Is taking extra vitamin C worthwhile?
Extra vitamin C offers little benefit for most people. Intensive athletes and people following a carnivore diet do have a good reason to supplement, and those who take it daily tend to experience slightly milder symptoms when they catch a cold.
For the average healthy person, taking extra vitamin C has no proven effect. Large-scale research involving nearly 884,000 participants shows no benefit for preventing colds, cardiovascular disease, or type 2 diabetes.1,2
There is one clear exception: people who exercise intensively, such as marathon runners or military recruits. In this group, daily vitamin C roughly halves the number of colds. For people with an ordinary, lightly active lifestyle, this benefit does not apply.
If you take vitamin C daily and still catch a cold, it does help somewhat. Fifteen studies with a combined total of more than 6,000 participants show that symptoms are on average 15% less severe. Higher doses of 6 to 8 grams per day appear to shorten the duration of a cold more than lower doses of 3 to 4 grams. Researchers say it is reasonable to try this for yourself, but it is not a firm recommendation. Starting once you are already ill does not demonstrably help; the studies contradict each other on this point.3,4
For memory and cognition, the evidence is extremely thin. A combination of low doses of vitamin C with vitamin E produced no improvement. Higher doses of vitamin C on its own occasionally showed positive signals, but this is insufficient to recommend supplementation.5
More is not automatically better, by the way. Under certain circumstances, vitamin C can also cause oxidative damage rather than protect against it. One group does have a genuine reason to supplement: people who eat only animal products. They are likely to get too little vitamin C from their diet. With a normal, varied diet you get enough, and taking extra then offers little benefit, unless you exercise intensively.6
All claims are based on randomised studies and meta-analyses (PMID 39803741, 36480969, 35268010, 32455696, 31963293, 39796574). Note: for PMID 31963293, two authors work at Bayer Consumer Care, a vitamin manufacturer. Read their positive conclusions about immune support with that interest in mind. The cognition claims (PMID 35268010) are partly associational and come from small studies.
Should I take vitamin B12 supplements as I get older?
Getting older increases the risk of a B12 deficiency, even if you eat healthily. Supplementation of 1000 micrograms per day is safe and corrects that deficiency effectively. Not sure? Then have your methylmalonic acid (MMA) measured alongside your B12 blood level -- that is the most reliable measure.
Can you get too much vitamin D?
Too much vitamin D is genuinely harmful, but that risk only arises at blood levels far above the recommended values. Stick to the dosage on the packaging, and unsure about your level? Have it measured by your GP.
Do antioxidant supplements make sense?
For healthy people, antioxidant supplements such as beta-carotene and vitamin E are not useful as protection against cancer or heart disease, and beta-carotene is frankly inadvisable for (ex-)smokers. The only well-supported exception is the AREDS formula for advanced macular degeneration: discuss this with your ophthalmologist.
How much vitamin D should you take per day?
For healthy adults under 75, extra vitamin D is probably not necessary, but for children, people aged 75 and older, pregnant women, and those at high risk of diabetes, supplementation is worthwhile. If you are unsure whether you belong to a risk group, it is worth discussing this with your general practitioner.
Does liposomal vitamin C work better than regular vitamin C?
Liposomal vitamin C reaches higher concentrations in your blood than the regular form, but whether that actually does anything for your health has not yet been proven. Until it is, the higher price is difficult to justify, unless you experience stomach complaints with high doses of regular vitamin C.
Does vitamin C actually help against a cold?
Taking vitamin C daily does not protect most people against colds, but does make a cold slightly shorter and milder. If you train intensively, the benefit is greater. Anyone who really wants an effect during a cold is better off looking at zinc.