A reader forwarded this study to me and asked:

Interesting study. I wonder whether the effect is due to high fat, high sugar or the combination?

In the database on Microbiome Prescription

• Sugar 57 Bacteria cited from
  • ¶ High glycemic diet {High-sugar diet (HSD)}
  • ¶ high-fat sucrose 
• Fat 233 Bacteria cited from
  • ¶ high-fat diets
  • ¶ high-saturated fat diet 

And thus have the ability to compute the theoretical differences.

We also have these collections of studies which we can use by flipping things to be negative cognitive function:

• Cognitive Function
• Intelligence:Comprehension, Cognitive Ability

This resulted in 71 bacteria.

Results

For Sugar we had agreement between reported shift and cognitive issues for the following:

1. Bacillota
2. Bacteroides
3. Coprococcus
4. Desulfovibrio
5. Dorea
6. Escherichia coli
7. Faecalibacterium prausnitzii
8. Lachnospiraceae
9. Ruminococcus
10. Streptococcus

For Fat we had agreement between reported shift and cognitive issues for the following:

1. Bacillota
2. Bacteroidaceae
3. Bacteroides
4. Clostridium
5. Coprococcus
6. Coriobacteriaceae
7. Dorea
8. Faecalibacterium prausnitzii
9. Oscillospira
10. Phascolarctobacterium
11. Porphyromonadaceae
12. Ruminococcaceae
13. Ruminococcus

With Fat we had significantly more contrary shifts than with Sugar.

Bottom Line

Both High Fat and High Sugar in isolation appear to impact cognitive function. High Fat has the appearance of having less impact in isolation than high sugar. The following shifts seem to be common with these:

• Bacillota
• Bacteroides
• Coprococcus
• Dorea
• Faecalibacterium prausnitzii
• Ruminococcus