The Nutrients Most Americans Don't Get Enough Of

Fiber is perhaps the most well-documented gap in the American diet. Most adults consume roughly half the recommended amount — around 15 grams per day, compared to a general guideline of 25–38 grams depending on age and sex. Fiber supports digestive health, helps regulate blood sugar, contributes to feelings of fullness, and feeds beneficial gut bacteria.

There are two main types: soluble fiber (found in oats, beans, and apples) and insoluble fiber (found in whole grains, nuts, and most vegetables). Both matter. Our guide on soluble vs. insoluble fiber explains how each type works and where to find them. The simplest upgrade: swap refined grains for whole grains and add a serving of legumes a few times a week.

Potassium is a mineral that helps regulate blood pressure, supports proper muscle and nerve function, and balances fluid levels in the body. It works in close partnership with sodium — and in a diet already high in sodium, low potassium intake compounds cardiovascular strain. Average American potassium intake falls well below established adequate intake levels.

Potassium is abundant in whole foods: bananas, avocados, sweet potatoes, white beans, lentils, spinach, and low-fat dairy are all strong sources. The challenge is that many of these foods are underrepresented in typical American eating patterns. Increasing produce and legume intake is the most direct path to improvement.

Vitamin D is unique because the body can synthesize it through sun exposure — yet deficiency and insufficiency are widespread, particularly in northern latitudes, among people with darker skin tones, and among those who spend most of their time indoors. It plays a critical role in calcium absorption, bone health, immune function, and muscle performance.

Few foods naturally contain significant vitamin D. Fatty fish (salmon, mackerel, sardines), egg yolks, and fortified foods like milk and some cereals are the main dietary sources. A healthcare provider can test your vitamin D status and advise on whether a supplement is appropriate for your situation — this is one case where supplementation is commonly recommended under medical guidance.

Calcium is essential for building and maintaining bone density, but it also plays roles in muscle contraction, nerve signaling, and heart rhythm. While dairy products are the most concentrated dietary source, calcium is also found in fortified plant milks, tofu made with calcium sulfate, leafy greens like kale and bok choy, canned fish with bones, and almonds.

Inadequate calcium intake over time, particularly when combined with low vitamin D (which the body needs to absorb calcium efficiently), is associated with increased risk of bone loss. Intake tends to drop in adolescence and again in older adulthood — two life stages when needs are especially high. Special-population considerations apply here; those who are pregnant, postmenopausal, or managing bone conditions should discuss calcium needs with a healthcare provider.

Magnesium is involved in more than 300 enzymatic reactions in the body, including energy production, protein synthesis, blood glucose regulation, and blood pressure control. Despite its broad importance, surveys suggest a substantial portion of Americans do not meet recommended intake levels.

Rich sources include dark leafy greens, nuts (especially almonds and cashews), seeds, whole grains, and legumes — foods that tend to be crowded out when diets center on ultra-processed options. Low magnesium intake has been associated in research with increased risk of type 2 diabetes, hypertension, and cardiovascular issues, though these are population-level associations rather than direct cause-and-effect proof. For a broader view of key micronutrients, see our micronutrients at a glance guide.

Vitamin A supports vision, immune function, skin integrity, and cell growth. There are two dietary forms: preformed vitamin A (found in animal products like liver, eggs, and dairy) and provitamin A carotenoids (found in orange, yellow, and dark green plant foods). Many Americans, particularly those eating few fruits and vegetables, fall short on the plant-based carotenoid form.

Foods like carrots, sweet potatoes, butternut squash, kale, and spinach are excellent sources of beta-carotene, which the body converts to vitamin A as needed. The conversion is less efficient than preformed vitamin A, so consistent consumption of these vegetables matters. Unlike preformed vitamin A from supplements, which can accumulate to harmful levels at very high doses, carotenoids from food are considered safe.