What is vitamin A and how does it support our health?

Updated: Jul 8

Author: Lee Reicheneder

Vitamin A are a family of fat-soluble compounds known as retinoids (retinol, retinoic acid, and retinal) which are divided into subcategories known as preformed vitamin A and proformed vitamin A (Huang et al., 2018; Oruch & Pryme, 2012). The vitamin A micronutrient is an essential nutrient by the body, this means that the body cannot make this nutrient by itself and must obtain it through other means, such as food. The difference between the subcategories are in the fact that proformed vitamin A (provitamin A) must be synthesised by the body into usable forms in order to be transported, used , and stored by the body, whereas preformed vitamin A (previtamin A) enters the body as readily digested retinyl esters which are then absorbed as retinol (Oruch & Pryme, 2012).

Consumption of food from animal sources provide the body with previtamin A; whereas, plant sources generally provide the body with provitamin A (Whitney et al., 2016, p.385 & 393; National Institute of Health Office of Dietary Supplements, 2021).

Great previtamin A food options are:

· Fortified milk

· Cheese

· Eggs

· Liver

· Cream

· Butter

· Fortified margarine

Great provitamin A food options are:

· Deep orange fruits

· Dark leafy vegetables

In addition, the bioavailability of vitamin A can be enhanced through cooking your vitamin A rich foods (Ghavami et al., 2012; Lee et al., 2017). So in the instance of vitamin A it may be best to cook up those vitamin A rich foods to obtain the most out of them rather than consuming them raw. In either situation ensure you have washed/peeled your foods first and prepared them in a clean environment to reduce any potential risk of food-borne illness or unwanted toxin consumption (Tchounwou et al., 2012; Food Standards Australia & New Zealand, 2020).

Dependant on the age, pregnancy status, and lactation status the amount of vitamin A needed by the body is between 300 µg/day to 900 µg/day (Australian Government National Health and Research Council, 2014). There is also an upper-level (UL) intake for vitamin A, this is the highest level at which a vitamin or mineral can be obtained without adverse effects in the general population, as with anything individual tolerance levels come into play and every individual may vary slightly in their unique tolerance levels. However, it is unwise and potentially dangerous to take amounts exceeding UL; in extraordinary circumstances where benefits outweigh risks a healthcare provider may prescribe a treatment plan where levels exceed UL but this is not a regular occurrence as this comes with risks and it is safest to avoid exceeding UL in most circumstances (National Institutes of Health Office of Dietary Supplements, 2021; World Health Organization, 2006, p 21-31).

The good news is provitamin A through deep orange fruits and leafy green vegetables has not demonstrated a toxicity risk, so go ahead and eat as many fruits and vegetables as you would like; however, you may get some orange-yellow skin if you eat too much (Oruch & Pryme 2012). In fact, eating plenty of deep orange fruits and leafy greens can be a fantastic way to help you safely increase and maintain vitamin A levels during pregnancy where risk of foetal malformations, preterm birth, and low vitamin A stores in the newborn infant can arise from deficiency (Bastos Maia et al, 2019). According to several studies’ toxicity arises from use of pharmaceutical supplementation, foods fortified with vitamin A, and/or excessive consumption of provitamin A (foods derived from animal sources) the following unwanted side effects can occur:

  • Osteoporosis

  • Pathological fractures