Has ‘clean’ really become a dirty word? BBC Horizon’s latest instalment sheds some much-needed light on the term to help distinguish promise from proof

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Did you tune into BBC Horizon’s latest instalment, Clean Eating: The Dirty Truth? We definitely did and it was a corker. Dr Giles Yeo, Geneticist from the University of Cambridge and President of the British Society of Neuroendocrinology dug down into the ‘clean’ eating phenomenon in an attempt to sort truth from the pseudoscience. As an Instagram hashtag, the term has had more than 27 million posts and has spawned legions of social media stars. What does it really mean though and what influence is it having on our eating habits and our health?

Dr Yeo took a closer look at some of the best-known pillars of clean eating such as plant-based, gluten-free, grain-free and alkaline diets. By interviewing those who advocate them, he hoped to get to the bottom of the advocacy vs science debate to see whether the health benefits that many of them claim are founded or unfounded. He looked at the influence of social media; interviewing one of its biggest stars, Deliciously Ella and setting up his own ‘clean eating’ Instagram account, which saw him attract over 200 followers in less than two weeks.

The term ‘clean eating’ has seen a huge shift in meaning in recent times, with Deliciously Ella (Ella Mills, often dubbed the ‘queen of clean’ for her plant-based diet) telling Dr Yeo, “My problem with the word 'clean' is that it’s become too complicated, too loaded.” She adds, “I haven't used it, but as far as I understood it when I first read the term, it meant natural, kind of unprocessed, and now it doesn't mean that at all. It means diet, it means fad.”

Ella put up a good and balanced defence. While she eats a plant-based diet, for her, it essentially means recipes created largely on plant-based ingredients, which can be adapted. Her stance was that she’s never claimed to be an expert and that her cookbooks were designed to provide inspiration rather than prescription - a way to make vegetables all the more appetising.

Ella credits The China Study as one of her key sources of information when trying to find ways to overcome her Postural Tachycardia Syndrome. The study, which has sold two million copies worldwide, put forward the theory that a plant-based diet was the best way to reduce the likelihood of developing chronic diseases, and recommended that animal based products be avoided. But is it?

To dig a little deeper, Dr Yeo travelled to the States to interview its author, Professor Campbell. Discussing the findings that led to the study’s conclusion, Dr Yeo raised the issue that the study didn’t take into account factors such as genetics, thereby casting doubt on the direct link between eating animal protein and increased risk of disease.

What about the trend for going gluten-free? This was another one of the clean eating pillars that Dr Yeo set out to investigate. Despite only one per cent of the UK population actually suffering from a clinical gluten allergy (coeliac disease specifically), the number of people going gluten-free is much higher. He spoke to the author of Wheat Belly, Dr William Davis, a cardiologist who advocates going one step further and going completely grain-free. Citing that the Hemsleys have taken inspiration from his work, Dr Yeo sought to find out more about his findings. Dr Davis goes on to tell Dr Yeo that grains are harming all of us, to some degree, "without exception,” and claims that grains lead to increased risk of heart disease and autoimmune disorders. Controversial claims to say the least. But do they hold any merit? In order to find out, Dr Yeo interviewed Dr Alessio Pasano, the pediatric gastroenterologist and researcher credited by Dr Davis for highlighting the connection. However, Dr Pasano didn't believe that the link was founded. According to him, gluten is only a problem if you have four other problems already: genetic predisposition, a leaky gut, a faulty immune system, and imbalanced gut microbes. So it appears that Dr Davis’ claims may simply be helping to fuel unfounded fears generated by the #eatclean phenomenon.

To test the next pillar of the clean eating empire, Dr Yeo travelled across the Atlantic to interview Robert Young, dubbed ‘The Godfather of alkaline.’ This was probably the most shocking case of clean eating’s negative side highlighted on the show. Having run programs where cancer patients were treated with alkaline food at his home, one person died while at his ranch and following an investigation by the Medical Board of California, Young was convicted on two of seven charges of practising without a medical licence. He faces up to 3 years in prison.

Clean eating is deservedly under the spotlight, but was the programme balanced? It would have been helpful to have seen interviews with other leading healthy foodies such as the Hemsleys (who Dr Yeo alleges have taken inspiration from Dr Davis' work) and Natasha Corrett, who credits Robert Young as an influence in her book, Honestly Healthy, all of whom were approached to appear. The Hemsleys did release a statement saying: “Grains are already abundant in a modern diet so our recipes celebrate other ingredients. We don't believe in absolutes and no one way of eating suits everyone.” Natasha Corrett refused to comment initially, but since the making of the programme, she provided the following statement: "We believe that our bodies should be fuelled with healthy and nutritious ingredients, but we also believe that life is about having things in moderation."

So is ‘clean’ eating a dirty word? According to the programme, context is key and the bigger the claim, the more research should be done. We certainly welcome the fact that the programme has ignited debate and is making us all more aware not only of the health claims that are made for certain eating regimes but the language we use around food, the money to be made in ‘healthy’ cookbooks and the ease with which foods can be demonised.

Speaking on Radio 4, Dr Yeo said that his findings from the programme wouldn’t make him rich – in fact, he said the conclusion he came to was the world’s most boring answer – everything in moderation.