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Vitamin A plays an important role in the healthy functioning of the immune system.

Health Claims

Vitamin A is an essential fat-soluble vitamin. Clinically, vitamin A has been employed in large doses in the treatment of measles, respiratory syncytial virus (RSV), and acne vulgaris.

What is Vitamin A?

Vitamin A occurs in three different chemical states: retinol, retinal, and retinoic acid, collectively called preformed vitamin A. A precursor to vitamin A, beta-carotene, is converted into retinol as needed by the body and hence is known as pro-vitamin A. Although synthetic extracts and derivatives of vitamin A are common prescriptive agents for conditions such as sun-damaged skin and acne, the information that follows focuses only on the actions of whole preformed vitamin A-retinoic acid and retinal. Vitamin A is found in a number of foods, including beef liver, butter, carrots, sweet potatoes, and dried apricots.

How does Vitamin A Work?

Retinal forms one of four types of vitamin A photopigments called rhodopsin. Also called visual purple, this is found in the rod cells of our retinas, and is responsible for night vision. Retinoic acid is involved with cell growth. Consequently, without adequate amounts of whole vitamin A we encounter classic symptoms of vitamin A deficiency: dry eyes (xerosis) and the development of rough skin on the back of the upper arm (follicular keratosis).

Vitamin A also plays an important role in the healthy functioning of the immune system. It not only activates circulating T-lymphocytes, but also helps macrophages and monocytes in the destruction of viruses and bacteria.

What Evidence Supports the Use of Vitamin A?

The immune-stimulating effects of vitamin A were confirmed in a clinical study employing high doses of supplementary vitamin A (100,000 to 200,000 IU) administered once or twice to 60 African children with measles. By the eighth day, 96 per cent of the children had recovered, compared with 65 per cent in the placebo group.

High dose, short-term vitamin A therapy is also highly touted in the treatment of respiratory syncytial virus (RSV), a viral illness common in children. Not all children infected with RSV benefited; however, some children experienced a significantly shorter hospital stay and a quicker resolution of their shortness of breath symptoms.

Supplementary vitamin A has also been administered to adults with acne vulgaris at doses of 300,000 IU per day for three to four months. Although patients in the study noted that they had a good to excellent response in decreasing inflammatory skin lesions, a large number of vitamin-A-related side effects were experienced.

How Should I Take Vitamin A?

Vitamin A is stored in the liver and intake of this vitamin exceeding 10,000 IU per day can be toxic. Symptoms of toxicity include dry skin, brittle nails, hair loss, headache, lack of appetite, fatigue, and nausea.

Vitamin A supplementation (as retinol or retinol palmitate) should not exceed 5,000 IU during pregnancy as excessive consumption of this vitamin can lead to birth defects. Those employing synthetic vitamin A (e.g., isotretinoin) or statin-type cholesterol-lowering drugs, and suffering from liver cirrhosis or active hepatitis should not take supplementary vitamin A.

The Bottom Line

The use of vitamin A is a double-edged sword: it can either restore or retard health depending on the individual’s biochemical makeup.

References available upon request. Dr. Ronald G. Reichert is a naturopathic physician practising in Vancouver. He lectures to professional and public audiences throughout North America on complementary and integrative medicine subjects. We welcome your feedback at editorial@alive.com.

Source: alive #253, November 2003