The dose‐response effects of the amount of oil in salad dressing on the bioavailability of carotenoids and fat‐soluble vitamins in salad vegetables

Abstract

The objectives were to define the dose‐response relation of the amount of added oil and: 1) the absorption of carotenoids, phylloquinone and tocopherols in salad vegetables; 2) the absorption of retinyl palmitate formed from the ingested provitamin A carotenoids, α‐ and β‐carotene. Women (n = 12) each consumed 5 salads containing equivalent amounts of carrot, cherry tomato, romaine lettuce and spinach. The salads with salad dressings containing 0, 2, 4, 8 or 32 g tocopherol‐stripped soybean oil were ingested in random order separated by ≥ 2 weeks. Blood samples were collected at baseline and 2, 3.5, 5, 7, and 9.5 h postprandially. Chylomicron fractions were extracted and analyzed by HPLC with coulometric array electrochemical detection. When the salads were ingested with 0 g oil, there was negligible absorption of α‐ and β‐carotenes, lutein, lycopene, phylloquinone, retinyl palmitate, α‐ and γ‐tocopherols. For α‐ and β‐carotenes, lycopene, retinyl palmitate, and α‐ and γ‐tocopherols, absorption was increased with each amount of oil compared with 0 g oil (P < 0.05). The absorption of each carotenoid and fat‐soluble vitamin was highest with 32 g ingested oil (P < 0.002). Supported by Unilever.