Vitamin A is essential for your sight and eye health because it is required for the following two main functions:
- Prevention of xerophthalmia (drying, thickening, and other abnormalities of the cornea and conjunctiva)
- Formation of photoreceptor pigment in the retina (detection and absorption of visible light, vision in darkness or lightness, and immunity of the eye)
Vitamin A is also important for bone growth, proper immune function, reproduction, and the function and maintenance of your heart, lungs, kidneys, and other organs.
Symptoms of Vitamin A Deficiency
Vitamin A deficiency can result from inadequate consumption of vitamin A, fat malabsorption, or liver disorders. Although vitamin A deficiency is supposed to be minimal in developed countries like US, if you experience any of the following symptom(s), you might want to check your vitamin A level:
- Night blindness
- Impaired dark adaptation*
- Macular degeneration
- Retinitis pigmentosa
- Diabetic retinopathy
- Ulcers or thinning of the cornea
- Conjunctival deposits
- Grayish spots on eye lining (Bitot sots)
- Impaired immunity
- Weak bones or teeth
- Weak or ridged fingernails
- Repeated infections, especially viral and fungal
- Drying, scaling, and follicular thickening of the skin
- Dry mucous membranes in the GI, respiratory, and urinary tracts
- Thyroid dysfunction
- Chronic inflammation
- Growth retardation and infections among children
(*Note: Impaired dark adaptation could be from severe refractive errors, retinitis pigmentosa, cataracts, or diabetic retinopathy.)
Two Forms of Vitamin A
There are two dietary forms of Vitamin A: preformed Vitamin A and provitamin A.
- Preformed vitamin A (retinol, retinal, retinoic acid, and retinyl esters) is the most active form of Vitamin A; it is fat soluble and mostly found in animal sources of food such as fish liver, dairy products, and animal liver. The liver is rich with Vitamin A because about 50–85% of the total body retinol is stored in the liver. Retinol is readily useful to the body and is converted to retinal which helps for vision health and healthy growth of the body cells.
- Provitamin A, also known as carotenoids, is a water-soluble precursor to vitamin A and is found in plant foods. Carotenoids need to be converted into bioavailable retinol to be used as vitamin A. Beta carotene is the most efficient form of carotenoids. The healthy human liver converts 3 IU of beta carotene into 1 IU equivalent of retinol*.
*Note: Diabetics and those with low thyroid function may have difficulty converting beta carotene into retinol. In that case, they might have to get their vitamin A from retinol.
Absorption of Vitamin A is another story
For your body to utilize retinol and convert carotenoids to retinol, you need to have:
- A healthy digestive system – especially liver, gall bladder, pancreas, and small intestines – for optimal digestion and absorption.
- The specific enzymes to break-down the carotenoids to convert it to retinol
Risk Factors for Absorption of Vitamin A
If you have one of more of the following conditions which interferes with absorption, storage or transport of vitamin A, you might experience vitamin A deficiency:
- Zinc deficiency (Zinc influences absorption, transport, and utilization of Vitamin A)
- Excessive alcohol (adding more problem to the liver where vitamin A is stored)
- Digestive track issues such as Crohn’s disease, IBS, duodenal bypass
- Pancreatic disorder causing enzyme deficiency
- Celiac disease that limit the absorption of nutrients
- Liver disease such as cirrhosis
- Gallbladder disease
- Cystic fibrosis
- Radioiodine treatment for thyroid cancer
- Toxic exposure from cancer treatment and other sources
- Certain prescription drugs
Which Foods Give You Vitamin A?
Most vitamin A is stored in the liver and about five percent of it is used up daily. As such, it needs be replenished by dietary sources.
Animal food sources of retinol
- Fresh, organic and extra virgin cod liver oil
- Liver of organic grass-fed beef, duck, etc.
- organic free-range egg yolks
- Raw organic butter, cheese and milk
Three ounce of beef liver contains 305% of vitamin A; one tablespoon of cod liver oil 272%; one tablespoon of butter 7%; one slice of cheddar cheese 5%; 1 large egg yolk 4%; 1 cup of whole milk 2%; 7 ounce of salmon 1%. Fish oil zero%.
(Note: Vitamin A here means retinol and percent daily values are based on a 2,000-calorie diet. Data from Wikipedia Nutrition Facts.)
You need to be careful when you consume animal sources of Vitamin A as toxicity, acidosis and high cholesterol can occur if excessive quantities are consumed.
Plant based food sources for carotenoids
Green leafy and yellow vegetables and deep- or bright-colored fruits contain good amount of beta carotene as well as lutein, zeaxanthin, phytonutrients, antioxidants, vitamins and minerals.
- Fruits – Cantaloupes, Mango, Apricots, Papaya, Watermelon, Goji berry, Orange
- Vegetables – Carrots, Sweet potatoes, kale, Spinach, Collard greens, Broccoli, Turnip greens, Swiss chard, Butternut squash, Pumpkin, Tomatoes (consume these vegetables with healthy fat such as organic olive oil, butter, nuts, or seeds)
Top source of fruits for carotenoids are cantaloupe, mango, and apricot. For example, one medium size cantaloupe contains 373% of vitamin A, one mango 72%; one cup of sliced apricot 63%.
As for vegetables, 1 medium carrot 203%; 1 cup of sweet potato 377%; 1 cup kale 133%; 1 cup spinach 56%; .1 cup collard greens 36%)
(Note: Vitamin A here means carotenoids and before the conversion to retinol occurs. Percent daily values are based on a 2,000-calorie diet and data obtained from Wikipedia Nutrition Facts. Consume organic produce as much as you can.)
How Much Vitamin A Do You Need?
The recommended daily allowance (RDA) of vitamin A is between 2,310 IU (0.7 milligrams) per day for adult women (more for women who are pregnant or breastfeeding), and 3,000 IU (0.9 milligrams) per day for men, with children needing less as shown below. Data provided by National Institutes of Health. Note that 1 mcg retinol = 3.33 IU.
|0 to 6 months old||400 micrograms (mcg)|
|7 to 12 months||500 mcg|
|1 to 3 years||300 mcg|
|4 to 8 years||400 mcg|
|9 to 13 years||600 mcg|
|14 to 18 years||900 mcg for males, 700 mcg for females|
|14 to 18 years/pregnant females||750 mcg|
|14 to 18 years/breastfeeding females||1,200 mcg|
|19+ years||900 for males, 700 for females|
|19+ years/pregnant females||770 mcg|
|19+ years/breast-feeding females||1,300 mcg|
Watch out for too much vitamin A causing toxicity
Vitamin A toxicity can be caused by ingesting high doses of vitamin A—acutely or chronically (for example, as mega-vitamin therapy or treatment for skin disorders). Symptoms of vitamin A toxicity may vary, however, headache and rash usually develop during acute or chronic toxicity.
Some of the signs and symptoms of chronic vitamin A toxicity include:
- Double or Blurred vision
- Hair loss in the head and eyebrows
- Liver dysfunction
- Fractures especially in elderly
- Lack of muscular coordination
- Dry, rough skin, itchy or peeling skin
- Cracked fingernails and lips
- Mouth ulcers, skin cracks at the corners of your mouth
- Respiratory infection
- Confusion or other central nervous system effects
- Inflammation of the tongue (glossitis)
Vitamin A is important to your sight, vision health, bone growth, immunity, and many other functions throughout the body as noted above. You can get all of the vitamin A your body needs from a healthy diet alone.
There’re two forms of vitamin A: retinol and carotenoids. Retinol is known to be more efficiently used as vitamin A by your body than carotenoids. Although carotenoids need to be converted to retinol before it can be used as vitamin A, it’s much safer than retinol. While retinol can be toxic in large doses, carotenoids are non-toxic in its natural form and converted to retinol only when your body is low in vitamin A. It’s not possible to overdose on carotenoids. Moreover, plant based foods containing carotenoids are easy to digest, free of cholesterol, alkalizing, and provide your body with Lutein and zeaxanthin which are also very important nutrients for your eyesight.
According to the Centers for Disease Control and Prevention (CDC), vitamin A deficiency in US is less than one percent of population. However, if your body has difficulty converting carotenoids to retinol; or you just don’t seem to consume enough of colorful fruits and vegetables daily (even eating two carrot sticks a day is not that easy some days :), you could intake very small amount of animal foods containing retinol. Which animal food? Depends on what you like to eat – bloody liver doesn’t look that appealing. You have to consume lots of dairy and eggs to meet the RDA. Hmmm, How about less than one teaspoon of “fresh, wild and raw extra virgin cod liver oil,” from companies like corganic? This type of cod liver oil is not only fresh (most fish oils are manufactured in high heat thus rancid) and high quality of retinol, but it’s also a good source of vitamin D and omega 3 fatty acids (EPA and DHA).
As far as taking vitamin A supplements whether it’s in the form of retinol or beta carotene, be aware that synthetic supplements could add more load to your liver and toxicity to your body. When taken as a supplement, beta-carotene has been associated with increased cancer risk (per International Journal of Cancer 2009).
It’s always a better idea to obtain nutrients from real whole foods. It’s also wise to have a balanced diet including proper amount of macro-nutrients (protein, carbohydrate, and fat) from healthy sources which in addition supply you with good vitamins, minerals and anti-oxidants.
With love and seeing,
Mimi Shekoski, PhD, Natural Vision Teacher | Holistic Natural Health & Nutrition Doctor
Please note that teachers or coaches at Happy Eyesight do not purport to diagnose, treat or cure any eye condition or disease. Natural Vision Improvement is an educational self-help program which assists those with refractive error to train their visual system towards improved clarity and perception. Individuals must use their common sense in applying any activities or principles and take into account specific individual conditions that may be adversely affected. The information contained on this website are in addition to and are not intended to replace the care and advice of your medical professionals. Regular exams with your optometrist or ophthalmologist are important to assess both visual acuity and eye health. When using the principles or activities outlined in Natural Vision Improvement, students should always remain under the care of these health professionals. We provide the products and information on this website for your benefit, however must state that their use is entirely at your own risk.