Vitamin A: What You Should Know

Sources, Benefits, Forms, Dosage 

What is Vitamin A?

Vitamin A is one of thirteen essential vitamins. Essential vitamins need to be present in the diet because the human body cannot make the nutrients on its own, or in sufficient amounts to sustain normal and healthy bodily functions.1 Vitamin A is considered an essential vitamin due to its many physiological health benefits. Along with being essential, Vitamin A is also fat-soluble, which means unlike water-soluble vitamins, these nutrients are stored in the liver and the fat cells of fatty tissue. Since the four fat-soluble vitamins, Vitamin A, D, E, and K are stored in tissue and not as easily flushed out of the body, there is a risk to develop toxic side effects. However, toxicity only occurs when the vitamin is taken in very high concentrations.

Benefits of Vitamin A – There are many

Vitamin A is a popular micronutrient known to support vision and ocular health. This vitamin supports vision as it is needed by certain components of the eye, such as the cones and rods which are needed to see and process light, color, and black and white.1,2 Vitamin A also plays a role in prevention of age-related macular degeneration and night blindness.1,2

In addition to eye health, Vitamin A also supports a healthy immune system, bone health, and cellular functions such as growth, development, and differentiation throughout all stages of life.2 Due to Vitamin A’s carotenoid antioxidant properties, research demonstrates probable cause that Vitamin A in the form of beta-carotene may play a role in the prevention of certain types of cancers. 1

Forms of Vitamin A – Which is best?

Vitamin A is found in multiple forms. The main sources are preformed Vitamin A, which are retinoids found from animal sources and provitamin A, which are carotenoids found from plant sources.1

Retinoids are divided into the compounds retinol, retinoic acid, and retinal.1 Retinol is the most active and bioavailable form of Vitamin A.1 Retinal can be converted into retinoic acid and retinol, and retinol can form into a retinyl ester which is a storage form of Vitamin A.1,3

Carotenoids have a two subgroups, provitamin A carotenoids that can be converted into Vitamin A, which includes beta-carotene, and another group of nonprovitamin A carotenoids, which cannot be converted into Vitamin A and are considered to be phytonutrients instead of vitamins.1 Caroteniods, such as beta-carotene are less efficiently absorbed, as the body must convert them to retinal and again to retinol for absorption.4

Because of the absorption difference, Vitamin A is measured as Retinol Activity Equivalents (RAE).2 For example, 1 mcg (microgram) RAE is equivalent to 12 mcg of beta-carotene.4 Even though the bioavailability may not be equal, carotenoids have many unique and beneficial functions as they are antioxidants and aid in prevention of chronic illness.1

The video below explains more about the different forms of Vitamin A and their benefits.

Sources of Vitamin A – From food and nutrition supplements

Animal food sources high in Vitamin A include eggs, milk, cheese, liver, and herring.2 Plant food sources high in Vitamin A are sweet potatoes, carrots, collard greens, kale, and cantaloupe.5 Vitamin A from animal sources is approximately six times more potent than from vegetable sources, however, take caution when consuming organs because the high amounts of Vitamin A can accumulate to toxic levels.6 The common forms of Vitamin A that are found in nutrition supplements are retinyl, beta-carotene, retinol, and a combination of retinol and beta-carotene.2,7 When consuming fat-soluble vitamins it is best to accompany these nutrients with a dietary fat for optimal absorption.1,7

Recommended daily dose of Vitamin A – What physicians advise

The recommended daily dose for nutrients is unique to a person’s age, gender, and other personal factors. Since all forms of Vitamin A are not equally absorbable the recommended dietary allowance (RDA) of Vitamin A is expressed in micrograms (mcg) of Retinol Activity Equivalents (RAE).2 The RAE accounts for the total Vitamin A content of a food source, and also makes it possible to compare retoind and carotenoid forms.1 The RDA of Vitamin A for healthy adults is 900 mcg RAE (3,000 IU) for men and 700 mcg RAE (2,334 IU) for women.

Recommended Dietary Allowance
(RDA) Vitamin A
Infants (0 – 12 months) 400 – 500 mcg/day RAE
Children (1 -8 years) 300 – 400 mcg/day RAE
Adolescents (9 – 18 years) 600 – 900 mcg/day RAE
Adults (19+ years) 700 – 900 mcg/day RAE
Pregnant and Lactating Women 750 – 1,300 mcg/day RAE

Table 1: Daily Vitamin A Recommended Dietary Allowance (RDA) to Meet the Needs of Healthy Individuals2,7

Certain populations may need to be more mindful when evaluating their Vitamin A needs. For example, individuals taking weight loss drugs such as Alli® or Xenical® are typically recommended to increase their intake of Vitamin A and fat-soluble vitamins as these medications may inhibit vitamin absorption.2 Another group that should take close consideration when evaluating Vitamin A needs includes individuals prescribed retinoids to treat certain skin conditions as they may risk Vitamin A toxicity.2  With any particular medication or health condition it is always best to consult with your primary healthcare provider before taking the Healthycell® products or any nutrition supplement.

Vitamin A toxicity is uncommon

Vitamin A is a fat-soluble vitamin and is stored in the liver and fat cells of fatty tissue, therefore, it can be toxic when taken at high levels. An excessive consumption of Vitamin A can lead to hypervitaminosis A, a condition characterized by toxic levels of Vitamin A in the body effecting the eyes, liver, and bones.1 Other complications of toxicity include nausea, drowsiness, headache, dry skin, hair loss, bone and muscle pain, liver damage, and birth defects.Excessively high levels of carotenoids can also produce a non-dangerous side effect of yellowing-skin called hyerpcerotenemia.1

Since there are health complications when Vitamin A is consumed at very high levels, a maximum level that may cause an adverse event, also known as a tolerable upper intake level (UL) displayed in Table 2 has been established for Vitamin A.

Tolerable Upper Intake Level (UL) of Vitamin A
Infants (0 – 12 months)

600 mcg/day RAE

(2,000 IU)

Children (1 -8 years) 600 – 900 mcg/day RAE

(2,000 – 3,000 IU)

Adolescents (9 – 18 years) 1,700 – 2,900 mcg/day RAE

(5,667 – 9,333 IU)

Adults (19+ years) 3,000 mcg/day RAE

(10,000 IU)

Pregnant and Lactating Women 2,800 – 3,000 mcg/day RAE

(10,000 IU)

Table 2: Daily Vitamin A) Tolerable Upper Intake Level (UL)2,4

Vitamin A deficiency, symptoms, and people at risk

Vitamin A deficiency is a less common micronutrient deficiency in the United States, but more prevalent in other countries.2 Certain developing countries do not have accessible food sources rich in Vitamin A and risk Vitamin A Deficiency Disorder (VADD).1,2 VADD mostly effects children and can result in eye complications that can cause night blindness, dry eye, and even permanent blindness.1,2 Other populations at risk include malnourished vegetarians, alcoholics, those involved with drug abuse, diagnosed with HIV/AIDS, and those with a fat malabsorption condition.4

Other symptoms of Vitamin A deficiency include night blindness, dry eye, hardening and drying of the skin, Bitot’s spots (white spots on the eye), and a weakened immune system.4

Vitamin A in Healthycell® Pro – Only the best form

Healthycell® Pro uses the form of Vitamin A as natural beta-carotene. The dosage of Vitamin A in Healthycell® Pro is 2,500 IU or 375 mcg in the morning formula and 2,500 IU in the evening formula, for a daily dose of 5,000 IU or 750 mcg, satisfying 100% of the Daily Value (%DV).

Healthycell® uses the form of Vitamin A as retinyl palmitate. The dosage of Vitamin A in Healthycell® is 2,500 IU in the morning formula and 2,500 IU in the evening formula, for a daily dose of 5,000 IU, satisfying 100% of the Daily Value (%DV). Nutrition supplement labeling and food labeling guidelines use Reference Daily Intake (RDI) as the standard for dosage.

References:

1. McGuire, Michelle, PhD, and Kathy Beerman A., PhD. “Chapter 11 Fat Soluble

Vitamins.” Nutritional Sciences: From Fundamentals to Food. 2nd ed. Australia:

Thomson/Wadsworth, 2007. 486-93. Print.

2. “Vitamin A — Health Professional Fact Sheet.” U.S National Library of Medicine.

U.S. National Library of Medicine, 31 Aug. 2016. Web. 07 Sept. 2016.

3. O’Byrne, Sheila M., and William S. Blaner. “Retinol and Retinyl Esters: Biochemistry

and Physiology Thematic Review Series: Fat-Soluble Vitamins: Vitamin A.” The Journal

of Lipid Research(2013): 1731-743. JLR. American Society for Biochemistry and Molecular

Biology, Inc. Web.

4. Brasaemle, Dawn, PhD. “Vitamin A Lecture.” Rutgers University – Vitamin A. New

Brunswick. 2015. Lecture.

5. Moore, Marisa, MBA, RDN, LD. “The Roles of Vitamin A.” Eat Right. Academy of

Nutrition and Dietetics, 15 Apr. 2014. Web. 07 Sept. 2016.

6. Balch, Phyllis A., CNC. Prescription for Nutritional Healing. 4th ed. New York: Avery, Print.

7. Higdon, Jane, PhD, and Victoria Drake, PhD, and Barbara Delage, PhD. “Vitamin A.”

Oregon State University. Linus Pauling Institute, 23 June 2016. Web. 07 Sept. 2016.

8. Higdon, Jane, PhD, and Victoria Drake, PhD. “Carotenoids.” Oregon State University.

Linus Pauling Institute, 01 Jan. 2016. Web. 07 Sept. 2016.

9. Ehrlich, Steven D., NMD. “Vitamin A (Retinol).” University of Maryland Medical

Center. N.p., 5 Aug. 2015. Web. 07 Sept. 2016.