The benefit of Vitamin C on cognitive and immune health

Vitamin C is found in high concentrations in the brain, especially in the hippocampus and frontal cortex regions – areas that are important for memory consolidation, learning, and aspect of executive function. But here’s a surprise:

The brain retains vitamin C during times of deficiency at the expense of other tissues.

That’s really important because evidence suggests that vitamin C plays roles in the brain throughout the lifespan from development all the way up through older age, when it helps preserve cognitive function.

But the effects of vitamin C on brain development were particularly evident in a study in guinea pigs. Like humans, guinea pigs can’t synthesize their own vitamin C – they have to get it from their diet. Hippocampal development in guinea pigs that are deficient as newborns is reduced roughly 30 percent.

Vitamin C influences fatty acid oxidation, often referred to as “fat burning.” In fact,…

Vitamin C levels are inversely correlated with body weight, particularly among people who are obese.

This might be because vitamin C is essential for the synthesis of carnitine – a compound that plays an important role in the utilization of fatty acids as energy. It’s possible that low vitamin C levels contribute to increased fat storage, which could have implications for people trying to lose weight.

This became evident in a study in mice that were fed a Western diet – one that’s high in fat and sugar – with or without vitamin C. The mice that received vitamin C gained less weight, particularly in terms of fat mass, compared to mice fed the Western diet alone.

The real surprise is the sheer magnitude of variation in the bioavailability of vitamin C.

The bioavailability of vitamin C is frequency- and dose-dependent. But the form of vitamin C impacts bioavailability, too.

For example, high dietary intake of vitamin C-rich fruits and vegetables produce steady-state plasma vitamin C concentrations of around 80 micromoles per liter or less. Even with supplemental oral intake of 3 grams, taken six times a day, plasma vitamin C concentrations peak out at 220 micromoles.

By contrast, intravenous vitamin C can produce plasma concentrations as high as 15,000 micromoles per liter.

A few studies suggest that oral bioavailability of vitamin C can be increased when consumed in liposomal form but only in doses higher than 5 grams. Liposomal vitamin C doses less than 5 grams achieve similar plasma vitamin C concentrations as non-liposomal vitamin C.

The differences in the various forms of vitamin C aren’t limited to their bioavailability.

The forms of vitamin C differ in terms of their mechanisms of action.

For example, while oral vitamin C acts primarily as an antioxidant, pharmacologic doses of intravenous vitamin C greater than 1 gram generate hydrogen peroxide, a type of reactive oxygen species that can damage DNA, RNA, and proteins, leading to tissue damage. Multiple studies suggest that high dose intravenous vitamin C can assist in cancer cell death primarily due to the formation of hydrogen peroxide but that damage does not occur in normal, healthy cells.

Of course, we’d be remiss if we didn’t talk about how critical vitamin C is to immune function. Immune cells actively participate in eliminating pathogens such as bacteria or viruses from the body.

Vitamin C is highly concentrated in immune cells, with neutrophils and leukocytes having roughly 50 to 100 times higher vitamin C concentrations than plasma.

One of the early stages of the body’s immune response to viral or bacterial infection involves neutrophil infiltration into an affected tissue, where the cells engulf the pathogens and initiate their removal.

Neutrophils also generate large quantities of reactive oxygen species. But the high levels of vitamin C present in immune cells protect them from reactive oxygen species-induced DNA damage while also promoting neutrophil reactive oxygen species production.

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