second world war heightened concern over food shortages. This coincidence of scientific discovery and geopolitics produced a strong focus on single nutrient deficits.

By 1980, less than 50 years later, these diseases had been largely eradicated in wealthier nations through successes in nutrition science and improvements in farming and food production. As chronic diseases such as cancer and heart disease began to take centre stage, the previously successful, reductionist approach to nutrition science was carried forward1: identify the relevant nutrient for a disease, establish its target intake, and translate this as a simple message. Thus, saturated fat and dietary cholesterol became “the” causes of heart disease and …

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