Background:
Seasonal variation of vitamin C in fresh fruits and vegetables is not reflected in food composition database average values, yet many factors influence content and retention.
Results:
Fresh fruits and vegetables were sampled on three occasions in each season, from the same local retail outlets, for one or two years. Vitamin C was significantly higher in winter-sampled spinach (436 mg kg-1 ) compared to spring (298) and summer/fall (180); in potatoes in summer/fall (156) versus winter/spring (106); and oranges in winter (616), spring (592), and summer (506). Ranges were dramatic among sampling occasions for broccoli, oranges, potatoes, spinach (700-1210, 420-780, 70-280, and 90-660 mg kg-1 , respectively). Mean values for apples, bananas, tomatoes, and potatoes differed from the USDA National Nutrient Database for Standard Reference (SR) average by ≥10% of the Daily Recommended Intake (90 mg). For broccoli, oranges, and spinach vitamin C was substantially above or below the SR range in 50-100% of the samples. For spinach, the average content did not differ from SR, but vitamin C in winter was 55% higher than SR.
Conclusion:
Database average values for vitamin C in fresh produce can significantly over-or underestimate the content in a specific food supply.