What is the Role of Vitamin C in Health and Immune Function?

What is the Role of Vitamin C in Health and Immune Function?

How much do you know about vitamin C? First, your body can’t make it so it must come from food or dietary supplements and because vitamin C is water-soluble, it needs to be constantly replenished because the body can’t store it.1

What is Vitamin C?

Vitamin C is an important antioxidant that supports collagen production, iron absorption from plant foods, heart and eye health, and immune function.2 Antioxidant nutrients like vitamin C help protect cells from free radical damage.2

Vitamin C and Immune Function

Regarding the immune system, a 2023 review reiterated the fact that vitamin C supports the function of immune system cells including important T and B cells and white blood cells.3

A small, randomized study from 2019 also demonstrated that taking vitamin C as a dietary supplement could potentially help individuals support their blood sugar and blood pressure levels, too.4

What Foods Have Vitamin C?

Citrus fruits are the best food source of vitamin C, but it is also found in vegetables such as broccoli, tomatoes, peppers, spinach, and other green leafy vegetables. Keep in mind that the vitamin C content in foods is reduced if they are cooked, steamed, or stored for a long time.1 

Remember because vitamin C is water-soluble, it needs to be constantly replenished so people who are not eating a high fruit and vegetable diet may want to add a daily dietary supplement to their routine. In addition, people who smoke or are exposed to secondhand smoke and people with certain medical conditions may not be getting enough vitamin C from diet alone and may want to take a daily supplement.1 Taking extra vitamin C during certain times of the year may also be wise.

Other Ways to Get Vitamin C

The vitamin C powder used to make dietary supplements is typically the ascorbic acid form. Vitamin C is almost always included in a multivitamin-mineral supplement, and it is also often combined with other nutrients such as zinc, elderberry, acerola fruit extract, citrus bioflavonoids, and rose hips to provide additional support. Vitamin C is available as a chewable, powder, tablet, or tasty gummy.

Vitamin C+ Gummies are made with a unique combination of 270 mg of vitamin C plus added bioflavonoids, rose hips and acerola to round out the immune support. And they’re delicious.

What is the shelf life of vitamin C? Like most dietary supplements, vitamin C will have an expiration date on its packaging. While the supplement will not become unsafe if taken after the manufacturer’s expiration date, it may lose its potency.

Vitamin C supports health on many levels. It must be replenished daily to get the health benefits, so don’t forget to get enough vitamin C, especially during cold and flu season.

Follow @zhou_nutrition for more fitness and wellness tips!


  1. Harvard School of Public Health. Vitamin C. The Nutrition Source. 2023;March. https://www.hsph.harvard.edu/nutritionsource/vitamin-c/
  2. National Institutes of Health Office of Dietary Supplements. Vitamin C fact sheet for consumers. 2021;March 22. https://ods.od.nih.gov/factsheets/VitaminC-Consumer/
  3. Moore A, Khanna D. The role of vitamin C in human immunity and its treatment potential against COVID-19: a review article. Cureus. 2023;15(1). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9925039/
  4. Mason SA, Rasmussen B, van Loon L, et al. Ascorbic acid supplementation improves postprandial glycaemic control and blood pressure in individuals with type 2 diabetes: findings of a randomized cross-over trial. Diabetes Obes Metabl. 2019;21(3):674-682. https://pubmed.ncbi.nlm.nih.gov/30394006/