Nutrients That Commonly Fall Short in American Diets

Vitamin D supports bone health, immune function, and muscle performance. The body can synthesize it through sun exposure, but geography, indoor lifestyles, and darker skin tones reduce synthesis significantly for many Americans. Dietary sources are limited: fatty fish such as salmon and mackerel, fortified dairy and plant milks, and egg yolks are the primary options. National Health and Nutrition Examination Survey (NHANES) data has consistently found that a large share of the US population has insufficient blood levels. Because correcting a genuine deficiency through food alone can be difficult, a clinician may assess levels and discuss appropriate options.

Calcium is best known for its role in bone and tooth strength, but it also plays a part in nerve signaling, muscle contraction, and blood pressure regulation. Dairy products are the most concentrated dietary source, but calcium is also found in fortified plant milks, canned fish with soft bones (like sardines), tofu made with calcium sulfate, and dark leafy greens such as bok choy and kale. Absorption from plant sources is often lower than from dairy, so variety matters. Adequate intake across a lifetime is especially important because bone mass peaks in early adulthood and declines thereafter.

Potassium helps regulate blood pressure, supports heart rhythm, and counterbalances the blood-pressure-raising effects of sodium — a nutrient Americans typically overconsume. Yet most adults fall well short of the adequate intake level. The richest sources include bananas, potatoes (especially with the skin), white beans, lentils, avocado, yogurt, and leafy greens. Because potassium is widely distributed in whole plant and animal foods, low intake is generally a signal of a diet too reliant on processed foods rather than a reflection of any single missing ingredient.

Magnesium participates in hundreds of enzymatic reactions in the body, including those involved in energy production, DNA synthesis, and muscle and nerve function. It also supports bone health alongside calcium and vitamin D. Good sources include dark leafy greens (spinach, Swiss chard), pumpkin seeds, almonds, black beans, edamame, whole grains, and dark chocolate. Refined grain processing strips out a significant portion of magnesium, so the shift from whole to refined grains in the American diet is a major contributor to shortfalls.

Fiber supports digestive health, helps regulate blood sugar and cholesterol levels, and feeds beneficial gut bacteria. Most US adults consume roughly half the recommended amount. Legumes, whole grains, vegetables, fruits, nuts, and seeds all contribute. Unlike the other nutrients on this list, fiber comes exclusively from plant foods — making plant food variety a central goal. Our overview of dietary fiber types explains the difference between soluble and insoluble fiber and why both matter for overall health.

Vitamin A supports vision, immune function, and cell growth. While outright deficiency is uncommon in the US, surveys show many Americans fall below recommended intake levels, particularly for provitamin A carotenoids — compounds found in orange and yellow vegetables (carrots, sweet potatoes, winter squash) and dark leafy greens that the body converts to active vitamin A. Preformed vitamin A is also found in liver, dairy, and eggs. A diet with regular servings of deeply colored vegetables and fruits is typically sufficient to maintain adequate levels for most healthy adults.