Abstract
Vitamin C is an essential nutrient in humans and must be obtained through the diet. The
aim of this study was to determine vitamin C uptake in healthy volunteers after consuming
kiwifruit (
Actinidia chinensis
var.
Hort. 16A
), and to
determine the amount of fruit required to raise plasma vitamin C to ‘healthy’ (i.e.
>50 µmol/l) and ‘optimal’ or saturating levels (i.e. >70 µmol/l). Leucocyte
and urinary vitamin C levels were also determined. A total of fifteen male university
students with below average levels of plasma vitamin C were selected for the study. Weekly
fasting blood samples were obtained for a 4-week lead-in period and following
supplementation with, sequentially, half, one, two and three Gold kiwifruit per d for 4–6
weeks each, followed by a final 4-week washout period. The results showed that addition of
as little as half a kiwifruit per d resulted in a significant increase in plasma vitamin
C. However, one kiwifruit per d was required to reach what is considered healthy levels.
Increasing the dose of kiwifruit to two per d resulted in further increases in plasma
vitamin C levels as well as increased urinary output of the vitamin, indicating that
plasma levels were saturating at this dosage. Dividing the participants into high and low
vitamin C groups based on their baseline plasma and leucocyte vitamin C levels
demonstrated that it is critical to obtain a study population with low initial levels of
the vitamin in order to ascertain a consistent effect of supplementation.