With a week to go until the start of 2022 – and so much demand for a better year ahead than the one we are leaving behind – the time is ripe for making New Year’s resolutions. Few lists will be significantly different than those of years past. Every year, polling companies find the most popular resolutions to be the same the world over: eating better, exercising more and losing weight. It is hardly a wonder why; the holiday season at the end of December is, in many wealthier countries, responsible for up to half of the average weight gained over the course of the year. In a world ridden with Covid-19, old ambitions for a slimmer waistline have gained a new urgency. Diet, exercise and overall fitness are major factors in staying healthy during this pandemic. Maintaining a healthy diet is arguably the trickiest of these, particularly so soon after one has spent days feasting on Christmas dinners, Boxing Day lunches and New Year’s brunches. According to a new study carried out in the UAE, however, diet may play an even larger role than was previously thought in maintaining the body’s defences against Covid-19. Scientists at the University of Sharjah and Khalifa University of Science and Technology, among others, found that the make-up of the body’s gut microbiome – the ecosystem of bacteria inhabiting our bellies – may influence the severity of a Covid-19 infection. It is a surprising hypothesis for what is primarily a respiratory disease. But the foreign bacteria residing in the gut, introduced there mainly through our food, play a role in fighting infections and helping to boost immune response. Covid-19 can threaten these bacterial colonies directly, by entering a protein called the ACE2 receptor, which sits on the surface of many cells, including those found in the lungs and intestines. ACE2 receptors regulate gut bacteria, and so an invasion of Covid-19 virus particles has the potential to disrupt the gut microbiome, which could result in worse symptoms and a poorer immune response. Maintaining a healthy microbiome, by eating nutritious and probiotic foods (ie, foods that promote the growth of good bacteria), can reduce the threat and long-term impact. Prof Tim Spector, a genetic epidemiologist at King’s College London, suggests that more plants and vegetables in one’s diet, and fewer processed foods, are an easy way to achieve this. Most resolution-writers would respond by saying: “Tell me something I don’t know”. But there are other ways to improve one’s gut microbiome. Adding fermented foods to one’s diet – such as kimchi, miso, sauerkraut, pickled vegetables, kefir and yoghurt – is among the simplest. It is not a solution that is to everyone’s taste (although some will certainly be delighted). But part of the tradition of passing into a new year is to make necessary sacrifices, whether it is to absolve oneself of the guilt of a holiday season’s gluttony, or to ensure that each new year is happier – and healthier – than the last.