The researchers also found positive gut microbiota changes in patients who took such a diet and suggested that the changes could have occurred via the gut-brain axis.
Forty-five patients completed the trial in the First and Second Affiliated Hospital of Soochow University and the research findings were recently published in Nutrients.
During the three-month trial, the control group took a low-fat diet consisting of vegetables, staple food, oil, fruits, and protein from fish and dairy sources.
The intervention group took the same diet except that they took in only half the amount of carbohydrate given to the control group, while half of the other portion was replaced by almonda.
Their blood samples were then obtained to measure the amount of glycated haemoglobin (HbA1c), their level of depression was also assessed via a self-reported assessment. The higher the score, the more serious the depressive symptoms.
In addition, their fasting glucagon-like peptide (GLP-1) concentration and faecal samples were assessed to track changes in the gut microbiota.
The research was funded by Suzhou Science and Technology Project
Less glycated haemoglobin
Both groups saw a drop in their percentage of glycated haemoglobin by the end of the trial, but the decline in the intervention group was significantly lower.
For instance, the percentage of glycated haemoglobin in the intervention group dropped from 7.67 ± 1.60 at the start of the trial to 6.85 ± 1.02 by the end of the trial.
A smaller reduction was seen in the control group, as the percentage went down from 7.54 ± 1.31 to 7.37 ± 1.29.
The researchers said this showed that the hypoglycemic effect of the almond low carbohydrate diet was better than the low-fat diet.
Lower depression score?
The intervention group also had a significantly lower self-reported depression score compared to the control.
Their depression score for the intervention group dropped from 48.41 ± 8.05 to 42.07 ± 5.80, while that of the control group was a marginal decline from 49.57 ± 8.46 to 48.65 ± 7.69.
The researchers described the findings as “controversial”, since they were not consistent with previous studies.
Nonetheless, they believe that this could be due to the difference in the food composition used in the trial.
“The important reason for the inconsistent effect of low carbohydrate diet on depression may be due to the difference in the composition of the food.
“A major difference was that we used almond to replace [part of the] carbohydrate,” they said, explaining that several studies have shown that the positive effect of nuts on mental health.
They cited a RCT published in 2013 which showed how Mediterranean diet supplemented with nuts caused a 40% lower risk of depression in patients with type II diabetes.
Gut microbiota change
A number of changes in the gut microbiota was seen in the intervention group.
For instance, by the end of the trial, they recorded a significant drop in Bacteroidetes which have been reported to exist in higher level in depressed patients.
A reduced population of the pathogenic bacterium Bacteroides was also seen in the intervention group.
Moreover, the almond low carbohydrate diet increased the relative abundance of short chain fatty acids (SCFAs) producing the bacteria Roseburis and Ruminococcus.
“The above result showed that the almond low carb diet could regulate the gut bacteria and the improvement of depression score may be through modulating of the microbiome-gut-brain [axis],” the researchers said.
“Based on the results of this study, we speculate that the role of almond low carb diet in improving depression in patients with type II diabetes may be associated with it stimulating the growth of SCFAs-producing bacteria, then increasing SCFAs and GPR43 activation, further maintaining GLP-1 secretion.”
However, the theory will require validation in future studies as they did not measure the actual changes in SCFAs and GPR43 activation in the present trial.
An Almond-Based Low Carbohydrate Diet Improves Depression and Glycometabolism in Patients with Type 2 Diabetes through Modulating Gut Microbiota and GLP-1: A Randomized Controlled Trial
Authors: Ren M, Zhang H, Qi J, Hu A, Jiang Q, Hou Y, Feng Q, Ojo O, Wang X.