Vitamin C (ascorbic acid) is the single biggest category in vitamin and supplement sales and it’s getting even bigger. Demand for Vitamin C increased by 20% amid coronavirus fears and the usefulness of Vitamin C to boost the immune system. Vitamin C is just one nutrient thought to help prevent viral infections by promoting specific immune system functionality and via antimicrobial action.
Vitamin C has been shown to shorten duration of hospital stay due to viral pneumonia and some studies show it helps the body thwart common colds. This ability to fight disease may well be due to the importance of Vitamin C to mucosal integrity. Vitamin C helps maintain the lining or mucosa of all of the openings to our bodies. This delicate, moist tissue is responsible for controlling foreign substances like dust, bacteria, and other particles from getting into our mouths, stomachs, lungs, eyes, ears, and urogenital tracts. A healthy mucosa, creates a barrier that is semi-permeable or selective on what gets in and out of our bodies. The mucosa is a very busy place. It is responsible for secretion of waste products, absorption of nutrients, exchange of gases like oxygen, and even transmission light. Any loss of integrity of the mucosa results in a breach in our body’s barrier which is a primary defense mechanism. This makes Vitamin C an important nutrient to the physical foundation of our bodies.
Another way Vitamin C supports our physical foundation is in bone health. By supporting the formation of collagen, Vitamin C aids bone mineralization and helps create stronger bones. Ascorbic acid is important for heart health, and also helps the body absorb more iron. Both supplemental and native (found in food) Vitamin C enhance the bioavailability of iron making it more absorbable, especially in foods containing phytates and tannins-–compounds that can interfere with iron absorption.
While Vitamin C is most commonly thought of as a safe to supplement water soluble vitamin, it can be problematic at high doses when taken for long periods of time. As I’ve mentioned before, there are no nutrients that act alone without interaction with other nutrients in the human body. There are also optimal amounts of nutrients to consume. In the case of excessVitamin C, it is excreted as oxalate in the urine. This can increase the risk of kidney stones is susceptible people. Doses as low as 1g (1000 mg) per day have been associated with an increased risk of kidney stones, and gastrointestinal upset is also common at higher doses, including loose stools and diarrhea.
While many Vitamin C supplements are formulated at 1000 mg per dose, this is not necessarily because this is the preferred dose. Supplement production is regulated but there is no regulation regarding how much Vitamin C manufacturers can put in each product. The RDA for Vitamin C is 75 mg for women and 90 mg for men. It is recommended that smokers increase that by about 35 mg per day. It is generally thought that 500 mg of supplemental Vitamin C per day is safe and without risk of unwanted side effects. I would emphasize that it is always best to get Vitamin C from food first. Vitamin C in food is often found with other nutrients that work in concert with it. Oranges, lemons, limes, and kiwi contain bioflavonoids which are also important antioxidants. Kale and broccoli contain Vitamin C and fiber that nourishes the gut bacteria. These healthy gut bacteria work with Vitamin C to discourage unwanted bacteria growth in our intestines and promote specialized immune cells within it. We don’t know exactly how much of these specialized antioxidants we need so you don’t hear as much about them. These additional antioxidants are very often left out of Vitamin C supplements.
So take a few minutes to review your supplement labels and identify all the pills from which you might be getting Vitamin C. Limit total amount of supplemental Vitamin C to 500 mg per day unless you are working with a knowledgable practitioner that has determined a higher dose that is okay for you. Be sure to add foods high in Vitamin C to your shopping list and include them at two or more meals each day. About 2 1/2 cups of fruits and vegetables can provide about 150-200 mg of Vitamin C. You’ll get more nutrition from food than you can ever get from a pill. For a more thorough review of Vitamin C, you can check out Oregon State’s Linus Pauling Institute.