Over the past year, vitamin D has become a hot topic, with multiple studies suggesting a link between low vitamin D levels and an increased risk of catching COVID or developing more severe symptoms from the virus. Unfortunately, insufficient levels of vitamin D affect more people than you may realize—a 2011 study published in the journal Nutrition Research found that, among 4,495 U.S. adults studied, approximately 42% were vitamin D deficient.

Not getting your levels of vitamin D up to snuff can do more than weaken your immune response—read on to discover the potential side effects of not taking vitamin D supplements, according to a dietitian. And if you’re adding to your supplement routine, start with the Best Supplements To Buy at Costco, According to Experts.

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If you’re not taking vitamin D supplements, you may find that your immune system isn’t working as well as you might hope.

“Insufficient vitamin D is associated with poor immune function,” says Heidi Moretti, RD, resident nutritional advisor to Sovereign Laboratories. “This occurs because vitamin D is critical to forming a balance of T cells by increasing T-regulatory cells, which keep the immune system healthy. It also increases a protein that helps fight infections known as cathelicidin.” For some easy ways to boost your immune health, check out the 30 Best Immune-Boosting Foods.

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Whether you have a family history of cancer or have risk factors for certain types of cancer, not taking vitamin D supplements may put you at greater risk for various types of the disease.

“Almost all types of cancer risk are increased in relation to low vitamin D. This is thought to be because of the impaired immune response that occurs with deficiency,” says Moretti. In fact, 2019 research published in the Journal of the National Cancer Institute found that higher levels of vitamin D were linked to significantly lower colorectal cancer risk, while a 2016 study published in the journal Endocrinology found a link between low vitamin D levels and breast cancer growth and metastasis.

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If you find yourself struggling to find the energy to complete daily tasks that once came easily to you, your vitamin D status may be to blame.

“This is because vitamin D is involved in bone health and muscle strength. Having enough vitamin D can also reduce inflammation in these tissues, which can calm down pain, while sometimes simultaneously reducing fatigue. Vitamin D is the central regulator for many hormones, so it is no wonder that people who are deficient end up feeling tired and achy,” explains Moretti.

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Heart disease is the number one killer globally, and your vitamin D status may play a significant role in your risk of developing cardiovascular issues.

“The heart muscle requires vitamin D to help improve the uptake of electrolytes in the heart muscle,” says Moretti. In fact, according to a 2018 review of research published in the journal Clinical Hypertension, low vitamin D levels are associated with higher rates of hypertension, death from cardiovascular disease, and death from all causes. If you want to improve your heart health, check out The Best Foods That Can Help Lower Your Risk of Heart Disease, and for more healthy living news delivered straight to your inbox, sign up for our newsletter!

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