Vitamin D, Health, and Immunity
Over the last few years, there has been an incredible amount of interest in the role that vitamin D plays in health and wellness. With the arrival of Covid-19 at the beginning of 2020, this immunity-supporting vitamin became even more important.
What is Vitamin D?
Vitamin D is a fat soluble vitamin that is a bit different from other vitamins you typically get from food. Your body can actually make all the vitamin D it needs. The skin contains receptors that are able to make vitamin D from cholesterol when exposed to the sun.
The main roles of vitamin D include calcium metabolism, maintaining bone strength, gut integrity, and immunity. A deficiency in vitamin D can result in a variety of different health problems, mostly related to bone health and poor immune function.
Even though the body can make the vitamin D it needs, it is estimated that approximately 50% of people are deficient in this important vitamin. The reason is that many of us spend a lot of time indoors these days or live in colder areas, where the sun isn’t strong enough for most of the year. This wide-spread deficiency has been linked to a variety of health problems, including the severity of Covid-19.
Vitamin D and Health
Here are just a few of the roles vitamin D plays in the body:
Maintaining a healthy weight.
People who are obese tend to have lower levels of vitamin D. Being a fat soluble vitamin, D can get trapped inside fat cells, preventing circulation to areas of the body where it is needed. Research has also found that vitamin D may also help increase weight loss for those on a calorie-controlled diet.
Vitamin D helps the body absorb calcium and plays a role in maintaining strong bones and healthy muscles. A deficiency of vitamin D can increase the risk of bone fractures and osteoporosis.
Vitamin D helps support a strong immune system by reducing inflammation and helping maintain gut integrity, an important part of strong immunity. A 2017 meta-analysis found that daily supplementation with vitamin D is protective against respiratory infections. This effect may be even more pronounced for those with vitamin D deficiency.
Vitamin D and Covid-19
Vitamin D has received a lot of attention for the role it plays in the severity of Covid-19. Although there is still a lot to be learned about the progression of this disease and why certain people experience such severe symptoms, there seems to be an emerging correlation between vitamin D deficiency and severe Covid.
A study published in August of 2020 found that of those in the ICU with severe Covid-19 symptoms, 81% also had vitamin D deficiency. Although this was a small correlational study of only 42 patients, it demonstrates that there might be some connection between vitamin D and the severity of the disease.
Another study from November 2020 compared the vitamin D levels of asymptomatic Covid-19 patients to severely ill patients requiring ICU admission. Of the asymptomatic group, approximately 33% were deficient in vitamin D, whereas in the symptomatic group 97% were deficient. Inflammatory markers were also found to be higher in those with severe Covid-19.
Both of these are correlational studies, which at this time are the best we have. As we begin to learn more about Covid-19, the understanding of the connection between vitamin D and this illness will continue to emerge.
How Much Vitamin D Do You Need?
Since vitamin D is a fat soluble vitamin, it does hold a risk of toxicity when you take it in supplement form. You will never develop a vitamin D toxicity from too much sun exposure or from food.
The upper limit for vitamin D is 4000 IU. Too much vitamin D beyond the upper limit for an extended period of time can dangerously increase calcium levels in the body, which leads to kidney stones, dehydration, and possibly renal failure.
Ideally, before you take a vitamin D supplement, you should get your levels checked by your doctor. Knowing your level will help determine the optimal dose for you. A vitamin D less than 30 mmol/L is considered a deficiency, but optimal levels are likely 50 mmoL/L or higher. Depending on your number, your doctor may give you a high dose vitamin D supplement for a period of time to get your levels up.
If your vitamin D level is normal or you cannot get tested at this time, a maintenance dose of 1000-1500 IU per day is recommended for most people. If you live in colder areas, spend a lot of time inside, are above 65 years old, or have darker colored skin, you may want to consider a higher dosage above 2000 IU. It is always best to speak to your doctor before taking any supplements.
Getting Your Vitamin D
If you need to get your vitamin D levels up, or just want to support your health and immunity, you can use a combination of supplements, sunshine, and food.
If you live in a warmer climate or it is summer time, aim to get outside for 15-30 minutes a day with direct sun exposure on your skin. The amount of time you need to spend in the sun to get enough vitamin D can vary, depending on latitude, your skin color, and your age. People above 65 years old or with darker skin may have a hard time getting enough vitamin D from sun exposure alone.
Additionally, anywhere above 37 degrees latitude (which covers about half of the United States) you will have a hard time getting enough vitamin D during most of the year. This means you may need to turn to food or a supplement.
Food is a poor source of vitamin D, most people are only able to get about 5-10% of their vitamin D needs in food. Foods that contain small amounts of the vitamin include: fatty fish, fortified milk, and eggs.
For most people, to maintain adequate levels of vitamin D, they will need a supplement. Look for one that contains vitamin D3 (cholecalciferol), which is better absorbed than the other form D2 (ergocalciferol). One thing to note is that not all vitamin D3 is vegan. It can be sourced from plant lichen, but most supplements come from animal sources.
With so many important roles, vitamin D is an important vitamin to be aware of and monitor from time to time. Keeping your levels up can help make weight management easier, help you maintain strong bones, and support optimal immune function.
Ana Reisdorf, MS, RD
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