Park Choi Lee, 2020

“The study had a randomized, single-blind design and was conducted for 8 weeks. The volunteers were randomly divided into 2 groups of 20 participants each, the FR and FL groups.”

The study was conducted by randomly dividing people into 2 separate groups of 20. They were both given drinks twice a day over 8 weeks. One group was given orange juice that is high in beneficial plant chemicals called flavonoids, while the other group was given an orange-flavoured drink that was low in flavonoids. Only the researchers conducting the study knew which group had which kind of drink.

“Therefore, this study aimed to evaluate the effects of flavonoids on depression in young adults by observing the changes in the gut microbiome and depressive symptoms of participants consuming flavonoid-rich orange juice. Furthermore, this study attempted to establish a theoretical basis for providing basic data and policy direction to develop a dietary program for alleviating and preventing depressive symptoms.”

The study wanted to find out if drinking orange juice that is high in plant chemicals called flavonoids could change the organisms that are found inside your gut. They also wanted to see if changing the amount of the organisms found in your gut could improve depression in young people, and they were going to use this as a guideline for creating a diet that could help people with depressive symptoms.

“The results of real-time PCR showed that the relative abundance of Lachnospiraceae_uc and Bifidobacterium_uc was significantly increased in the FR group compared to that in the before FR group (Figure 5A,C). However, the relative expression of Lachnospiraceae_uc was increased and that of Bifidobacterium_uc was decreased in the FL group compared with those in the before FL group, but there was no significant difference (Figure 5D,F).”

They found that the group drinking orange juice high in flavonoids had a statistically higher amount of two gut bacteria after the study, and the group with the low flavonoid drink had more of one of the bacteria, but less of the other after the study. However, they could not statistically prove this difference in the low flavonoid group.

“Although the particular association between flavonoids and depression is still unclear, we found that a high intake of flavonoids changed the relative abundance of the gut microbiome, especially the butyrate-producing Lachnospiraceae family. Therefore, we suggest the efficacy of FR than FL in improving depression.”

The researchers found that drinking orange juice that was high in flavonoids increased the presence of different families of gut bacteria, specifically one that produces a compound that has been found to have beneficial effects in people with depression. They suggest that ingestion of a high amount of flavonoids would be beneficial over a lack of them for improving depression.

I would suggest a sample size to be used for their research so they could find more significant differences in the effects of the treatment, specifically in people with depression, and more research into the specific effects contributed to the presence of flavonoids versus a change in the composition of the gut microbiome.

Some of the most confusing material of the paper was the statistical difference in the CES-D scores after the treatment. Their values were (p < 0.0001) compared to (p < 0.001). There is obviously a difference of a factor of ten, but I am not sure the actual significance of the values, or what meaning they are drawing from these results.