Vitamin A is an essential, fat-soluble vitamin with many diverse health benefits. It promotes eyesight by converting light into brain signals that allows to us to perceive images. It aids in the differentiation of cells of the skin and helps the heart, kidneys, and other organs to function properly. It protects against infection by helping create healthy white blood cells and promotes healthy skin.
Since Vitamin A cannot be produced in our body, it has to be derived from our diet. While eat, fish, poultry and dairy foods have preformed Vitamin A, plant-based foods such as fruits and vegetables contain the other type - pro-Vitamin A. Deficiency of Vitamin A may lead a decrease in immune function, dry skin, problems with reproduction and cessation of bone growth. But this new study, published in the Journal of Leukocyte Biology, shows that excess of vitamin can also be harmful.
Too much Vitamin A shuts down the body's trained immunity, opening door to infections to which we would otherwise be immune, says a new study. According to the study, excess Vitamin A makes the body 'forget' past infections. The findings suggest that although Vitamin A supplementation can have profound health benefits when someone is deficient, supplementation of the vitamin above and beyond normal levels may have negative health consequences.
"This study helps to explain the mechanisms of anti-inflammatory effects of vitamin A and by doing so opens the door to identifying novel ways to modulate the immune response and restore its function in situations in which it is dis-regulated," said one of the researchers Mihai Netea from the Radboud University Medical Center in Nijmegen, The Netherlands.
The amount of vitamin A needed depends on age and reproductive status. Getting too much vitamin A can also cause dizziness, nausea and even death.
To make this discovery, Netea and colleagues stimulated immune cells, isolated from volunteers, with Vitamin A and saw that the cells produced fewer cytokines, key proteins that help ward off microbes, upon stimulation with various mitogens and antigens. Furthermore, the cells were also stimulated with various microbial structures, which resulted in long-term activation or training of the cells. When the same experiments were performed in the presence of vitamin A, the microbial structures were no longer able to activate the immune cells.