TWO new studies in mice and humans suggest that some individuals may produce insufficient quantities of vitamin A from the beta carotene in their diets. To compensate, they may need to eat more foods containing vitamin A to maintain good cardiovascular health.
Beta carotene is a pigment in all fruits and vegetables, and carrots and sweet potatoes are particularly rich sources.
Various findings indicate that people with high blood levels of beta carotene tend to have lower serum concentrations of the “bad” cholesterol that causes atherosclerosis — narrowing of the arteries that supply blood to the heart.
As a result, they have a lower risk of ischemic heart disease, which is the most common cause of death worldwide.
The molecular mechanisms that link beta carotene to lower blood cholesterol levels are poorly understood, however.
Now, two new studies have discovered that the body needs an active version of a certain enzyme to reap the full benefits of beta carotene for cardiovascular health.
The enzyme in question converts beta carotene into vitamin A, which reduces the amount of low-density lipoprotein (LDL) cholesterol produced in the liver.
However, up to 50% of people make a less active form of the enzyme, according to Jaume Amengual, an assistant professor of personalized nutrition at the University of Illinois at Urbana-Champaign who was involved in both studies.
Having a less active form of this enzyme makes the body less efficient at producing vitamin A from the beta carotene in fruits and vegetables.
To reap the full benefits to cardiovascular health, Amengual says, a person may need to get more vitamin A directly from animal sources, such as dairy, milk, oily fish, or cheese, for example.
In the first study, the scientists began by measuring the impact of the enzyme, called beta carotene oxygenase 1 (BCO1), on cholesterol levels in mice. Their findings have been published in The Journal of Nutrition.
The team compared the effects of a beta carotene-rich diet in one group of regular mice and another group of mice without the gene for making BCO1.
After 10 days on the diet, the mice without the enzyme had more beta carotene in their blood and higher cholesterol levels than the normal mice.
Next, the researchers analyzed DNA and blood samples from 475 healthy young adults aged 18–25. The participants also filled out questionnaires about their diets.
