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by Candy Sagon
Updated September 19, 2022
“This study focused only on citrus, but eating more fruits and vegetables will also do that for you. It’s hugely protective.” —Fiona Harrison, assistant professor at Vanderbilt University Medical Center and a researcher on the role of vitamin C in brain development
Move over, apple-a-day folks. Research suggests that eating a daily orange could keep your brain healthier as you age.
In a study published in the British Journal of Nutrition, Japanese researchers found that older adults who ate more citrus fruits were less likely to develop dementia, perhaps because of anti-inflammatory flavonoids in the rind, flesh and juice of produce like oranges, grapefruits, lemons and limes.
After tracking more than 13,000 Japanese adults age 65 and older, the researchers discovered that those who ate citrus fruit daily (primarily Satsuma oranges, similar to clementines or tangerines) were 23 percent less likely to develop dementia than those who ate it two or fewer times a week.
In countries like Japan, with a sizable aging population, “it is hoped this new dietary approach could be both a simple and effective solution,” the researchers said in a statement.
They used health data gathered in December 2006 from a large survey of Japanese older adults that included information on citrus-fruit consumption. They then followed up with data gathered up to November 2012 to see how many of the subjects had developed dementia.
Even after adjusting for possible influencing factors, including other health conditions or higher cognitive scores at the beginning of the study, “the relationship between citrus consumption and incident dementia did not change substantially,” researchers wrote.
Healthier people eat fruit
But researcher Shu Zhang of the Tohoku University School of Public Health cautioned in an email that the findings only showed an association between citrus consumption and the development of dementia, not evidence of direct cause and effect.
Further studies are needed, she added, but “as researchers, we still would like to encourage people to eat more vegetables and fruits.”
Fiona Harrison, who studies the role of vitamin C in brain development and neurodegenerative diseases at Vanderbilt University Medical Center, agrees. “I can get behind any advice to increase fruit and vegetable intake.”
But the Japanese study has limitations, Harrison notes, including that those who ate the most citrus also ate the most fruits and vegetables, “so they were already doing better overall.” And while the researchers theorize that the lower dementia results might be due to the anti-inflammatory effects of certain flavonoids in citrus fruits, “there’s no [direct] evidence of that.”
On the other hand, it’s not surprising that eating more citrus fruits could have brain benefits. “Eating more fruits and vegetables will do that for you. It’s hugely protective,” Harrison says.
Vitamin C, memory
Harrison has studied the effect of low-level vitamin C deficiency on the brain and says the vitamin — found in abundance in citrus fruits — plays an important role in the development of dopamine (a brain chemical that can affect memory loss) and collagen, which may protect the brain against Alzheimer’s disease.
“Vitamin C is not just an antioxidant; it has very specific chemical roles in the body,” Harrison explains. Regularly eating citrus fruits and dark green leafy vegetables such as spinach and kale — both good sources of vitamin C — could play a protective role in brain health, she adds.
The bottom line, she says, to get the most vitamins, “add a lot of color to your plate. Citrus fruits certainly do that.”
“Citrus consumption and incident dementia in elderly Japanese: the Ohsaki Cohort 2006 Study,” British Journal of Nutrition, May 2017. The study looked at patterns of citrus consumption and dementia in 13,373 adults (ages 65 and older) living in Ohsaki City in northeastern Japan. Read the full study.