Is vitamin A good for your eyes? And if so, should you take a vitamin A supplement?
Vitamin A and eye health have been closely linked for centuries. In fact, it was the vitamin’s impact on eye health that helped researchers understand its importance.
Vitamin A is crucial for healthy vision, but high vitamin A doses can be harmful. In this post, we explain everything you need to know about this essential vitamin.
We will talk about the benefits of this vitamin on vision, vitamin A and retinol, and the vitamin A recommended daily intake.
First, though, let’s start with the origins of this vitamin.
How Was Vitamin A Discovered?
As its name implies, vitamin A was the first vitamin to have been named. But this wasn’t its initial name, nor was its discovery straightforward.
In the 19th century, physiologists began to understand that some foods provide certain substances without which animals as well as humans become sick.
French physiologist François Magendie fed test dogs only water and sugar. This led to corneal ulcers and high mortality, problems common among abandoned infants in Paris.
Later in the century, German physiologist Gustav von Bonge and his graduate students fed test animals diets with and without milk. They found that milk contains a substance that prevents corneal ulcers and other eye problems.
In the early 20th century, American biochemist Elmer Verner McCollum and his research partners tested the effects of different fats on lab mice. Mice fed with olive oil and lard grew well initially, only to fall sick later.
Meanwhile, milk-fed mice were doing fine. The researchers assumed that milk contained a substance that the other types of fat lacked.
McCollum and his lab partner Marguerite Davis tested this assumption. They mixed a fat-soluble compound derived from milk with olive oil and lard.
The mice fed this mixture thrived. McCollum named the compound “fat-soluble a,” with “a” reportedly being the first letter of the German name for dry eye disease, “augendarre.”
But this did not explain how mammals continued to grow and develop without health issues once they stopped consuming their mother’s milk. Another piece of the puzzle fell into place when researchers discovered that egg yolks, leafy green vegetables, and other foods also contain the fat-soluble factor.
Meanwhile, Polish-American biochemist Kazimierz Funk proposed that the absence of a substance from a diet can cause malnutrition diseases. He was among the first to formulate the concept of vitamins, calling them “vital amines,” or essential nutrients with specific functions. Today we call them vitamins.
Amines are components of amino acids, which in turn are the building blocks of proteins. McCollum didn’t like the idea of the compound “fat-soluble a” being called vitamin A because it wasn’t an amine. But the name stuck, and the first food compound that was found to prevent deficiency disease became vitamin A.
Vitamin A Explained
Seen through the lens of modern science, vitamin A is not one but a group of organic compounds that includes retinol, retinal (or retinaldehyde), retinoic acid, and provitamin A carotenoids such as beta-carotene. There are two main forms of vitamin A in the human diet:
- Preformed vitamin A. This can be as retinol or, when bound to a fatty acid, a retinyl ester. It’s commonly found in animal products, vitamin supplements, and fortified foods such as breakfast cereal.
- Provitamin A carotenoids. These come from plant sources. Humans and other animals have an enzyme that converts provitamin carotenoids to retinal and retinol in the small intestine.
Vitamin A is fat soluble. Because it doesn’t dissolve in water, your body can only absorb it when eaten along with fats from food. The body stores fat-soluble vitamins like vitamin A in fatty tissue and the liver.
Vitamin A and Eye Health
Vitamin A is one of the vitamins essential for eye health. In the form of retinal, it combines with the protein opsin to form the photopigment rhodopsin. Rhodopsin is a light-absorbing molecule that occurs in the retina located at the back of the eye. It plays a key role in both low-light vision and color vision.
Rhodopsin occurs in rod cells, which enable vision in low-light conditions. It senses light and converts it into electrical signals. When rhodopsin detects light, it breaks down and opens a channel within the rod cells, transmitting nerve impulses to the brain to produce vision.
The retina needs time to adapt to low-light conditions, transitioning from photopic (light-adapted) to scotopic (dark-adapted) vision. This process is known as dark adaptation, and rhodopsin plays a key role in it.
It takes 30 minutes or longer for the retina to adapt to dark vision. The brighter the light before the transition, the longer the retina takes to see well in the dark, possibly because rhodopsin stores are low after bright light exposure and the body needs to draw on its reserves of vitamin A to restore them.
When you don’t consume enough vitamin A, dark adaptation takes longer. You may also suffer from night blindness. A healthy intake of vitamin A means your body can readily convert it to retinol and combine it with opsin to form rhodopsin.
Vitamin A Eye Health Benefits
More than enabling seeing in the dark and dark adaptation, vitamin A plays an essential role in the normal functioning of the retina. There are several vitamin A pathways in the retina, linking blood circulation to photoreceptors, converting light to electrical signals, supporting the visual cycle, and clearing toxic derivatives from the retina.
Prolonged blue light exposure can lead to the abnormal development of excess blood vessels over the retina. This can interfere with the functioning of the macula and lead to AMD.
The macula is an oval-shaped area inside the retina responsible for the sharpest vision. A healthy intake of vitamin A can help support the functioning of the macula and the retina as a whole.
Vitamin A also plays a key role in the normal production of the tear film. The tear film lubricates and protects the surface of the eye. Vitamin A deficiency leads to severe dry eyes that affects the cornea and conjunctiva at the front of the eye.
The first National Health and Nutrition Examination Survey suggested that people who ate fruits and vegetables rich in vitamin A frequently had a lower risk of developing AMD.
A more recent study suggests that fruits and vegs that have the provitamin A carotenoid can reduce the risk of AMD. However, epidemiological studies could not verify these findings. More research is needed to determine whether vitamin A can indeed prevent AMD.
In addition to being crucial for healthy vision, vitamin A fulfills many other important functions in the body. It supports cell division, growth, the immune system, and reproduction.
It also helps maintain bone and has antioxidant properties, protecting your cells against the oxidizing effects of free radicals, molecules that are by-products of bodily functions, pollution, and radiation.
Vitamin A and Your Diet
More than 1,000 years ago, Tang dynasty medical scientist Sun Simiao (581-682 AD) gave his patients to eat animal livers to treat their night blindness. Animal livers are rich in retinol, which they store alongside fat. But they are not the only foods that contain this important vitamin for the eyes.
Foods rich in vitamin A include:
- Carrots, pumpkin, sweet potatoes, and other orange and yellow vegetables
- Spinach, kale, broccoli, and other leafy greens
- Red bell peppers
- Cod liver
- Beef liver
- Fish oil
Good to know: Breakfast cereals, plant-based milk, and other processed foods can be fortified with vitamin A.
Vitamin A Daily Recommended Dose
According to the National Institutes of Health, the vitamin A recommended daily intake between ages 14 and 51+ years is:
- 700 mcg RAE for females
- 900 mcg RAE for men
Important: Adult pregnant females need a vitamin A daily intake of 770 mcg RAE, and during lactation, 1,300 mcg RAE.
RAE stands for retinol activity equivalents, a measure of how much vitamin A the body can actively absorb.
Vitamin A Deficiency and Toxicity
In the Western world, vitamin A deficiency is uncommon. But it may still occur. Several conditions, including Crohn’s disease, celiac disease, and alcoholism can impair the absorption of this vitamin. People with these conditions may eat enough vitamin A, but due to poor absorption, they may have to take vitamin A supplements.
Signs and symptoms of vitamin A deficiency include:
- Night blindness
- Severe eye dryness that can lead to blindness (xerophthalmia)
- Patches on the white of the eye
- Dry skin
- Dry hair
- Frequent infections
People in the US may be more at risk of vitamin A toxicity than deficiency. Because vitamin A is fat-soluble, taking too much of it in supplement form can lead to unhealthy levels of it building in the body.
Studies indicate that taking 3,000 mcg (10,000 IU) of preformed vitamin A regularly increases the risk of hip fractures, bone loss, and birth defects. It may also limit the beneficial effects of vitamin D.
Signs and symptoms of vitamin A toxicity include:
- Blurry vision
- Dry skin
- Light sensitivity
- Bone pain
- Abdominal pain
Should You Take a Vitamin A Supplement?
The Mayo Clinic notes that a healthy and varied diet provides enough vitamin A for most people, making supplements unnecessary. It adds that food sources rich in this vitamin are the best way to take advantage of the antioxidant properties of vitamin A.
Vitamin A is not soluble in water, meaning that your body can’t flush it out easily. It may also have harmful interactions with anticoagulants, hepatotoxic drugs, retinoids, or certain topical cancer drugs.
That said, if you suffer from a medical condition that affects your body’s ability to absorb vitamin A, your doctor may prescribe a vitamin A supplement. Supplementing vitamin A may also be necessary if you take a drug like Orlistat that reduces vitamin A absorption from food sources.
According to most sources, the tolerable upper intake level for vitamin A per day is 3,000 mcg (10,000 IU) for adults. But the bottom line is that you shouldn’t take high doses of vitamin A as a supplement. A safe approach is not to exceed the recommended vitamin A intake unless instructed by your doctor.
If you’re concerned about your intake of this vitamin, eat more of the foods that have it, such as carrots, sweet potatoes, and leafy greens.
Keep Your Eyes Healthy
Eating foods rich in vitamin A helps support your eye health. But there’s more you can do for your eyes, without the risk of vitamin A toxicity.
SightC is a full-spectrum vision health supplement rich in antioxidants, lutein, zeaxanthin, and beta-carotene. It brings together superfoods like goji berries and turmeric with plants long used in Traditional Chinese Medicine like hawthorn and Chinese yams.
SightC nourishes dry and tired eyes, protects eye cells from oxidative damage, and provides nutritional support for myopia, presbyopia, floaters, astigmatism, macular degeneration, and glaucoma.
Packed into vegan capsules, SightC is made from 100% natural ingredients. It’s sugar-free and gluten-free.
Nourish and protect your eyes with SightC.