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The Importance of Vitamin D in the Fall & Winter

Updated: Oct 6, 2020

Vitamin D sunshine

Vitamin D is primarily produced in the body from absorbing UVB rays from sunshine. Although we receive a majority of vitamin D from exposure to the sun, there are some foods that contain vitamin D and well as various supplementations. In this blog we will discuss the importance of vitamin D, sources of the vitamin, why it's important to ensure you're getting enough vitamin D in the colder months, and the health benefits of vitamin D.

A recent study showed that an overwhelming amount of Americans (41.6%) are deficient in vitamin D all year round, not just the colder months. Vitamin D has a long list of health benefits but here is a list of the most common benefits (1):

1. Maintains the health of bones and teeth

2. Support the health of the immune system, brain and nervous system

3. Regulate insulin levels and aid diabetes management

4. Support lung function and cardiovascular health

5. Influence the expression of genes involved in cancer development

Low levels of vitamin D have been linked to serious health consequences and chronic diseases, including the following (1):

1. Osteoporosis

2. Cancer

3. Depression

4. Weight Loss

5. Diabetes

6. Hypertension

7. Multiple Sclerosis

So how much time in the sun is required to met our vitamin D recommendations? The amount of vitamin D produced from sunlight depends on where you live, the time of day, seasonal changes, and your pigmentation. Studies show that the best opportunity for direct exposure is midday, it is suggested that just 15-30 minutes in the sun (with certain circumstances discussed above) would be a sufficient amount of time to meet your recommended daily values. This becomes harder during the winter, thus the need for supplementation. (4)

Vitamin D levels tend to drop in the winter months for a few reasons: colder weather (less time outside=less exposure to the sun), shorter days in the winter, and the suns UVB rays become so indirect that our bodies struggle to produce adequate vitamin D levels. With prolonged decreased vitamin D issues in the colder months we run into an issue called Seasonal Affective Disorder.

The following is a table established by the Food and Nutrition Board (FNB). They determined these values as a recommended dietary allowance (RDA) for vitamin D, maintaining this amount is sufficient to maintain bone health and normal calcium metabolism in healthy people (3):

Vitamin D recommended values

Natural exposure to sunlight is the most common source of vitamin D but the vitamin is naturally found in a few foods as well as artificially fortified foods. The following table (2) highlights some of these foods:

Vitamin D-rich Foods

As you can see, it is important to make sure you have a sufficient amount of vitamin D, and sometimes that's hard when you're not experiencing enough daily sunlight with winter conditions and work. If you have any concerns about your vitamin D levels we have some great supplements in the office we'd love to discuss with you!



2. U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019.

3. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.



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