- Lack of sunlight. The sun is the best vitamin D source available, as our skin naturally produces vitamin D when exposed to the sun’s ultraviolet light. The farther you live from the equator, the less direct sunlight you receive, and if you use sunblock or sunscreen lotion, you’re also blocking your skin’s ability to produce vitamin D.
- Skin pigment. This one is simple, but unfortunately you don’t have any control over it. It’s in your genes. The darker your skin, the harder it is to produce vitamin D from sun exposure.
- Obesity. Because fat absorbs vitamin D and makes it unusable, overweight people have greater vitamin D needs... meaning a higher likelihood for deficiency.
- Age. Your ability to produce vitamin D naturally decreases with age. A 70-year-old makes just 25% of what they made when they were 20.
- Lifestyle. As a civilization, we’re living more and more indoors, reducing our exposure to natural sunlight. The less time you spend outside, the fewer opportunities your skin has to produce vitamin D.
- Culture. Just as we live mostly indoors, some cultures still maintain traditions of covering oneself while in public (i.e. outdoors). See a recurring theme here?
- Pregnant and breastfeeding mothers. Even though a minimal amount of vitamin D passes into breast milk, new moms might need more to maintain healthy blood levels. Plus, the American Academy of Pediatrics now recommends an intake of 400 IU per day for all babies.
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