Long before vitamin C was recognized as an essential nutrient, Dr. James Lind found that a component in citrus fruits could cure scurvy in British sailors, supporting England’s naval dominance and helping shape the world we live in today (1). Years later, a hexuronic acid (now known as ascorbic acid) was identified as “vitamin C” and its important role in the biochemical mechanism of collagen formation was elucidated (2,3). While this is the primary reason that vitamin C is considered an essential nutrient, recent research suggests that vitamin C may also be important for other chronic diseases. In addition, the levels of intake required for optimal health may be higher than currently recommended.
Immune function is one of the most well-recognized benefits of vitamin C. Vitamin C is preferentially taken up by circulating immune cells, resulting in levels 20-60 times those of surrounding cells (4). This may protect neutrophils from the reactive oxygen species that are used to kill pathogenic bacteria or viruses. Vitamin C also influences the movement of immune cells to sites of infection, and decreased vitamin C levels have been observed in individuals with infections (5). A recent Cochrane meta-analysis of clinical trials of vitamin C supplementation in humans concluded that supplementation of 200 mg or more of vitamin C reduced the duration of common cold symptoms in both adults and children (6).
Vitamin C is also associated with certain non-communicable diseases such as cardiovascular disease, cancer and even Alzheimer’s disease. Population studies have reported associations between vitamin C and decreased cardiovascular risk (7). Several meta-analyses of clinical trials with vitamin C supplementation have reported improvements in endothelial function (8) and blood pressure (9). Vitamin C intake has also been associated with decreased incidence of certain cancers (10–12) and Alzheimer’s disease (13,14), although cause and effect relationships are unclear. Recently, there has been increased medical interest in the possible benefits of intravenous vitamin C to support quality of life in patients receiving chemotherapy (15).
In light of this recent evidence, some experts have advocated for increasing the daily recommended intake to 200 mg or more per day (16), an amount that can be obtained by consuming 5 servings of fruits and vegetables. However, in many parts of the world, marginal or outright vitamin C deficiency is surprisingly common. Marginal deficiency or depletion in vitamin C (<28 µmol/L) has been reported in 34-46 percent of a low-income UK population (17), and suboptimal vitamin C status (<53 µmol/L) has been reported in 46 percent of the U.S. population (18).
Clearly, vitamin C is important for more aspects of health beyond simply the prevention of scurvy. Many individuals don’t consume the recommended amounts of fruits and vegetables, and many have vitamin C levels in the body that are below recommendations. Considering the possible benefits, there is an opportunity to advocate for increased consumption of foods high in vitamin C or supplements that can help individuals reach the levels of vitamin C in the body that are associated with optimal health.
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