When you're trying to stave off the common cold or a more serious virus, conventional wisdom tells you to take as much vitamin C as possible. While vitamin C does have benefits, don't go loading up on vitamin C supplements — it could do you more harm than good.
If you take more than 3,000 milligrams of vitamin C in a day, you could see some unpleasant symptoms. This is more likely to happen from taking vitamin C supplements rather than consuming foods rich in vitamin C.
Read more: The Best and Worst Foods to Eat When You're Sick
Understanding Vitamin C Benefits
Vitamin C is a micronutrient with an array of benefits. The Mayo Clinic notes that it supports normal growth and development and helps the body absorb iron, which is needed to transport oxygen to cells.
Harvard Health Publishing points out that people who get their recommended amounts of vitamin C tend to have a decreased risk of cancer, particularly cancer of the mouth, esophagus, stomach, colon and lungs (though it's not clear whether this is specifically attributable to vitamin C or just general healthy nutrition).
Because the body doesn't produce or store vitamin C, people need to include vitamin C in their diet every day. The recommended amount is about 75 to 90 milligrams a day for adults. Most people turn to oranges or orange juice for their vitamin C, but other great sources include bell peppers, broccoli, tomatoes, kale, strawberries, lemons, mango and cantaloupe, reports Harvard Health.
Most people think of vitamin C as an immunity booster, so they'll load up on vitamin C during cold and flu season. But it turns out that this conventional wisdom is a little misguided. According to the Harvard T.H. Chan School of Public Health, this misconception started in the 1970s with double Nobel laureate Linus Pauling, who claimed that daily megadoses of vitamin C could prevent colds and chronic diseases.
A half-century later, people are still taking unnecessary amounts of vitamin C for this purpose. Harvard Health explains that the most you can expect from taking a high dose of vitamin C is a shortened period of sickness (but only by about one day). Vitamin C might also reduce a person's risk of getting sick in extreme circumstances — as examples, Harvard Health lists skiers, marathon runners and soldiers working in sub-Arctic conditions.
Read more: 5 Uncommon Ways to Fend Off Cold and Flu
Don’t Exceed the Recommended Dosage
While getting plenty of vitamin C in your diet won't cause you any harm (it's a water-soluble vitamin, so any excess amounts will be excreted in your urine), Harvard Health discourages anyone taking supplements to not exceed the upper limit of the vitamin C dosage per day. This is because excessive supplemental vitamin C could be too much at one time, and your body can't excrete it quickly enough.
While the vitamin C dosage for adults that is typically found in a supplement might be far higher than the 75 milligrams a day that adults actually need, you don't need to worry until you exceed the upper limit of 2,000 milligrams, per the advice of the Mayo Clinic. The Harvard T.H. Chan School of Public Health states that people can take up to 3,000 milligrams before they start to see adverse symptoms.
Those who take megadoses of vitamin C might suffer diarrhea, nausea, heartburn, gastritis, fatigue, headaches and insomnia. The National Institutes of Health notes that people with hemochromatosis, in which the body stores too much iron, could suffer iron overload and damage body tissue if they take excessive amounts of vitamin C.
To avoid these symptoms, your safest bet is simply to focus on getting your vitamin C from food. As the National Institutes of Health explains, vitamin C deficiency is rare. Individuals who could benefit from getting more than the usual amount of vitamin C are people who smoke or who are exposed to secondhand smoke, people who eat a limited variety of food, and people with medical conditions such as malabsorption, types of cancer and kidney disease.
It's important to note that if you've been trying to reap extra vitamin C benefits by taking supplements and are now ready to cut back, you should do so slowly. Harvard Health highlights that people who have taken too much for a prolonged period of time will metabolize vitamin C faster than normal, and cutting back too quickly could mean your body won't absorb enough.