2002: A number of Japanese studies have found
that many vegetables grown in season contain more vitamin
A, C and carotene than their off-season counterparts
grown under plastic. Joel Gruver, from the Department
of Soil Science at NC State University emailed us these
findings, from Kagawa Nutrition University, Laboratory
of Bio-organic Chemistry, 3-9-21 Chiyoda, Sakado-shi,
Saitama, 350-0288 Japan:
The content of vitamin C seems to be significantly influenced
by the cropping season. In spinach, for example, the
vitamin C content was reduced by 1/5th to 1/8th in off-season
produce compared to its peak in in-season produce. It
was also reduced in tomatoes and broccoli by up to 1/2
in off-season produce.
The content of carotene, a preceding substance of vitamin
A, was also affected by the crop season. In off-season
broccoli, it was sreduced by 1/4th, and in off-season
carrots it was reduced by more than half, compared to
peak in-season levels.
Vegetables not affected by
The vitamin C and carotene content of some vegetables
and fruits, such as sweet peppers, celery and kiwifruit,
was fairly stable across seasons.