The ‘you are what you eat’ connection between food consumption and health outcomes is so well-established it’s practically irrefutable. Search ‘diet and disease’ on PubMed (the go-to database for scientific research) and you’ll get over 150,000 results – and that’s just one search term. There’s robust evidence that a diet rich in fruit, veg, wholegrains, fish and nuts can dial down your risk of heart disease, Type 2 diabetes, cancer and stroke, while dietary villains like soft drinks and processed meat do the opposite. You can drill down further, and link specific nutrients to health outcomes – for instance, we know insufficient iron causes anaemia, zinc promotes immunity, while magnesium regulates blood pressure.
Still, our knowledge wasn’t always at this level – it’s taken some fearless scientists with a keen interest in self-experimentation to prove that what we ingest impacts our disease risk, as British doctor and science presenter Dr Michael Mosley reveals in episode three of Medical Mavericks.
Food is more than just basic fuel
It’s hard to believe, but back in the 18th century, Mosley tells us, “the human body was simply a machine which burnt fuel and it really didn’t matter what the fuel was.” Then, along came Dr William Stark, who in 1769, disproved this. To discover which foods were good and which were bad, he put himself on a diet of bread and water, adding in large amounts of unhealthy foods such as honey pudding, one by one. It was his decision to add Cheshire cheese next, instead of fruit, which ultimately led to his death from scurvy. “He might have gone on to become one of the early pioneers of vitamin research, instead he became the first martyr of nutritional science,” says Mosley.
The power of essential fatty acids
Another case of self-experimentation that Mosley investigates in the episode is that of late scientist Dr Hugh Sinclair. Convinced that heart disease was caused by eating too little – rather than too much – fat, he put himself on an Inuit diet rich in oily fish and seal blubber. It was a perilous experiment: while fish oils produce less cholesterol than saturated fat, consuming them in excess can interfere with blood clotting. “He would have had a risk of a severe gastric bleed on that diet and possibly having a stroke,” says Professor Tom Sanders from King's College London, who appears in the episode.
It was his decision to add Cheshire cheese next, instead of fruit, which ultimately led to his death from scurvy.
After three months on the diet, Sinclair's blood had thinned significantly from the diet - from four minutes to a whopping 50. “He’d finally proven the potency of essential fatty acids,” Mosley tells us.
Deprivation in the name of long-term gains
Calorie restrictors are other self-experimenters under Mosley’s microscope in this episode. These sticklers for self-denial dramatically slash their energy intake, with the pay-off being reduced oxidative stress, which in turn protects against age-related disease.
According to a 2019 Lancet Diabetes & Endocrinology study, people who stuck to a calorie-restriction diet for two years had a “persistent and significant reduction” in cardiometabolic risk factors, plus improvements in C-reactive protein (a marker of inflammation), insulin sensitivity and metabolic syndrome scores.
“There is a core of probably 50 people who are doing a real experiment on themselves because they are the people who are really convinced that calorie restriction will allow them to live longer,” says Dr Luigi Fontana from the Italian National Institute of Health in Medical Mavericks. In the episode, Mosley meets calorie restrictor Dave Fisher, who has been living on less than two-thirds of the normal calorie intake for 17 years. Both men go through a batch of health tests (such as sight, hearing, lung capacity and reaction times, all of which deteriorate with age), with Fisher coming up trumps. “Thankfully I did beat him with my lung function test,” Mosley notes with relief.
Mosley braves a fish binge
As a self-professed ‘human guinea pig’, Mosley can’t resist an extreme experiment of his own in this episode, putting himself on a two-month-long “fish binge”, involving bountiful oily fish and fish oil. “It’s claimed eating oily fish reduces the risk of blood clotting,” declares Mosley. “So at the start and end of my experiment, I'm going to measure my bleeding time.”
His initial bleeding time clocks in at four minutes and 11 seconds. Skip to the end of the experiment and it nearly doubles, to eight minutes and 12 seconds. “It means I’m much less likely to develop blood clots which in turn means I’m much less likely to have a heart attack,” he says. Thankfully, there’s no need for the rest of us to dabble in kooky experiments: a balanced, wholefoods-based diet is pretty hard to go wrong with.
Dr Michael Mosley explores the ways in which pioneering doctors laid the foundations of modern medicine by experimenting on themselves. Michael mosley: Medical Mavericks, Diets & Disease airs on Monday, March 16 at 9:40pm on SBS and then it will be available via SBS On Demand.
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