You may think that if you’re eating three square meals every day, you’re fueling your body properly—but that may not actually be the case. In the latest edition of the Dietary Guidelines for Americans, the USDA warned that some Americans are falling short on their intake of a number of key nutrients.

Of the most under-consumed, five are flagged as “nutrients of public health concern,” which means low intakes are associated with health issues: calcium, potassium, dietary fiber, vitamin D, and iron.

Before you panic, know this: Overall, choosing diverse, whole foods goes a long way in helping you get your daily needs. “Eating a variety of foods is the best way to make sure you are consuming all of your essential nutrients,” says Lauren Manganiello M.S., R.D.N., C.D.N., C.P.T. But if you’re unsure where you stand with these important nutrients, you can always talk to your doctor about annual blood testing, says Lisa R. Young, Ph.D., R.D..

Read on to learn why these nutrients are so important, how much you really need per day, and how to up your intake.

Calcium

Remember being told to drink your milk growing up? Well, it was for good reason. Dairy products like milk, yogurt, and cheese are rich sources of calcium, according to Manganiello.

“Calcium supports bone and teeth structure and formation,” says Manganiello. “It also aids in muscle function, nerve transmission, and intracellular signaling.” And according to the Office of Disease Prevention and Health Promotion, more than 40 percent of the population falls short of the estimated average requirement (EAR).

Over time, a limited calcium intake can cause low bone mass and increase your risk of fractures and osteoporosis, according to the National Institutes of Health.

Men and women between the ages of 19 and 51 should shoot for 1,000 milligrams of calcium per day, says Manganiello. (A cup of milk contains 299 milligrams.)

If you’re dairy-free, there are a number of plant-based sources of calcium, including sardines, Chinese cabbage, kale, and broccoli, she says. (Two cups of raw broccoli contain about 86 milligrams.)

Potassium

Most of us think about exercise when we think about this mineral. “Potassium helps regulate blood pressure by counteracting some of the effects of sodium,” says Amy Gorin, M.S., R.D.N. The electrolyte also supports exercise performance and hydration, and too-low levels might lead to muscle cramping, she says.

That’s not all, though. Potassium is actually the third most-abundant mineral in the body, and is required for the function of several organs, including the heart, kidneys, brain, and muscular tissues, says Vanessa Rissetto, M.S., R.D., C.D.N.

A 2012 USDA report found that the country’s potassium intake has remained pretty much the same since the 1990s. Which is a problem, since fewer than 25 percent of men and one percent of women hit the target goal of 4,700 milligrams per day when surveyed.

Low potassium can lead to muscle cramps, feelings of fatigue or weakness, constipation, and issues with blood pressure and heart rhythm, according to The Mayo Clinic.

Though we  typically think of bananas as the potassium source, foods like spinach, salmon, sweet potatoes, avocados and—believe it or not—kiwis also contain the nutrient, Rissetto says. (A medium banana packs 422 milligrams of potassium, while a medium sweet potato provides 542 milligrams.)

Fiber

Yes, fiber is key for keeping your bathroom habits regular, but that’s not all it does. “Fiber helps to keep us full and satiated after eating, and may help keep cholesterol levels in check,” says Gorin.

There are two types of dietary fiber: soluble and insoluble. Soluble fiber slows our absorption of carbohydrates and cholesterol, while insoluble fiber—which we can’t digest—draws in water and helps make our time on the toilet easier.

Considering this nutrient works triple duty, it’s pretty shocking that only five percent of the population exceeds the recommended daily intake, according to the Office of Disease Prevention. The average person needs at least 25 grams per day.

Missing the mark on fiber can negatively impact your cholesterol (and put you at risk for heart disease), leave you more susceptible to a blood sugar roller-coaster and potential weight gain, and cause constipation, according to The Cleveland Clinic.

Many plant foods contain varying degrees of both types of fiber, says Rissetto. Oatmeal, for example, provides mostly soluble fiber, while brown rice provides mostly insoluble fiber. Other fiber sources include quinoa, kale, and fruit (raspberries and avocados are two more fiber-packed options).

If you’re still struggling to get enough fiber, Rissetto recommends adding psyllium husk, a type of fiber used in many supplements, to your routine. “I like to add it to my overnight oats for more nutrient density,” she says.

Related: 8 Overnight Oats Recipes That Make Breakfast Taste Like Dessert

Vitamin D

Of all the nutrients on this list, Vitamin D is probably the trickiest to get enough of. It tops the list of the most under-consumed nutrients, with more than 90 percent of the population falling below the EAR, according to the Office of Disease Prevention. After all, it’s not found in too many foods! Anyone between ages nine and 70 should be shooting for 600 IUs a day, says Rissetto.

“Vitamin D’s main role is to make calcium available to the body,” says Young. The vitamin is crucial for mineralizing our bones and teeth (a.k.a. helping them become hard and strong). Plus, it also supports our immune function, she says.

Without ample vitamin D, you risk decreased bone density—which could mean fractures or osteoporosis. In extreme cases, you risk of a condition called osteomalacia, which involves weak bones, bone pain, and muscle weakness, according to the U.S. National Library of Medicine.

You can get some vitamin D from foods like salmon, sardines, and egg yolks. (Three ounces of baked sockeye salmon contain 570 IUs, while two hard-boiled eggs contain 87 IUs.) You get the rest of your vitamin D through skin exposure to sunlight.

Related: An Ode To Egg Yolks (Yes, They’re Good For You!)

Many people fall far short on vitamin D through diet and sunshine time alone, however, says Young. “This may be one that you might need to take a supplement for,” she says. So talk to your doc or a nutritionist about incorporating a vitamin D supp into your routine.

Iron

While this nutrient might not be an issue for everyone, the USDA flags low iron intake as a health concern for young children and women who are pregnant or of menstruating age. The National Institutes of Health recommends 15 grams of iron per day for adolescent girls and 18 grams per day for women between ages 19 and 50. Pregnant women, though, need 27 grams per day.

“The main role of iron is that it carries oxygen in the red blood cell,” Young says. And red blood cells transport oxygen throughout your entire body. Pretty dang important.

Consuming too little iron can lead to iron deficiency anemia, which is often marked by extreme fatigue and weakness, pale skin, lightheadedness or dizziness, and/or cold hands and feet, according to The Mayo Clinic. (This is most commonly an issue for menstruating or pregnant women and vegetarians.)

According to Young, we absorb iron from animal sources (called ‘heme’ iron) more easily than iron from plant sources (called ‘nonheme’ iron)—but pairing plant sources of iron with vitamin C can boost your absorption if you don’t do meat.

Animal sources of iron include meat, fish, and chicken, while plant sources include beans, legumes, and enriched breads. (Three ounces of sirloin steak contain 1.6 milligrams of iron, while half a cup of black beans contains 2.3 milligrams.)