The role of vitamin D in dry eyes
What are the benefits of vitamin D and can it help with dry eyes? Read about the importance of the “sunshine vitamin.”
What is vitamin D?
Vitamin D is both a vitamin that we can get through diet and supplementation, and a hormone because your body can produce it when exposed to the sun – hence its nickname, the “sunshine vitamin.” When your skin is exposed to sunlight, it transforms UVB rays into vitamin D which can then be used by your body.
When taken in as part of your diet, vitamin D comes in two forms: D2 and D3. D2 is plant-based, while D3 is animal-derived and is usually what you find in supplements and some vitamin D-fortified foods, like milk and orange juice. While there is still debate in the medical community on whether there is a significant difference between the two forms, the best way to know whether your food or supplements are working is to have your blood tested.
Vitamin D is both a vitamin that we can get through diet and supplementation, and a hormone because your body can produce it when exposed to the sun – hence its nickname, the “sunshine vitamin”.
What are the benefits of vitamin D?
There are a variety of benefits associated with vitamin D but it is perhaps most commonly known for its importance for bone health. If you take a calcium supplement, you might have noticed that there is also some vitamin D added; this is because it helps your bones absorb the calcium, instead of remaining in your bloodstream.
However, there are also many other benefits of vitamin D, including the prevention of cardiovascular disease, aiding in autoimmune diseases, infectious diseases and schizophrenia, as well as the prevention of some cancers.
How does vitamin D affect dry eyes?
Interestingly enough, some parts of your eye, like the outer layer of the cornea and the lens, actually contain vitamin D receptors.
There have been numerous studies on vitamin D’s impact on dry eyes and while it’s still unknown whether or not vitamin D supplementation can prevent dry eye disease, it does seem to alleviate the symptoms. Some researchers suggest that using topical vitamin D could be an even more effective mode of delivery for the prevention of dry eyes.
Researchers have consistently seen that people with vitamin D deficiency seem to be more prone to dry eyes, which is why it could be interesting for ophthalmologists to consider testing vitamin D blood levels in patients presenting with this issue.
Vitamin D deficiency is associated with tear hypersmolarity (increase in the saltiness of the tears) and tear film dysfunction. Adding vitamin D to a dry eye patient’s regimen has been proven to enhance tear production, reduce ocular surface inflammation, reduce tear instability, and even enhance the effects of dry eye medications.
Some researchers suggest that using topical vitamin D could be an even more effective mode of delivery for the prevention of dry eyes.
Where is vitamin D found?
Vitamin D deficiency is uncommon, so it’s important to speak with your doctor before supplementing your diet with extra vitamin D. However, some people could be at higher risk for vitamin D deficiency, like those with inflammatory bowel disease, liver disease, and untreated celiac disease.
For optimal health, most doctors recommend 1,000 international units (IU) of vitamin D per day for adults, although this is dependent on whether you are deficient or not, or have other health factors that could influence your levels. It is generally recognized that adults can safely consume up to 4,000 IU per day. If you decide to consume more than this, it could be a good idea to get your vitamin D levels checked through a blood test.
For optimal health, most doctors recommend 1,000 international units (IU) of vitamin D per day for adults, although this is dependent on whether you are deficient or not, or have other health factors that could influence your levels. It is generally recognized that adults can safely consume up to 4,000 IU per day.
If you are looking to get your vitamin D from the sun, the amount of time you need to spend outdoors will depend on your skin colour, where in the world you live and how much of your skin is exposed, but usually 10-15 minutes three times per week is enough. However, most people are conscious of the negative effects of UVA and UVB ray exposure and wear sunblock, which will reduce how much vitamin D one gets. Furthermore, getting vitamin D from the sun is more difficult for people living in the northern hemisphere during the winter months as there is less sunlight, they spend more time indoors, and the cold temperatures mean less skin is exposed to the sun.
Vitamin D is not water-soluble and needs fat to metabolize, which is why it can be better to take supplements as an oil or through a pill with oil inside (instead of a tablet), or to consume in tablet form alongside high fat foods. This will make it easier for your body to use the vitamin D you’re taking in, instead of putting it into storage (your body’s fat) first, before tapping into that reserve to absorb into your bloodstream and use. It’s important to note that because vitamin D is fat-soluble, your body can store what it doesn’t need.
While it is difficult to get enough vitamin D from food alone, here are some examples of where you can find it:
FOOD | International units (IU) of vitamin D |
3.5 oz. salmon | 360 |
3.5 oz. canned tuna | 200 |
8 oz. fortified orange juice | 100 |
8 oz. fortified milk | 98 |
1 large hard boiled egg | 44 |