Bacteria and other microbes (including fungi and viruses) are often thought of as sources of disease, but in fact many play an essential role in keeping you healthy. Your body contains trillions of microbes, most of which are beneficial. The densest microbe population is found in your gut, where they play a critical role in digestion, immune function and weight regulation, vitamin production. What you eat can quickly change your microbes, but are you eating the right foods to help your good gut bacteria? This article explores how to improve your gut bacteria profile, things that can damage it, and whether there is a link to obesity.
Which dietary patterns help your good gut bacteria?
- Eat a wide range of plant-based foods – A healthy gut has a diverse community of microbes, each of which prefers different foods. Fruits, vegetables, wholegrains, nuts, seeds and pulses are all beneficial for your gut bacteria
- Eat more fibre – Most people eat less than they should, but high fibre foods help to feed healthy bacteria. Examples include fruit, vegetables, pulses, nuts and wholegrains. They are often termed ‘prebiotics’, which are foods that fertilise the existing gut bacteria and encourage a diverse community of microbes
- Choose extra-virgin olive oil over other fats when you can – It contains the highest number of microbe-friendly polyphenols
- Eat probiotic foods if you enjoy them – They might encourage more microbes to grow. Examples include foods (e.g. live yoghurt, some cheeses, fermented foods) and supplements. Please see the later section which explores these foods further.
Which dietary patterns can damage your gut bacteria profile?
- Highly processed foods – These often contain ingredients that either suppress ‘good’ bacteria or increase ‘bad’ bacteria. Examples include pre-packaged cakes, biscuits, confectionery and processed meats
- A low fibre diet – Fibre is needed to help ‘feed’ your gut bacteria. If your diet is low in fibre, a sudden increase can cause wind and bloating. This is less likely if you make gradual changes and drink extra water
- Antibiotics kill ‘good’ bacteria as well as ‘bad’ – If you need antibiotics, make sure you focus on including lots of foods that boost your microbes afterwards.
Claims about specific foods
There are lots of foods and supplements on the market that claim to help improve your gut bacteria profile. However, is there any evidence to support you eating / taking these? This next section highlights some of the common foods and what the evidence is suggesting.
- Probiotic supplements – They might be helpful but it’s not proven that they reach the gut intact. Some probiotics have well-established effects but are very expensive.
- Fermented foods – These foods, e.g. kimchi, miso, kombucha and many pickles, contain bacteria, but we can’t be certain that the bacteria they contain actually reaches the gut. However, in countries where these types of food are eaten frequently, people appear to have better gut health and less bowel disease (although other factors could be responsible). Fermented foods can be cheap and easy to make at home, so eat them if you enjoy them. Mass-produced pickles use vinegar instead of traditional methods of fermentation, so these don’t have the same benefits. Fermented foods are also good sources of other nutrients, for example:
- Kefir is also a good source of calcium
- Miso (made from fermented soyabeans) is also a good source of copper
- Tempeh (also made from fermented soyabeans) is high in protein
- Sauerkraut is also a good source of fibre and iron
- Kimchi (made from fermented vegetables like cabbage and radish) is high in vitamins A, B and C
- Raw milk – The variety of microbes found in raw milk is very similar to pasteurised milk – there’s just much more of them in raw milk. There is a strong correlation between drinking raw milk in childhood and a reduced incidence of allergies. This might be because of the high numbers of microbes in raw milk, but we can’t be sure. Children who drink raw milk often live on farms, which also brings microbial advantages. However, raw or unpasteurised milk may contain harmful bacteria that can cause food poisoning.
- Sourdough breads – These breads are fermented slowly using a wide range of bacteria and fungi found naturally in the air and ingredients. Commercial yeast, used in most breads, is a single strain that causes bread to rise much faster. It is not known if the additional microbes in sourdough survive cooking. Many people claim that they find sourdough easier to digest than other bread, but it is likely that the lengthy fermentation process is most beneficial. This is because microbes have had more time to break down the protein strands that might otherwise cause digestive problems. It also takes longer to digest, which is good for your blood sugar levels.
- Traditionally produced cheese – They contain a huge array of probiotics (from the natural bacteria used in the production of the cheese). Some studies have found that these can benefit health, but more research is required. We cannot be sure the bacteria in some cheeses survive digestion for long enough to be beneficial. However, it is possible that other properties of cheese help preserve bacteria during digestion. Mass-manufactured cheeses don’t have this potential benefit because of the way they are made.
- Traditionally produced yoghurts, ‘live’ yoghurts and yoghurt drinks – These contain probiotic cultures, but it’s not clear whether they survive the acidic environment of the stomach and reach the intestines intact. Some yoghurts state the cultures used to make them in the ingredients list and diversity is usually beneficial. Stick to natural yoghurts; fruity yoghurts usually contain sugar and additives, which might cancel out any potential health benefits. Some yoghurt drinks contain very high numbers of bacteria that are considered to promote health – far more than you would find in a normal yoghurt. However, they can also contain lots of sugar and can be expensive.
Is there a link between gut bacteria and obesity?
Whilst research from the last 30 years has clarified the role of the imbalance between energy intake and expenditure, unhealthy lifestyle, and genetic variability in the development of obesity, the potential link between gut bacteria and obesity is very much a hot topic with lots of research currently being carried out. The composition and metabolic functions of gut bacteria and microbes have been proposed as being able to affect obesity development. Put simply, it’s possible that if you have a poor gut bacteria profile, this can be a cause of obesity (likely not the only cause, but a causal factor nonetheless).
There is evidence for a link between gut bacteria and microbes and obesity both in infancy and in adults. There are several genetic, metabolic, and inflammatory mechanisms involved in this link. Studies show, for example, that people with long-term weight gain have a lower diversity of the microbiota in their gut. The imbalance between the ‘good’ and ‘bad’ bacteria may negatively affect gut hormone regulation and proinflammatory mechanisms. That, in turn, may play a role in diet-induced obesity and metabolic complications.
The bottom line = if you are obese or gaining weight, take the opportunity to review your diet and make changes to help improve your gut bacteria profile.