The Alphabet Soup of Nutrition - Vitamin A
As I was sitting down to my home-cooked creation of Indian food this week, (not the usual fare in our home), I began to wonder which vitamins and minerals were buried in the concoction. It is essential that we eat foods or take supplements that contain vitamins because they cannot be synthesized within our bodies.
When it was first recognized that eating liver could cure night blindness, researchers began to investigate and Vitamin A was the first vitamin discovered in 1913. Since vitamin A has an effect at the retina (back of the eye), it became designated a retinoid of which there are 3 forms; retinols, beta carotenes and carotenoids.
In humans, retinol is the predominant and most potent form, coming mostly from animal sources in the diet. The plant form is called beta carotene (aka provitamin A) and gives us our greatest (most abundant) dietary source.
If you eat organ meats like liver and kidney, you are likely getting enough vitamin A, but I don’t know many people who enjoy those foods. Other rich animal sources are cod, halibut and fortified dairy products.
Plant sources are plentiful but the vitamin A from colored fruits and vegetables (cantaloupe, pink grapefruit, apricots, carrots, pumpkin, sweet potato, broccoli, leafy greens and many others), are less well absorbed by the body so we need more servings to get adequate amounts.
Beyond vision, vitamin A is essential for fighting infections, bone health, repairing damage to our organs, especially lungs, bladder and intestines. It is paramount in reproduction and ensures development of a healthy baby during pregnancy but too much has been shown to cause birth defects.
Noteworthy is that research has shown smokers who take too much vitamin A in their supplements are more prone to lung cancer, but too little puts them at greater risk than smoking alone. That's why it's essential to know which type and how much your body needs!
The first signs of deficiency include poor night vision and being more prone to infections. If your hair, nails and skin are dry, vitamin A deficiency could be the culprit, but be very careful with supplementation because vitamin A is fat soluble and can accumulate in the body.
Most vitamin A is stored in the liver, up to a full year supply at once, but it is also found in fat tissues, lungs and kidneys. To make things more complex, the liver needs zinc and certain amino acids to make the binding protein (called RBP) that controls how much vitamin A is released into the blood from the liver at any given time. Because of this tight control, blood levels do not drop until the body’s liver stores are dangerously low but can happen quickly in young or sick children. Blood levels are, therefore, related to infections, the foods we eat, how well we can absorb it from the gastrointestinal tract and multiple other little “helpers”, like zinc and iron. Vitamin A supplementation in children can even help combat anemia.
Although vitamin A deficiency in the United States is uncommon, there is greater concern in young children, people with gallbladder dysfunction or fat malabsorption, Crohn’s disease or ulcerative colitis, gastric bypass weight loss surgery, alcoholism, vegans or recent immigrants from developing countries.
With vitamin A being only the first of many alphabetical, nutritious discoveries, aren’t we all glad that Mom made us eat our veggies? Stay tuned for "2B or not to B, that is the vitamin".
If you would like to understand how to get the best source and safe dose of vitamin A in a supplement (so you don't get too much or too little), this personal, unique to YOU, information is available for you HERE.
Ref: Medscape, accessed Nov 12, 2014. http://emedicine.medscape.com/article/126004-overview