Reacción a "The relationship between gut bacteria and diseases could be overestimated"

Numerous studies have already demonstrated that 'microbial load', meaning the number of microbes per gram of fecal material, can vary greatly between individuals and under different clinical conditions. This suggests a limitation in many microbiome studies, which only measure relative (not absolute) abundances of species.

The novelty presented by this study is the development of a predictive algorithm that estimates microbial load from patterns of relative abundance. This algorithm has been trained using hundreds of data points from two studies that measured both relative abundance and microbial load. While the algorithm’s estimations are not perfect, its correlation coefficients are significant, but somewhat modest, especially when the algorithm is trained on one study but applied to the other (0.56 where the maximum possible is 1).

This degree of uncertainty in prediction should be considered when drawing conclusions from the study. Noteworthy are the differences in the distribution of microbial load between the two studies, which the authors attribute to methodological differences in its determination. This indicates that the baseline data may not be representative of other studies.

In summary, it is interesting to note that relative abundance and microbial load are not entirely independent (it is possible to infer one from the other), but there is still room to improve this relationship and understand how each of these variables relates to lifestyle factors or clinically relevant characteristics. Therefore, despite this predictor, more studies that directly examine both variables are needed.