Tell us the truth about nutritionists
Authors: Ben Goldacre
Journal: BMJ (2007)

They're certainly keen to praise themselves, but if you really wanted to do some primary prevention work in the community, would you start with the media nutritionists? The answer, for reasons of increasing seriousness, is no. 

Firstly, to anyone who's interested in science, it's simply offensive to find newspapers and television channels filled with people who adopt a cloak of scientific authority while apparently misunderstanding the most basic aspects of biology. “Dr” Gillian McKeith has a non-accredited correspondence course doctorate from the United States and a primetime show on Channel 4 television. She writes that sprouting seeds contain “all the nutritional energy necessary to make a fully grown plant” and that chlorophyll is “high in oxygen,” and she recommends that you eat “lots of dark green leaves, because they will really oxygenate your blood.” 

As any 14 year old biology student could tell you, plants only make oxygen in light: it's very dark in your bowel; and even if, to prove a point, you put a searchlight up your bottom, you probably wouldn't absorb too much oxygen through the gut wall. 

But if we excuse their silliness, do these characters improve the nation's health? If they do, it comes at a cost: because even the most superficially plausible media nutritionists distort the scientific evidence to justify their profession. The reality is that intervention trials looking at dietary changes are hard to do. Broad brush interventions, such as eating fresh fruit and vegetables, have a reasonable evidence base, but there's rarely any convincing data for the finicky, obsessive dietary changes detailed in the popular media. 

At worst, media nutritionists will, in response to this absence of evidence, simply make it up. There are plenty of examples in the archives at my site www.badscience.net. More commonly they cherry pick the literature, selecting only favourable studies and ignoring the overall picture. But most corrosive is the way they misrepresent, from their position of dominance in the mainstream media, what scientific evidence for a clinical assertion would actually look like. 

The entire field is based on a small palette of simple academic errors. Food gurus extrapolate wildly, creating hypotheses from metabolism flow charts or interesting theoretical laboratory bench data, and then using them to justify a clinical intervention. One newspaper nutritionist, in the Daily Express, tells us that turmeric is “highly protective against many forms of cancer, especially of the prostate.” But the only evidence for the link between turmeric and prostate cancer is from speculative laboratory studies of cells, usually from rats, growing (or not growing) in glass dishes. Interesting findings these may be, but they are not a sound scientific foundation for real world advice on curry. 

Similarly, the media nutritionists extrapolate from observational data to giving “evidence based” interventional advice. In the Mirror recently a “registered nutritionist” wrote, “An Australian study in 2001 found that olive oil (in combination with fruit, vegetables and pulses) offered measurable protection against skin wrinkling.” But the paper she referred to (Journal of the American College of Nutrition 2001;20:71-80) was an observational study, not an intervention study. It surveyed the diets and wrinkles of people in a pool of four different groups, from different countries, with a range of lifestyles: the confounding variables are hardly tricky to spot. 

Media nutritionists speak with a grain of science, but all too often it's like the difference between astrology and astronomy. Nutrition is one of the few areas where the notion of scientific evidence for health interventions is popularly discussed: the nutritionists take this opportunity and use it to promote the public misunderstanding of science, laying fertile ground for health scares and a misled population. 

But most offensive to me, as a hard working NHS doctor, is the way that media nutritionists assume the moral high ground, as if they were somehow the source of all that is right and good in the management of lifestyle risk factors for cardiovascular disease and cancer. Nutritionists trade on a peculiarly obsessive, overcomplicated, narcissistic, and—dare I say it—right wing, individualist take on the management of risk factors. But in reality the most important lifestyle risk factors for ill health are difficult and unglamorous ones, such as social inequality. 

Public health interventions to address these real problems are far less lucrative and far less of a spectacle than anything a food crank or a television producer would be willing to delve into. What prime time series looks at food deserts created by drive-in supermarkets, companies with which media nutritionists so often have lucrative commercial contracts? Which television shows deal with social inequality as a driver of health inequality? Where's the human interest in prohibiting the promotion of bad foods, using taxation to make nutrient rich foods more accessible, or maintaining a clear labelling system? Where is the spectacle in “enabling environments” that naturally promote exercise or in urban planning that prioritises cyclists, pedestrians, and public transport over the car? 

Basic, uncomplicated dietary advice is effective and promotes health. Overly complicated, confusing, tinkering nutritionism is poorly evidenced, because it's a branch of the entertainment industry—it's there to make money, to create a new market for a new profession, to soup up a recipe show, to titillate, to distract us from social inequality and the real lifestyle causes of ill health, and to pander to our collective modern obsession with food. It tarnishes and undermines the meaningful research work of genuine academics studying nutrition. 

The media are now wading into the confusion with programmes such as The Truth About Food, but their efforts are misplaced: it's the truth about nutritionists that needs to be told. 

Basic, uncomplicated dietary advice is effective and promotes health. Overly complicated, confusing, tinkering nutritionism is poorly evidenced, because it's a branch of the entertainment industry