Interactions of beta-carotene with other agents (micronutrients, foods):
Interactions between carotenoids
Metabolic studies show that when high doses of beta-carotene are absorbed, it competes with lutein and lycopene when they are consumed within a meal. However, consumption of high doses of beta-carotene had no adverse effect on serum carotenoid levels.
Dietary supplements versus food
In general, purified carotenoids in oil-derived dietary supplements have higher bioavailability than carotenoids from foods. In particular, the bioavailability of beta-carotene is much higher in dietary supplements than in foods. The bioavailability of beta-carotene from spinach is – compared to the bioavailability from purified beta-carotene in oil, i.e. a food supplement – only 14%.
The relatively low bioavailability of carotenoids from foods is partly due to the fact that they are tightly bound to the proteins of the plant matrix. Carotenoids from green leafy vegetables are associated with chloroplasts, while those from red fruits are associated with chromoplasts. Fine crushing, homogenization and cooking destroy the plant matrix and thus increase the bioavailability of carotenoids.
The human body can absorb carotenoids through the intestine only if fat is present at the same time. However, a small amount of fat, as little as 3-5 g of fat in a meal, is sufficient to ensure absorption of carotenoids.
Margarine with vegetable sterol
Regular use of margarine with vegetable sterol may result in a 10-20% decrease in serum carotenoid levels. However, with the additional intake of carotenoids from fruits or vegetables, this deficiency can be compensated.
Alcohol – tobacco consumption
For isolated beta-carotene from supplements and fortified foods, two studies in smokers and asbestos workers show an increased risk of bronchial carcinoma:
- In the so-called ATBC (The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Trial) study of 29,133 participants, daily intake of 20 mg of beta-carotene, taken for 5 to 8 years, resulted in an 18% higher bronchial cancer rate.
- The CARET (The Beta-Carotene Cancer and Retinol Efficiency Trial) study of 18,314 participants showed a 28% higher rate of bronchial carcinoma with 30 mg of beta-carotene per day, taken for 21 months, compared with the placebo group.
Participants in both studies were heavy smokers, weaned smokers, or former asbestos workers.
Fat substitute Olestra (sucrose polyester)
Daily consumption of 18 g of the fat substitute Olestra resulted in a 27% decrease in serum carotenoid levels after three weeks. People who consumed only 2 g of Olestra daily were shown to have a 15% decrease in serum carotenoid levels.
