Scientists verify bioaccessibility measure for vitamin E, carotenoids
have shown that an in vitro digestion model could be a valuable
tool to quantify potential bioaccessibility of vitamin E and
carotenoids from functional food.
The research tallies with previous human-based studies and could offer industry an inexpensive, labour- and time-efficient method of measuring the potential impact on the consumer's nutritional status.
According to Euromonitor International, the fortified and functional packaged foods market was worth €7.9bn at retail in the 14 biggest Western European markets.
However, bioaccessibility and bioavailability of the nutrients in these foods is dependent on a range of factors, most notably the food matrix and the method of food processing.
Human studies to measure bioaccessibility and bioavailability are labour- and time-intensive, as well as being expensive, but those already performed provided the essential data to verify the applicability of the in vitro method, wrote the researchers in the Journal of Agricultural and Food Chemistry (doi: 10.1021/jf061818s).
Corresponding author, Dr. Patrick Borel told NutraIngredients.com: "Industry produced fortified foods can test the bioavailability of vitamin E and carotenoids in this food by using this in vitro model.
There is already a working group set up by HarvestPlus to promote the use of this model," he said.
The simulated digestion model used by the researchers is being increasingly used to measure bioaccessibility and bioavailability, but comparison and verification with human studies had not yet been done, said the researchers.
To simulate digestion a series of media were prepared to replicate the human stomach and intestine. A pH of four was used for the stomach, while the intestinal pH was set at six and bile salts introduced to mimic digestion.
The results showed that "the significant positive relationship between percentage of carotenoids transferred into micelles in the in vitro model and per cent of carotenoids transferred into micelles observed in vivo suggests that the model is suitable for predicting the bioaccessibility of carotenoids from foods," wrote lead author Emmanuelle Reboul from INSERM, Marseille.
The researchers went on to use the method to quantify the bioaccessibility of vitamin E (alpha-tocopherol) and the carotenoids, alpha-carotene, bete-carotene, lycopene and lutein from their main dietary sources, such as almonds, carrots, tomatoes, and spinach.
"The fact that the bioaccessibility of carotenoids and vitamin E varied strongly between different food sources confirms that the food matrix has a marked effect on bioavailability," wrote Reboul.
Previous studies looking at the bioavailability of vitamin E is scarce, said the scientists, and their analysis of various vitamin E sources, "provides the first comparison of vitamin E bioaccessibilities between its main dietary sources." This could provide industry and academia with a valuable insight and reference tool for future studies.
Work is on-going in this area, confirmed Dr. Borel, and the scope is being extended to other fat-soluble micronutrients like vitamin D and K, as well as the mechanism of absorption.
"We are continuing our research into the mechanisms of absorption of carotenoids and from the vitamin E. We very recently demonstrated that the absorption is not passive diffusion but requires membrane transporters," he said.
