Does Vitamin C prevent colds?

Kristen Kaethler

"You've got to go out on a limb sometimes because that's where the fruit is" -Will Rogers

“Eat some vitamin C!” is one of the most common recommendations given to people who start to feel under the weather. Many companies take advantage of the presumed link between vitamin C and the common cold, marketing products like Emergen-C for immune boosting support. In the past, I have also been guilty of increasing my Vitamin C intake when I feel sick because I’ve been told that’s what I should do. But does Vitamin C actually help prevent or decrease the duration of the common cold?

The Basics

Nandhini Kumar

Before getting into details, it’s important to know a little bit about Vitamin C. Vitamin C is a water-soluble vitamin also known as ascorbic acid or ascorbate. Vitamin C comes mainly from fruits and vegetables. Most people know citrus fruits, like oranges, contain high amounts of vitamin C, but other food sources included peppers, broccoli, strawberries, avocados, and sweet potatoes. Simply ½ cup of green bell peppers provide all the vitamin C you need in a day. The Recommended Dietary Allowance (RDA) for vitamin C is 90mg/day for men and 75mg/day for women. The Tolerable Upper Limit (TUL) is 2,000mg/day, more than 20 times the RDA! The TUL for a nutrient refers to the amount that we can safely consume daily before it becomes toxic.

The TUL is set so high because we can easily excrete excess dietary Vitamin C. An important thing to note about most of the water-soluble vitamins is that the more we take in the less our body will absorb. Eating excessive amounts of vitamin C does not mean our body will be able to take that all in. Our bodies are really good at regulating Vitamin C levels, so when we take in more than we need, we will just excrete it. A fun fact about Vitamin C is that it is made from glucose! So a high intake of glucose can also decrease Vitamin C absorption.

Vitamin C is stored in most places in the body but primarily in the adrenal and pituitary glands. The concentration of Vitamin C is so high in the adrenals because Vitamin C helps with the synthesis of stress hormones produced there, like adrenaline and cortisol.

Vitamin C and colds

Kelly Sikkema

The common cold is an upper respiratory tract infection that lasts about 10 days. The average person gets between 2-6 colds per year. There is no evidence to suggest that supplementing with high doses of Vitamin C (200mg/day-1,000mg/day) has any effect on preventing colds. Some evidence suggests that Vitamin C supplementation can decrease the incidence of colds by 40-90% in athletes, but this was only studied in runners and skiers.

In addition to prevention research, studies have looked at the effectiveness of Vitamin C for treating colds. People who regularly supplement with Vitamin C may have colds that are 1-4 days shorter than the average person consuming 75-90mg/day. However, people who start taking Vitamin C supplements when they feel a cold coming on (for example, downing Emergen-C packets the first day of a cold) do not see any change in cold duration.

What else does vitamin C do?

Besides its affiliation with colds, vitamin C has other functions. Most notably it acts as an antioxidant. Antioxidants are beneficial compounds in the body that protect our cells from free radicals. Free radicals damage cells like DNA and may play a role in a number of chronic diseases. For example, cancer is initiated by free radical damage to DNA. Therefore, Vitamin C is thought to prevent or delay the development of cancer.

Another way Vitamin C is thought to decrease cancer risk is through its role in collagen formation. Collagen is the most abundant protein in the body. It provides structure to our bones, muscles, skin, and tendons. It’s also important for walling off tumors and slowing the spread of cancer. Vitamin C’s function as an antioxidant and in the synthesis of collagen goes hand-in-hand with possibly decreasing the risk of cancer development. These benefits occur with normal Vitamin C consumption, thus supplementing with Vitamin C to prevent specific cancers is not recommended.

Supplementing with vitamin C may also decrease the incidence of cataracts in older adults.

Summary

To summarize, Vitamin C is an essential nutrient needed to maintain good health. It functions as an antioxidant, helps the adrenal glands produce stress hormones, and plays a role in conditions such as cancer, cataracts, and colds. We can’t prevent or shorten our colds by upping our Vitamin C intake. If you regularly supplement with Vitamin C, your cold may last 7 days instead of 10 days.

Remember, our body can only take a certain amount of Vitamin C and will pee out the rest. As my professor likes to remind us, because of our obsession with supplements, we have “the most expensive urine in the world”!

Keep thriving,

Erica

Ben White

References

Varady, Kristina. “Vitamin C.” Nutrition Science II, 15 January 2020, University of Illinois at Chicago, Applied Health Science Building, Chicago, IL. Lecture.