Vitamin D benefits: a handful to consider

There’s nothing sunny about vitamin D deficiency. Unfortunately, that’s a situation 41.6% of adults in the United States are facing since they don’t get enough of the “sunshine vitamin” (Forrest, 2011).

And people with darker skin are at an even higher risk; 82.1% of African Americans and 69.2% of Hispanics don’t get enough. At those rates, it’s clearly a public health concern. But maybe knowing the benefits of vitamin D will give you more incentive to boost your intake.

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Vitamin D (calciferol) is actually a group of steroids that act like hormones in the body. For humans, there are two main essential forms: vitamin D2 (ergocalciferol) and D3 (cholecalciferol).

It’s important to note that each form of vitamin D offers the same health benefits. It’s also a fat-soluble vitamin, which means it’s stored in your body’s fat tissue and is absorbed along with fats in your diet.

We can produce the Ds through sun exposure thanks to UVB rays, but the risk of skin cancer means increasing your dietary intake, and taking vitamin D supplements are likely the safest options for preventing deficiency (translation: we’re not giving you an excuse to go out without sunscreen).

But simply not being deficient doesn’t get you off the hook health-wise. Vitamin D is vital enough to your body that even low blood levels have been associated with increased risk of cardiovascular disease, asthma in children, and cognitive impairment in older adults (Kent, 2009).

The Ds are also essential for bone health, critical cellular functions from cell growth to death, and potentially even diabetic health (Judd, 2009; Ali, 2017).

Chances are good your vitamin D levels aren’t where they should be, but it’s always advisable to get your numbers checked by a medical professional. Too much vitamin D can also be dangerous, so you shouldn’t start taking a supplement before knowing where you stand.

Since the gut plays a key role in absorbing vitamin D and your liver and kidneys convert D2 and D3 into their active forms, people suffering from conditions affecting any of these may struggle to get enough of the nutrient.

So if you have inflammatory bowel disease (such as Crohn’s disease), celiac disease, liver disease, or are an alcoholic, you should work closely with your healthcare provider to get enough of the vitamin through dietary supplements and hitting your recommended dietary allowance.

Additionally, many of the studies that look into the efficacy of supplements are only conducted in specific populations or in people who are already deficient in the vitamin, such as people who have a vitamin D deficiency. The following items are some of the benefits that may be seen in some people who take vitamin D, but these benefits might not apply to everyone.

1. Protects against the flu

There’s no better reason to start watching your vitamin D intake than the approach of flu season. The sunshine vitamin regulates your immune system, and one study found that vitamin D supplementation may reduce your chances of catching the flu (Urashima, 2010).

2. Reduces the likelihood of MS

More research needs to be done in some areas about the benefits of vitamin D. This is one of them. But a study did find an association between higher levels of vitamin D and lower risk of developing multiple sclerosis (MS) (Munger, 2006). 

Another found that the sunshine vitamin might have a protective effect from MS, but this association was found only with vitamin D supplements and not with dietary vitamin D (Munger, 2004).

3. Reduces the risk of heart disease

Deficiency in vitamin D has long been associated with increased risk of heart disease, hypertension (high blood pressure), coronary artery disease, cardiomyopathy (which makes it harder for your heart to pump), and heart failure (Judd, 2009).

Researchers aren’t sure how the Ds affect heart health, only that not getting enough clearly puts you at an increased risk. One study from 2012 found that insufficiency was linked to cardiovascular events and low survival, taking supplements boosted survival, especially in people with low vitamin D levels (Vacek, 2012).

4. Reduced risk of diabetes

Researchers have been torn over the links between vitamin D deficiency and the risk of type 2 diabetes for years now. A study from 2011 showed a clear association between insulin resistance and the risk of developing type 2 diabetes and low levels of the vitamin (Kayanijil, 2010).

But other past research disagreed. Despite supplementing at 4000 IU (international units) or 100 mcg for three years in one study, there was only a 2% difference between the group that developed type 2 diabetes and the group that did not (NIH-funded trial finds vitamin D does not prevent type 2 diabetes in people at high risk).

But even more, recent work found that perhaps that’s because this amount of vitamin D wasn’t high enough. A 2019 study used 5000 IU dosages (or 125 mcg) for six months. They found that these high doses were enough to significantly reduce the risk of patients developing type 2 diabetes who had a high-risk factor (Lemieux, 2019).

5. Reduced depression

For a while, it was unclear to researchers how exactly depression and vitamin D were connected, although there was an association between the sunshine vitamin and anxiety and depression (Armstrong, 2006).

But another study might have helped clarify that. People suffering from depression self-reported alleviation of their symptoms when they were given vitamin D supplements by researchers (Jorde, 2008).

6. Improves bone health

Many people know that vitamin D helps build strong bones, support bone health, and prevent conditions like osteoporosis––and that all of this has something to do with calcium.

In fact, vitamin D works in the gut to boost the absorption of calcium. But it also plays a role in how our body remodels bone tissue. There’s a strong link between lower levels of vitamin D in blood serum and low bone mineral density in menopausal and postmenopausal women (Bener, 2015).

And osteoporosis isn’t the only condition it can help prevent. Low D levels can also cause osteomalacia, a softening of the bones, in older adults, which can help prevent dangerous bone fractures (Sitta, 2009).

7. Reduces certain complications in pregnancies

A woman’s vitamin D needs to go up when she’s pregnant. But most prenatal vitamins only include 400 IU of the Ds (10 mcg), and these doses of vitamin D just aren’t enough, especially if dietary intake is low. 

One study found that 4000 IU of the vitamin was actually ideal for keeping pregnant women from developing low levels. The sunshine vitamin is essential for the proper development of a baby’s bones, but another study also found that getting enough is associated with a much lower risk of preeclampsia, high blood pressure during pregnancy, in expecting moms (Sasan, 2017; Hollis, 2011).

8. Supports healthy infants and early child development

Vitamin D status is essential for the healthy growth of children, even in the womb. Getting enough of the Ds is vital for bone health because of its role in calcium absorption, and deficiency has been linked to respiratory problems, infection, allergies, lower immune function, and more specifically in children (Shin, 2013).

Kids who don’t get enough of the sunshine vitamin also have a higher risk of developing rickets, a serious condition characterized by stunted growth and bone deformity (Rauch, 2003).

9. Help prevent certain cancers

Research is a bit torn here, too. We do know that one role of vitamin D is playing a part in cell growth.

And some studies have found that having enough may help prevent prostate, breast, and colon cancer. In the case of breast cancer, for example, it is believed that vitamin D helps with normal breast cell growth and may even stop the growth of cancerous cells (Trump, 2018).

Even if it takes longer for researchers to come to the same conclusion on prevention, it looks like there is a cancer-related benefit on which past studies agree. A 2019 meta-analysis of 10 clinical trials found that there was a lower risk of dying from cancer in those already diagnosed who were supplementing with vitamin D (Samji, 2019).

10. Helps improve cognitive function

Women given vitamin D supplements in a 2019 study showed improvement in learning and memory, but it did come with a side effect: Their reaction time was slower (Castle, 2019).

And past research has been more focused on preventing cognitive decline that comes with old age than improving mental functioning. Indeed, low vitamin D status is associated with accelerated loss of cognitive functions (episodic memory and executive functioning, specifically) (Miller, 2015).

So it might be worth monitoring your blood levels, so hold onto what you have for as long as possible.

11. Topical treatment can help treat psoriasis

This essential vitamin has anti-inflammatory properties, which researchers believe may help in the treatment of psoriasis (a chronic autoimmune condition) when taken as a supplement (Fu, 2011).

But it also offers benefits when applied topically. The Ds have a hand in cell growth and can actually slow it. Topical treatments for psoriasis using vitamin D take advantage of this, and they help thin the plaque on existing flares. It should be noted, though, that these aren’t for preventing new flares.

Healthcare practitioners cannot safely recommend any amount of time in direct sunlight without sunscreen. That means your best options for getting enough of the Ds are supplements and lifestyle changes that work more vitamin D foods into your diet.

Get your vitamin D status checked through a blood test before beginning supplements, though, since too much can also be dangerous. Dietary reference intakes advise that everyone between the ages of 1 and 70 get 600 IU of this vitamin daily (or 15 mcg). For those above 70, that increases to 700 IU (17.5 mcg).

If that sounds like too much vitamin D to work into your daily diet, rest assured hitting those numbers through food alone is, in fact, possible. People who enjoy fatty fish like sardines and mackerel will find it especially simple, as will those who add cod liver oil (an excellent source of vitamin D) to their supplements cabinet.

But food sources also include common items like egg yolks and dairy products like milk and cheese. Fortified foods such as orange juice and certain breakfast cereals are also good sources of vitamin D. Vitamin D3 may not be suitable for vegetarians and vegans since they’re mostly found in animal products (with some exceptions), but D2 supplements are vegan-friendly and offer the same health benefits.

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Current version

December 05, 2021

Written by

Linnea Zielinski

Fact checked by

Mike Bohl, MD, MPH, ALM

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About the medical reviewer

Mike Bohl, MD, MPH, ALM

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.