A newly published study by Korean researchers looked at the possibility of helping to treat depressive disorders with a dose of orange juice – and its rich range of flavonoids. Their paper was published in the academic journal Nutrients.
The title explains the focus and their methods: Effects of Flavonoid-Rich Orange Juice Intervention on Major Depressive Disorder in Young Adults: A Randomized Controlled Trial
Depression, the gut & flavonoids
Depression affects many people around the world, and so the search for effective and safe treatments is ongoing. Many treatments are available, but often drug therapies result in unwanted side effects.
The researchers wanted to study major depressive disorder (MDD) in otherwise healthy men and women aged 18 to 29. A group of 40 individuals were randomly assigned to one of two groups:
- One received flavonoid-rich orange juice (FR);
- One consumed a flavonoid-low orange cordial (FL);
- Each group drank the juice three times a day for an 8-week period.
The blood work showed differing results for each group.
- Brain-derived neurotrophic factor (BDNF) – used by the body to protect neurons – levels increased for the FR group;
- Ditto for zonulin, a protein that regulates what can pass through the intestinal walls, and claudin-5, a protein crucial to the blood-brain barrier, were also significantly increased;
- What’s important is that these proteins are often found to be deficient in people with various types of mental illness.
Other findings in the blood tests showed significant results, some of which created favorable conditions for Butyricicoccus pullicaecorum, a key probiotic bacterium in the gut microbiota with strong anti-inflammatory properties.
That’s a key point. Other tests have found links between diminished gut bacteria and many mental illnesses, including schizophrenia.
- Flavonoids reduce inflammation and oxidative stress;
- Both of those processes are also associated with depression and anxiety.
The authors write, “It is possible to alter the gut microbiota–brain axis and reduce the occurrence of MDD via the diet by altering the gut microbiota profile and regulating intestinal permeability.”
It is the way that dietary polyphenols such as flavonoids are digested by the body that makes them crucial to gut bacteria. Only a small portion is digested directly from the stomach. The remainder digests more slowly in the intestines, developing into metabolites which directly feed the gut bacteria.
As the researchers conclude, in addition to the physical changes, the FR group showed a decrease in symptoms of depression. The study used standard measures such as the Hamilton Rating Scale for Depression (HAM-D), the Beck Depression Inventory-II (BDI-II) and Center for Epidemiologic Studies Depression Scale (CES-D)
It’s just one study, but the results are very promising and show a need for more research into using orange juice flavonoids as a probiotic treatment for depression.