Vitamin D is an essential micronutrient for humans. Called the “sunshine vitamin,” it’s a building block of strong bones and involved in a number of processes. Recent research has also identified it as important to the immune system, particularly in the fight against COVID-19 coronavirus.
A study published October 27, 2020 in the Journal of Clinical Endocrinology and Metabolism found that while about 47 percent of those in the study not infected with COVID-19 were vitamin D-deficient, a whopping 82.2 percent of those who tested positive were deficient in serum vitamin D levels. (1)
They also noted that the vitamin d-deficient COVID-19 patients exhibited more hypertension and cardiovascular disease than those who weren’t deficient. The deficient group also had longer hospital stays.
At the risk of sounding like I’m saying “I told you so,” I wrote about this issue back in May of this year. (Vitamin D And The Risk Of Infection And Severity Of Symptoms Of COVID-19 Coronavirus) Since that time, multiple studies have reinforced this reality. Makes you wonder why this “science” isn’t making it into the mainstream news…but I digress.
If you ask your doctor how much vitamin D you need to be healthy and boost your immune system, he may tell you that you get enough from your diet or to take a cheap, over-the-counter multi-vitamin. It’s possible (not likely) that you may get enough from food. Cheap multi-vitamins? Save your money.
Your doctor might also warn you of vitamin D toxicity. Unless you’re cramming down vitamin D supplements like candy, this is highly unlikely. How much “D” do you need? I’m glad you asked!
The US National Academy of Medicine suggests 600 – 800 IU per day, which is also the current Reference Daily Intake (RDI,) while the US Endocrine Society says adults need 1,500 – 2,000 IU per day. (2,3) The important measure is the serum, or blood levels of vitamin D. Currently, the optimal blood level of vitamin D is thought to be between 20 and 50 ng/ml. (4, 5)
Interestingly, in the study that found 82.2 percent of COVID-19 patients deficient in vitamin D, the average serum levels were just at or below the low end of the optimal range, 20 ng/ml. Previous studies have linked low vitamin D levels to more severe symptoms as well.
Vitamin D is important for healthy bones, a healthy immune system and certainly may help you fend off COVID-19. But how do you ensure you’re getting enough of it?
I’m going to share three basic ways you can boost your vitamin D to levels that are likely to work for you.
Get Some Sun
Beneath and within your skin is a unique form of cholesterol. It is key to helping you convert sunlight into vitamin D. But it needs direct sunlight exposure to do its job. Sitting inside by the window won’t cut it. Go outside, get some fresh air and get as much skin as possible exposed to the sun!
Of course, the further you live from the equator, the less intense this effect becomes. Even with that reality, 30 minutes of sunlight exposure in a place like New England or Toronto can give you the same effect as taking 10 – 20,000 IU of vitamin D.
The best way to maximize your vitamin D boost from the sun is to get exposure on your “big parts.” Legs, stomach, back, shoulders and arms have large surface areas and absorb sunlight well. While the sun feels good on your face, it may not be a good idea to get too much exposure on it, as it may age you prematurely.
Why make the effort to get your vitamin D from sun exposure? Research has shown that vitamin D generated this way circulates in the body significantly longer than supplemental “D,” perhaps up to twice as long. (6) That’s a pretty good return on your sunbathing investment!
Of course, there are factors which can mitigate your efforts at sunshiny vitamin D boosting. Those with darker skin will need more exposure than their paler counterparts. This is due to a greater presence of melanin in darker skin, which impedes vitamin D production. Age, too, is an influence. Older folks don’t produce “D” as efficiently.
If you just read all that and said ” I live in Seattle” (or anywhere else with mostly cloudy weather,) don’t give up yet. Any lamp that emits UVB light will also stimulate vitamin D production in the skin. Be careful, though. Limit your exposure based on the strength of the UVB light and the paleness of your skin. 15 minutes is likely about the maximum UVB exposure that you can or should handle.
Get It From Food
You have a number of foods to choose from that have naturally high vitamin D levels. On top of that, many foods are fortified with vitamin D, including some cereals and instant oatmeal. These can provide between 50 and 140 IU per serving (1/2 cup.)
Milk, both cow’s milk and soy milk, are fortified with vitamin D in some countries. Fortified cow’s milk can contain 115 – 130 IU of “D” per cup, as well as riboflavin, calcium and other nutrients. Soy milk can be fortified to contain 105 to 117 IU per cup. Soy milk is a good choice for vegans to get their vitamin D, since almost all foods containing vitamin D are animal products.
Fortified orange juice contains 100 IU per cup. This is a good choice for people who are lactose intolerant or have allergies to milk and milk products.
The only plant-based food that is a good source of vitamin D is mushrooms. While they produce vitamin D2, which likely is not as effective as D3 (animal-sourced foods contain this type,) they are a good choice for vegans and vegetarians.
Whenever possible, choose wild or those grown pastorally or organically over commercial mushrooms. Mushrooms synthesize “D” much like humans do, meaning they need sunlight to do it. Commercial mushrooms are grown in the dark, so will have much lower vitamin D levels. Wild or outdoor-grown mushrooms can yield as much as 2,300 IU per 100 gram serving!
Egg yolks are also a good source of vitamin D. This is especially true for free-range or pastorally grown chickens. They spend more time in the sun and typically eat a richer, more natural diet.
While the average commercial egg yolk has about 37 IU of “D” per serving, eggs from pasture-raised chickens can have levels 3 – 4 times that high. (7) If the chickens have been fed a vitamin D-enriched feed, you can expect vitamin D yields of up to 6,000 IU per yolk! (8) That’s a serious dose of vitamin D!
Those who eat fish, particularly oily fishes, have a good shot at getting enough “D” in their diets. Canned light tuna, for example, packs 268 IU into a 3.5 ounce serving. The downside to tuna is the relatively high mercury content, in the form of methylmercury. White tuna is a better choice due to the lower mercury content. Most people can eat up to 6-8 ounces per week with minimal mercury risk.
How do you feel about sardines? These oily little critters are another good source of vitamin D, with about 175-180 IU in a typical 3.8 ounce can. Mackerel and halibut are even better. with a half a filet of mackerel having 360 IU of vitamin D and half a filet of halibut packing 384 IU.
What about herring? This silvery fish is considered a delicacy in some parts of the world. It’s eaten raw, smoked and even pickled. While pickled herring has a nice 112 IU dose of vitamin D per 3.5 ounces, it’s also high in sodium, which can be an issue for some folks.
Fresh Atlantic herring, however, is a better choice. This variety provides 216 IU of “D” per 3.5 ounce serving.
When it comes to serving up serious doses of vitamin D, salmon leads the way among our fish choices. However, how your salmon was raised makes a difference. Wild caught salmon contains far more vitamin D than the farmed version. In fact, farmed salmon typically contain only about 25 percent of the vitamin D found in wild caught fish. (9)
Farmed Atlantic salmon delivers about 525 IU of vitamin D per 3.5 ounce serving. On average, wild caught salmon provide a whopping 988 IU of vitamin D per serving, with some studies finding vitamin D levels as high as 1,300 IU per serving. (10)
Get It From Supplements
Supplementing with vitamin D is really our last choice, but for some people, it may still be the best way to ensure adequate vitamin D levels. Cod liver oil is a popular supplement for supplying vitamin D.
Cod liver oil provides 488 IU of vitamin D per teaspoon. That’s one reason it has been used in the past to bring sagging vitamin D levels up in some people. It’s an easy way to get large amounts of vitamin D into a person in order to restore baseline healthy levels.
One issue with cod liver oil is that it’s also a great source of vitamin A, offering 1 1/2 times the amount recommended for humans in a give day. Great, right? A 2 for 1? Not really, vitamin A is toxic in high amounts. So be cautious if you’re using it as a source of vitamin D.
If you decide to use a supplement, look for one that provides the vitamin in the form of D3, or cholecalciferol. This type is shown to be better at getting vitamin D levels up and keeping them there than it’s counterpart, D2 (ergocalciferol.) (11)
Vegans will have a hard time finding D3 supplements that aren’t animal-derived. A few are available that have been synthesized from lichens, but the majority of D3 comes from animals. Most vegan vitamin D supplements are plant-based.
Unless your current vitamin D levels are dangerously low, you can probably begin by taking about 1,000 to 4,000 IU a day. (12) If you’re unsure about your levels, you may want to have them checked. If they’re low, ask your doctor, nutritionist or dietitian about how to safely raise them.
With everything we’re learning about vitamin D and our health, especially immune health, it may be worth the time and effort to get yours checked and get serious about raising those levels. With so many good options for getting more vitamin D, it’s a precaution just about everyone can take.
Keep the faith and keep after it!