As we all know by now, there are many things we can do to reduce our risk of infection by the coronavirus SARS-CoV-2: Frequent hand-washing, social distancing, disinfecting door-handles and surfaces, and hunkering at home.

In addition to these external measures, we can also reinforce our defenses from the inside. One powerful way of doing that is to nurture healthy gut microbes (a.k.a. microbiome).

Research is increasingly showing that the micro-organisms that live in our digestive tract — an estimated 100 trillion — play a key role in ensuring our overall health. They don’t just support our digestion, they’re also involved in regulating our metabolism, our nervous system and brain function, our weight, sex hormones and many other functions.

One of the most important functions of the microbiome is to help regulate our immune system. Indeed, about 70% of our immune cells are located in the gut and depend for their proper functioning on a healthy population of gut microbes.

As Tim Spector, Professor of Genetic Epidemiology, King’s College London, points out, the gut microbiome plays an essential role in the body’s immune response to infection and in maintaining overall health.

“As well as mounting a response to infectious pathogens like coronavirus, a healthy gut microbiome also helps to prevent potentially dangerous immune over-reactions that damage the lungs and other vital organs.” These excessive immune responses can cause respiratory failure and death. (This is also why we should talk about “supporting” rather than “boosting” the immune system, as an overactive immune response can be as risky as an under-active one, he notes.)

A healthy microbiome is a delicate balance. When the microbes in our gut are out of balance (a situation called dysbiosis), this can contribute to a range of conditions, including inflammatory bowel disease, chronic fatigue syndrome and even cancer. Many factors can cause our microbes to get out of whack, including stress, illness, alcohol use, a high intake of sugary, refined and processed foods, being overweight and not getting adequate sleep.

Gut health starts with food

Rather than taking expensive (and unproven) probiotic supplements to support gut health, I usually advise my clients to focus first on eating food that nourishes their microbiome, for our diet has a powerful effect on the types and number of microbes in the gut.

There are many ways to improve the gut microbiome:

  • Eating a wide variety of foods: A highly diverse diet can foster a wide variety of microbes in our gut, which in turn makes for a more effective and resilient microbiome. Microbiome diversity declines as we get older, which may help to explain some of the age-related changes we see in immune responses; so it’s important to nurture a diverse microbiome throughout life. In particular plant foods like legumes and fruit contain the fibers and starches that can promote the growth of healthy gut bacteria (see studies here, here, here and here). Excellent article on microbial diversity here.
  • Eating a Mediterranean diet; this way of eating has been shown to improve gut microbiome diversity and reduce inflammation (esp. among older folks). The Mediterranean diet I recommend is rich in vegetables, low-glycemic fruits, nuts, seeds and legumes; healthy fats like high-quality extra virgin olive oil; and moderate amounts of meat, fish, eggs and fermented dairy foods.
  • Eating fermented foods: Fermented foods such as yogurt, sauerkraut and kefir all contain healthy bacteria, mainly Lactobacilli, and can reduce the amount of disease-causing species in the gut.
  • Avoiding/minimizing artificial sweeteners: There is some evidence that artificial sweeteners like aspartame stimulate the growth of unhealthy bacteria like Enterobacteriaceae in the gut microbiome, which can lead to increased blood sugar.
  • Eating prebiotic foods: Prebiotics are a type of fiber that stimulates the growth of healthy bacteria. Prebiotic-rich foods include garlic, onions, leeks, artichokes, bananas, asparagus, dandelion greens, barley, oats, cocoa, flaxseed, seaweed and apples. Foods that are high in so-called resistant starch, like parboiled rice, beans and cooked-and-cooled rice and potatoes, may also promote the well-being of our gut bacteria. In my recipes I use all these ingredients frequently.
  • Eat foods rich in polyphenols: These are plant compounds found in red wine, green tea, coffee, dark chocolate, olive oil and whole grains. They are broken down by the microbiome to stimulate healthy bacterial growth (studies here and here). Yes, chocolate is a health food! (When low in sugar and high in cocoa solids.)
  • Take antibiotics only when necessary: Antibiotics kill many bad and good bacteria in the gut microbiome, possibly contributing to weight gain and antibiotic resistance. Thus, only take antibiotics when medically necessary. And if you do have to take antobiotics, then may help to take a probiotic supplement to restore the gut microbiome to a healthy state.
  • There are many non-dietary ways to modify gut and immune function, too – these include sleep, stress management and exercise. This paper, for example, discusses how sleep and immunity are connected via the gut. Moderate exercise is a big plus for the gut flora and immune system, while psychological stress can erode both.
Gut-friendly foods at every meal

So how does all this translate into practice? It means eating a wide variety of meals each day that are packed with gut-friendly plant foods. On my Instagram account I show how I get gut-friendly foods into every meal I eat.

Thus, breakfast could be Bircher muesli comprising oats, seeds, nuts, yogurt and berries; a fried egg with baked beans, mushrooms and tomatoes; or flax-and-oat pancakes topped with Greek yogurt and berries, the lot accompanied by a cup of unsweetened green or black tea or coffee.

Lunch could be a gluten-free seeded cracker topped with sardines, accompanied by a serving of sauerkraut salad, or a plate of chickpea-vegetable hash with fried eggs washed down with a small glass of kombucha or water kefir.

Finally, dinner might feature Spanish baked cod on a bed of beans, garlic and peppers, Asian-inspired kimchi-and-egg-fried cauliflower rice with seaweed salad or Indian chicken-and-chickpea curry with cauliflower rice and cucumber salad. For dessert, a few squares of dark chocolate (here’s my favorite) would round off a wonderfully pro-biotic day!