Vital Nutrition: Common Vitamin Deficiencies

Although modern diets provide plenty of our most vital nutrients, many of us underconsume a few key vitamins and minerals. Learn about the most common vitamin deficiencies and how to ensure you’re getting enough.

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Although they are relatively lower in calcium, plant-based diets correlate with good bone health.

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In an age when crackers, cookies and even bottled water are vitamin-fortified, vitamin and mineral deficiencies are relatively uncommon. In fact, a 2014 study raised concerns that, between fortified foods and supplement use, consumption of micronutrients has begun to exceed recommended daily intakes. For many vitamins and minerals, high levels can impair health.

Nevertheless, when the Dietary Guidelines Advisory Committee made public their scientific report on the 2015 Dietary Guidelines for Americans, the group noted shortfalls in certain nutrients and linked them to underconsumption of vegetables, fruits, whole grains and dairy. Another potential reason for the nutrient shortfalls may involve modern agriculture, which has reduced soil levels of vital minerals such as calcium, magnesium and iron.

Much of the time, nutrient deficits can be corrected with improved diet and, in the case of vitamin D, sensible sun exposure. Our hope is that this list gets you thinking about your particular set of nutrient needs and whether you’re getting enough of these crucial vitamins and minerals. To document full-blown deficiency, blood tests are needed. If you fear you’re deficient or at risk for deficiency, your health practitioner can help you determine whether supplementation is wise and how much to take.

Vitamin D

Why it’s critical

Low levels of vitamin D have been linked with depression, obesity, heart disease and cancer. Vitamin D is also crucial for regulating calcium levels, improving muscle function and protecting lung function. Cells in most bodily tissues have vitamin D receptors.

How common is deficiency?

Deficiency is shockingly common and affects an estimated 1 billion people in the world. A study of young hospital doctors revealed that, at the end of winter, 47 percent were deficient. Widespread vitamin D insufficiency is a recent phenomenon reflective of modern lifestyles: We drink less milk, especially whole milk (one of the few dietary sources); and we are fatter, which correlates with low levels because this vitamin is taken up in fat cells. We also spend less time outdoors, and sunlight triggers our bodies to manufacture vitamin D. To further complicate matters, wearing sunscreen blocks our skin’s ability to make vitamin D.

Signs of deficiency

Problems can occur with insufficiency, a state between flat-out deficiency and adequate levels. Studies link low vitamin D with cardiovascular disease, diabetes, multiple sclerosis, infectious illnesses, autism and cancer. Severe deficiency softens bones, causing rickets in children and osteoporosis in older people. Muscles weaken and falls become more likely.

Pregnant women with vitamin D deficiency are more at risk for premature labor and the life-threatening condition called eclampsia. Their infants are at risk for low birth weight, reduced bone mineral content (relatively softer bones), wheezing in early years and type 1 diabetes.

Are you at risk?

Groups at high risk for vitamin D deficiency include those who:

• are chronically ill/debilitated

• have diseases that cause fat malabsorption

• take anticonvulsants, glucocorticoids (cortisone, prednisone, dexamethasone), or drugs to treat AIDS/HIV

• have darker skin (darker skin requires longer sun exposure to make vitamin D)

• are obese (vitamin D becomes sequestered in fat cells)

• are seniors (as we age, we make and absorb this vitamin less efficiently)

• are breast-fed infants (infant formula is generally fortified with vitamin D)

How to get enough

The main source for vitamin D is sunlight, but sunscreen blocks the ultra-violet (UV) rays that enable our bodies to manufacture the vitamin. If you’re young, fair and scantily clad, 10 to 15 minutes of peak summertime sunshine produces 20,000 international units (IUs). If you have darker skin, it can take three to five times longer to make the same amount. A 70-year-old makes a quarter of the vitamin D a 20-year-old produces. After a brief sunbath without sunscreen, protect your skin from those aging, cancer-provoking UV rays. Note that, above the 37th parallel latitude (from Santa Cruz, California, to Hampton, Virginia), winter sunlight is too weak to spark any vitamin D production.

The few food sources include cod liver oil, cold-water fish, shiitake mushrooms, egg yolks and fortified foods, but Americans rarely meet vitamin D requirements through diet. Supplements (vitamin D3 or D2) are often needed, especially during winter and for breast-fed infants, pregnant and lactating women, and others at risk for deficiency.

The Endocrine Society recommends the following daily amounts:

• Infants 0 to 12 months: 400 IUs

• Children 1 to 18: 600 IUs

• Adults 19 to 64: 600 IUs

• Adults 65 and up: 800 IUs

• Pregnant and lactating women: 600 IUs minimum, possibly 1,500 to 2,000 IUs to maintain optimum blood levels

Note: People in groups at risk for deficiency may need two to three times the minimum recommended daily amount; consult your health practitioner.


Why it’s critical

Calcium contributes to the mineral content in bones and teeth. It’s required for the normal functioning of muscles, nerves, blood vessels and glands. Hormones tightly regulate blood calcium levels. When levels fall, calcium is released from bones. When blood levels rise, calcium is deposited into bones.

How common is deficiency?

 Quite common: Two-thirds of Americans fail to intake adequate calcium from our diets. Compared with men, women and teen girls are less likely to consume enough calcium. Older people often don’t absorb calcium well because of inefficient vitamin D synthesis and an increased risk of ailments related to low stomach acid production (stomach acid helps with intestinal calcium absorption).

Signs of deficiency

Because hormones maintain blood calcium levels, short-term insufficiency doesn’t produce obvious symptoms. To make up the deficit, calcium comes out of bone. Over time, bones weaken and risk of osteoporosis and bone fractures rises. If blood calcium levels fall below normal, symptoms include fatigue, poor appetite, muscle cramps, numbness/tingling of fingers, and heart arrhythmias.

Are you at risk?

Groups at high risk for calcium deficiency include:

• menopausal women (declining estrogen is tied to decreased absorption)

• people who are lactose intolerant or allergic to cow’s milk (and who don’t otherwise consume enough plant foods high in calcium)

• vegetarians who consume plants high in oxalic and phytic acids (details at right)

• reproductive-age women who have stopped having menstrual cycles (but aren’t pregnant), such as women with anorexia nervosa and female athletes who don’t eat enough to maintain normal body weight

• people with chronic gastritis (stomach inflammation)

How to get enough

The recommended dietary allowance (RDA) for adults is 1,000 milligrams (mg). Women older than 50 should aim for 1,200 mg a day; pregnant and nursing women, 1,300 mg. Calcium-rich foods include dairy products, calcium-fortified dairy substitutes and juices; sardines and canned salmon (with bones); tofu made with calcium sulfate; broccoli; Chinese cabbage; and leafy greens (kale, chard, dandelion leaf, nettles).

Spinach and collard greens also contain calcium, but their oxalic acid content inhibits absorption. The same is true of rhubarb, sweet potatoes and beans. Whole grains, seeds and nuts contain phytic acid, which also binds to calcium, interfering with absorption.

Excessive intake of salt and caffeine increase calcium lost in the urine, whereas chemicals abundant in green tea have protective effects on bone. (A cup or two of coffee a day isn’t enough to cause significant calcium loss.)

Acidic foods—meat, poultry, cheese and grain-based foods—leach calcium from bone. Fruits and vegetables tend to be alkalinizing, which spares calcium. While relatively lower in calcium and vitamin D, plant-based diets provide other bone-friendly vitamins and minerals. Diets high in fruits and vegetables correlate with good bone health. A 2012 study found that female Asian vegans did not face an increased risk of bone loss, but that women whose diets were high in animal protein did.

For people who don’t get enough calcium from food, supplements are often recommended. Opt for calcium citrate, which absorbs well when taken with or without food, causes fewer side effects and is more effective in people whose stomachs don’t make enough acid. Side effects of supplemental calcium can include constipation, gas and bloating. Also keep in mind that taking too much calcium has been linked with higher rates of hip fractures in older women, prostate cancer in men and heart attacks.


Why it’s critical

This nutrient is required for more than 300 bodily systems. It’s essential for blood sugar control and normal functioning of our hearts, muscles and nerves.

How common is deficiency?

Some experts call magnesium deficiency the “invisible deficiency” because it’s so difficult to assess. Simple blood tests can’t measure magnesium levels because it’s stored in bones and cells. Inadequate intake is common: Half of kids and adults, and more than two-thirds of teens and those older than 70, don’t get enough.

Signs of deficiency

Symptoms of deficiency include fatigue, loss of appetite, vomiting, muscle cramps, and numbness/tingling in hands and feet. The kidneys restrict urinary magnesium loss, so signs of outright deficiency are uncommon. But persistently low intake increases risk of a number of conditions, including heart disease, type 2 diabetes, osteoporosis, asthma, anxiety, migraines and Alzheimer’s disease.

Are you at risk?

People at high risk for deficiency include those who:

• have conditions that impair intestinal absorption or speed excretion, such as type 2 diabetes, celiac disease, Crohn’s disease and alcohol dependence

• have had surgeries that shorten the small intestine

• take proton-pump inhibitors and some diuretics

• are seniors

How to get enough

The RDA is 420 mg for men and 320 mg for women. Good sources include leafy vegetables, legumes, avocados, whole grains, nuts and seeds. When it comes to supplements, magnesium bound to citrate, aspartate, lactate or chloride is better absorbed than magnesium sulfate or oxide.

Vitamin B12

Why it’s critical

 The body needs vitamin B12 for proper neurologic function such as clear thinking and reasoning, DNA synthesis and the formation of red blood cells. Vitamin B12 deficiency usually develops gradually over many years and is sufficiently common that the Centers for Disease Control and Prevention offers a course for physicians called “Why Vitamin B12 Deficiency Should Be on Your Radar Screen.”

How common is deficiency?

Up to 15 percent of the population is deficient. Healthy children and adults usually consume enough, but deficiency is fairly common among older adults—even among elders who consume plenty of vitamin B12-rich foods. One large study found that nearly 40 percent of people older than 65 had low or borderline low blood levels of vitamin B12. Most of the time, deficiency results from poor intestinal absorption rather than inadequate dietary intake.

Signs of deficiency

Until deficiency becomes severe, signs and symptoms are subtle or absent. Signs and symptoms, when present, include fatigue, weakness, diminished appetite, weight loss, sore mouth and tongue, and megaloblastic anemia (too few normal red blood cells and the presence of large, immature red blood cells). Nerve damage leads to numbness and tingling of the hands and feet. Changes in the central nervous system may produce depression, confusion, unsteady gait, faulty memory (and overall cognitive decline) and, eventually, outright dementia (persistent erosion of memory, reasoning and personality). Low vitamin B12 levels are also associated with cardiovascular disease and stroke.

Are you at risk?

People at high risk for deficiency include those who:

• are vegetarian or vegan, as only animal-based foods offer this nutrient

• have pernicious anemia or atrophic gastritis

• take metformin (used to treat type 2 diabetes) or stomach acid-reducing medications long-term. These drugs include proton-pump inhibitors (Prilosec, Prevacid, Nexium) and histamine H2 blockers (Tagamet, Pepcid, Zantac)

• have had surgery to remove part of the stomach or small intestine (as in weight-loss surgery)

• have conditions compromising intestinal absorption such as Crohn’s disease, celiac disease, cystic fibrosis and bacterial overgrowth in the gut

How to get enough

We don’t need much of this vitamin. The RDA for adults is 2.4 micrograms (mcg) and 2.6 mcg during pregnancy and 2.8 mcg while lactating.

Vitamin B12 is found naturally only in animal-based foods—seafood, poultry, meat, eggs and dairy products. Breakfast cereals and some nutritional yeasts are fortified with this vitamin.

Dietary supplements usually contain B12 as cyanocobalamin, as well as methylcobalamin. The Academy of Nutrition and Dietetics recommends pregnant and nursing vegetarians take vitamin B12 supplements to ensure sufficient levels for the fetus and infant. Doctors treat people with documented B12 deficiency with injections or high oral doses of the vitamin.


Why it’s critical

Part of hemoglobin, a protein that carries oxygen in the blood, and myoglobin, which stores and releases oxygen to muscles, iron is crucial for energy levels and mental health. It also contributes to enzymes, molecules that speed biochemical reactions in the body.

How common is deficiency?

Iron deficiency used to be common, mainly due to insufficient dietary intake. Now that many grain-based foods are iron-fortified, healthy adults infrequently run a deficit.

Signs of deficiency

Some common symptoms include fatigue, weakness, shortness of breath with exertion, rapid heart rate, tongue inflammation and increased risk of infections. Iron-deficient infants can have developmental delays; deficient teens can experience problems with mental function. Research links deficiency in childhood and adolescence with psychiatric disorders such as depression, anxiety, attention deficit/hyperactivity disorder and autism.

Are you at risk?

People at risk for deficiency include those who:

• have lost blood (bleeding ulcers, trauma, surgery)

• are vegetarian or vegan

• are pregnant

• are exclusively breast-fed infants (infant formula is iron-fortified)

• are elders with atrophic gastritis (reduces stomach acid, which helps with the intestinal absorption of iron)

• are chronic users of nonsteroidal anti-inflammatory drugs (Motrin, Advil, Naprosyn, Aleve, aspirin), which can inflame the gut and cause bleeding

• are chronic users of antacids, proton-pump inhibitors and calcium supplements, which all interfere with iron absorption

How to get enough

The RDA is 8 mg for men, 18 mg for women 50 and younger, and 8 mg for women older than 50. Poultry, seafood and meat (especially organ meat) contain a readily absorbable form called heme iron. Plants contain nonheme iron, which is not as bioavailable. Sources include dandelion and nettle greens; legumes (soybeans, white beans, kidney beans, garbanzo beans, navy beans, lentils); pumpkin seeds; almonds; blackstrap molasses; apricots; raisins; prune juice; and fortified grain-based foods (cereals, pasta, rice, breads).

Although spinach contains iron, it also contains oxalic acid, which interferes with absorption. So do calcium and the phytates in high-fiber foods.

On the other hand, vitamin C increases iron absorption. Vitamin C-rich foods include citrus, bell peppers, cantaloupe, Brussels sprouts and broccoli.

More is not better. Excessive iron is stored in organs, which can damage them. Furthermore, iron overload increases risk of heart disease, diabetes and possibly cancer. (A large study found that, while less than 3 percent of people 67 and older were deficient, 13 percent had abnormally high iron levels.) Take supplements only if directed by a health-care practitioner. Men and postmenopausal women who take multivitamin supplements should choose a brand without iron.

Boost your consumption of these essential vitamins and minerals with our Mineral-Rich Vegetable Stir Fry.

For more information on vitamins and minerals, go to the National Institutes of Health Office of Dietary Supplements.

Linda B. White, M.D. is a freelance writer and the coauthor of 500 Time-Tested Home Remedies and the Science Behind Them; Health Now: An Integrative Approach to Personal Health; The Herbal Drugstore; and Kids, Herbs & Health.