Diverse gut bacteria may help lower long-COVID risk

A diverse gut microbiome is thought to be a key component of a healthy immune system, and now Chinese scientists have found a link between gut bacteria diversity and your risk of developing long COVID.

The University of Hong Kong researchers found patients with long COVID has a less diverse and abundant gut microbiome.

The study, published in the BMJ Gut, involved analysing the faecal microbiome of patients, with varying degrees of disease severity, and controls who didn’t have COVID.

At six months, 76 per cent of patients had long COVID or post-acute COVID-19 (PAC), with fatigue, poor memory and hair loss being the most common symptoms.

Long-COVID patients’ gut bacteria less diverse

The patients with PAC had lower diversity and richness of bacteria, on admission to hospital and at a six-month faecal analysis, compared with control patients and those who had fully recovered, the study says.

“At six months’ follow-up, bacteria diversity and richness (as measured by Shannon index diversity and Chao1 richness index, respectively) in patients with PACS were significantly lower than in those without PACS and controls. In addition, bacteria Shannon diversity and richness of gut microbiome were significantly lower at admission in patients who developed PACS than non-COVID-19 controls, but there was no difference in Shannon diversity and richness between patients without PACS and controls.”

The long COVID patients had fewer ‘friendly’ bacteria and more ‘unfriendly’ bacteria than COVID-19-free people, the researchers say.

They also identified bacterial species linked to specific long-COVID symptoms. For example, respiratory symptoms were linked with ‘unfriendly’ microbes, including Streptococcus anginosus, Streptococcus vestibularis, Streptococcus gordonii and Clostridium disporicum.

The researchers suggest profiling patients’ microbiomes may help identify those at risk of developing PAC.

Study limitations

This was a relatively small study, involving 106 COVID patients and 68 controls, and was observational, so can’t establish causation, just an association.

5 ways to diversify your gut microbiome

If you’re hoping to lower your risk of long COVID,  making sure you’re up to date with your vaccinations is your best bet, but improving your gut health is beneficial for your overall immunity.

There are simple diet changes you can make to increase the abundance of ‘friendly’ gut bacteria you have and decrease the volume of more problematic bacteria.

1. Eat plenty of plant foods and focus on variety. Studies have shown eating mostly vegetables, fruit, legumes and whole grains is linked to a higher abundance of gut bacteria. And aiming to eat a wide variety of around 30 different plant foods over a week has the best results.

2. Try to eat all three types of fibre. Fibre, through fermentation, provides food for your gut bacteria. There are three types and it’s important to consume them all.

• Insoluble fibre is found in wholegrain flour, bread and cereals, fruit and vegetable skins and nuts. It’s also known as ‘roughage’ because it is slowly and only partially fermented during digestion, softening your bowel motion.
• Soluble fibre is highly fermentable and is found in oats, seeds legumes, barley and vegetable and fruit flesh.
• Resistant starch is completely fermented during digestion and feeds the good bacteria in your bowel. You can get it from slightly unripe bananas, beans, peas, cooked and cooled pasta, rice or potatoes, uncooked rolled oats and freekeh.

3. Enjoy fermented foods. Yoghurt, sourdough bread, cheese, kombucha, kefir, kimchi sauerkraut, tempeh and miso are just some examples of fermented foods you can consume every day to benefit your gut microbiome.

4. Limit alcohol and opt for wine or beer over spirits. Alcohol can increase the growth of bacteria that potentially increase toxins in the gut, and spirits may be the worst culprit.

5. Get your omega-3s. Regular consumption of omega 3-rich oily fish has been shown to encourage an abundance of inflammation-fighting gut bacteria. If you don’t eat fish, you can get omega 3 from plant sources, including canola, flaxseed and soy oils, tofu, walnuts, pumpkin seeds and some green vegetables.