If you’re eating the way most people in America do these days, you’re probably falling short of the vital nutrients you need. Fewer than 10% of us meet the daily recommended intake for vegetables (2 to 3 cups a day), and only 20% of us eat enough fruit (1 1/2 to 2 cups daily). The situation is even worse with what the U.S. Department of Agriculture and Department of Health and Human Services call shortfall nutrients, which are important but underconsumed nutrients.

The current shortfall list includes vitamins A, D, E and C, along with folate, calcium, magnesium, fibre and potassium. For adolescent and premenopausal females, iron is also a shortfall nutrient. Of these, four have been classified as “nutrients of public health concern” because their underconsumption has been linked in scientific literature to adverse health outcomes. Those vital four are fiber, calcium, vitamin D and potassium.

It’s a downward trend that concerns nutrition experts. Registered dietitian nutritionist Sharon Palmer said: “Unfortunately, our diets are not as nutrient-rich as we wish they could be, for reasons that include access and affordability of healthful foods and reliance on overly processed foods over minimally processed foods. People aren’t cooking as much as they used to, and they’re snacking more instead of sitting down to meals. That adds up to more refined foods, and fewer nutrients, on the plate.”

The situation, for Palmer, has less to do with the sludge we’re currently consuming than with all the important things we aren’t eating: “We’re missing out on nutritious foods that are so rich in these nutrients, such as fruits, vegetables, whole grains and beans.”

We asked nutrition experts to tell us more about these “public health concern” nutrients — to find out why they’re so important and how to eat enough of them.

Nearly every nutritionist interviewed for this story led off with a plea for us to eat more fibre, right now. They are really serious about this, explaining that it’s important for many more reasons than just avoiding constipation.

Registered dietitian Kara Landau said: “Dietary fibre is essential not only for a healthy digestive tract, but it also plays an important role in our metabolic health, such as protection from heart disease and improving blood glucose regulation.”

Eating more fibre comes with other benefits, too, said registered dietician nutritionist Chelsey Amer: “When you focus [on] boosting fibre intake, you’ll also consume more of other shortfall nutrients, like vitamins A, D, E and C, which are found in fruits and vegetables, or the magnesium and iron found in beans.”

Most of us are falling woefully short of fibre goals, said registered dietician Morgan Walker, an adjunct professor at Lebanon Valley College: “The recommended daily intake of fibre is 25 grams for women and 38 grams for men, but most Americans consume fewer than 15 grams per day,” she said.

And fibre under-consumption can’t just be solved with a morning bowl of Colon Blow, Landau said: “You need to look for diversity, so rather than just selecting one high-fibre bran-based cereal, it’s more beneficial to include different high-fibre choices all day long.”

We all grew up hearing that calcium would help build strong bones, but now that we’re done growing, many of us feel that we don’t need it anymore. But this under-appreciated nutrient is of lifelong importance, Landau said. “It’s important for ongoing bone and heart health,” she said, adding a reminder that vitamins D and K2 enhance its absorption.

Registered dietician nutritionist Lauren Manaker highlighted the benefits of keeping up with calcium, D and K2: “Together, they reduce the risk of osteoporosis and fractures later in life.”

The recommended daily calcium intake is 1,000 milligrams for most adults, increasing to 1,200 milligrams for women over 50 and men over 70. While dairy is a great source of calcium, there are plenty of other options, the experts said. “It’s becoming more well-accepted that there are other great sources such as broccoli, leafy greens, chia and basil seeds,” Landau said. “A great example of a calcium-rich snack would be Greek yogurt topped with chia seeds and fruit.”

The role of vitamin D is continuing to be studied, and it seems as if new benefits emerge all the time. “It’s well-known for its role in bone health, but emerging research has also highlighted its broader role in overall health,” Walker said, noting that it’s been shown to boost immune function and has been linked to a lower risk of chronic diseases such as heart disease, diabetes and certain cancers. “There’s also research showing an influence on mental health, with vitamin D deficiencies associated with conditions like depression,” she added.

The recommended daily intake of vitamin D is 600 international units, or IU, for adults under 70 and 800 IU for adults over 70. Walker noted that many experts believe that higher amounts may be necessary for optimal health. Approximately 35% of adults in the United States have a vitamin D deficiency, research shows.

It’s an increasingly common situation, said registered dietician Amy Shapiro, lead nutritionist at ButcherBox. “Almost everyone is deficient in vitamin D, which can be hard to get from food,” she said. “Lean into sustainably sourced salmon, grass-fed beef, crate-free pork and mushrooms, and you’ll get a good dose. By setting up your plate to be 1/4 lean protein, 1/2 vegetables and 1/4 complex carbohydrates, you can improve your odds of meeting nutrient needs.”

If you can’t remember the last time you ate a banana or a potato (chips and fries don’t count), you might be one of the millions who are falling short of the amount of potassium you need.

“Most people eat less than 2,600 milligrams of potassium per day, which is significantly lower than the recommended 4,700 milligrams,” said registered dietician nutritionist Jen Hernandez. One of the reasons it’s important to get enough of this nutrient, she said, is because potassium plays an important role in regulating blood pressure. “But the foods richest in potassium — fruits, vegetables, nuts, seeds and legumes — aren’t eaten enough as part of the standard American diet,” she said.

One reason for this imbalance, said registered dietician nutritionist Cory Mygrant, is the high sodium content in our diets. “Many people consume too much sodium, often due to processed foods, and so they aren’t getting enough potassium to balance it out. Potassium is a crucial nutrient that works alongside sodium to help maintain the right balance of fluids and electrolytes in your body. This imbalance can lead to high blood pressure, which is a major contributor to cardiovascular disease.”

Two top sources of potassium, potatoes and bananas, have been “demonised” in some circles, Hernandez said, but they’re great sources of a vital nutrient: “A medium baked potato has 164 calories and 952 milligrams of potassium, and a medium banana has just 105 calories, but 422 milligrams of potassium.”

All this talk of shortfalls might leave you wondering if it’s at all possible to keep yourself well nourished these days. But if you’re reaching for a bottle of multivitamins right to supplement the gaps, you may want to slow your roll, experts said.

Registered dietician nutritionist Marissa Karp had this advice: “While supplements can help us bridge the gap and serve as an insurance policy, they aren’t a replacement for eating nourishing foods. If you aren’t already eating well, moving your body, drinking water and managing your stress, don’t waste money on supplements. Taking supplements and then eating processed foods is not the same as eating a whole foods diet and using supplements to help ensure you’re getting enough.”

She offered this example of the joy of whole foods: “When you eat an avocado, it’s not just about the potassium or dietary fibre, but the synergy of the nutrients working together. It’s how the fat and fibre in the avocado slow down your gastric emptying and help keep you fuller longer. It’s also about how satisfying it tastes.”

Staying well-nourished is much simpler than you might think, Walker said. “We don’t need extreme diets or supplements to fill these nutrient gaps, but simple, intentional dietary shifts that can make a significant impact. By increasing whole foods like fruits, vegetables, whole grains, legumes, nuts, seeds, dairy and lean proteins, you can improve your intake of these critical shortfall nutrients, leading to better long-term health and disease prevention.”