Apparent Nutrient Changes in Government Data for a Selection of Fruits & Vegetables: 1951 vs 1999.

Based upon tabulated data provided by CTV News (1) there appear to be some marked differences in the two minerals (Calcium & Iron) and five vitamins (Vitamin A, Vitamin C, Thiamin, Riboflavin and Niacin) included in the comparison made for 25 different fruits and vegetables obtained from government documents for 1951 and 1999.

This analysis reveals that for some commonly consumed foods such as apples, broccoli, carrots, corn, onions, potatoes and tomatoes:

a) calcium levels decreased (range 30-63 per cent) for all but apples and corn where it increased by 20 and 35 per cent, respectively;
b) iron levels decreased (18-57 per cent) for all but corn where it increased 12 per cent;
c) Vitamin A levels decreased (range 43-100 per cent) for all but corn and carrots where it increased by 60 and 135 per cent, respectively;
d) Vitamin C levels deceased (range 2-57 per cent) in all but apples, corn and carrots where there were increases of 16, 8 and 47 per cent, respectively;
e) Thiamin levels decreased in apples, broccoli and potatoes by 75, 40 and 18 per cent, respectively, did not change in tomatoes and increased in carrots, corn and onions by 67, 125 and 33 per cent, respectively;
f) Riboflavin levels decreased in all (range 43-67 per cent) except corn and tomatoes where it increased by 80 and 25 per cent, respectively, and carrots where no change was observed; and
g) Niacin levels decreased in apples and broccoli by 30 and 3 per cent, respectively but increased in the remaining commonly consumed items listed here (range 45 – 135 per cent).

When all 25 fruits and vegetables were examined for changes over time the Table provided reveals that about three quarters of them appear to have lost Calcium and Iron while the remainder either stayed the same or gained one or both minerals.

With respect to changes in the vitamin levels in the fruits and vegetables examined; 17 fruits & vegetables lost Vitamin A, 20 gained Niacin and the remainder either stayed the same or similarly lost or gained vitamins.

While significant declines in important nutrients that we obtain mainly from only one or two foods in our diet might affect our overall intake of them, Canadians are encouraged to consume a wide variety of foods from all four Food Groups (1). Furthermore, Health Canada recently made it mandatory to add folic acid to flour and pasta (2) in an effort to improve the overall folate nutriture of Canadian women.

While many factors (see below) may help explain some of the differences tabulated by CTV News, Health Canada may wish to make similar comparisons of the nutrient content (possibly include additional nutrients) of the same (or other) fruits and vegetables as outlined above and report their findings to the public.

Some of the factors that may have contributed to the apparent differences in nutrient content of fruits and vegetables over time e.g., those outlined above, include:

a) genetic differences between current and past varieties / cultivars e.g., McIntosh vs Delicious;
b) selection of higher yielding crops;
c) differences or improvements in the lab tests used for nutrient analysis;
d) soil/region produce was grown in, Ontario vs British Columbia;
e) soil moisture conditions (irrigated or natural rainfall);
f) amount of sunlight;
g) ambient temperature (greenhouse crop);
h) stage of maturity when harvested;
i) type and amount of fertilizer used;
j) storage or shipping conditions after harvest;
k) differences in sampling method;
l) database from which values may have be drawn etc.

L. A. Piché PhD RD
Associate Professor
Nutrition Program, Brescia University College
@ The University of Western Ontario