Harvard Health Columns

Important nutrients you could be missing

How to identify—and treat—a nutritional deficiency before it endangers your health.

Most of us worry about eating too much of the wrong foods. Yet we also have to worry that we're not eating enough of the right foods. Skimping on certain food groups can leave us susceptible to vitamin and nutrient deficiencies.

Some of the medicines we take can also rob our bodies of important nutrients. "As people get older they tend to be on more medicines, and that can lead to nutritional deficiencies," explains Dr. Helen Delichatsios, assistant professor of medicine at Harvard Medical School.

Older adults are most susceptible to deficits of the B vitamins, vitamin D, and calcium. Getting too little of these and other nutrients can lead to confusion and memory loss, infections, heart disease, and brittle bones.

Let's look at these and other common vitamin deficiencies, and how you can avoid them.

Calcium

  • Why you need it: Calcium keeps your bones strong and helps muscles and nerves function correctly.
  • How much you need: 1,000 to 1,200 milligrams (mg) daily
  • Where to get it: Low-fat yogurt (415 mg), sardines (325 mg), nonfat milk or soymilk (299 mg), calcium-fortified orange juice (261 mg), tofu (253 mg). (All measurements are per serving.)
  • Conditions that can lead to calcium deficiency: Poor absorption of calcium after menopause, lactose intolerance, and a diet low in calcium-rich foods.
  • Symptoms of a deficiency: Weak bones (osteoporosis), fractures.
  • What to do if you might be deficient: Try to increase your calcium intake through foods high in this nutrient. If you're still low in calcium, ask your doctor whether you should take a supplement. Try not to take more than 500 mg a day in supplement form, because higher-dose calcium supplements have been linked to increased heart disease risks in women.

Iron

  • Why you need it: Iron is involved in many different cell functions, including the transport of oxygen from the lungs to the rest of the body.
  • How much you need: 8 mg/day (for women ages 51 and over)
  • Where to get it: There are two types of iron: heme and non-heme. Heme is found in animal products, such as beef (3 mg), chicken livers (11 mg), oysters (5.7 mg), and turkey (2 mg). It's the easiest form of iron for your body to absorb. Non-heme iron is found in fortified cereals (18 mg), soybeans (8.8 mg), and tofu (3.4 mg). It's more plentiful in foods than heme iron, but it's also harder for your body to absorb.
  • Conditions that can lead to iron deficiency: Blood loss, a lack of iron in the diet (for example, from eating a vegetarian diet), and medicines that reduce iron absorption (such as antacids and gastroesophageal reflux drugs).
  • Symptoms of a deficiency: Fatigue, weakness, and slowed thinking
  • What to do if you might be deficient: See your doctor for a blood test. "If someone is low in iron it means they are either nutritionally deficient or they are bleeding, so that should be looked at," Dr. Delichatsios says. Bleeding can be caused by a number of conditions, from a peptic ulcer to colorectal cancer. First the cause of bleeding should be treated, if possible. You may need to eat more iron-rich foods or take a supplement to correct an iron deficiency.

Folate (folic acid)

  • Why you need it: Your body uses folate to produce new cells. During pregnancy, folic acid is essential for preventing birth defects of the baby's brain and spine.
  • How much you need: 400 micrograms (mcg) daily
  • Where to get it: Spinach (131 mcg), black-eyed peas (105 mcg), fortified breakfast cereals (100 mcg), asparagus (89 mcg).
  • Conditions that can lead to folate deficiency: Lack of folic acid in the diet; excess alcohol consumption; poor absorption of folate (from conditions such as celiac or inflammatory bowel disease); and drugs such as methotrexate (Rheumatrex, Trexall) for psoriasis and cancer, phenytoin (Dilantin) for seizures, trimethoprim (Primsol) for urinary tract infections, or triamterene (Dyrenium) for high blood pressure.
  • Symptoms of a deficiency: Diarrhea, fatigue, weakness, shortness of breath, fast heartbeat (palpitations), swelling of the tongue, and anemia (a lack of enough oxygen-transporting red blood cells). Folate deficiency has been linked to an increased risk for cardiovascular disease and certain cancers.
  • What to do if you might be deficient: See your doctor for a blood test. You may need to take a daily folate supplement or multivitamin.

Vitamin B12

  • Why you need it: Vitamin B12 is vital for making red blood cells, nerve cells, and DNA.
  • How much you need: 2.4 mcg daily
  • Where to get it: Clams (84.1 mcg), beef liver (70.7 mcg), fortified breakfast cereals (6 mcg), trout (5.4 mcg), and supplements (after age 50, vitamin B12 from fortified foods and supplements is easiest for your body to absorb).
  • Conditions that can lead to vitamin B12 deficiency: Pernicious anemia (an autoimmune condition in which the body does not properly absorb vitamin B12), weight-loss or other gastrointestinal surgery, digestive disorders such as celiac or Crohn's disease, vegetarian or vegan diet, and heartburn medicines (proton-pump inhibitors) or diabetes drugs such as metformin (Glucophage).
  • Symptoms of a deficiency: Tingling or numbness in the hands and feet, fatigue, weakness, constipation, loss of balance, trouble walking, anemia, confusion or dementia (if the deficiency is severe), swollen tongue.
  • What to do if you might be deficient: If you're taking medicine that can cause vitamin B12 deficiency or you have symptoms of a deficiency, see your doctor for a blood test. You may need to take a vitamin B12 intramuscular injection each month or a daily oral supplement.

Vitamin D

  • Why you need it: Vitamin D helps the body absorb calcium and promotes bone growth. It can help protect against the bone-weakening disease osteoporosis.
  • How much you need: 600 to 800 international units (IU) daily
  • Where to get it: Go outside in the sun for 10 to 20 minutes a day without sunscreen. Eat foods such as salmon (447 IU), canned tuna (154 IU), vitamin D–fortified orange juice (137 IU), low-fat or skim milk (115–124 IU), and yogurt (80 IU).
  • Conditions that can lead to vitamin D deficiency: Lack of sun exposure, too little vitamin D in the diet, liver or kidney disorders, the use of antiseizure drugs, and obesity.
  • Symptoms of a deficiency: Muscle weakness and increased bone fractures. Research also suggests that a lack of vitamin D might contribute to heart disease, infections, and cancer.
  • What to do if you might be deficient: See your doctor for a blood test. You can bring up your vitamin D levels by taking a weekly and/or daily supplement.

Don't overdo it

Take a supplement if you need it to correct a vitamin deficiency, but don't take too much. "It is possible to overload on the fat-soluble vitamins—A, D, E, and K," Dr. Delichatsios says. The B vitamins and vitamin C are less worrisome because they're water-soluble. That means your body will flush out whatever excess it doesn't use in the urine. Let your doctor know about every supplement you're using, and take only the amount of the nutrient your doctor recommends.

Don't skimp on other dietary basics

In addition to eating important nutrients in the right balance, you need to get enough calories and protein daily to support your body. A lack of enough protein can rob you of the muscle strength you need to accomplish your daily activities. Too few calories will erode the reserves needed to sustain you if you get sick.

If you're losing weight and muscle mass, try these steps:

  • Switch from low-fat to whole-fat milk and cheese. These foods also provide a good source of protein.
  • Add alternate protein sources to your diet, such as beans and tofu, which are easier to chew and healthier than meat.
  • Supplement your diet with a fortified nutritional supplement such as Ensure or Boost. Just don't substitute these drinks, which can be high in sugar and calories, for regular meals unless you are unable to eat.
  • Make an appointment with a dietitian, who can help you design a healthy, balanced diet that meets all of your nutritional needs.

Medicines that can cause vitamin deficiencies

Drug

Nutrients it can deplete

Antacids

Vitamin B12, iron (very rare)

Antibiotics

B vitamins (very rare)

Antiseizure drugs

Vitamin B6, folate, vitamin D

Chemotherapy drugs

Folate

Corticosteroids

Vitamin D

Diuretics

Vitamin B1 (thiamine), folate (with long-term use)

Laxatives

vitamins D, B6

Proton-pump inhibitors (for reflux)

Vitamin B12 (rare)

Ulcer medicines (H2 blockers)

Vitamin B12

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