NOW Foods Vitamin C-500 with Rose Hips

Vitamin C· evidence: Moderate

Vitamin C (ascorbic acid, or mineral ascorbates such as sodium, calcium or magnesium ascorbate) is an essential vitamin found in fruit and vegetables. Adults need about 40 mg a day in the UK, and most people who eat fruit and vegetables get enough. The body cannot store much, and absorption falls off at higher doses, so the extra from a 1,000 mg tablet is largely passed in urine.

The best evidence on colds (a Cochrane review) found that taking vitamin C every day does not stop most people catching colds, but may shorten them slightly. People doing very heavy physical exercise are the exception, where regular vitamin C roughly halved the number of colds in trials.

A supplement makes sense if your diet is low in fruit and vegetables, if you smoke, or around periods of hard training. Most people do not need mega-doses, and fancy forms (liposomal, ester or buffered) have little evidence of meaningful benefit over plain ascorbic acid, though buffered forms can be gentler on the stomach.

Typical dose: The UK reference intake for adults is 40 mg a day (NRV on labels: 80 mg). Supplements commonly give 200 to 1,000 mg.

Safety: The FSA advises that 1,000 mg (1 g) a day or less from supplements is unlikely to cause harm. Higher doses can cause stomach pain, diarrhoea and wind. People with a history of kidney stones, haemochromatosis (iron overload) or kidney disease should speak to their GP before taking high doses. Chewable and powder forms are acidic and can affect tooth enamel.

Research we looked at:
NHS. Vitamin C. nhs.uk/conditions/vitamins-and-minerals/vitamin-c
Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev 2013;(1):CD000980.
EFSA NDA Panel. Scientific opinion on dietary reference values for vitamin C. EFSA Journal 2013;11(11):3418.
Carr AC, Vissers MCM. Synthetic or food-derived vitamin C: are they equally bioavailable? Nutrients 2013;5(11):4284-4304.

Citrus bioflavonoids, rose hip and rutin· evidence: Insufficient

Citrus bioflavonoids (such as hesperidin), rutin and rose hip powder are plant ingredients often added to vitamin C products, usually on the idea that they help the body use vitamin C, as they come together in fruit.

Human studies have not shown that adding bioflavonoids makes a meaningful difference to how much vitamin C the body absorbs or keeps. Rose hip has been studied for joint comfort in small trials with mixed results, and the amounts in vitamin C tablets are usually far lower than those used in studies.

These are botanical ingredients with no authorised health claims. In most vitamin C products they are present in small amounts and are best seen as a minor extra, not a reason to pay more.

Typical dose: No established dose. Vitamin C products typically add 25 to 500 mg.

Safety: Generally well tolerated at the amounts used in vitamin C products. Anyone on blood-thinning medicines or taking several herbal products should check with a pharmacist.

Research we looked at:
Carr AC, Vissers MCM. Synthetic or food-derived vitamin C: are they equally bioavailable? Nutrients 2013;5(11):4284-4304.
Christensen R, Bartels EM, Altman RD, et al. Does the hip powder of Rosa canina (rosehip) reduce pain in osteoarthritis patients? A meta-analysis of randomized controlled trials. Osteoarthritis Cartilage 2008;16(9):965-972.