When many people think of Vitamin A (Retinol), they think carrots and eyesight. Indeed vision is reliant on adequate quantities of this fat soluble vitamin, and carrots are an excellent source of beta carotene, the precursor to Vitamin A. Sufficient dietary sources are essential as the body is not able to synthesise Vitamin A.
Vital roles of this vitamin include vision, particularly in low light. Night blindness is one of the key indications that this nutrient may be deficient. However, other roles include healthy cellular growth and function; red blood cell formation and healthy immune function.
What causes more confusion though, is what foods contain Vitamin A in its preformed state of retinol, what foods contain the precursor carotenoids and what is the difference…
Preformed Vitamin A is the biologically active form and is found in animal products, most abundantly in liver, and also present in good quantities in fish (particular fish liver oils), eggs and dairy.
The best known carotenoid which is converted to Vitamin A is beta carotene, however there are many variations of carotenoids, not all of which are converted into Vitamin A.
Beta carotene needs to be converted biochemically into Vitamin A. Important in this process is healthy thyroid function. This means that in people with hypothyroidism there may be impaired capacity to convert beta carotene to Vitamin A. Good sources of beta carotene include sweet potato, carrots, red capsicum, spinach, broccoli, papaya and mango.
Unlike water soluble vitamins, fat soluble vitamins can be stored. Vitamin A is stored in the liver. This means there is also high propensity for toxicity, which in most cases arises through supplementation, not food sources, unless consuming large quantities of liver. Excess Vitamin A has been associated with birth defects for example, and for this reason it is important to be mindful of Vitamin A contained in multi vitamins etc. and to supplement with the guidance of a health practitioner.
Some findings highlighting the crucial role of Vitamin A include:
- Complications of Measles: Adequate vitamin A status has been shown to be an important factor in the severity of measles in children. That is, those in areas where Vitamin A deficiency is prevalent, have a higher risk of complications following measles infections, such as blindness, according to a study of African children.
- Age Related Macular Degeneration: Vitamin A, amongst other nutrients, including Vitamin E and carotenoids such as Lutein and Zeoxanthin, are considered to have an important role in the prevention of this condition, which causes blindness.
- Skin: Vitamin A’s role in cellular renewal means that it also has an important role in skin integrity.
- Recurrent infections: Vitamin A is required to help the body’s immune system fight infections. This nutrient can therefore become depleted after an infection, so it is important to consider foods such as nourishing pumpkin and sweet potato soups during convalescence to help replenish stores.
Factors increasing demand:
- Certain medications
- Infancy and childhood
- Pregnancy and lactation (* note excess can also occur and be toxic to fetus, as stated above)
- Premature babies
- Certain medical conditions such as Hypothyroidism
- Excessive Alcohol intake
- Restrictive diets