Vitamin A

What is Vitamin A?

Vitamin A is a generic term for a group of fat soluble vitamins that is divided into two main subtypes, preformed Vitamin A which includes retinol and its esterified form retinyl ester. The second subtype being provitamin A which includes beta-carotene, alpha-carotene and beta-cryptoxanthin. As Vitamin A is fat soluble it can be stored throughout the body in adipose tissue and the liver. Vitamin A is also essential for cell differentiation.

Why is it important?

Vitamin A is essential for many functions within the body including pigment production in the eyes for vision, all epithelial tissue including skin and respiratory tract, immune function and reproduction. 

Vitamin A deficiency can result in a number of conditions such as impaired dark adaption of the eyes leading to night blindness. Keratinisation of skin, gastrointestinal and urinary tracts and, mucous membranes. This can lead to dry scaling and thickening of the skin. Respiratory infections can also result. In younger populations growth retardation and infections are common. Impaired immunity is also associated with deficiency.

Where in the diet can I get it?

Vitamin A is quite abundant in the diet. It is found through an array of vegetables and fruits including sweet potato, carrot, pumpkin, capsicum, tomatoes, mangos, spinach, broccoli and more. For those who consume an omnivorous diet, it can also be found in high amounts in organ meats such as liver.

How much do I need?

According to nrv.gov.au, Men aged 19 years old and above require a recommended daily intake of up to 900 micrograms a day and women requiring an intake of 700  micrograms a day. Both men and women have an upper limit of what is recommended as 3000 micrograms however there is no established upper limit to beta-carotene intake from food alone as the conversion is determined by vitamin A levels already present in the body.

Excessive and chronic supplementation of vitamin A can be associated with conditions such as increased intracranial pressure, dizziness, nausea, headaches, skin irritation, pain in joints and bones, coma and potentially death.

References

https://www.msdmanuals.com/en-au/professional/nutritional-disorders/vitamin-deficiency,-dependency,-and-toxicity/vitamin-a

https://www.nrv.gov.au/nutrients/vitamin-a

https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/