If many health and fitness sites around the Internet are to be believed, bananas are a miracle cure for many conditions, including depression. The theory goes that they contain serotonin, a substance which the brains of depressed people seem to be short of, so eating them should increase the level of serotonin in your brain and relieve your depression.
While it is true that bananas contain serotonin, this serotonin is not able to cross the blood-brain barrier. What this means is that the serotonin found in bananas can't possibly increase your brain's serotonin content because it is physically unable to get inside it. If it can't get inside the brain where it is needed, then it can't help your depression.
Eating bananas may not be completely useless in helping depression, however. While they can't directly supplement serotonin, they may be able to affect it indirectly due to the fact that they are high in vitamin B6. Vitamin B6 is necessary for your body to synthesize its own serotonin, and, if you are low on this important vitamin, getting more of it in your diet can help boost your natural serotonin production.
The current RDA for Vitamin B6 for adult men and women aged 19 to 50 is 1.3 mg daily. One medium banana will give you about 20% of the RDA.
Other excellent sources of vitamin B6 include:
- Beef liver and other organ meats
- Potatoes and other starchy vegetables
- Fruit (other than citrus)
- Fortified cereals
Young, Simon N. "How to increase serotonin in the human brain without drugs." Journal of Psychiatry and Neuroscience 32.6 (2007) : 394-9.
"Dietary Supplement Fact Sheet: Vitamin B6." Office of Dietary Supplements. National Institutes of Health. Accessed: March 27, 2012.