Objective: Coumarin 7-hydroxylation was investigated in 21 Finnish vegans (20 females, one male) consuming a strict, uncooked vegan diet ("living food diet") and in their matched omnivorous controls, by means of an in vivo coumarin test.
Method: A capsule containing 5 mg of coumarin (Venalot) was taken after an overnight fast, and urine samples were collected before and 2, 4 and 6 h after the drug administration. The extent and rate of urinary excretion of 7-hydroxycoumarin was determined using HPLC.
Results: The total urinary excretion of 7-hydroxycoumarin during 6 h was 58 (range 23-85) and 64 (range 39-92)% of the administred dose in the vegan and control groups. The coumarin index (excretion of 7-hydroxycoumarin during the first 2 h as percentage of total excretion) was 72% in the vegan and 78% in the control groups. A negative correlation was observed between the coumarin index and the consumption of wheatgrass juice by the vegans (r = -0.60, P < 0.01, n = 21). Proportion of slow hydroxylators (excreting 7-hydroxycoumarin after 4 h) was not statistically different between the groups (5/21 in the vegans vs 8/20 in the controls).
Conclusion: According to the present study, the clearly different dietary patterns and nutrient intakes between the vegans and the omnivores resulted in similar extent and rate of 7-hydroxycoumarin formation, indicating only a minor effect on coumarin hydroxylase (CYP2A6) activity by the plant substances in the uncooked vegan diet.