I've learned a lot about vitamin C in my chemistry class. It's absolutely fascinating. It used to prevent pirates from getting scurvy, by eating lemons.
Ohh yeah, I love citrus too so I'm a fan.
Many people take very large doses of vitamin C to prevent things like a cold but the  United States Institute of Medicine recommends against it.
Oh like those powder supplements?
Vitamin C megadosage
Vitamin C megadosage is a term describing the consumption or injection of vitamin C (ascorbic acid) in doses well beyond the current Recommended Dietary Allowance of 90 mg/day, and often well beyond the Tolerable upper intake level of 2,000 mg/day. There is no scientific evidence that megadosage helps to cure or prevent cancer, the common cold, or a variety of other medical conditions.
Historic advocates of vitamin C megadosage include Linus Pauling, who won the Nobel Prize in Chemistry in 1954. Pauling
The vitamin C (specifically acid) in citrus fruits prevented scurvy , and helped to make these sailors some of the healthiest of the time. At that time "lemon" and "lime" were used interchangeably to refer to citrus fruits. Initially, lemon juice (from lemons imported from Europe) was used as the additive to grog on the Royal Navy ships, but was later switched to limes (grown in British colonies), not realizing that limes did not contain sufficient Vitamin C to prevent the disease. 
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