Are you getting enough B vitamins?

Eight different vitamins make up the B complex, and all play vital roles in the body, including helping produce energy, maintaining a healthy nervous system, and promoting cell development. If eight sounds like a lot to remember, it’s worth noting that research has focused on five: thiamine (B1), riboflavin (B2), niacin (B3), folate (B9), and cobalamin (B12).

The body can only store a limited amount of these vitamins, so they must be consumed regularly to maintain normal levels and health. Most B vitamins are obtained from animal and dairy products, legumes, eggs, nuts, seeds, some vegetables (especially leafy greens and legumes), and fortified cereals and breakfast cereals.

“A balanced, healthy diet provides enough B vitamins for most people,” says gastroenterologist Joel Mason, a senior scientist at the U.S. Department of Agriculture’s Human Nutrition Research Center (HNRCA) and a professor at the School of Nutrition and Policy and Tufts University School of Medicine.

"However, for certain groups of the population, even a nutritious diet may not be enough. For example, older people's ability to absorb vitamin B12 decreases with age - in which case supplements are definitely necessary. The same goes for vegans, pregnant women, and those who have had gastric bypass surgery."

Additionally, some commonly used medications, including metformin (for diabetes) and proton pump inhibitors (such as omeprazole), reduce the absorption of vitamin B12 and may increase the risk of deficiency.

Plant foods do not contain cobalamin (B12), so people who follow a vegan diet may be at risk for deficiency. In most cases, taking a multivitamin containing 2.4 micrograms of vitamin B12 will cover the need.

Adequate intake of these essential nutrients is important for maintaining health, but Mason warns against overdoing it—more is not always better. Excessive intake of some vitamins can have side effects.

One example is vitamin B6, which is toxic in high doses. In the 1980s, taking high doses of B6 to relieve premenstrual pain became popular. With the recommended dose being about 2 mg for men and 1.6 mg for women, some women took up to 200 mg a day. This led to permanent damage to the nerves in the arms and legs, called peripheral neuropathy.

Another example is niacin (B3), which is sometimes prescribed in high doses to lower cholesterol. However, high doses can cause severe skin redness, rashes, and itching.

B Vitamins and Pregnancy

In the United States, corn, rice, and wheat flour have been fortified with thiamine (B1), riboflavin (B2), and niacin (B3) since the 1940s to help prevent diseases such as pellagra and beriberi. In 1998, folic acid, a synthetic form of folate (B9), was added to the mandatory fortification to ensure adequate levels of the vitamin during pregnancy and to help prevent neural tube defects in the fetus.
The neural tube forms the brain and spinal cord of the fetus early in pregnancy, often before a woman even knows she is pregnant.

Because up to 50% of pregnancies are unplanned, the United States and about 70 other countries require manufacturers to fortify flour with folic acid. These measures have reduced the incidence of nervous system defects in newborns to 70%.

Folate and Cancer

Research over the past 30 years has consistently shown that people with low folate intake have an increased risk of developing certain types of cancer.

"Our research at Tufts, primarily focused on colon cancer, has shown in both animals and humans that chronically low folate intake significantly increases the risk of colon cancer, and possibly pancreatic and postmenopausal breast cancer as well," Mason says.

However, his animal experiments also showed that excessive consumption of folic acid may actually increase the risk of developing certain tumors. This has become the subject of scientific debate.

Tufts scientists have noticed that when animals are given too much folic acid, the incidence of cancer increases.

“Intuitively, it makes sense,” Mason says. “Folate is a ‘fertilizer’ for cell growth. If you have mutated cells that could become cancerous, then giving them extra folate can speed up their reproduction.”

However, he adds that several large epidemiological studies have shown that this carcinogenic effect is not widespread and, if it exists, is likely to occur only in those who consume multiple sources of folate at the same time.

Thiamine and gastric bypass

Thiamine (B1) deficiency is a poorly recognized complication following gastric bypass surgery, Mason says.

“In the past, thiamine deficiency in the United States was seen almost exclusively in people with alcoholism,” he recalls.
But after gastric bypass, because of impaired vitamin absorption and frequent vomiting, patients may arrive in the emergency room with lethargy, weakness, confusion, poor eye coordination, and other symptoms.

If left undiagnosed and untreated, thiamine deficiency can lead to the disease beriberi, brain and nerve damage, and even death.

“Surgeons, emergency room physicians, and other professionals should be aware of the possibility of thiamine deficiency in patients undergoing gastric bypass. If this is suspected, it is important to administer the vitamin intravenously immediately, without waiting for test results,” Mason says.
“If you suspect you have a deficiency or excess of B vitamins, see your doctor.”

How much do you need per day?

The National Institutes of Health (NIH) recommends the following daily intakes of B vitamins for adults:

Vitamin	Norm (per day)	During pregnancy	When breastfeeding
B1 (thiamine)	1–1.2 mg	1.4 mg	1.4 mg
B2 (riboflavin)	1.1–1.3 mg	1.4 mg	1.6 mg
B3 (niacin)	14–16 mg	18 mg	17 mg
B5 (pantothenic acid)	5 mg	6 mg	7 mg
B6 (pyridoxine)	1.3 mg (up to 50 years), 1.5–1.7 mg (after 50)	1.9 mg	2.0 mg
B7 (biotin)	30 mcg	—	35 mcg
B9 (folate)	400 mcg	600 mcg	500 mcg
B12 (cobalamin)	2.4 mcg	2.6 mcg	2.8 mcg

Sources:

• B1: One serving of fortified cereal provides 100% of the daily value.
• B2: Two eggs provide about 1/3 of the daily requirement.
• B3: 170g fried chicken - more than 100% of the daily requirement.
• B6: 170 g tuna - 100% of the norm.
• B9: Half a cup of cooked spinach is a third of the daily value.
• B12: 85 g of salmon or ground beef - 100% of the norm.