While carotenoids and vitamin A serve similar functions, there are some key differences that exist, such as the way these nutrients are metabolized and stored in the body, as well as the source from which they are derived. Vitamin A is found in animal-based foods such as liver, dairy, and fish oil, and is referred to as pre-formed vitamin A (1,2). Readily absorbed (up to 90%) (1), pre-formed vitamin A is converted to retinyl esters and then stored primarily in the liver to be used, as needed, for supporting healthy vision, epithelial cell growth, and the immune system (1,2). The majority (95%) of pre-formed vitamin A is stored in the liver and the rest in adipose tissue (1,2).

Carotenoids, on the other hand, are found only in plant-based foods. There are more than 560 carotenoids that have been isolated in nature (1,2), the most well known being beta carotene, lycopene, lutein, zeaxanthin, beta cryptoxanthin, and alpha carotene (1,2). Alpha carotene, beta carotene, and beta-cryptoxanthin are the only carotenoids that can be converted into vitamin A and are referred to as pro-vitamin A carotenoids (1,2). The most biologically active of the group is beta carotene (1,2). These carotenoids are the pigment molecules in fruits and vegetables that account for colors ranging from bright yellows to deep reds (1,2). Pro-vitamin A carotenoids are not as easily absorbed (as little as 3%) as pre-formed vitamin A (1,2). The bioavailability of pro-vitamin A cartotenoids and conversion into vitamin A is highly unpredictable and can be affected by many factors including dietary fat intake, bile salt concentration, presence of other food components, whether or not the food was cooked, and even the farming and cultivation methods used (1,2). The carotenoids that are absorbed are generally stored in the adipose tissue under the skin and in the liver. When the body is low on pre-formed vitamin A, stored carotenoids are then released from adipose tissue and sent to the liver where they are converted into the vitamin A-active compounds retinyl esters, retinol, and retinoic acid, collectively called retinoids (1,2). Because the body converts carotenoids only as it needs, a vitamin A-related toxicity from carotenoid consumption has not been reported to date.

Vitamin A supplementation from either pro-vitamin A carotenoids or pre-formed vitamin A has been shown to support healthy vision and immune function. In general, most adults can safely take up to 25,000 IU of pre-formed vitamin A per day (3,4). For women who could become or are pregnant, less than 10,000 IU per day is advised. Pure Encapsulations Vitamin A is sourced from preservative-free cod liver oil. The most common dose recommendation for carotenoids (mainly beta carotene) is 25,000 IU or less; however, up to 100,000 IU per day may be used (5). Pure Encapsulations Beta Carotene (with mixed carotenoids) is sourced from Dunaliella salina algae. Pure Encapsulations multivitamins, Nutrient 950™, Nutrient 280™, and UltraNutrient™ all contain mixed carotenoids as its vitamin A source.