The easiest way to get vitamin D is through sunlight, but multiple factors limit our exposure. COVID-19, heatwaves, wildfire smoke, and increased crime have kept many of us indoors more than usual. Now, with the change in season and time, the days have become shorter. Some people wonder about their vitamin D status while others are assured, unconcerned, or unaware. Are you getting enough vitamin D? What is vitamin D? Why should we care? How much do we need? How can we get it now? Here is what, why, and how.
Notes: This post was last updated October 18, 2021 and shares general public health recommendations but does not offer or replace any individualized health advice, which is best provided by your medical care providers.
What is Vitamin D?
Vitamin D, like other vitamins, is an organic substance that is vital for cells to work. Vitamins come from living matter (plants and animals) and are 1 of 6 nutrients (vitamins, minerals, water, carbohydrate, protein, and fat). Like minerals, vitamins are micronutrients — meaning they are needed in tiny amounts and supply no calories or energy but rather help the body obtain them from macronutrients (carbohydrate, protein, and fat). Vitamin D, like vitamins A, E, and K, is fat-soluble — meaning it dissolves in fat. It is not excreted as readily as water-soluble vitamins (B and C) and is stored in body fat. Because it can be made when sunlight reacts with a cholesterol compound in the skin, it is called the “sunshine vitamin.”
Why Should We Care?
Vitamin D helps the body absorb calcium, so it supports bone development and maintenance, muscle contraction, and nerve messaging. A deficiency can lead to soft deformed bones (rickets) in children, muscle weakness in children and adults, and bone pain (osteomalacia), bone porousness (osteoporosis), falls, and fractures in adults.1 With sensors on cells throughout the body, vitamin D also has roles in cell differentiation and growth, immune response, and hormone signaling and has been linked to some cancers, immunity, diabetes2, and depression.3
Although vitamin D can be obtained easily through sunlight, certain factors may limit one’s exposure, such as living primarily indoors or in locations where the altitude is high, the latitude is far from the equator, or the air is polluted with smog, avoiding the sun due to skin cancer risk, and wearing correctly applied sunscreen and full clothing.2 Certain situations and conditions may also hinder intake or processing of vitamin D, such as restricted diet due to personal belief or preference and food allergy or intolerance, maldigestion due to pancreatic or liver disease, malabsorption due to intestinal disorder, decreased metabolism due to dark or aged skin and kidney or liver disease, and decreased release due to excessive body fat.3
How Much Do We Need?
According to the Food and Nutrition Board of the Institute of Medicine, healthy Americans who get minimal sunlight need the amounts above to maintain normal calcium metabolism and bone health.3 In general, the Recommended Dietary Allowances (RDAs) are based on the nutritional needs of different genders at different stages of the life cycle. Some professional societies and many other countries have different guidelines.3
How Can We Get It Now?
1. Take Advantage of Available Sunlight
Soak up some sun while walking, gardening, or taking a lunch break outside. Five to 30 minutes to the face, arms, and hands between 10 a.m. and 4 p.m. at least twice weekly has been suggested.3 Up to 15 minutes around noon daily may provide 25 micrograms (1000 international units) of vitamin D for light-skinned people during spring, summer, and fall months.2 Skin cancer is a concern with sun exposure, however, so sunscreen and protective clothing have been recommended.1,3 Tanning beds also pose a risk.1,3 Fortunately, vitamin D is obtainable from the diet, too.
2. Consume Good Dietary Sources
Eat foods and drink beverages that contain significant amounts of vitamin D. Examples include fatty fish, fish canned in oil, fish oil, mushrooms treated with ultraviolet light; and milk, milk substitutes, orange juice, and ready-to-eat cereals fortified with vitamin D.4 Eggs from hens fed the vitamin are also available.2
Check package labels for vitamin D content. If the percent daily value (%DV) is between 10 and 19, the item is a good source. If the %DV is 20 or more, the item is high in vitamin D and if it is 5 or less, it is low.5
3. Ask a Health Care Provider About a Supplement
If adequate vitamin D cannot be obtained through sunlight, the diet, or both, or processed due to a health condition, one can ask a doctor, pharmacist, or dietitian about a supplement. Supplements can be toxic, interact with medications,3 and compete with other nutrients. A clinician can assess signs and symptoms of insufficiency including a blood test and recommend an appropriate supplemental form, dose, and preparation.
In the U.S., supplements are regulated by the Food and Drug Administration after they enter the market. A seal of approval can verify that a product contains the ingredients that are listed and that there are no harmful levels of contaminants. However, it cannot verify that the product is safe or effective.6 Food and beverage should always be the first choice for nutrients. Not only do they bring pleasure and satisfaction with eating and drinking, but they provide energy and other beneficial substances3 in the most balanced way.
Are You Getting Enough?
Do you think you’re getting enough vitamin D? Are any factors limiting your sun exposure or hindering your intake or processing? Are you getting sunlight, consuming good dietary sources, or both? Could you be getting too much? Can you think of any other good sources? Please comment and share this post below.
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- U.S. Department of Health & Human Services National Institutes of Health Office of Dietary Supplements. (Updated March 22, 2021). Vitamin D Fact Sheet for Consumers. https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
- Oregon State University Linus Pauling Institute Micronutrient Information Center. (Last Updated 2/11/21). Vitamin D. https://lpi.oregonstate.edu/mic/vitamins/vitamin-D
- U.S. Department of Health & Human Services National Institutes of Health Office of Dietary Supplements. (Updated March 26, 2021). Vitamin D Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
- U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at https://health.gov/our-work/food-nutrition/previous-dietary-guidelines/2015.
- U.S. Food and Drug Administration. (2020, May 5). Daily Value on the New Nutrition and Supplement Facts Labels. https://www.fda.gov/food/new-nutrition-facts-label/daily-value-new-nutrition-and-supplement-facts-labels
- U.S. Department of Health & Human Services National Institutes of Health. Frequently Asked Questions (FAQ). (Reviewed June 10, 2021). https://ods.od.nih.gov/HealthInformation/ODS_Frequently_Asked_Questions.aspx#Regulatory