As we get older, it feels natural to start taking things that are said to be good for us. These days it is easy to come across videos claiming that a particular supplement gives you energy or helps you walk better, and many people begin taking supplements such as vitamin C. If you are going through cancer treatment, however, it is worth pausing to think about how much and in what form you take even something widely considered healthy, because the same nutrient can help or add strain depending on the dose.
Vitamin C is a water-soluble vitamin, so much of any amount beyond what the body needs is passed out in the urine. That means the idea that more is always better does not really apply. For adults, the recommended daily intake is roughly 100 mg, and a common upper limit is around 2,000 mg per day. Taking far more than this at once can cause an upset stomach or diarrhea, and can raise oxalate levels in the body, increasing the risk of calcium-oxalate kidney stones. People with reduced kidney function or a history of stones should be especially careful with high doses.
Feeling that you have more energy to walk is a welcome change, but it is hard to be certain that vitamin C alone is the cause. A naturally good stretch of days may have overlapped, or the reassurance of taking something may itself play a role. Above all, opinions still differ on how antioxidant compounds affect chemotherapy and radiation therapy, so high-dose supplements or intravenous vitamin forms should be decided only after discussing them with your treatment team.
In practice, it helps to rely first on foods such as vegetables and fruit, and if you do use a supplement, to stay within the labeled daily amount and drink plenty of water. Bringing a list of the supplements and doses you take to your appointments lets your clinicians check whether anything overlaps with your treatment medicines.
This article is general information intended to aid understanding and does not replace medical care for your individual condition. Please decide on starting, stopping, or adjusting any supplement together with your treatment team.