Vitamin C, a vital nutrient the body cannot produce on its own, plays a critical role in maintaining health—especially in supporting the immune system and protecting against oxidative damage. Found naturally in foods such as bell peppers, strawberries, broccoli, and tomatoes, vitamin C has gained popularity both as a dietary staple and a supplement.

In a recent discussion with Eat This, Not That, registered nurse Sean Marchese, an oncology specialist with over 15 years of patient care experience, broke down the many roles of vitamin C in the body—and why moderation matters.

Antioxidant Powerhouse

Vitamin C functions as a potent antioxidant, helping to neutralize free radicals—unstable molecules that can damage cells and trigger inflammation. According to Marchese, daily intake of vitamin C can support the body’s defense systems by reducing oxidative stress and promoting the activity of other antioxidants, like vitamin E. This process is essential in healing, especially following infections or injuries.

A Key Player in Immune Defense

Beyond its antioxidant benefits, vitamin C is deeply involved in immune function. It strengthens immune cells, including neutrophils and macrophages, enhancing the body’s ability to fight infections. Marchese emphasizes that vitamin C contributes to clearing out used immune cells after an illness, minimizing the risk of lingering inflammation or tissue damage.

However, he notes that vitamin C is a supportive tool—not a substitute—for a balanced diet or vaccinations. “It works best as part of a broader approach to wellness,” he added.

Possible Role in Cancer Prevention and Treatment

While vitamin C supplements are not necessary for everyone, they may offer added protection for people with deficiencies or those undergoing cancer treatment. Marchese shared that vitamin C could help reduce inflammation and support nutrient absorption in patients, and early research has linked vitamin C intake to a lower risk of certain cancers, including pancreatic, prostate, and esophageal cancers.

Vision Protection for Aging Eyes

Vitamin C may also contribute to eye health, particularly when combined with other essential nutrients. Studies suggest it could slow the progression of age-related macular degeneration and reduce the risk of cataracts. Although it won’t reverse existing eye issues, it may help preserve vision over time.

Don’t Overdo It: Risks and Side Effects

Despite its many benefits, excessive intake of vitamin C isn’t without risk. Marchese warned that taking large doses—especially over 2,000 mg daily—can lead to unpleasant side effects like nausea, diarrhoea, heartburn, and abdominal cramps. More significantly, consuming too much vitamin C has been linked to a higher risk of developing kidney stones, particularly in men.

Additionally, high levels of vitamin C may interfere with certain medications, such as chemotherapy drugs and blood thinners. People with chronic health conditions or those taking prescription medications should consult a healthcare provider before starting a vitamin C supplement.

Final Takeaway

Vitamin C is a cornerstone nutrient that supports immunity, combats oxidative stress, and may aid in disease prevention. But like any supplement, it should be used wisely. Marchese recommends meeting daily vitamin C needs through a nutrient-rich diet, reserving supplements for specific medical reasons and under professional guidance.

In the quest for better health, vitamin C is a powerful ally—but it’s most effective when part of a well-rounded lifestyle.