Vitamin A refers to any one of a number of related compounds. Retinol (an alcohol) and retinal (an aldehyde) are often referred to as preformed vitamin A. Retinal can be converted by the body to retinoic acid. Retinol, retinal, retinoic acid and related compounds are known as retinoids. Beta-carotene and other carotenoids that can be converted by the body into retinol are referred to as provitamin A carotenoids.
• Vitamin A has a great deal of controversy surrounding its possible toxicity.
• In the past, it was common for people to regularly eat beef liver which has over 27,000 i.u. of vitamin A in a three-ounce cooked portion.
• Just like vitamin D, vitamin A needs vitamin K2 to do its job properly and what will make large amounts of vitamin A toxic is a deficiency of vitamin D or vitamin K2. These three fat soluble vitamins are all necessary for each one individually to maximize its potential.
• Unless someone has liver disease or abuses alcohol, as much as 25,000 i.u. has been shown not to cause toxicity.