5 Best Ways to Get Enough Vitamin D with Inadequate Sun Exposure

May 1, 2022

by Cathe Friedrich

Vitamin D is a must for healthy bones and the immune system. Yet, up to 40% of the population falls short of meeting their body’s vitamin D needs. Vitamin D deficiency is more common in:

People with darker skin color
The elderly
Those who are obese
Those who get little sunlight

The best source of vitamin D is sun exposure. When you expose your bare skin to the sun ray’s, your body transforms a vitamin D precursor on your skin to a vitamin D precursor. Then, with a little help from your liver and kidneys, makes active vitamin D. To get enough vitamin D from sunlight, you need around 15 minutes of sun exposure on bare skin 4 or 5 days per week. If you have darker skin, you need even more sun exposure to raise your vitamin D level to a healthy range.

During the winter months, when there’s less direct sunlight, vitamin D levels can fall. So, how can you get enough vitamin D if you don’t get enough sunlight? Let’s look at some possible ways.

Fatty Fish

One of the best sources of vitamin D at the supermarket is wild-caught salmon. Wild-caught means the fish was caught from the ocean rather than raised on a farm. A study found wild-caught salmon contains around 988 IU of vitamin D per serving. Sardines are another fatty fish that contains vitamin D, around 200 IU per serving, while canned tuna has around 268 IU of vitamin D per serving. Since you need around 800 IU of vitamin D per day, it’s hard to meet your body’s vitamin D requirements by eating fatty fish alone.

Eating fish can help, if you’re still able to get some sunlight. To get enough vitamin D from fatty fish alone, you’d need to eat fish, like wild-caught salmon daily. Most experts don’t recommend that, since some fish contain heavy metals and toxins they absorb from the polluted ocean.

Egg Yolks

Egg yolks can have variable amounts of vitamin D. While the average egg yolk only contains around 40 IU of vitamin D, egg yolks from chickens that eat feed enriched with vitamin D may contain much higher quantities, as much as 6,000 IU per egg yolk. So, the amount of vitamin D in eggs is variable. If you’re counting on egg yolks to be a significant source of vitamin D, look for ones from chickens that consume feed high in vitamin D. These are available at some markets. The white portion of eggs contains no vitamin D, although they’re high in protein.

Fortified Foods

Fortified foods are packaged foods that manufacturers add vitamin D to. Some of the most common are packaged yogurt, dairy milk, plant-based milk substitutes, breakfast cereals, and orange juice. These products can boost your vitamin D intake, but be careful. Not all products have added vitamin D and some contain trivial quantities. So, read the label.

Also, the form of vitamin D in fortified foods is usually vitamin D2. Vitamin D2 comes from non-animal sources, while vitamin D3 is animal based. However, some research suggests vitamin D2 may not be as efficient at raising your vitamin D level. The research isn’t clear on this. One study found vitamin D3 was 87% more efficient at increasing vitamin D than vitamin D2. Still, foods that contain vitamin D2 can increase your vitamin D level. One study found both vitamin D3 and vitamin D2 raise vitamin D levels, but vitamin D3 stays in your system longer.

Mushrooms Exposed to Sunlight

When you expose mushrooms to ultraviolet light from the sun, they produce vitamin D2, and it only takes a few minutes of light exposure after harvest to boost vitamin D production in mushrooms. Surprisingly, mushrooms exposed to ultraviolet light can be a better source of vitamin D than salmon. One study found that exposing mushrooms to light can lead to as much as 164 micrograms of vitamin D per 100 grams. That’s far more than the 30 micrograms per 100 grams in salmon. You can get the benefits at home by placing mushrooms in direct sunlight for an hour or so on a bright, sunny day. Repeat the next day to ensure the mushrooms had enough time to produce vitamin D2.

Vitamin D Supplements

If you can’t get enough vitamin D from the above food sources, and your sun exposure falls short, consider taking a vitamin D supplement. Most doctors recommend taking 800 IU to 1000 IU per day, but if your vitamin D level is already low, that might not be enough. Your healthcare provider can check your level and tell you how much to take. If you don’t know your level, don’t take more than 2,000 IU per day.

The Bottom Line

Now you know some of the best food sources of vitamin D. Since most people don’t eat enough of these foods, they depend on sun exposure or a vitamin D supplement to maintain a healthy vitamin D level. If you take a supplement, talk to your physician first and consider checking your vitamin D level so you can fine-tune your dose.

References:

J Agric Food Chem. 2011 Aug 24;59(16):8724-32. doi: 10.1021/jf201255b. Epub 2011 Jul 25.
Cashman KD, Kiely M, Seamans KM, Urbain P. Effect of Ultraviolet Light-Exposed Mushrooms on Vitamin D Status: Liquid Chromatography-Tandem Mass Spectrometry Reanalysis of Biobanked Sera from a Randomized Controlled Trial and a Systematic Review plus Meta-Analysis. J Nutr. 2016 Mar;146(3):565-75. doi: 10.3945/jn.115.223784. Epub 2016 Feb 10. PMID: 26865648.
Food Chem Toxicol. 2013 Jun;56:278-89. doi: 10.1016/j.fct.2013.02.009. Epub 2013 Feb 26.
Lu Z, Chen TC, Zhang A, Persons KS, Kohn N, Berkowitz R, Martinello S, Holick MF. An evaluation of the vitamin D3 content in fish: Is the vitamin D content adequate to satisfy the dietary requirement for vitamin D? J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):642-4. doi: 10.1016/j.jsbmb.2006.12.010. Epub 2007 Jan 30. PMID: 17267210; PMCID: PMC2698592.
“UV light turns mushrooms into vitamin D bombs.” 10 Jul. 2012, sciencenordic.com/a/1374265.
J Clin Endocrinol Metab. 2011 Mar;96(3):E447-52. doi: 10.1210/jc.2010-2230. Epub 2010 Dec 22.
N Engl J Med 2019; 380:33-44. DOI: 10.1056/NEJMoa1809944. January 3, 2019.