Although all vitamins are essential and serve unique and important functions in the body, many health experts agree that vitamin D is the most important vitamin because it plays a profound role in our overall health and vitamin D deficiency is very prevalent. It has been estimated that vitamin D insufficiency affects roughly 50 percent of the population worldwide 
. At Elo approximately 90 percent of our members have low vitamin D upon joining.
What is vitamin D and what does it do?
is a fat-soluble vitamin that is obtained through diet and sun exposure. Vitamin D plays an important role in bone health, calcium absorption, blood sugar regulation, cell proliferation and turnover, and immune function. Optimizing vitamin D levels may even help protect against severe COVID-19, type 2 diabetes, depression, as well as some autoimmune diseases, neurodegenerative diseases, and cancers [2
]. Vitamin D is so important that its receptor is found in nearly all (if not all) cells in the body 
Several factors contribute to low vitamin D levels:
Limited sun exposure: Sun exposure is the best way to get vitamin D but today people are spending more time indoors and avoiding the sun to minimize sun damage and skin cancer risk.
It’s difficult to obtain through food: Few foods contain vitamin D, which makes it difficult to consume enough from food alone. It’s found mostly in fatty fish and fortified dairy products.
Older age: Vitamin D synthesis in skin declines gradually with older age.
Dark complexion: Melanin in dark skin reduces the skin’s ability to absorb UV radiation needed to synthesize vitamin D.
Living in cold or northern climates: People who live above 37°N latitude typically don’t get enough sun to synthesize vitamin D year-round.
Pregnancy and breastfeeding: Pregnant or breastfeeding women have increased vitamin D needs.
Obesity: Subcutaneous fat appears to sequester more of the vitamin, often resulting in low vitamin D levels.
Certain health conditions: Some conditions including cystic fibrosis, Crohn's disease, celiac disease, kidney or liver diseases, can interfere with vitamin D absorption and/or synthesis. People who have had gastric bypass surgery are also at greater risk for deficiency due to decreased absorption.
How to get enough vitamin D
Increase consumption of vitamin D-rich foods like salmon, herring, canned tuna, eggs (with the yolk), and fortified foods like milk, yogurt, and breakfast cereals.
Get 10–30 minutes of unprotected midday sunlight most days.
Take a vitamin D supplement. Dosage will depend on your vitamin D level. For very low levels (<20 ng/mL) you may need to take 5,000 IU daily for several months to significantly improve your vitamin D status. For those in the 20-40 ng/mL range, a daily dose of around 2,0000 IU may be adequate, however it’s best to work with a health professional.