We all know the old expression, “An apple a day keeps the doctor away”. While that may be somewhat true for your physical health, a new study has shown that oranges may be beneficial for your mental health. In fact, according to the study, eating one orange every day can potentially lower your depression risk by 20%! The researchers believe that this may be because the growth of a specific type of gut bacteria is stimulated by citrus. Known as Faecalibacterium prausnitzii, these bacteria play a role in producing mood-elevating molecules such as dopamine and serotonin. Life-disrupting clinical depression affects around 15% of people at some point or another. With around 280 million individuals living with clinical depression around the world, finding potential treatments has become more crucial than ever.
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The Origins and Results of the Orange Study
The study was led by an instructor in medicine at Harvard Medical School, Raaj Mehta. Raaj was reading through the available literature on depression when he came across a paper from 2016 that mentioned that citrus could potentially lower depression risk. Since they had access to a large dataset, they decided to delve deeper into this finding. The dataset was sourced from a study that started in 1989, called the Nurses’ Health Study II (NHS2). The study focused on identifying various risk factors associated with women’s chronic diseases. Involving more than 100,000 participants, the women were asked to provide comprehensive information regarding their health, medication use, diet, and lifestyle. Their ultimate goal was to use the data to try and find evidence that the participants who consumed large quantities of citrus experienced less depression than those who didn’t.
The researchers used the results of DNA sequencing taken from participants’ stool samples to look for links between citrus consumption and various species of gut bacteria. The researchers found a link between citrus consumption and an abundance of 15 gut microbiome species. They also found that there was more F. prausnitzii in the guts of people who weren’t depressed. Furthermore, eating large quantities of citrus was linked to higher levels of the bacteria. Their study revealed that consuming a single orange every day potentially lowered depression risk by a significant 20%. Strangely, this relationship with depression risk was not observed in other foods and the effect appeared to be unique to citrus fruit. The same link was observed in another study involving male participants called the Men’s Lifestyle Validation Study.
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Potential Mechanisms and the Path Forward
The researchers theorize that F. prausnitzii uses the S-adenosyl-L-methionine cycle I pathway to influence dopamine and serotonin levels. These are neurotransmitters produced in the gut. The role of these neurotransmitters is to regulate how foods pass through your digestive tract. However, they can also make their way to the brain, resulting in an elevation in mood. F. prausnitzii bacteria is also linked to other health benefits, such as a lower inflammatory bowel disease risk. It has also been shown to help with obesity and even type 2 diabetes in animal studies. The researchers hope to see a clinical trial conducted next that would specifically focus on the link between citrus consumption and lower depression risk.
As evidence of a link between the gut and brain is uncovered, more researchers will start to explore this field. Finding affordable, easily obtainable treatments for depression is crucial if we wish to help the millions of people afflicted globally. Researchers are learning more about the role of the gut microbiome and its effect on the brain every day. This could open potential therapies that don’t rely on medications that often present their own range of side effects. Other foods that may be beneficial to gut bacteria are fiber-rich vegetables and fruits, as well as fermented foods. These foods help balance the gut which helps influence neurotransmitters like serotonin.
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