Micronutrient Deficiencies: The Nutrients Most Commonly Missing from Everyday Diets

Iron is essential for making hemoglobin, the protein in red blood cells that carries oxygen around the body. When iron runs low, the body struggles to deliver adequate oxygen to tissues — a condition known as iron-deficiency anemia, the most widespread nutritional deficiency globally according to the World Health Organization.

Common symptoms include persistent fatigue, paleness, and difficulty concentrating. Women of reproductive age, pregnant individuals, and people following plant-based diets are at the highest risk. Red meat and shellfish contain heme iron, which the body absorbs efficiently. Plant sources like lentils, beans, and spinach contain non-heme iron, which is less readily absorbed — pairing them with a vitamin C–rich food (such as a squeeze of lemon juice) meaningfully improves uptake.

Vitamin D supports bone health, immune function, and muscle performance. The body can synthesize it when skin is exposed to sunlight, but many people — especially those living in northern latitudes, working indoors, or regularly using sunscreen — produce far less than they need. Dietary sources are limited: fatty fish, egg yolks, and fortified dairy or plant milks are among the few practical options.

Low vitamin D is associated with weakened bones (increasing the risk of osteoporosis over time), compromised immunity, and low mood. Older adults are particularly vulnerable because skin becomes less efficient at producing vitamin D with age. This is one deficiency where supplementation is frequently recommended by clinicians, but the appropriate dose varies by individual — a blood test is the only reliable way to assess your level.

Iodine is a mineral the thyroid gland uses to produce hormones that regulate metabolism, growth, and development. Severe iodine deficiency was once a major public health crisis worldwide; the widespread introduction of iodized salt largely resolved it in many countries, but it has resurfaced in populations that limit salt intake or rely on non-iodized specialty salts.

Pregnant individuals with inadequate iodine face a particularly serious risk because the fetal brain depends on maternal thyroid hormones during early development. Good food sources include seafood, dairy products, and eggs. If you primarily use sea salt, pink salt, or kosher salt — none of which are routinely iodized — consider whether your diet provides iodine through other means.

Calcium is the most abundant mineral in the body and the primary building block of bones and teeth. Beyond structural support, it plays essential roles in muscle contraction, nerve signaling, and blood clotting. Many people associate calcium exclusively with dairy, which can lead to shortfalls in those who avoid it without finding alternative sources.

Non-dairy calcium sources include fortified plant milks, canned fish with soft bones (like sardines), tofu made with calcium sulfate, almonds, and dark leafy greens such as kale and bok choy. Adequate vitamin D is also needed for the body to absorb calcium effectively — the two nutrients work closely together. Prolonged low calcium intake is a key driver of osteoporosis later in life.

Magnesium is involved in over 300 enzymatic reactions, including those that produce energy, synthesize protein, and regulate blood pressure. It also supports nerve and muscle function and plays a role in sleep regulation. Despite its wide importance, surveys consistently find that a substantial portion of adults in the United States fall short of recommended intake levels.

Magnesium is found in whole grains, legumes, nuts, seeds, and dark green vegetables. Refined grain processing strips away much of the natural magnesium content, which helps explain why diets high in white bread and processed foods can lead to inadequacy. Subtle signs of low magnesium include muscle cramps, irregular sleep, and fatigue — symptoms that are easy to misattribute to other causes.

Vitamin B12 is required for producing red blood cells, maintaining nerve function, and synthesizing DNA. It is found almost exclusively in animal products — meat, fish, dairy, and eggs — which means people following vegan or strict vegetarian diets are at significant risk of deficiency without supplementation or fortified foods. Older adults are also vulnerable because the stomach produces less acid with age, reducing B12 absorption from food.

A B12 deficiency can take years to produce obvious symptoms because the body stores a reserve, but once depleted it can cause neurological symptoms — including numbness, balance problems, and memory difficulties — that may not fully reverse if left untreated for too long. This makes it one deficiency worth monitoring proactively, especially for plant-based eaters. Fortified nutritional yeast, plant milks, and B12 supplements are the standard strategies for those avoiding animal products.