Vitamin C (ascorbic acid) is a potent antioxidant essential for the immune system, collagen synthesis and iron absorption. Adults need 90mg/day (men) or 75mg/day (women). Smokers need an additional 35mg.
Vitamin C is sensitive to heat. To maximize its intake, consume fruits and vegetables raw or briefly steamed.
Red bell pepper (128mg) surpasses the orange (53mg) in vitamin C. Kale (120mg) and kiwi (93mg) are also excellent sources.
No, if you eat 5+ servings of fruits and vegetables per day. One orange and one pepper already cover 100% of daily needs.
It does not prevent colds, but it can reduce their duration by 8% in adults and 14% in children according to Cochrane meta-analyses.