Diet and Gut Microbes Change the Composition of Your Blood
By: Gunnar De Winter
Tags: Health, Diet, Biology, Science, Machine Learning

Diet and Gut Microbes Change the Composition of Your Blood

(Pixabay, swiftsciencewriting)

The highways of the body

Our circulatory system — all the veins, arteries, and capillaries — shuttles oxygen, nutrients, and many other chemicals through our body. At the same time, it transports carbon dioxide to the the lungs, and other waste products to the kidneys and liver.

At any given time, our blood vessels are busy highways with many hundreds of chemical compounds rushing to and fro (add to that all the different types of blood cell and traffic gets even worse).

This is why the first step in in disease diagnosis is getting your bloodwork done. Of course, there are things we can’t see in our blood, but in many cases a snapshot of the chemical composition of our blood can provide at least an indication of what’s going on.

We know where several of the chemicals in blood come from, but the reason they can vary in healthy individuals is not always clear. Disease aside, there are many possible factors that can regulate changes in the chemical composition of blood: genetics, diet, exercise, medication, gut microbes…

Of all these possible factors, which ones matter most? (I know, spoilers in the title of the post. The question is good for the narrative, though…)

(Pixabay, OpenClipart-Vectors)

Mapping the traffic

A new study now aims to map the traffic in our blood vessels, and more importantly, map the factors that drive the composition of that traffic. (Don’t worry, that’s as far as I will take the metaphor.)

The research team analyzed the chemical composition of the blood of 491 healthy individuals in great detail.

They looked at 1251 metabolites in total. All the participants were also asked to fill in questionnaires on lifestyle, diet, and so on. Clinical parameters (blood pressure, heart rate, etc.) were measured, stool samples collected… The participants were, as it is called in a clinical setting, ‘deeply phenotyped’.

Then, the researchers let loose a machine learning algorithm to hunt for associations within the complex and very varied dataset.

Hocus pocus, and:

Diet and microbiome had the strongest predictive power, and each explained hundreds of metabolites — in some cases, explaining more than 50% of the observed variance.

(Note: variance refers to ‘how far’ from the mean a value lies making it more specific than the generic ‘variation’.)

Of course, diet and microbiome are not independent. What we eat affects our gut residents, and they, in turn, can influence how our body processes certain nutrients. Still, further analysis showed that these two factors, diet and gut microbiome composition, can often provide independent predictive information:

Because the diet modulates the gut microbiome, we compared the explained variance of metabolites obtained by models based on either. Although some metabolites — mostly related to coffee consumption — were significantly predicted by both diet and microbiome data, many were not.

Next, and this is a really excellent step in the study, the scientists validated their findings in an independent cohort of people (which was not included in the training data for the algorithms).

Their machine learning-based findings suggested that eating whole-wheat bread affected the levels of metabolites such as betaine and cytosine. To test this, they had ten people eat whole-wheat bread, ten others regular white bread. Only one week later, the levels of betaine and cytosine had gone up significantly in the whole-wheat eaters.

Validation.

As they conclude: