Bioavailability of folate from processed spinach in humans: Effect of food matrix and interaction with carotenoids

The effect of the food matrix and dietary fibre on the bioavailability of folate is not known. In a controlled, 3-week dietary intervention study, 28 men and 42 women were divided into six groups to receive either a control diet (n = 10), or the control diet plus 20 g/MJ per day (n = 12 per group) of whole-leaf spinach, minced spinach, liquefied spinach, or liquefied spinach to which dietary fibre (10 g/kg wet weight) was added. The sixth group received the control diet plus a synthetic carotenoid supplement with similar amounts of β-carotene and lutein as found in spinach. A significantly higher plasma folate response was found for the pooled spinach groups than for the control group. Among the spinach groups no significant differences were detected. However, the plasma folate response of the pooled minced and liquefied spinach groups was greater than that of the whole-leaf spinach group (p = 0.03). Re-addition of dietary fibre to the liquefied spinach to compensate for the fibre broken down during liquefaction did not reduce the plasma folate response. The consumption of the carotenoid supplement did not have an effect on plasma folate concentrations compared with the control group. The food matrix in which the folate is entrapped plays a role in folate bioavailability.