The Cognitive Benefits of Vitamin C
They're nothing to sniffle at.
By Hara Estroff Marano published January 2, 2018 - last reviewed on April 17, 2018
Our brain is a power consumer of vitamin C, the vitamin that cuts your colds short. Brain concentrations of the vitamin are far greater than those in the rest of the body, and long after the body is depleted of the vitamin, the brain maintains its levels. That's partly because the metabolic furnaces in neurons churn through glucose to power all your thoughts and feelings and movements, and as an antioxidant, the vitamin's job is to surrender electrons to neutralize rogue oxygen molecules given off in the process—free radicals that damage DNA and generally age your cells. But vitamin C also does more, and some 80 years after its discovery, its additional roles are just coming to light.
Chief among them are actions in the nervous system. Vitamin C plays a role in the differentiation and maturation of neurons and in the formation of the myelin sheath that protects them and speeds impulse transmission, making the vitamin crucial to cognitive performance. It is a cofactor in the synthesis of several neurotransmitters, it's needed to convert dopamine to serotonin, and it modulates neurotransmitter release in nerve cells. And while it's long been known that the vitamin is a component of collagen, a stabilizing force for teeth, bones, and blood vessels, only now is its role in ensuring blood vessel integrity seen as a factor in cognitive capacity, especially as we age.
In a recent review of 50 studies of vitamin C levels and cognitive function, all conducted between 1980 and January 2017, Australian researchers found a striking relationship between vitamin C status and mental function, as measured by a well-established questionnaire, the Mini Mental State Examination (MMSE). Those who were cognitively intact had significantly higher blood concentrations of vitamin C than those who were cognitively impaired. And among those who were cognitively intact, blood levels of vitamin C correlated with cognitive ability. No linear correlation was seen in those with cognitive impairment.
Severe vitamin C deficiency is known to cause scurvy. But scientists recognize that the human body needs far more than the minimal amount required to prevent the once-common disease. Just how much is necessary to support all body functions is not clear. Complicating matters is the fact that the amount consumed does not always translate into adequate blood levels. And factors like smoking, toxin exposure from air pollution, and alcohol consumption make extra demands for the nutrient as they place the body under oxidative stress. Studies have shown that such conditions as fatigue, depression, and poor wound healing are consequences of inadequate levels of vitamin C.
As little as 10 milligrams a day is needed to prevent scurvy. The RDA for adults is set at 90 mg/day for males, 75 mg/day for females. But vitamin C insufficiency is widespread.
A major longitudinal study of midlife adults underway in New Zealand, known as the CHALICE study, finds that 62 percent of 50-year-olds from all income levels, and more men than women, have inadequate blood concentrations of vitamin C. Almost all—93 percent—are below the optimal blood-saturation level for the nutrient. The researchers report that vitamin C status correlates with several markers of cognitive health as well as of metabolic health.
Higher blood levels of C were correlated with lower levels of cognitive impairment. And even small increases in blood concentrations of the nutrient significantly reduced the odds of cognitive impairment. Those whose blood levels were below what the researchers believe is a minimal requirement for all functions had twice the likelihood of cognitive impairment as those who met it. Interestingly, rates of vitamin C inadequacy are higher in the United States than in New Zealand, the researchers report in the journal Nutrient.
An array of studies suggest that, day in, day out over the long haul, vitamin C plays some role in preventing the neural loss that typifies dementia, although studies of the vitamin as a treatment have proved equivocal. Researchers believe that it's long-term vitamin C status that matters, the amount of the antioxidant available over time.
Oxidative damage to the brain is pervasive in Alzheimer's disease and other forms of dementia. Oxidative stress activates an enzyme that cleaves beta amyloid from its precursor protein, accelerating amyloid production and setting the stage for its accumulation, one of the cardinal features of the disorder. Oxidative stress also impedes clearance of debris from brain cells, promoting the buildup of toxins, setting off inflammatory processes, and leading to cell death. Further, it impairs the ability of cells to utilize their glucose fuel.
Preserving brain function hinges on many factors, from physical exercise to stimulating activities to a fruit- and vegetable-rich diet. Consuming substantial amounts of vitamin C, especially starting in young adulthood, is part of that equation.
Recommended Dietary Allowances
Males & Females: 1-3 years 15 mg
Males & Females: 4-8 years 25 mg
Males & Females: 9-13 years 45 mg
Males: 14-18 years 75 mg
Females: 14-18 years 65 mg
Males:19+ years 90 mg
Females: 19+ years 75 mg
C in the Brain
- Most concentrated in the cerebral cortex, hippocampus, and amygdala
- Cofactor in the synthesis of the neurotransmitters
- Helps convert norepinephrine from dopamine in brain cells
- Modulates release and reuptake of neurotransmitters
- Prevents neuronal overstimulation by glutamate
- Helps maintain vascular function
The ABCs of C#
- Papayas and bell peppers are the foods with the highest concentrations of vitamin C.
- Most plants and animals can produce vitamin C, but humans and other primates (along with bats and guinea pigs) cannot make or store it so require it from their diet.
- As a powerful antioxidant, vitamin C helps protect the body from toxins in air pollution and cigarette smoke.
- Smokers need more vitamin C than nonsmokers.
- The collagen tissue supporting teeth and bones is made from vitamin C.
- Vitamin C is a cofactor for at least eight enzymes involved in critical body processes.
- Vitamin C helps boost heme iron absorption from the gastrointestinal tract.
- Vitamin C is vital to the biosynthesis of carnitine, a major regulator of energy production from fat.
- Regular intake of vitamin C attenuates colds, shortening their duration and severity.
- High levels of vitamin C intake are linked to a lessened chance of developing eye cataracts and macular degeneration.
- Delayed wound healing may be a sign of vitamin C deficiency.
- Vitamin C is delicate and can be destroyed in the high temperatures generated by broiling, grilling, and frying foods.
- Body absorption of vitamin C depends on the dose; a greater percentage of the nutrient is absorbed at lower doses.