Most animals produce their own vitamin C, but humans (along with other primates and, incidentally, guinea pigs) do not. We get vitamin C only from what we eat, specifically vegetables and fruits.
The recommended daily intake of vitamin C — the bare minimum to prevent deficiency and keep the body’s immune response operating properly — is 75 mg per day for an adult woman and 90 mg per day for an adult man. (Younger children need less, but those 14 and up also require 75 mg per day.)
Smokers, who are under greater oxidative stress than nonsmokers, are advised to consume an additional 35 mg daily. Functional physician Gregory Plotnikoff, MD, suggests that smoking one cigarette may burn up as much as 25 mg of a body’s vitamin C on its own.
Functional providers tend to recommend significantly more than the RDA because of the vitamin’s essential role in handling oxidative stress. “For the average person who isn’t suffering from a chronic illness, I think aiming for 400 mg a day is reasonable,” Plotnikoff advises. “That’s doable by intentionally getting a lot of fresh produce in one’s diet. You don’t necessarily need supplementation.”
For those diagnosed with any chronic illness requiring the body to manage ongoing inflammation, he recommends as much as 1,000 mg per day.
The need for C also increases when everyday illnesses strike, adds functional-medicine physician Terry Wahls. “The amount that you need daily if you’re well is lower than the amount you need if you’re not well,” she says.
You likely burn through your stores during any illness, so it’s wise to consume extra vitamin C afterward to rebuild them, ideally by upping your quotient of vegetables and fruits.
This article originally appeared in Experience Life, Life Time’s whole-life health and fitness magazine.