Carrots are a very good source of beta-carotene, which is itself a precursor of vitamin A (provitamin A of plant origin). A vitamin recognized for its very important role for the health of the eyes, the skin and the immune system. But to reap the full health benefits of this superfood, you need to have an active enzyme to produce this vitamin. This is the observation made by researchers from the University of Illinois (United States) in a published study in the “Journal of Nutrition”. The latter remind us in the first place that beta-carotene is the bioactive compound that gives carrots their beautiful orange color.
Studies in humans and mice have shown that the conversion beta-carotene in vitamin A reduces “bad” cholesterol in the blood. Thus, beta-carotene can help protect against the development of atherosclerosis, when arteries narrow and eventually become blocked due to a build-up of fat. The researchers conducted two studies to better understand the effects of beta-carotene on cardiovascular health which allowed them to confirm its importance in this area, but identified a critical step in the process. This is because beta-carotene is converted into vitamin A using an enzyme called beta-carotene oxygenase 1 (BCO1).
A more or less active enzyme
However, a genetic variation determines whether a person has a more or less active version of this BCO1 enzyme. ” The people having a less active enzyme may need other sources of vitamin A in their diet. », Explains Jaume Amengual, main author of the work. The first study analyzed blood and DNA samples from 767 healthy young adults. As expected, the researchers found a correlation between the activity of BCO1 and bad cholesterol levels. “People who had a genetic variant associated with making the enzyme more active had lower cholesterol levels in their blood. », Adds the researcher.
To follow up on these findings, the researchers conducted a second study, published in the Journal of Lipid Research, on mice. The latter adds: “in human study, we have seen that cholesterol was higher in people who do not produce a lot of vitamin A. To know if this observation has a long-term effect, one would have to wait 70 years to see if they develop cardiovascular illnesses. In real life, this is not feasible. That’s why we use animals for some studies, in order to speed up the process. The main results of the mouse study turn out to replicate what the scientists found in humans.
What impact on cholesterol?
“We have seen that when we give beta-carotene to mice, they have lower cholesterol levels. These mice develop smaller atherosclerotic lesions in their arteries. This means that the mice fed with beta-carotene are more protected against atherosclerosis than those fed on a diet without this bioactive compound. ”, notes Professor Amengual. In the second study, the researchers also studied the biochemical pathways of these processes, to determine where the effect occurs. The key would be the liver, the organ responsible for producing and secreting lipoproteins into the bloodstream, including those called bad cholesterol.
The scientists further observed that “in mice with high levels of vitamin A, the secretion of lipids into the bloodstream slows down. The latter consider that their discovery is important since it is essential to fully understand how this BCO1 enzyme is linked to cholesterol. While high levels of beta-carotene in the blood are associated with health benefits, this could also be a sign of a less active BCO1 enzyme that does not convert beta-carotene supplied through the diet into vitamin A. According to the scientific team, nearly 50% of the population has the variant the least active of the enzyme.
What does this imply for these people? “Their bodies are slower to produce vitamin A from a plant source, they might need to get this nutrient from an animal source such as milk or cheese, for example. », Conclude the researchers. According to ANSES, vitamin A is also present exclusively in the form of retinol and its derivatives. in animal products : the livers of fish and farm animals have the highest levels. And among the vegetables that are the foods richest in beta-carotene are, besides carrots, sweet potatoes, pumpkin, parsley and other aromatic herbs.