You might associate vitamin C with immune system support, but new research suggests it may play a key role in brain health. The study, published in PLOS One, found that older adults with lower vitamin C levels showed brain changes associated with cognitive decline.1
Previous studies have linked diets rich in vitamin C to a lower risk of cognitive decline.2 But little research has measured vitamin C levels in participants’ blood, and no studies have explored whether vitamin C levels affect the default mode network (DMN), a network of brain regions involved in internal thought processes such as memory and self-reflection.3
Declines in DMN connectivity have been linked to neurological conditions, including mild cognitive impairment, Alzheimer’s disease, and Parkinson’s disease.45
In the new study, researchers gathered data from about 2,000 Japanese adults aged 65 and older. Participants had MRI scans to measure their DMN connectivity and brain structure, including gray matter, white matter, and total brain volume. Researchers compared the results with vitamin C levels in participants’ blood samples.
People with lower vitamin C levels tended to have reduced DMN connectivity and less gray matter, which plays a key role in memory, decision-making, and other everyday functions.6
“Decreased gray matter and lower DMN connectivity are closely linked to age-related cognitive decline and are early signs of conditions like Alzheimer’s disease,” explained study author Tomohiro Shintaku, MD, PhD, an assistant professor of radiology at Hirosaki University Graduate School of Medicine.
The link between low vitamin C levels and signs of cognitive decline held true even after accounting for factors such as age, education level, lifestyle, and conditions like diabetes and hypertension. However, the research only found an association, not a cause-and-effect relationship, Shintaku told Health.
He also noted that the study relied on a single blood draw from each participant, which may not reflect long-term vitamin C levels. And while the researchers controlled for many variables, they did not account for factors like BMI and socioeconomic status that could influence the results.
Vitamin C acts as an antioxidant throughout the body, helping neutralize free radicals that contribute to oxidative stress and inflammation. “The brain is highly vulnerable to oxidative stress, and vitamin C’s potent antioxidant properties likely help protect neurons from damage,” Shintaku said.
Lynette Gogol, DO, a board-certified neurologist and lifestyle medicine physician, who was not affiliated with the study, also noted that vitamin C helps enzymes carry out important functions in the brain and may support communication between brain cells, which could improve cognitive function.7
Although, Gogol told Health that many mechanisms could be behind vitamin C’s link to brain health, and further research may shed more light on the connection.
While the new study can’t prove that vitamin C protects brain health directly, experts said foods rich in vitamin C can contribute to a brain-healthy diet—and a nutritious diet overall.
The recommended daily intake of vitamin C for adults is 90 milligrams (mg) for men and 74 mg for women.8 “Most people can get enough vitamin C through their diet, as long as they eat a variety of fruits and vegetables,” Anne Danahy, MS, RDN, an Arizona-based dietitian and founder of Craving Something Healthy, told Health.
However, older adults are more likely to have insufficient vitamin C levels, Danahy said, since aging bodies absorb the nutrient less efficiently. People with certain conditions, such as diabetes, heart disease, or cancer, may also want to aim for a higher amount of vitamin C.
Danahy recommended citrus fruits, sweet peppers, kiwi, strawberries, broccoli, and Brussels sprouts as excellent sources of vitamin C. If you’re considering a vitamin C supplement, Danahy advised taking less than the safe upper limit of 2,000 mg per day.
“It’s in a wide range of fruits and vegetables,” Danahy added, “so the best way to cover your needs is to eat a few servings of fruits and vegetables each day.”
