Vitamin D deficiency and dry eyes

Vitamin D for Dry Eyes

Research shows that a deficiency in vitamin D may be behind dry eyes, also known as Keratoconjunctivitis sicca (KCS) or dry eye syndrome (DES). KCS means that the tear film doesn’t function properly, which leads to chronically dry eyes. While it may seem like a minor inconvenience, it is actually quite serious. In addition to regulating the hydration of the cornea, the tear fluid is responsible for the majority of the oxygen supply to the outermost layer of the cornea. The tear fluid also contains bactericidal substances, which help wash away irritating particles and dead cells.

When adjusting for age, gender, obesity, eczema, various diseases, depression, thyroid issues, a history of eye surgeries, regular exercise, and work, two factors stood out as influencing dry eyes: a lack of vitamin D and insufficient sun exposure.

How much vitamin D should one take per day?

Professor Heaney from Creighton University suggests that 70–80 IU of Vitamin D3 per kilogram of body weight from all sources (sunlight, diet, and supplements) will result in vitamin D levels in the body of around 40 ng/ml, which is roughly what one should aim for (Vitamin D Council states that 40–80 ng/ml is optimal). A man weighing 70 kg should therefore aim for at least 4900–5600 IU per day. A woman weighing 50 kg should aim for at least 3500–4500 IU per day. This aligns with what the world-renowned vitamin D researcher Hollick writes in a study: "We recommend that the D-vitamin dosage be 2–3 times higher for individuals suffering from obesity and 1.5 times higher for those who are overweight." In other words, the dosage depends entirely on weight, and 70–80 IU of D3 vitamin per kg of body weight is a good starting point.

On average, women get 170 IU per day from their diet, men get 205 IU per day, and children aged 2–19 get 195 IU per day from food. The rest needs to be supplemented unless one is exposing 80% of the body to sunlight without sunscreen between 11 am and 3 pm for at least 20 minutes when the UV index is 4 or higher.

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