A decade ago, while it was certainly acknowledged that our diet could have an impact on our health (and illness), for the most part research focused on human metabolism. Now, with the newfound appreciation that we contain more microbial cells than we do human cells, looking at our diet through the lens of our microbes (how they metabolise and how food influences them) will be key to looking after our health.

Here are Dr Megan Rossi’s top five recommendations for dietary habits to optimise gut health.

The diversity of our gut microbiota (GM) is an indicator of gut health and targeting the diet is one of the most effective ways we can boost our GM diversity. Most of the research done so far has found that people with high-fibre diets from a wide range of plant-based foods have greater diversity.

Essentially, the more plant-based diversity in our diet, the more diverse the nutrient supply for your GM. Having a more diverse GM also increases our resilience to infection. Our profession has been advocating a Mediterranean diet for a long time and this pattern of eating has also been linked with greater microbial diversity.

Dietary fibre is an essential nutrient for our GM that our microbes break down to produce short-chain fatty acids (SCFAs), which can also stimulate our immune system and are known to directly impact fat tissue, the liver and our brain. There are further tangible benefits of increasing fibre intake too, with research linking an increase of just 8g of fibre per day to reducing the risk of heart disease by 19%, type 2 diabetes by 15% and colon cancer by 8% (1).

Traditional fermented foods have been around for thousands of years and there are lots of different varieties, such as live yoghurt, sour cream, sourdough, sauerkraut, miso, kimchi and kefir. They are thought to be an important part of our diet and researchers have advised that fermented foods should be an additional food group within dietary guidelines.

Outside of the more common fermented foods such as yogurt and cheese, for which there is evidence for a benefit in weight management and heart disease, the most widely investigated more traditional fermented food so far is dairy kefir, with evidence from at least one RCT suggesting beneficial effects in both lactose malabsorption and Helicobacter pylori eradication.

As with their non-fermented counterparts, dairy-based fermented foods such as kefir and yoghurt can also be good sources of calcium, as well as containing protein, b-vitamins, iodine, potassium and phosphorus.

Anecdotally speaking, I have witnessed the immune and physical benefits of including fermented foods in the diet. Nonetheless, more research needs to be done as the clinical evidence for traditional fermented foods to date is limited (2).

Only a few days of being on an extreme diet can change our GM, the function of our microbes and the metabolome (what they produce). In fact, the rapid weight-regain that can be common with ‘yo-yo’ dieting is thought to be influenced by our GM.

Interestingly, animal research has shown this tendency to regain weight rapidly could be reversed through nutrition (3). In contrast, adding more variety of plant-based foods into your diet can positively influence your GM. In fact, a large scale observational study has shown that the biggest predictor of GM diversity is the number of different plant-based foods people consume, regardless of the addition of some animal products (4).

What we eat and drink can have a significant impact on how our gut moves. Some people are more sensitive than others, whereby fatty foods and alcohol can slow down the movement of the stomach and delay gastric emptying. This may be why many people with more sensitive gastrointestinal tracts can suffer from issues such as reflux when they consume alcohol and fattier foods.

Piecing it all together

The truth is, there is no single ‘gut health’ diet. There are, however, guiding principles that underpin an eating pattern that supports good gut health. What this looks like on a plate is individualised depending on preferences and where you are at on your gut health journey.

References
1. Reynolds, Mann, Cummings et al. 2019
2. Dimidi, Cox, Rossi et al, 2019
3. Davis, 2016
4. McDonald, Hyde, Debelius et al, 2018