Give Me an "A!" The Benefits and Dangers of Vitamin A

This article was published recently in my company's wellness newsletter. It's the second installment in the vitamins and minerals series.

Many a parent has coaxed a child into consuming carrots and leafy greens with promises of eagle eyes or superhero vision. These claims are not entirely unfounded....

Carrots, leafy greens, and lots of other plant and animal foods contain Vitamin A—a fat-soluble nutrient that not only plays an important role in eye health, but also in cell growth and a variety of other important biological processes. While Vitamin A will never give you built-in binoculars or X-ray vision, it can help prevent dry eye and cataracts: conditions which can be linked to blindness later in life. It can also boost your immune system, helping your body prevent and fight off infections and diseases like the measles and even some types of cancer.

There are two basic types of Vitamin A:

• Preformed retinoids, a “processed” form of Vitamin A found in animal foods like dairy, liver, and eggs.
  


• Provitamin carotinoids, an “unprocessed” form of Vitamin A found in plant foods like carrots, leafy greens, and other colorful fruits and vegetables. The human body converts provitamin carotinoids into preformed retinoids.

Since Vitamin A is a fat-soluble nutrient, it’s often stored in your liver and other body tissues and does not pass out of your body easily. For this reason, you should avoid consuming excessive amounts of Vitamin A. Too much can lead to Vitamin A toxicity, which can cause headaches, dizziness, fatigue, blurry vision, and nausea. Severe toxicity can result in permanent eye and liver damage and even birth defects in pregnant women.

Getting the Right Amount in Your Diet
The best way to consume the right amount of Vitamin A is to eat a normal, well-balanced diet that includes lots of fruits and vegetables. The U.S. Institute of Medicine and the National Academy of Sciences have developed Vitamin A recommendations based on life stage and age. Recommended Dietary Allowance (RDA) represents the amount of Vitamin A needed to meet basic biological needs. Upper Limit (a.k.a. tolerable upper intake level) represents the highest amount of Vitamin A a healthy person can consume on a regular basis without risk to his or her health.

Sources of Vitamin A
Vitamin A comes from a variety of animal and plant foods, such as:

• Skim milk (1 cup) 150 μg


• Cheddar cheese (1 ounce) 75 μg


• Lowfat yogurt, plain (1 cup) 34 μg


• Eggs (1 large) 84 μg


• Beef liver (3 ounces) 6,450 μg


• Carrots (1 large) 433 μg


• Spinach (1 cup) 140 μg


• Mango (1 cup) 63 μg


• Tomato juice (1 cup) 56 μg


• Cantaloupe (1 cup) 264 μg

It’s fairly easy for most people to meet their daily requirements. However, some people on restrictive diets or those who suffer from medical conditions that interfere with fat absorption (like celiac disease, Crohn’s disease, or pancreatic disorders), may need to take a Vitamin A supplement.

Multivitamins often contain 60 percent or more of the Recommended Dietary Allowance. Check the label to make sure your supplement does not contain excessive amounts of Vitamin A. As we mentioned in the last issue of Alive & Well, make sure your supplement has the United States Pharmacopeia (USP) seal of approval. This means the supplement has been tested and contains the amount of vitamins and minerals shown on the label.

Handy Online Vitamin Gauge
Want to make sure you’re getting enough Vitamin A and other essential nutrients from the food you eat? Visit http://www.mypyramidtracker.gov/ and register to use the Assess Your Food Intake tool.

Vitamin A-Rich Menu
See how easy it is to get the Vitamin A your body needs. Try this sample menu:

• Breakfast: 1 cup plain oatmeal with ½ cup skim milk, 1 banana,1 cup orange juice (90 μg)


• Lunch: 1 cup vegetable soup, 1 cup romaine salad with ½ medium tomato (385 μg)


• Dinner: 1 broiled boneless skinless chicken breast, ½ cup green beans, 1 small roasted sweet potato (675 μg)
  
  Total = 1,150 μg

Sources: American Dietetics Association, the National Institutes of Health Office of Dietary Supplements, the Mayo Clinic

Vitamin A amounts calculated using the USDA Center for Nutrition Policy and Promotion Assess Your Food Intake tool.