8 Signs of Selenium Deficiency You May Be Ignoring

What is selenium?

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You may not think much about this nutrient when vitamins like C and D or calcium get all the buzz. (Here are the signs you’re  not getting enough calcium.) “It’s a forgotten trace mineral,” says Staci Small, RD, of Indianapolis-based The Wellness Philosophy. “You need it in much smaller quantities than many other nutrients, but there are many ways selenium benefits the body,” she says. Selenium plays a role in reproductive health, thyroid function, DNA synthesis, and it’s also an antioxidant, according to the National Institutes of Health.

How much do you need?

Women and men need 55 mcg per day of selenium, which is considered a trace element. (Women who are pregnant or breastfeeding need 60 and 70 mcg, respectively.) Most people in the United States do get adequate amounts in their diet, though those who have an inflammatory bowel disease (like ulcerative colitis or Crohn’s disease) could be at risk for selenium deficiency, one study found. A simple blood test can tell you your numbers—and the following signs of deficiency will let you know if something is really wrong.

Selenium Deficiency Symptom: You’re losing your hair

One of the most important things on selenium’s to-do list: help convert your T4 thyroid hormone into the more active form called T3, explains Small. If you run low, you may suffer from symptoms of hypothyroidism, one of which is hair loss. “There can be many reasons for hair loss, so it’s your health practitioner’s job to know what to test for,” says Small.

Selenium Deficiency Symptom: You’re so tired

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Another common hypothyroid symptom: fatigue. This may be a result of poor selenium levels slowing down your thyroid. “We want to knock out the obvious lifestyle factors before looking at selenium,” says Small. That may be ensuring that your diet has adequate levels of carbohydrates, protein, and fat, looking for a vitamin D deficiency, or analyzing iron levels. Then, be sure to follow these healthy habits for your thyroid.

Selenium Deficiency Symptom: You’re gaining weight

When you experience unwanted weight gain, you’ll want to get to the root cause. Once again, your thyroid’s thirst for selenium may play a role, and fixing that inadequacy can help your thyroid get back online. Although Small first looks at diet when a client is gaining weight, she will consider testing selenium levels down the line. To find out why you’re packing on the pounds, consider these surprising causes of weight gain.

Selenium Deficiency Symptom: You’re not functioning at your best

Selenium is needed to form selenoproteins, says Small, including glutathione peroxidase: “It’s one of the body’s main ways to take harmful toxins and turn them into harmless byproducts,” she says. “Deficiencies in this can lead to pretty serious health consequences,” she notes.

Selenium Deficiency Symptom: You may be at a higher risk for certain cancers

You’re probably up for doing whatever you can to prevent cancer—and maintaining optimum levels of selenium may reshuffle the deck in your favor. In a 2014 Cochrane Review, researchers analyzed 55 observational studies to look at the link between selenium and cancer. They found a 31 percent lower risk of cancer associated with higher selenium exposure, particularly with stomach, bladder, and prostate cancer. But other trials failed to show a benefit from selenium. Without concrete evidence, the authors conclude that supplements probably aren’t the answer. Instead, focus on the foods you can eat that will provide a range of health benefits, including selenium-rich foods like asparagus, broccoli, and mushrooms. And while you’re at it, you may want to avoid these 10 surprising things that can cause cancer.

Selenium Deficiency Symptom: You’re sick all the time

First, make sure you’re washing your hands regularly, you got the flu shot, and you’re sleeping long enough and soundly (try these 13 secrets from sleep doctors). But you’re not doing yourself any favors if your selenium levels are low. “Without the ability to adequately make glutathione peroxidase, your immune system can’t function properly, and you may find you’re sick more often,” says Small.

Selenium Deficiency Symptom: Your body is under a lot of stress

Selenium is a powerful disease-fighting antioxidant. “Oxidative stress causes damage to cells throughout your body. Any time you can protect your cells from oxidative stress is a good thing,” says Small. Find go-to ways to simmer down in the moment, sleep enough to help your body recover, and eat well—including getting enough selenium in your diet.

Selenium Deficiency Symptom: You have shortness of breath

Those selenoproteins have another vital job: to protect your heart. A man who had Crohn’s disease recounted his case: He suffered from swollen legs and shortness of breath and it was later discovered that he had a selenium deficiency that caused his heart failure. But the jury is still out on supplements: Although low selenium levels have been associated with a higher risk of heart disease, experts hesitate to recommend taking selenium pills. Instead, stick to a healthy, selenium-rich diet.

Should you take a supplement?

Ask your doctor first. “I caution people that they shouldn’t run out and supplement right away,” says Small. You also have to make sure that you’re not inadvertently taking too much—more than 400 mcg—which can happen easily if you take, say, a multivitamin plus a selenium supplement. If you do choose to supplement, a safe dose is 100 mcg, says Small.

Where can you get it in your diet?

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You may not need a supplement because you can easily get what you need from food sources alone. Seafood, like tuna, halibut, and canned sardines are great sources, says Small. Vegetarian options include spinach, oatmeal, and whole-wheat bread. One of the best sources are Brazil nuts; an ounce will net you over 700 percent of the daily value. Too much selenium can cause toxicity, so be sure not to get more than 400 mcg. in your food or supplements.