The role of vitamin C in cognitive function in older adults and smokers

As the population ages, the number of people experiencing cognitive decline of varying degrees is also on the rise. Diet and lifestyle play a major role in brain function, and higher vitamin C intake has been associated with better cognitive performance in older adults. Evidence also suggests that smokers may benefit the most, according to a study published in Frontiers in Nutrition.

Cognitive decline refers to a reduced ability to process information, think, and remember. It can also impair focus, communication, and orientation, affecting quality of life, social interactions, and work performance. Cognitive decline occurs in varying degrees, and mild cognitive impairment can sometimes be an early sign of dementia.
According to the WHO, 5-8 percent of the global population over 60 suffers from some form of cognitive impairment, including dementia and Alzheimer’s disease. With an increasing elderly population, cognitive decline and dementia represent a significant human and socioeconomic burden. Since diet and lifestyle significantly influence cognitive health, new preventive strategies are needed.
Vitamin C has attracted attention in this context, as it both supports the nervous system and serves as a potent antioxidant that protects cells from damage caused by free radicals and oxidative stress.
The new study aimed to investigate the relationship between vitamin C intake and cognitive function in older American adults. Researchers analyzed data from the NHANES (National Health and Nutrition Examination Survey), a large U.S. study that tracks lifestyle and dietary habits over time.
The study included nearly 3,000 adults aged 60 and older. Participants’ total vitamin C intake from diet and supplements was assessed via questionnaires. Cognitive function and risk of dementia or Alzheimer’s disease were evaluated using various tests, including CERAD (Consortium to Establish a Registry for Alzheimer’s Disease), AFT (Auditory Fluency Test), and DSST (Digit Symbol Substitution Test).
The study found a direct, non-linear relationship between cognitive function and vitamin C intake. The top quartile of participants with the highest vitamin C intake performed better on the AFT test compared with the bottom quartile, suggesting that vitamin C helps improve memory, including recollection of older memories. The top quartile also performed better on the DSST, indicating superior attention, concentration, symbol recognition, and working memory.
Further analysis indicated that around 120 mg of vitamin C per day yielded the best results on the AFT test, while 500 mg per day was optimal for the DSST. These doses are considerably higher than the official recommended intake of (80-100 mg), which is primarily intended to prevent classic deficiency diseases such as scurvy.
The study also found that the cognitive benefits of higher vitamin C intake were greatest in smokers, likely because smoking generates free radicals that cause oxidative damage to cells.
The researchers concluded that higher vitamin C intake is associated with better cognitive function in older Americans, and that smokers, in particular, should ensure sufficient vitamin C intake.

Vitamin C and its role in the brain, nervous system, and cognitive function

It is no coincidence that the brain contains the highest concentration of vitamin C in the body. The study authors highlight several ways in which vitamin C supports the nervous system and cognitive function:

• Involved in the synthesis of the neurotransmitter dopamine, which affects attention, learning, movement, motivation, and pleasure
• Involved in the synthesis of the neurotransmitter norepinephrine, released during stressful situations
• Regulates the permeability of the blood-brain barrier
• Reduces deposition of harmful proteins (β-amyloid) implicated in Alzheimer’s disease
• Functions as a powerful antioxidant, counteracting damage caused by free radicals and oxidative stress

Vitamin C also plays a role in connective tissue formation. Reduced collagen production in brain blood vessels may impair blood supply, limiting oxygen and nutrient delivery to neurons and slowing waste removal in the brain’s high-metabolism environment.
Additionally, vitamin C is believed to support the protective myelin sheath of neurons and the branching structures that are critical for functional brain networks.

Sources of vitamin C and relevant supplementation

Vitamin C is abundant in citrus fruits, red bell peppers, berries, cabbage, herbs, and other fruits and vegetables. A healthy diet can provide the official daily recommendation for the nutrient. However, many people in developed countries consume too little fruit and vegetables.
The study suggests that older adults may benefit from higher vitamin C intake, potentially up to 500 mg daily, to support brain health and cognitive function. Factors such as stress, pregnancy, smoking, stimulants, and high sugar intake can further increase vitamin C requirements, meaning that many people may need more than the official recommendations.

References:

Xingchen et al. Vitamin C intake and cognitive function in older U.S. adults: nonlinear dose-response associations and effect modification by smoking status. Frontiers in Nutrition 2025

Minju Sim et al. Vitamin C supplementation promotes mental vitality in healthy young adults: results from cross-sectional analysis and randomized, double-blind, placebo-controlled trial. European Journal of Nutrition. 2021