麻豆传媒

IN THE space of less than a week, I read three front-page stories about 鈥渞evolutionary鈥� science-based diets that shield against covid-19. Intriguingly, all three eating patterns seemed rather different to each other, despite all being published in the same newspaper. The only thing that seemed to unite them was that the proponents, helpfully, also had new diet books out.

There are dozens of 鈥渃orona diets鈥�, hailing everything from meat and ultra-low carbs to 鈥渟uperfoods鈥� and veganism as ways to boost your immune system and protect you from the virus. It is a minefield. What does the evidence really say?

Covid-19 is such a new disease that there is very little research in this area. Most of the tiny handful of studies that have been done to date are just weeks old and haven鈥檛 been peer-reviewed. It is impressive, then, that fully illustrated cookery books with hundreds of recipes could have been developed based on this scientific evidence, despite being published at the same time.

First up, supercharging your immune system with specific foods, like garlic and honey, is an old debunked idea. 鈥淪imply put, you cannot 鈥榖oost鈥� your immune system through diet, and no specific food or supplement will prevent you catching COVID-19/Coronavirus,鈥� said the .

This is just as well. An overactive immune response seems to be responsible for the worst effects of covid-19. So even if you could 鈥渟upercharge鈥� your immune system, it might be a very bad idea.

In the absence of evidence for boosting immunity, many stories have focused on early evidence of a link between obesity and more severe covid-19 outcomes. The argument seems to be that, as thinner people tend to experience fewer complications from covid-19, any weight-losing diet will lead to a reduction in risk. But this oversimplifies the evidence.

Although there are plausible reasons for a potential causal link, such as people with obesity often showing poorer lung function, there is currently no evidence that weight loss reduces the likelihood or severity of infection, merely that people who are already lean tend be at lower statistical risk. Correlation does not equal causation.

鈥淭he only thing that seems to unite the diets is that the proponents also have new diet books out鈥�

To put this in context, people who are obese are more likely to be in other covid-19 risk groups, such as belonging to a black or Asian ethnic group and being over 65 years of age, but that doesn鈥檛 mean that going on a diet will make you younger or affect your ethnicity.

However, research has consistently shown that obesity disproportionally affects people living on lower incomes, who are also more likely to experience chronic stress, poor diet and physical inactivity 鈥� all risk factors for compromised immunity. So obesity may in fact be a symptom of underlying risk factors rather than a risk factor in its own right.

Given this list of complex, poorly understood factors, it is tricky to claim that any diet will reduce covid-19 risk. We just don鈥檛 have enough information.

What we do know is that some nutrients are essential to a healthy immune system, such as vitamin C, zinc and selenium. Certain dietary patterns, such as eating plenty of fruit, vegetables and wholegrains, may help reduce the inflammation that can contribute to complications in covid-19. And of course, a healthy weight is associated with a lower risk of an enormous array of other health risks.

If you think that sounds like boring standard dietary advice, that is because that鈥檚 exactly what it is. The most up to date and comprehensive review of the effect of diet on the potential mitigation of covid-19 by : 鈥淔ollowing any healthy diet at this time鈥� will support immune function.鈥� Not much of a book in that though.