Vitamin A is most commonly recognized for its beneficial effects on eye health, while its other important functions are often overlooked. As with other vitamins, there are different forms of vitamin A one form that is most readily absorbed in the body is known as retinol, which is found in liver, eggs, and milk. Retinoids (including retinol) have many important and diverse functions throughout the body including roles in vision, regulation of cell proliferation and differentiation, growth of bone tissue, immune function, and activation of tumor suppressor genes. These functions are especially important with respect to pregnancy and childbirth, infancy, childhood growth, night vision, red blood cell production, and resistance to infectious disease.1
Another way for the body to get the vitamin A it needs it to convert pro-vitamin A carotenoids like beta carotene to retinol. Beta carotene is found in yellow and orange fruits and vegetables including carrots, sweet potatoes, spinach and cantaloupe. The carotenoid form of vitamin A also provides unique health benefits. Most carotenoid forms of vitamin A function as antioxidant and anti-inflammatory nutrients. There are two forms of carotenoids that play a specific role in eye health which are known as the xanthophylls lutein and zeaxanthin.2 Foods such as spinach, kale and Swiss chard are sources of foods that contain both forms of carotenoid for optimal eye health.1 Eggs provide small amounts of lutein and zeaxanthin and research shows these nutrients in eggs may be more bioavailable (better utilized by the body) than that from sources with higher content including supplements.2
While vitamin A provides the body with many benefits, its important to remind clients that too much of a good thing can turn into a bad thing. Vitamin A is fat soluble which means the body stores it most often in the liver. This also means that vitamin A can build up to toxic levels in the body. This rarely happens from food sources because, if the body builds up supplies of vitamin A, it will slow down the conversion of beta carotene. Vitamin A toxicity usually occurs when people take too much in supplement or pill form. Toxic levels can cause liver problems, central nervous system problems, deterioration of bone density, and birth defects.4 Below is a chart that outlines the Recommended Daily Allowance (RDA) for Vitamin A as well as the upper limits.3
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RDA for Preformed Vitamin A (Retinol) |
||
| Age | Males: mcg/day (IU/day) | Females: mcg/day (IU/day) |
| 0-6 months | 400 (1,333 IU) | 400 (1,333 IU) |
| 7-12 months | 500 (1,667 IU) | 500 (1,667 IU) |
| 1-3 years | 300 (1,000 IU) | 300 (1,000 IU) |
| 4-8 years | 400 (1,333 IU) | 400 (1,333 IU) |
| 9-13 years | 600 (2,000 IU) | 600 (2,000 IU) |
| 14-18 years | 900 (3,000 IU) | 700 (2,333 IU) |
| 19 years and older | 900 (3,000 IU) | 700 (2,333 IU) |
| Pregnancy (18 years and younger) | 750 (2,500 IU) | |
| Pregnancy (19 years and older) | 770 (2,567 IU) | |
| Breastfeeding (18 years and younger | 1,200 (4,000 IU) | |
| Breastfeeding (19 years and older) | 1,300 (4,333 IU) | |
|
Tolerable Upper Intake Level (UL) for Preformed Vitamin A (Retinol) |
|
| Age Group | UL in mcg/day (IU/day) |
| Infants 0-12 months | 600 (2,000 IU) |
| Children 1-3 years | 600 (2,000 IU) |
| Children 4-8 years | 900 (3,000 IU) |
| Children 9-13 years | 1,700 (5,667 IU) |
| Adolescents 14-18 years | 2,800 (9,333 IU) |
| Adults 19 years and older | 3,000 (10,000 IU) |
In addition to lutein and zeaxanthin, eggs contain the retinoid form of vitamin A and in fact, butter, cheese, and eggs are among the top 10 sources of vitamin A for U.S. adults. Carrots, tomatoes, leafy greens, and sweet potatoes are also found in the top 10 pro vitamin A-containing foods in the U.S.4Try this recipe that perfectly pairs eggs with kale and sweet potatoes and get all the benefits vitamin A provides.
Eggs over Kale and Sweet Potato Grits
Servings: 4
Ingredients:
- 1 large sweet potato
- 2 cups fresh kale, chopped
- 1 tbsp vegetable oil, divided
- 1 ? cups water
- 1 cup nonfat milk
- ? cup grits, quick cooking
- ? tsp salt
- 4 eggs
Directions
- Step 1: Heat oven to 350°F. Coat 4 individual souffl? dishes (or 2-quart casserole dish) with 1 tsp. vegetable oil. Make 3-4 slits in sweet potato; cook in microwave until just soft. When cool enough to handle, peel, cut into chunks, and puree in a food processor.
- Step 2: Heat remaining vegetable oil in sauce pan, and saut? kale about 5 minutes. In a medium sauce pan, boil water and milk, add grits and sweet potatoes; cook 5 minutes
- Step 3: Remove from heat; stir in saut?ed kale. Divide grits mixture evening among 4 souffl? dishes (or place all in casserole dish). Make 4 depressions in the grits mixture with the back of a large spoon. Carefully break one egg into each hollow. Bake uncovered for 30 minutes until eggs are cooked. Let cool 10 minutes before serving
Nutrition information per serving:
Calories: 280; Total fat: 9g; Saturated fat: 2g; Protein: 12g; Carbohydrates: 38g; Cholesterol: 185g; Dietary Fiber 4g; Sodium: 410mg
Each serving provides: An excellent source of vitamin A, vitamin C, thiamine, niacin, folate, phosphorus, and iodine, and a good source of protein, fiber, vitamin D, riboflavin, vitamin B6, vitamin B12, pantothenic acid, potassium, calcium, iron, and magnesium
References
1) Evert, A. (2013, February 18). Vitamin a: Medlineplus medical encyclopedia. Retrieved fromhttp://www.nlm.nih.gov/medlineplus/ency/article/002400.html
2) Goodrow EF, et al. Consumption of one egg per day increases serum lutein and zeaxanthin concentrations in older adults without altering serum lipid and lipoprotein cholesterol concentrations.JN 2006; 136(25):19-24.
3) Higdon, J. (2007, November). Vitamin a: Micronutrient information center. Retrieved fromhttp://lpi.oregonstate.edu/infocenter/vitamins/vitaminA/index.html
4) USDA Database of Vitamin A (mcg RAE) and Vitamin E (mg AT) for National Health and Nutrition Examination Survey 1999-2000. 2006. Beltsville, MD: Agricultural Research Service, Food Surveys Research Group.