Nutrition for Winter – vitamin C

vitamin C won't cure this

Judging from the walls of vitamin C supplements in grocery stores, pharmacies and vitamin stores, I’d say the quasi-religious belief that vitamin C cures the common cold and the flu is alive and well 40+ years after the idea was first proposed by Linus Pauling.   Proposed, but never proven.  According to the Natural Standards Database,

The use of vitamin C in the prevention/treatment of the common cold and respiratory infections remains controversial…..  For cold prevention, more than 30 clinical trials including over 10,000 participants have examined the effects of taking daily vitamin C. … no significant reduction in the risk of developing colds has been observed.  In people who developed colds while taking vitamin C, no difference in severity of symptoms has been seen overall, … For cold treatment, numerous studies have examined the effects of starting vitamin C after the onset of cold symptoms. So far, no significant benefits have been observed.

It’s not like researchers haven’t been trying to prove this for decades.  Nevertheless in flu and cold season, people buy megadoses of vitamin C, still believing in a magical effect against respiratory illness.  In fact, vitamin C is a nutrient, meaning you have to consume some everyday for health.  The minimum daily intake for an adult, to prevent deficiency symptoms, ranges from 75 mg/day (female) to 90 mg/day (male), with variations for smoking and pregnancy.   An average orange has at least that much, along with most multi-vitamins.  The controversy and wishful thinking concerns what an “optimal” dose might be.  Will more than the minimum prevent disease?  If so, how much more?

The problem with taking more vitamin C is the fact that our kidneys are really good at detecting and flushing any and all excess very quickly, once tissue storage capacity is full.  Excess vitamin C in the blood is potentially toxic.  If you take a 2000 mg pill (the upper limit of acceptable intake, by the way), your digestive system absorbs that as the pill disintegrates.  As blood levels start to go up, the kidneys go into action right away, dumping the excess into urine.   All that vitamin C you paid for goes to waste.

One promising new use is outside the realm of nutrition.  Intravenous doses of vitamin C are being tested as anti-cancer treatments.  Giving vitamin C intravenously can achieve extremely high blood levels very quickly.  Those levels cannot be reached by taking supplements.  At such high levels, vitamin C starts to act more like a drug, and may create a metabolic environment that is hostile to tumors.  As yet, this is an experimental use of vitamin C, as a cancer treatment.  Not useful against the flu.

How much vitamin C is optimally healthy?  The more rational recommendations range from 200-400 mg/day for adults, which is about the intake necessary to saturate tissues.  Happily, some high vitamin C fruits are in season during winter months to help you achieve that intake: oranges, grapefruit, tangerines and clementines (or “cuties”).  Vitamin C does help immune function, but it’s not the only nutrient necessary for fighting colds and flu.  So get enough, but don’t trust vitamin C pills to cure anything.  Think about it: do you know anyone who got the flu or a cold in past years, who didn’t take vitamin C and still has the flu?

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