There is an association between low vitamin D levels and increased risk of viral respiratory tract infections, including SARS-CoV2. One study of Japanese school children showed that significantly fewer children had an occurrence of the seasonal flu when given 1,200 IU/day of vitamin D as compared to controls who did not receive the supplement. Another study looked at 20 different European countries and found that higher vitamin D levels were associated with lower cases of COVID-19 infection and mortality.
 
So how much is enough?
 
This is a tricky question to answer, because there is no international consensus. It’s best to go to your doctor and have your blood levels tested. Then, if they are low you can start supplementing and retest later to see if your levels have reached optimal ranges.
 
Which would be…
 
…51-70 ng/mL
 
What’s that?
 
Nanograms per milliliter – the unit used to measure the amount of vitamin D in your blood. A measurement that falls between 51 and 70 ng/mL is optimal for good health in a slew of ways – immunity, cancer risk reduction, cardiovascular health, bone strength, mental health … you get the picture.
 
Where do I get vitamin D?
 
The sun. Our skin can make its own vitamin D from the sun, but the amount of vitamin D obtained from sun exposure is wildly unpredictable. There are a ton of variables that will determine the amount of vitamin D you make including how much skin is exposed, the natural color of your skin, your age, the time of year, and where you are located.
 
Location?
 
Location matters. Those who live above the 35^th parallel north or below the 35^th parallel south are not going to be able to get enough sun exposure to make their own vitamin D from October through April. This happens to be most of North America, Europe, and Asia. However, in May through September you can try exposing your skin to the sun for 15-30 minutes – or until you know you will start to burn – and become a natural vitamin D-making machine!
 
What about skin color?
 
The darker your skin the harder it is to make vitamin D and the more likely you are vitamin D deficient.
 
And age?
 
The older you are, the harder it is to naturally produce vitamin D on your own, especially when you reach your 80s or 90s – bless your heart!
 
Anything else?
 
Pregnancy. It’s a huge drain on all your physical resources including vitamin D, so you are more susceptible to deficiencies.
 
Can I get vitamin D from anything other than the sun?
 
Yep! From foods such as:
 
Cod liver oil
Trout/salmon/sardines/tuna
Mushrooms
Fortified soy, almond, oat, and cow milk
Fortified cereals
Eggs
Liver
Cheese
Chicken/beef
 
And from supplements. Be sure to use a supplement that is D3 – the most bioavailable form of the vitamin.
 
How much vitamin D do I need?
 
Like mentioned before, it’s best to have your doctor test your blood to see where you are and where you need to be. Your doctor will recommend how much to supplement daily to raise your levels, but the Endocrine Society recommends the following:
 
0-6 months      1000 IU/day               
6m-1year         1500 IU/day
1y-3y              2500 IU/day
4y-8y              3000 IU/day
8y+                 4000 IU/day
 
FYI – an “IU” is an international unit and the standard way of measuring vitamin D supplementation.
 
Vitamin D toxicity is rare, but if your blood levels go above 100-150 ng/mL it’s time to pull back on the vitamin D. Signs of vitamin D toxicity include GI upset, fatigue, and a condition known as hypercalcemia – too much calcium in the body. Signs of vitamin D deficiency include bone pain, fatigue, muscle weakness/pain/cramping, and depression.