Location: Nutrient Data LaboratoryTitle: Season plays a role in variability in vitamin C content of fresh fruits and vegetables in a local retail market
|PHILLIPS, KATHERINE - Virginia Tech|
|TARRAGO-TRANI, MARIA TERESA - Virginia Tech|
|RASOR, AMY - Virginia Tech|
|MCGINTY, RYAN - Virginia Tech|
Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2018
Publication Date: 2/6/2018
Citation: Phillips, K.M., Tarrago-Trani, M., Rasor, A., Mcginty, R.M., Haytowitz, D.B., Pehrsson, P.R. 2018. Season plays a role in variability in vitamin C content of fresh fruits and vegetables in a local retail market. Journal of the Science of Food and Agriculture. https://doi.org/10.1002/jsfa.8941.
Interpretive Summary: Fruits and vegetables are primary sources of vitamin C. Research on diet and health relies on food composition databases to estimate nutrient intake. Database average values can incorporate seasonal samples, but often do not reveal seasonal variation or bias in a local food supply. The objective of this research is to assess seasonal variation of vitamin C in highly consumed fruits and vegetables procured from a local market and to compare them to values in USDA food composition databases (http://www.ars.usda.gov/nutrientdata). Apples, bananas, broccoli, green leaf lettuce, navel oranges, peaches, potatoes, spinach, tomatoes, and summer squash were sampled on three occasions, each season, from three major local retail outlets in Blacksburg, VA, for one or two years. Sampling occurred three different times during the week at least two weeks apart. Total ascorbic acid was measured by HPLC. Vitamin C (mg/100g) was significantly higher in winter-sampled spinach (43.6) compared to spring (29.8) and summer/fall (18.0), in potatoes in summer/fall (15.6) versus winter/spring (10.6), and oranges in winter (61.6), spring (59.2), and summer (50.6). Vitamin C (mg/100g) ranges were dramatic among sampling occasions for several foods, particularly broccoli, oranges, potatoes, spinach (70 -121, 42 -78, 7 -28, and 9 -66, respectively). Mean vitamin C (mg/100g) differed (10 -12 mg/serving) from the database average for apples, bananas, tomatoes, and potatoes (apples lower, the others higher). Overall mean vitamin C in spinach did not differ from the database average (16.9), but was 55% higher in winter; in broccoli, oranges and spinach it was substantially above or below the database range in 50-100% of the samples. Vitamin C in a specific food supply can differ by a nutritionally significant amount from the national database average, and among seasons for some fresh produce. Researchers using food composition data should consider this factor when studying intake in a given population.
Technical Abstract: 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. 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. Database average values for vitamin C in fresh produce can significantly over-or underestimate the content in a specific food supply.