Common Nutrient Deficiencies and Who Is at Risk

Most people who eat a varied diet get enough vitamins and minerals. But some deficiencies are genuinely common, particularly in certain groups, and their early signs are vague enough to be mistaken for stress or a busy life. The profiles below cover the deficiencies doctors see most often in wealthy countries, who is at risk and what helps. Tiredness, hair loss or tingling can have many causes, so the right next step is a conversation with a doctor and, where appropriate, a blood test, not a cabinet full of supplements.

Vitamin D

Who is at risk: people who get little sun on their skin, including those living at high latitudes in winter, people who cover most of their skin, older adults, people with darker skin, and people with obesity or conditions that affect fat absorption.

Possible signs: often none. Severe or long-lasting deficiency can cause bone pain and muscle weakness, and in children it can cause rickets.

Sources: sunlight on the skin, oily fish such as salmon and sardines, egg yolks, and fortified foods such as some milks and cereals. Some health authorities, including the UK's NHS, advise everyone to consider a daily vitamin D supplement in autumn and winter.

Vitamin B12

Who is at risk: vegans and some vegetarians, since B12 is found naturally almost only in animal foods; older adults, who absorb it less well; people with pernicious anemia, an autoimmune condition; and people who have had stomach or bowel surgery. Long-term use of the diabetes medicine metformin and of acid-reducing medicines can also lower levels.

Possible signs: tiredness, pale skin, a sore or smooth tongue, pins and needles, problems with balance and memory, and mood changes. Nerve damage from long-term deficiency can become permanent, so it is worth treating early.

Sources: meat, fish, eggs, dairy, and fortified foods such as some plant milks, cereals and nutritional yeast. People on a vegan diet are generally advised to take a B12 supplement or eat fortified foods reliably.

Iron

Iron is a mineral rather than a vitamin, but iron deficiency is the most common nutritional deficiency worldwide, according to the World Health Organization.

Who is at risk: women with heavy periods, pregnant people, infants and toddlers, frequent blood donors, people with conditions such as celiac disease, and people on diets low in iron-rich foods.

Possible signs: tiredness, shortness of breath, pale skin, headaches, brittle nails, restless legs and, sometimes, cravings to eat ice or non-food items, known as pica.

Sources: red meat, poultry and fish provide heme iron, which is absorbed easily. Beans, lentils, tofu, dark leafy greens and fortified cereals provide non-heme iron, which is absorbed better alongside vitamin C, such as citrus or peppers. Tea and coffee with meals can reduce absorption.

Iron deficiency in men or in women after menopause can be a sign of blood loss, for example from the gut, and should always be investigated by a doctor.

Folate

Who is at risk: people who drink heavily, people with diets low in fresh vegetables and legumes, and people taking certain medicines. Folate matters especially before and during early pregnancy, when adequate intake reduces the risk of neural tube defects such as spina bifida. Health authorities recommend that anyone who could become pregnant take a folic acid supplement.

Possible signs: tiredness and anemia, similar to B12 deficiency, which is why doctors often check both together.

Sources: leafy greens, legumes, citrus fruits and fortified grains. In the US and many other countries, some flour or grain products are fortified with folic acid by law.

Iodine

Who is at risk: people who don't use iodized salt and eat little dairy or seafood, which can include some people on plant-based diets, and pregnant and breastfeeding people, who need more.

Why it matters: iodine is needed to make thyroid hormones. Deficiency can cause an enlarged thyroid, known as a goiter, and during pregnancy it can affect a baby's development.

Sources: iodized salt, dairy, fish, seafood and eggs.

Calcium and magnesium

Many adults, particularly older women and people who avoid dairy, eat less calcium than recommended, which matters for bone health over time. Dairy products, calcium-set tofu, fortified plant milks, canned fish with soft bones and some leafy greens are good sources. Magnesium intake is also below recommendations for many people, and levels can be lowered by some medicines, such as long-term use of proton pump inhibitors, and by heavy alcohol use. Nuts, seeds, whole grains, beans and leafy greens provide it.

Testing and supplements

Blood tests can confirm most of these deficiencies, and the right treatment depends on the cause and severity. Supplements are useful when a deficiency is confirmed or for groups advised to take them, but more is not better. Vitamins A and D and minerals such as iron can build up to harmful levels, and iron supplements are a leading cause of poisoning in young children, so keep them out of reach. Tell your doctor or pharmacist about any supplements you take, since some interact with medicines.