You’re probably not getting enough D year-round

You're probably Vitamin D deficient if you live in the Pacific Northwest. Sun exposure is the most effective way to get Vitamin D – but it's not the only way. And lack of sun is not the only indication of low D levels.

So, what is Vitamin D exactly? It's not a vitamin. It's a prohormone created by the body. Short-wave (UVB) ultraviolet rays from the sun help your body synthesize Vitamin D.

Storage of Vitamin D in the body lasts about three weeks. Studies show it takes 15 minutes of summer sun in a bathing suit to produce an average of 20,000 IU of Vitamin D. This would last for about 100 days - not enough to carry you through our sunless winter (and fall, and spring) months. So, if you live in the northern hemisphere, you’ll be deficient by December, if not earlier. Even rushing out to catch some rays on the rare sunny winter day won’t work. The sun must be intense enough – and up north, that only happens during the summer months.

But cloudy weather isn't the only indicator of being at higher risk for developing Vitamin D deficiency. Sunscreen also blocks Vitamin D production and higher melanin skin tones with more natural protection from UV radiation. Covering up in clothes has the same effect.

Those with higher levels of fat also struggle to produce enough accessible Vitamin D. Even with enough sun exposure or supplemental D, overweight individuals will store this fat-soluble vitamin on a stand-by basis rather than have it enter the bloodstream.

Fat malabsorption conditions like Crohn’s disease, celiac disease, and cystic fibrosis and some medications can cause this same issue.

Why enough Vitamin D matters

Vitamin D deficiency may be linked to several serious health conditions, and ongoing research continues to uncover more ways effective, or ineffective, prohormone production impacts health.

Your bones: Traditionally, Vitamin D is linked to maintaining bone density and preventing bone loss. Bone-softening diseases are attributed to vitamin D deficiency include rickets in children, and osteomalacia, osteopenia, and osteoporosis in adult patients.

Vitamin D is an essential nutrient for skeletal health.

Your mood: Vitamin D helps produce serotonin, a neurotransmitter that can help you feel calm, relaxed, and happy. Vitamin D deficiency is associated with low mood, PMS, seasonal affective disorder, mood disorders, and depression.

Your susceptibility to serious illnesses: Vitamin D deficiency has been linked to many health issues, from heart disease to Parkinson’s disease, multiple sclerosis, dementia, and Alzheimer's disease. More recent studies have connected some cancers like breast cancer, colon cancer, and prostate cancer. While it's not clear that the deficiency is related to their cause, sufficient levels appear to improve treatment outcomes.

Asthma is another condition with which vitamin D levels are associated.

Some symptoms of Vitamin D deficiency include:

• Getting sick more frequently
• Feeling tired and sluggish constantly
• Unexplained back pain or other aches and pains
• Depression and anxiety
• Slow healing from wounds
• Hair loss

How to get enough Vitamin D

The best way to get the Vitamin D you need is through the sun. Yes, sunscreen is important. But even five to 10 minutes of midday sun exposure is enough to synthesize a week's worth of Vitamin D. Religious sunscreen users can benefit from waiting a few minutes before slathering.

Some foods do contain D – the most absorptive version of D is D3, so that’s the one to look for.

Some options include:

• Cod liver oil (1300 IU per tablespoon)
• Wild salmon (1000 IU per serving)
• Farmed salmon (250 IU)
• Sardines (600 IU)
• Fortified milk or orange juice (100 IU)
• Egg yolk (25 IU)
• Fresh shiitake mushrooms (trace)
• Some organ meats (trace)

Supplements are the best way to go for most people. The Institute of Medicine (IOM) recommended dietary allowance is 600 to 800 units (IU) per day, but that amount is likely underestimated. To get the bone benefits of D, you should pair your supplement with at least 1,000 mg of calcium because the two work in tandem.

The IOM defines the safe upper limit for vitamin D consumption as 4,000 IU per day. Check with your doctor about what dose is right for you. Overdosing on vitamin D is hard, but you should monitor higher ingestion levels with your doctor.