Avocado consumption enhances human postprandial provitamin A absorption and conversion from a novel high-β-carotene tomato sauce and from carrots

Abstract

Dietary lipids have been shown to increase bioavailability of provitamin A carotenoids from a single meal, but the effects of dietary lipids on conversion to vitamin A during absorption are essentially unknown. Based on previous animal studies, we hypothesized that the consumption of provitamin A carotenoids with dietary lipid would enhance conversion to vitamin A during absorption compared with the consumption of provitamin A carotenoids alone. Two separate sets of 12 healthy men and women were recruited for 2 randomized, 2-way crossover studies. One meal was served with fresh avocado (Persea americana Mill), cultivated variety Hass (delivering 23 g of lipid), and a second meal was served without avocado. In study 1, the source of provitamin A carotenoids was a tomato sauce made from a novel, high-β-carotene variety of tomatoes (delivering 33.7 mg of β-carotene). In study 2, the source of provitamin A carotenoids was raw carrots (delivering 27.3 mg of β-carotene and 18.7 mg of α-carotene). Postprandial blood samples were taken over 12 h, and provitamin A carotenoids and vitamin A were quantified in triglyceride-rich lipoprotein fractions to determine baseline-corrected area under the concentration-vs.-time curve. Consumption of lipid-rich avocado enhanced the absorption of β-carotene from study 1 by 2.4-fold (P < 0.0001). In study 2, the absorption of β-carotene and α-carotene increased by 6.6- and 4.8-fold, respectively (P < 0.0001 for both). Most notably, consumption of avocado enhanced the efficiency of conversion to vitamin A (as measured by retinyl esters) by 4.6-fold in study 1 (P < 0.0001) and 12.6-fold in study 2 (P = 0.0013). These observations highlight the importance of provitamin A carotenoid consumption with a lipid-rich food such as avocado for maximum absorption and conversion to vitamin A, especially in populations in which vitamin A deficiency is prevalent. This trial was registered at clinicaltrials.gov as NCT01432210.

FIGURE 1

Study 1: baseline-corrected plasma TRL concentrations of β-carotene (A) and retinyl esters (B) over 12 h after consumption of the high–β-carotene tomato sauce with avocado and the high–β-carotene tomato sauce alone in healthy men and women. Plasma TRL concentrations (nanomoles per liter of plasma) are expressed as means ± SEMs, n = 11. TRL, TG-rich lipoprotein.

FIGURE 2

Study 2: baseline-corrected plasma TRL concentrations of β-carotene (A), α-carotene (B), and retinyl esters (C) over 12 h after consumption of carrot with avocado and carrot alone in healthy men and women. Plasma TRL concentrations (nanomoles per liter of plasma) are expressed as means ± SEMs, n = 12. TRL, TG-rich lipoprotein.

FIGURE 3

A plot of the percentage conversion of provitamin A into vitamin A (Efficiency conversion A₁) in healthy men and women in study 1, following Eq. 1. Each data point represents a single participant (n = 11) and plots their percentage conversion efficiency from the tomato sauce meal alone (x axis) against their percentage conversion efficiency from the tomato sauce meal with avocado (y axis). The solid line through the origin (slope = 1) represents equivalent conversion for both meals. The linear equation provided in the graph can be further explained as follows: % Vitamin A conversion_{(tomato sauce + avocado)} = 0.64 × [% Vitamin A conversion_{(tomato sauce)}] + 18%. % Vit. A, percentage of vitamin A.