How can I raise my vitamin D levels quickly?
You can raise your vitamin D levels quickly in three main ways:
- Getting outside and exposing your skin to sunlight.
- Taking a vitamin D supplement.
- Increasing your intake of foods that contain vitamin D.
Get sun to boost vitamin D
When the UVB rays in sunlight hit your skin, a chemical process is triggered that ultimately results in the production of vitamin D. The amount of sun needed to produce enough vitamin D can vary, but research suggests that to maintain sufficient vitamin D levels:
- Aim to spend at least 5 to 30 minutes in the sun on a daily basis or at least twice per week between the hours of 10 a.m. and 4 p.m.
- Expose the skin of your face, arms, legs and hands in the sun, without sunscreen, for this minimal time period range.
The exposure to sunlight needs to be direct for this process to work—windows, clouds, smog, clothes and sunscreen can block or limit your skin's ability to take in UVB rays.
After the sun's rays hit your skin and initiate the production of a precursor of vitamin D, it takes an estimated 8 hours for this precursor to be converted into vitamin D3, which then binds to a protein that brings it to your liver. Then, there are a few other steps before this vitamin D can be turned into the vitamin's active form in your blood, called hydroxyvitamin D. When you get your vitamin D levels tested, it is hydroxyvitamin D that is measured.
Vitamin D3 from the sun’s rays has been shown to last longer in your body than the vitamin D3 from food or supplements.
However, while exposing yourself to sunlight may be one of the easiest and fastest ways to increase vitamin D levels, some downsides and other factors make it challenging or risky to get sufficient sunlight:
- More time in the sun raises your risk of skin cancer.
- Seasonal shifts and differing amounts of daylight hours can affect your ability to get enough direct sunlight.
- If you have a darker skin tone, you may need more time in the sun to produce the same amount of vitamin D as people with lighter skin tones.
Eat foods rich in vitamin D
Increasing your intake of foods and beverages that contain vitamin D is also an option if you're looking to boost your vitamin D levels. However, only a couple of foods contain vitamin D naturally, and many have only low levels of the vitamin. Foods that may help boost your vitamin D levels are:
- Cod liver oil*
- Fortified dairy and non-dairy milks
- Fortified cereals
*These foods provide 20% or more of your daily value of vitamin D per serving, and are considered high sources of vitamin D.
Try supplements, with your doctor’s supervision
The easiest and most efficient way to increase vitamin D levels may be to take supplements. Considering the skin cancer risks of using sunlight to boost vitamin D and the difficulty of getting enough vitamin D in your diet, supplements are often the primary recommendation for people who are deficient in vitamin D.
Vitamin D can be found in many multivitamin supplements, but it can also be taken on its own. There are two types of vitamin D: D2 and D3. Both types are available in supplement form, and their effect on overall vitamin D levels is roughly equivalent. However, some research has indicated that D3 may lead to a greater and more sustained elevation of vitamin D in the blood than D2.
Various studies have estimated that it takes up to 24 hours for vitamin D3 supplements to raise vitamin D levels in the bloodstream. However, vitamin D then needs to be converted to its active form (hydroxyvitamin D). After taking a high dose of vitamin D3, a study showed it can take approximately seven days for it to convert and cause a peak in hydroxyvitamin D levels, the active form tested by your doctor.
Since vitamin D is fat-soluble, the process of absorbing and converting vitamin D is aided by fat. It is helpful to take vitamin D alongside a meal that contains fat. People with health conditions like Crohn's disease, celiac disease or ulcerative colitis may have difficulty absorbing vitamin D because their condition affects the ability to absorb fat. These groups are among those who are more at risk of developing vitamin D deficiency, along with breastfed babies and people who are older, avoid the sun, have dark skin, are obese or have had gastric bypass surgery.
The critical takeaway is that vitamin D levels increase gradually. If a test reveals that your vitamin D levels are low, you'll need to consult with a doctor to determine how much vitamin D you need to take to raise your levels and keep them up.
There are mixed views on what counts as a healthy, normal or inadequate amount of vitamin D. To test vitamin D, the concentration of hydroxyvitamin D in blood serum is measured. According to the National Institutes of Health Office of Dietary Supplements:
- A serum concentration of 50 nanomoles per liter (nmol/L) or more is generally considered normal and healthy.
- A serum concentration between 30 and 50 nmol/L potentially indicates inadequate vitamin D.
- A serum concentration under 30 nmol/L means vitamin D deficiency.
- Measurements over 125 nmol/L may be too high and are associated with health risks.
While there is much debate about how much vitamin D people need, the Office of Dietary Supplements says:
- The recommended daily intake for adults is 600 IU (15 mcg).
- Older adults over the age of 70 should aim for 800 IU (20 mcg) daily.
- People deficient in vitamin D may need to take higher doses, but these decisions should be made with your doctor.
- Taking vitamin D supplements containing over 4,000 IU is not advisable without medical supervision.
- National Institutes of Health: Office of Dietary Supplements. Vitamin D Fact Sheet for Health Professionals. Last updated October 9, 2020. Available at: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. [Accessed March 25, 2021].
- Wacker M, Holick MF. Sunlight and Vitamin D: A global perspective for health. Dermatoendocrinol. 2013;5(1):51-108. https://doi.org/10.4161/derm.24494
- Heaney RP, Armas LA, Shary JR, Bell NH, Binkley N, Hollis BW. 25-Hydroxylation of vitamin D3: relation to circulating vitamin D3 under various input conditions. Am J Clin Nutr. 2008;87(6):1738-1742. https://doi.org/10.1093/ajcn/87.6.1738
- Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline [published correction appears in J Clin Endocrinol Metab. 2011 Dec;96(12):3908]. J Clin Endocrinol Metab. 2011;96(7):1911-1930. https://doi.org/10.1210/jc.2011-0385
- National Institutes of Health: Office of Dietary Supplements. Vitamin D Fact Sheet for Consumers. Last updated March 22, 2021. Available at: https://ods.od.nih.gov/factsheets/VitaminD-Consumer/. [Accessed March 25, 2021].
- Khan QJ, Fabian CJ. How I treat vitamin d deficiency. J Oncol Pract. 2010;6(2):97-101. https://ascopubs.org/doi/10.1200/JOP.091087
- Silva MC, Furlanetto TW. Intestinal absorption of vitamin D: a systematic review. Nutr Rev. 2018;76(1):60-76. https://doi.org/10.1093/nutrit/nux034
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