Vitamin D: How to Maintain Healthy Levels During Winter





Now that winter is setting in, your vitamin D level is dropping just when you need it the most. In fact, the average American’s level will drop well into the deficiency zone, increasing risk of illness, cancer, and a host of other health problems. Fortunately, latest research has provided some very simple guidelines for maintaining optimal levels of vitamin D throughout the winter.

How much vitamin D do we need?

Many current guidelines for vitamin D levels are too low because they only take into account what is needed for bone health, and will leave us susceptible to cancer and many other chronic diseases. Recently, the Endocrine Society took a bold step forward and created their own guidelines based on overall optimal health requirements. The society considers blood levels of vitamin D below 20 ng/mL to be outright deficient, 21-29 ng/mL to be insufficient, and 30—100 ng/mL to be sufficient for achieving optimal health. Unfortunately, latest research confirms that 33 percent of Americans and 30-50 percent of Canadians are outright deficient. And during the winter, your levels may drop as much as 50 percent, plunging you deep into deficiency territory. But this can be avoided with correct supplementation and, where possible, sunlight exposure.

Vitamin D from food and supplements: how much to take

In order to raise your vitamin D levels into the optimum range throughout the year, the Endocrine Society has recommended the following daily intake levels of vitamin D (from all sources):

children under one year old: 400–1,000 IU/day
children one - eighteen years old: 600-1,000 IU/day
adults: 1500-2000 IU/day

It’s next to impossible to get these amounts through food alone. Only oily fish, fortified foods, mushrooms, and eggs contain significant amounts. Recent studies in the US have estimated that, from food alone, women get less than 210 IU/day, men get less than 320 IU/day and children between one and eight years old get less than 250 IU/day of vitamin D. Correcting these gaps through supplementation is quite safe, as the current upper limits for most children and adults range from 4,000 IU/day (Institute of Medicine) to 10,000 IU/day for adults (Endocrine Society). Beyond supplements, sensible sun exposure can also be safely used to further increase vitamin D levels for optimal health.

Vitamin D from sunlight (real or artificial)

If you live south of Atlanta, Georgia, you’ll still be able to make vitamin D all year round from sensible sun exposure (i.e. exposing at least arms and face 5-30 minutes daily, every other day). But vitamin D production is no longer possible from November to February for those living north of Atlanta, and from mid-October to mid-March for those living north of New York City. During those times it is especially important to consider supplementation and/or safe use of indoor tanning facilities. If you do choose to use indoor tanning, seek out tanning beds with a high UVB ratio, because they damage the skin less for the same amount of vitamin D produced. A recent study found that bulbs with six percent UVB were twice as efficient at producing vitamin D (before erythema) compared to those with two percent UVB. For best results, some researchers recommend a minimum of 1.5 percent UVB. Does indoor tanning work? One study found that twice weekly tanning raised vitamin D levels to a healthy 46 ng/mL compared to the average (and insufficient) 24 ng/mL seen in comparable non-tanners.

So if you want to make this winter a healthy one, be sure to consider the Endocrine Society’s guidelines on optimal vitamin D supplementation and pursuing safe sun/indoor tanning exposure.




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