Diet advice depends on your gut

Chalmers University of Technology

​In the future, a blood sample may show how you should eat to stay healty. But the road to personalized recommendations is long and winding. It passes through the gut, where bacteria make us react differently to the food we eat. ​Researchers are working hard, attempting to come up with personalized or group-based dietary advice. It’s not easy. Much depends on the gut microbiota that is unique to us all.

One example is dietary fiber, which is an established component of a healthy diet. In a research study that attracted attention last year, Chalmers’ researchers show that whole grains from rye lowered cholesterol levels more than whole grain wheat, but that this effect was dependent of individual’s gut microbiota composition. The study clearly showed that the dietary advice is not equally effective for everyone – but that there is a great potential to increase the health benefits by matching the foods with gut microbiota of the individual.

Hot research area

According to Rikard Landberg, Professor of Food and Nutrition science at Chalmers and one of the speakers at the two-day event Engineering Health in April, research relating the importance of the gut bacteria to diet, dietary advice and health is hot right now.
“How and when should we take the gut microbiome into account? How do we design a diet that is optimal for the individual? We are yet quite far from individual dietary advice. There is a lot more we need to know first”, he says.
At the same time, there are already commercial apps where you can try to identify your ideal diet. But these tests are often not to be trusted, says Rikard Landberg. They are based on nothing more than existing knowledge about general effects of lifestyle and diet, and the connections between these and the gut microbiota. But already in five to ten years, the situation may be completely different:
“By then, I believe we will have the opportunity to identify groups of individuals who, for example, benefit from a certain diet”, says Rikard Landberg and explains:
“We should be able to identify the profile of a certain group, using gut microbiome and metabolites – molecules formed by bacteria. Then, we can also measure the body’s response to a certain diet through a blood sample. Based on such data, we can determine whether you belong to a particular profile that would benefit from, for example, eating vegetarian food or a certain type of dietary fiber. And knowing which diet is ideal for your group will of course be helpful if you have reason to review your diet, for example if you’re at increased risk of cardiovascular disease.”

Food and gut experts working together

Rikard Landberg collaborates with Fredrik Bäckhed, Professor at the Department of Molecular and Clinical Medicine at the University of Gothenburg. Fredrik Bäckhed is an expert on gut microbiome and its role in health and disease. Among other things, he is trying to optimize probiotic bacterial strains that can improve the health of our gut, and reduce risk of developing diseases. A permanent change in the intestinal microbiome is difficult to achieve, but vary between different parts of the bacterial flora.
“This autumn, we will start a study start where we take a closer look at diets that are composed to promote a healthy intestinal bacterial flora. The diet is designed based on a systematic literature review, where we have reviewed 8,000 scientific articles. We want to investigate whether it is possible, with an optimal diet based on “ordinary food”, to influence intestinal bacteria linked to an increased risk of cardiovascular disease. Strangely enough, this has not been done in any previous scientific study”, says Rikard Landberg.

New and climate friendly guidelines

A revision of Nordic Nutrition Recommendations and the Swedish dietary guidelines is currently underway. Around 100 experts review, and evaluate, research results. Among other things, they look at health impact of different nutrients and foods. The dietary advice is also put in a Nordic context, to take into account which nutrients we, in the Nordic countries, may need to boost – such as vitamin D, which we could lack in our sun-depraved countries – based on the type of food we normally eat. In addition, the dietary advice is climate-adapted; the guidelines should not only focus on what’s healthy, but also what is sustainable from a climate perspective.
But while waiting for updated dietary advice, and research on gut microbiota: What can we really say about what to eat in order to stay healthy? One problem is that many researchers – as well as the media – try to give advice based on individual studies, says Rikard Landberg, as there is a desire to go directly from research results to recommendations.
“Unfortunately, this might give people the perception that advices change all the time. Results from different studies often show different results, for varied reasons.”

Vegetarian diet possibly healthier

Still, if he would dare to give any advice, in addition to the official dietary guidelines, Rikard Landberg gives one that is aligned with a recent study performed together with Örebro University and Fredrik Bäckhed:
“I am quite convinced that a diet with more vegetarian food, and less meat, is better for most of us. But this will vary between individuals, and moreover, we must not forget the risks associated with such a diet for certain groups. Many women, for example, have an iron deficiency. For them, a vegetarian diet might lead to they getting too low intake of available iron – and that will not be healthy”, he says.
“Then, of course, the usual advice applies; for example, not eating too much, and avoiding sugar-sweetened beverages. People also tend to think that physical activity plays a large part in keeping a healthy weight, but diet is the most important thing for those who need to watch the kilos. But with that said, we need to be active in order to feel good and prevent illness. Furthermore, we should not forget that diet is much more than health! For example, we do not eat chocolate to be healthy, but because it tastes good. That’s also allowed!”
FACTS: Want to know more about diet and intestinal flora?
Watch Rikard Landberg’s and Fredrik Bäckhed’s lecture “Diet meets the gut microbiome – implications for cardiometabolic disease” at Engineering Health on April 14 at 11.00. The event will be broadcast live via YouTube. More information can be found here.
Text: Mia Malmstedt
Photo: Pixabay and Annika Söderpalm
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