Vitamin C on its own functions as an essential nutrient and antioxidant even without additional bioflavonoids – these are not necessary for its basic function. However, the addition of citrus bioflavonoids and rutin has been linked in the literature to potentially improved cellular (leukocyte) uptake of vitamin C, which could mean a somewhat more efficient utilization of the consumed dose, while the effect on plasma vitamin C concentration is not unequivocally confirmed (Calder, Kreider & McKay, 2025). It is therefore a scientifically supported but not essential addition – the product's core functionality is based on the 1000 mg of vitamin C.

Yes, based on the available composition data, the capsule is made from hypromellose (a plant-based cellulose capsule), and the excipients (stearic acid and magnesium stearate) are also listed as plant-derived, making the product suitable for vegetarians and vegans. This is a difference compared to some other supplements in this category that use animal-derived gelatin capsules. Nevertheless, for specific dietary restrictions, we recommend checking the current label on the packaging before purchase, as the manufacturer's formula may occasionally change.

For healthy adults, the upper safe limit (UL) for vitamin C is 2000 mg/day (EFSA), so 1000 mg on its own is not at a level generally considered dangerous. Nevertheless, in men, additional (supplemental) vitamin C intake of ≥1000 mg/day has, in a prospective cohort study, been associated with roughly double the relative risk of developing kidney (oxalate) stones compared to non-supplementing individuals, while this association was not confirmed in women (Ferraro et al., 2016). If you have a history of kidney stones, kidney disease, or other risk factors, consult a doctor before regularly taking this dose.

The main difference lies in the additional ingredients and formula transparency. In addition to the basic dose of vitamin C, NOW C-1000 also contains a citrus bioflavonoid complex and rutin, which, according to some data, are linked to improved cellular uptake of vitamin C (Calder et al., 2025), and it also uses a plant-based capsule, which matters if you are vegan or vegetarian. Ostrovit is a cheaper, more minimalist product without these additions, but it has an explicit warning regarding kidney stones and pregnancy, which NOW does not. The choice therefore depends on whether you prioritize additional plant-based ingredients and a plant-based capsule, or a lower price and more explicit warnings.