Nutrients That Are Commonly Deficient in American Diets

Vitamin D is arguably the most widespread nutrient shortfall in the United States. The body produces it through skin exposure to sunlight, but many Americans spend the majority of their time indoors, live in northern latitudes, or routinely use sunscreen — all of which limit synthesis. Dietary sources are limited: fatty fish (salmon, mackerel, sardines), egg yolks, and fortified foods like milk and some cereals are the main options.

Vitamin D supports calcium absorption, bone maintenance, immune function, and muscle health. Groups at heightened risk of low levels include older adults, people with darker skin tones, those who are rarely outdoors, and people with certain digestive conditions that impair fat absorption. A blood test can determine whether levels are insufficient.

Calcium is critical for building and maintaining bone density, as well as for muscle contraction and nerve signaling. Dairy products — milk, yogurt, and cheese — are the most concentrated food sources, but calcium is also found in fortified plant-based milks, canned fish with bones (like sardines), tofu made with calcium sulfate, and leafy greens such as kale and bok choy.

Intake tends to fall short particularly among adolescents, adults who avoid dairy, and older women, for whom adequate calcium throughout life is especially important for bone health. It's worth noting that vitamin D and calcium work in tandem — inadequate vitamin D limits how well the body absorbs calcium from food.

Potassium helps regulate blood pressure, fluid balance, and normal muscle and nerve function. The primary reason American diets fall short is straightforward: potassium is concentrated in fruits, vegetables, beans, and whole grains — food groups that are consistently under-consumed relative to dietary guidelines. Meanwhile, high sodium intake from processed foods compounds the issue, since the two minerals interact in ways that affect cardiovascular function.

Rich food sources include bananas, sweet potatoes, white potatoes, avocados, white beans, lentils, spinach, and plain yogurt. Increasing intake through whole foods is generally considered safe for healthy adults, though people with kidney disease should consult a provider before significantly raising potassium consumption.

Magnesium participates in more than 300 enzymatic reactions in the body, including energy production, protein synthesis, blood glucose regulation, and blood pressure control. Yet surveys consistently show that a significant portion of Americans consume less than the recommended amount. The shift away from whole grains toward refined grains — which lose much of their magnesium during processing — is a major contributor.

Good food sources include pumpkin seeds, chia seeds, almonds, dark chocolate, black beans, edamame, whole wheat bread, and dark leafy greens. Like potassium, magnesium is found predominantly in plant-forward foods, so overall dietary pattern matters more than any single food.

Iron is essential for producing hemoglobin, the protein in red blood cells that carries oxygen throughout the body. Iron deficiency is the most common nutritional deficiency worldwide, and certain U.S. populations — particularly women of reproductive age, pregnant individuals, toddlers, and people following plant-based diets — are at meaningfully elevated risk.

There are two forms: heme iron (from animal sources like red meat, poultry, and seafood), which absorbs efficiently; and non-heme iron (from legumes, tofu, spinach, and fortified cereals), which absorbs less efficiently but can be enhanced by pairing it with vitamin C-rich foods. Adequate iron intake matters particularly during periods of growth and pregnancy — consult a provider before considering iron supplements, as excess iron can be harmful.

Vitamin B12 is required for nerve function, DNA synthesis, and red blood cell formation. It occurs naturally almost exclusively in animal products — meat, fish, poultry, eggs, and dairy — which means people following strict vegetarian or vegan diets are at notable risk of falling short without intentional planning or supplementation. Older adults are another high-risk group: the stomach produces less acid with age, and adequate stomach acid is needed to free B12 from food proteins for absorption.

Fortified foods — including some plant-based milks, breakfast cereals, and nutritional yeast — can serve as non-animal sources. Because B12 deficiency can develop gradually and symptoms may be subtle early on, those in higher-risk groups benefit from periodic monitoring with a healthcare provider.