Feeling weak, sluggish, or anemic? You may not be getting enough B vitamins. These are a group of eight vitamins that have important metabolic roles in converting food into energy. They’re also necessary for a wide range of other processes, such as blood cell production, neurological function, cellular signaling, DNA production and repair, metabolizing amino acids, and more. B vitamins are also believed to help reduce stress, anxiety, memory loss, and heart disease risk.
Importantly, we have to replenish our B vitamins regularly. Because they’re water soluble, B vitamins aren’t stored in the body, and the ones that aren’t used get flushed out. That’s why we need to obtain B vitamins daily to avoid deficiencies.
B vitamin deficiencies, although uncommon, can be dangerous. There are eight great B vitamins, but let’s look at the four in which deficiencies may be more common and can be more serious.
Vitamin B1 (thiamine) deficiency
Most people in the United States get enough thiamine (vitamin B1). But for those who develop a thiamine deficiency, it can become a serious, potentially life-threating problem. Notably, people with chronic alcoholism frequently develop thiamine deficiency because ethanol reduces gastrointestinal absorption of thiamine, thiamine stores in the liver, and thiamine phosphorylation.
Other groups prone to thiamine deficiency include older adults, people with HIV/AIDS, people with diabetes, and those who have undergone bariatric surgery.
In its early stage, signs and symptoms of thiamine deficiency are nonspecific, and may include fatigue, irritability, poor memory, sleep disturbances, precordial pain, anorexia, and abdominal discomfort.
In severe stages, thiamine deficiency results in beriberi, which is characterized by peripheral neuropathy and muscle wasting, as well as impaired sensory, motor, and reflex functions. In rare cases, people with beriberi develop congestive heart failure that leads to edema in the legs and sometimes death. Although beriberi is rare in the United States, it does still occur here.
A more familiar consequence of thiamine deficiency in the United States is Wernicke-Korsakoff syndrome, which most commonly develops in people with chronic alcoholism—about 8-10 times more commonly than in the general population. Wernicke-Korsakoff syndrome often manifests in two phases. The first is Wernicke’s encephalopathy, an acute, life-threatening phase that’s characterized by peripheral neuropathy. Without supplemental thiamine treatment, up to 20% of people with Wernicke’s encephalopathy die.
Those who survive develop the second phase, Korsakoff’s psychosis, which is associated with severe short-term memory loss, disorientation, and confusion between real and imagined memories. Even with parenteral thiamine treatment, about one-quarter of patients with Korsakoff’s psychosis do not completely recover.
The daily Recommended Dietary Allowance (RDA) for thiamine is 1.2 mg in adult men and 1.1 mg in adult women. Primary food sources include whole grains, meat (notably pork), and fish. Americans get most of their thiamine from cereals and breads.
Vitamin B6 deficiency
Vitamin B6 deficiency is relatively rare in the United States, but some individuals can have low vitamin B6 status. Groups most likely to have inadequate vitamin B6 intake include people with poor renal function, including those with end-stage renal disease and chronic renal insufficiency, and people with autoimmune disorders, including rheumatoid arthritis. Other groups include patients with celiac disease, Crohn’s disease, ulcerative colitis, inflammatory bowel disease, and other malabsorptive autoimmune disorders, as well as people with alcohol dependence.
In addition, 24% of people in the United States who don’t take supplements containing vitamin B6 have low plasma concentrations of the vitamin. In particular, teenagers have the lowest vitamin B6 levels, followed by adults aged 21-44 years. Interestingly, the elderly do not have significantly low vitamin B6 plasma levels, even those who didn’t take supplements.
People with borderline vitamin B6 levels or mild deficiency may show no signs or symptoms for months or even years. In individuals with true vitamin B6 deficiency, symptoms can include anemia, seborrheic dermatitis, peripheral neuropathy, cheilosis (scaling on the lips and cracks at the corners of the mouth), glossitis (swollen/painful tongue), weakened immune function and, in adults specifically, depression, confusion, electroencephalographic abnormalities, and seizures. In infants, vitamin B6 deficiency causes irritability, abnormally acute hearing, and convulsive seizures.
People with low vitamin B6 concentrations should be sure to get adequate nutrients from food sources or vitamin supplements. Individuals with alcohol dependence or malabsorptive disorders may benefit from pyridoxine supplementation. Importantly, the patient’s underlying condition also needs to be addressed.
The daily RDA for vitamin B6 is 1.3 mg in adults up to age 50, and is higher in pregnant (1.9 mg) and lactating women (2.0 mg). In adults age 51 and older, the daily RDA is 1.7 mg for men and 1.5 mg for women.
Dietary sources of vitamin B6 include a wide variety of foods, particularly fish, beef liver and other organ meats, potatoes and other starchy vegetables, chickpeas, and non-citrus fruits.
Vitamin B9 (folate) deficiency
Although most Americans get enough vitamin B9 (folate), certain populations—including women of childbearing age and non-Hispanic black women—may not get a sufficient amount. Even among girls and women who take supplements with folic acid, 19% of those aged 14 to 18 years and 17% of those aged 19 to 30 years have an inadequate intake of folate. Likewise, 23% of non-Hispanic black women don’t get enough folate compared with 13% of non-Hispanic white women.
Other groups may also not get enough folate. For instance, pregnant women have a higher demand for folate, so they’re recommended to take a prenatal vitamin supplement that includes folic acid. Indeed, pregnant women with insufficient folate have an increased risk of giving birth to infants with neural tube defects. Inadequate folate intake in mothers is also associated with low infant birth weight, preterm delivery, and fetal growth retardation. The good news: Since 1998, the FDA has required manufacturers to add 140 mcg of folic acid to every 100 g of enriched breads, cereals, flour, cornmeal, pasta, rice, and other grain products to reduce the risk of these defects.
In addition, people with alcohol use disorder often have poor diets that don’t provide enough folate. Alcohol also interferes with folate absorption and hepatic uptake. Others who may not get enough folate include people with malabsorptive disorders and those with MTHFR gene polymorphism.
Although these groups may be at risk of insufficient folate intake, isolated folate deficiency is uncommon—it usually occurs along with other nutrient deficiencies related to poor diet, alcoholism, and malabsorptive disorders.
The primary clinical sign of folate deficiency (as well as vitamin B12 deficiency) is megaloblastic anemia, which is characterized by large, abnormally nucleated red blood cells. Symptoms include weakness, fatigue, difficulty concentrating, irritability, headache, heart palpitations, and shortness of breath.
Other signs and symptoms of folate deficiency are soreness and ulcerations on the tongue and oral mucosa; pigmentary changes in skin, hair, or fingernails; gastrointestinal symptoms; and elevated blood concentrations of homocysteine.
The RDA for folate in adults is 400 mcg dietary folate equivalents (DFE) per day, and is higher in pregnant and (600 mcg DFE) and lactating women (500 mcg DFE). Folate is naturally present in a wide variety of foods and found in the largest amounts in vegetables (especially spinach, asparagus, and brussels sprouts), meat (particularly beef liver), fruits and fruit juices, nuts, beans, peas, seafood, eggs, dairy products, poultry, and grains (notably breakfast cereal).
Bear in mind that some people are at risk of getting too much folic acid. About 5% of adults aged 51-70 years, as well as men aged 71 years and older, have folic acid intakes that exceed the tolerable limit of 1,000 mcg per day, mostly due to the folic acid they get from dietary supplements.
Vitamin B12 deficiency
Some people—particularly older adults and people with pernicious anemia—have difficulty absorbing vitamin B12. Consequently, vitamin B12 deficiency is common in the United States, affecting between 1.5% and 15% of the general population.
Older adults are prone to develop vitamin B12 deficiency due to atrophic gastritis, a condition that occurs in 10% to 30% of this population. Atrophic gastritis decreases the secretion of hydrochloric acid in the stomach, which reduces absorption of vitamin B12.
Similarly, some adults develop pernicious anemia, which is characterized by a lack of intrinsic factor in the stomach. Without enough intrinsic factor, people with pernicious anemia don’t properly absorb vitamin B12.
Other groups at risk of vitamin B12 deficiency include people with stomach and small intestine disorders (such as celiac disease and Crohn’s disease), people who have had gastrointestinal surgery (eg, for weight loss), and strict vegetarians (because animals are the only natural food source of B12).
Signs and symptoms of vitamin B12 deficiency include megaloblastic anemia, peripheral neuropathy, fatigue, weakness, constipation, loss of appetite, and weight loss. Other symptoms include difficulty maintaining balance, confusion, dementia and, rarely, soreness of the mouth or tongue.
The daily RDA for vitamin B12 in adults is 2.4 mcg, with higher amounts recommended for pregnant (2.6 mcg) and lactating (2.8 mcg) women. Vitamin B12 is naturally found in foods derived from animals, including seafood (eg, clams, trout, salmon, tuna), meat (notably beef liver), poultry, eggs, milk, milk products, and (for vegans) fortified breakfast cereals.
People with atrophic gastritis can absorb the synthetic vitamin B12 added to fortified foods and dietary supplements. So, adults older than age 50 are recommended to obtain vitamin B12 from vitamin supplements or fortified foods. People with pernicious anemia are usually treated with intramuscular injections of vitamin B12.
Other people who have trouble absorbing vitamin B12 from foods—as well as strict vegetarians who don’t eat foods derived from animal sources—can get their vitamin B12 from fortified foods, vitamin supplements, or vitamin B12 injections.