Effects of acute strawberry consumption on serum levels of vitamin C and folic acid, the antioxidant potential of LDL and blood glucose response: a randomised cross-over controlled trial

Abstract

Strawberry contains many bioactive compounds such as vitamin C and polyphenols as well as folate, a vitamin that is especially important for women of childbearing age. We investigated the effects of the acute consumption of strawberry on the serum levels of vitamin C and folate, and on the antioxidant potential of low-density lipoprotein (LDL). In a randomised, placebo-controlled, double-blind, crossover study, twenty-three healthy female volunteers (age 22⋅5 ± 1⋅4 years) ingested 500 g of a strawberry purée beverage or a sugar content-matched placebo beverage. Blood samples were collected at fasting and at 0⋅5, 1, 2 and 4 h post-ingestion. The serum concentrations of vitamin C and folate were significantly elevated from 0⋅5 to 4 h after the strawberry beverage ingestion (P < 0⋅001); the levels peaked at 2 h, with peak levels of 15⋅0 ± 2⋅5 μg/ml for vitamin C and 14⋅4 ± 7⋅0 ng/ml for folate. Notably, at 1 h after the strawberry beverage ingestion, the LDL oxidation lag time was significantly prolonged (P < 0⋅05), suggesting that the antioxidant potential of LDL was increased. After the ingestion of either beverage, the serum levels of glucose and insulin reached a peak at 0⋅5 h and then quickly returned to baseline levels. These results suggest that strawberries are a useful source of vitamin C and folate and may help enhance the antioxidant potential of LDL in healthy young women.

Keywords: Blood glucose level; Folate; LDL oxidation; Strawberry; Vitamin C.

Fig. 1.

A CONSORT diagram outlining the flowchart of the study. The study was conducted with twenty-three healthy women in a randomised, placebo-controlled, double-blind, crossover design.

Fig. 2.

Postprandial changes in serum vitamin C (a) and folate level (b) after the ingestion of the placebo (circles) or strawberry (squares) beverage. The data are mean ± sd (n 23). ⁺P < 0⋅05, ⁺⁺P < 0⋅01, ⁺⁺⁺P < 0⋅001 v. placebo, ^###P < 0⋅001 v. 0 h by pairwise comparisons with Bonferroni corrections.

Fig. 3.

Postprandial changes in the LDL lag time after the ingestion of placebo (circles) or strawberry (squares) beverage. The data are mean ± sd (n 21). ^#P < 0⋅05 v. 0 h by Dunnett's multiple comparison test after 1-way ANOVA.

Fig. 4.

Postprandial changes in blood glucose (a) and the serum insulin level (b) after the ingestion of placebo (circles) or strawberry (squares) beverage. The data are mean ± sd (n 23). ^###P < 0⋅001 v. 0 h by pairwise comparisons with Bonferroni corrections.