Health Guide | Should You Take Vitamin B12? Here’s What Doctors Say
Vitamin B12 may be one of the body’s most important nutrients, but that does not mean very high doses are healthy. Dr. M. Elizabeth Swenor, director of lifestyle, integrative, and functional medicine at Henry Ford Health System, notes that most healthy people get enough vitamin B12 through their regular diet. Only 1% to 2% of the population has a confirmed deficiency.
What Is B12?
Vitamin B12 is one of eight B vitamins and plays several essential roles. It helps produce red blood cells that carry oxygen throughout the body and is vital for nerve function, energy release, and even DNA formation. Dr. Lauri Wright, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics, says B12 has wide-ranging functions, but the body cannot make it and must obtain it from food or supplements.
After intake, B12 binds to intrinsic factor in the stomach. This protein acts like a taxi, carrying vitamin B12 from the stomach to the small intestine for absorption. Without enough intrinsic factor, B12 absorption is greatly reduced.
How Much B12 Do You Need Each Day?
Healthy adults need only 2.4 micrograms (mcg) of vitamin B12 per day. It is abundant in animal foods such as meat, fish, dairy products, eggs, and clams. A 3.5-ounce serving of baby clams provides as much as 4000% of the recommended daily value.
Dr. Lauri Wright notes that 3 ounces of tuna can meet a full day’s B12 requirement, while two eggs provide about half the recommended intake.
Who Is Most at Risk of Vitamin B12 Deficiency?
The following groups are most likely to develop vitamin B12 deficiency:
Adults over age 65
Vegetarians and vegans
People with gastrointestinal conditions such as Crohn’s disease or celiac disease
People who have undergone gastric bypass or other gastrointestinal surgery
Symptoms of B12 deficiency may develop gradually over several years and include fatigue, pale skin, numbness or tingling in the hands and feet, and confusion. If left untreated, long-term deficiency can cause nerve damage, impaired movement such as unsteady walking, pernicious anemia, heart failure, and even stomach cancer.
How Should B12 Be Supplemented?
Dr. Wright advises people at high risk to consult a doctor and have a blood test. If B12 deficiency is confirmed, doctors usually start with dietary changes and recommend supplements if those changes are ineffective. An initial dose may be as high as 500 micrograms, followed by a maintenance dose of 100 to 200 micrograms. People who lack intrinsic factor may need B12 injections.
Common Misconceptions About B12
Although B12 deficiency can cause several health problems, research does not support claims that high-dose B12 can treat a wide range of conditions. Common misconceptions and the current evidence include:
Alzheimer’s disease and memory problems: Low B12 levels are associated with memory problems, but no studies have shown that even a high dose of 1000 micrograms improves Alzheimer’s disease or memory.
Cancer: Both high and low B12 levels have been associated with cancer risk, but the mechanisms are unclear, and it is not known whether B12 is beneficial or harmful in cancer.
Cardiovascular disease and stroke: High homocysteine levels may increase the risk of heart disease and stroke. B12 can lower homocysteine, but this is effective only in people with B12 deficiency.
Infertility: B12 may improve sperm motility, but supplementation does not help when there is no deficiency.
Age-related macular degeneration: Some studies show that B12 combined with folic acid and B6 may reduce the risk of macular degeneration, but this is not routinely recommended.
Eczema: One study found that topical B12 cream relieved adult eczema, but large studies have not found a clear link between B12 levels and eczema risk.
Sickle cell anemia: B12 supplements may be ineffective or even harmful for this condition and should be used only after medical evaluation.
Energy and mood: B12 improves energy, concentration, and mood only in people with deficiency; it provides no significant benefit in people with normal levels.
Weight loss: The apparent weight-loss effect of high-dose B12 is largely a placebo effect and is not supported by scientific evidence.
Is High-Dose B12 Safe?
Dr. Wright emphasizes that even high doses of B12 do not pose a serious health risk because it is water-soluble and excess amounts are excreted in urine.
However, certain medications may lower B12 levels, including:
Acid suppressants and stomach medications such as omeprazole (Prilosec) and ranitidine (Zantac)
The diabetes medication metformin (Metformin)
Vitamin C in high doses
The antiseizure medication phenytoin (Dilantin)
The gout medication colchicine (Colchicine)
Cholesterol-lowering medications such as Colestid, Questran, and Welchol
Guide | Should you take vitamin B12? What doctors say
Health Guide | Should You Take Vitamin B12? Here’s What Doctors Say
Vitamin B12 may be one of the body’s most important nutrients, but that does not mean very high doses are healthy. Dr. M. Elizabeth Swenor, director of lifestyle, integrative, and functional medicine at Henry Ford Health System, notes that most healthy people get enough vitamin B12 through their regular diet. Only 1% to 2% of the population has a confirmed deficiency.
What Is B12?
Vitamin B12 is one of eight B vitamins and plays several essential roles. It helps produce red blood cells that carry oxygen throughout the body and is vital for nerve function, energy release, and even DNA formation. Dr. Lauri Wright, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics, says B12 has wide-ranging functions, but the body cannot make it and must obtain it from food or supplements.
After intake, B12 binds to intrinsic factor in the stomach. This protein acts like a taxi, carrying vitamin B12 from the stomach to the small intestine for absorption. Without enough intrinsic factor, B12 absorption is greatly reduced.
How Much B12 Do You Need Each Day?
Healthy adults need only 2.4 micrograms (mcg) of vitamin B12 per day. It is abundant in animal foods such as meat, fish, dairy products, eggs, and clams. A 3.5-ounce serving of baby clams provides as much as 4000% of the recommended daily value.
Dr. Lauri Wright notes that 3 ounces of tuna can meet a full day’s B12 requirement, while two eggs provide about half the recommended intake.
Who Is Most at Risk of Vitamin B12 Deficiency?
The following groups are most likely to develop vitamin B12 deficiency:
Adults over age 65
Vegetarians and vegans
People with gastrointestinal conditions such as Crohn’s disease or celiac disease
People who have undergone gastric bypass or other gastrointestinal surgery
Symptoms of B12 deficiency may develop gradually over several years and include fatigue, pale skin, numbness or tingling in the hands and feet, and confusion. If left untreated, long-term deficiency can cause nerve damage, impaired movement such as unsteady walking, pernicious anemia, heart failure, and even stomach cancer.
How Should B12 Be Supplemented?
Dr. Wright advises people at high risk to consult a doctor and have a blood test. If B12 deficiency is confirmed, doctors usually start with dietary changes and recommend supplements if those changes are ineffective. An initial dose may be as high as 500 micrograms, followed by a maintenance dose of 100 to 200 micrograms. People who lack intrinsic factor may need B12 injections.
Common Misconceptions About B12
Although B12 deficiency can cause several health problems, research does not support claims that high-dose B12 can treat a wide range of conditions. Common misconceptions and the current evidence include:
Alzheimer’s disease and memory problems: Low B12 levels are associated with memory problems, but no studies have shown that even a high dose of 1000 micrograms improves Alzheimer’s disease or memory.
Cancer: Both high and low B12 levels have been associated with cancer risk, but the mechanisms are unclear, and it is not known whether B12 is beneficial or harmful in cancer.
Cardiovascular disease and stroke: High homocysteine levels may increase the risk of heart disease and stroke. B12 can lower homocysteine, but this is effective only in people with B12 deficiency.
Infertility: B12 may improve sperm motility, but supplementation does not help when there is no deficiency.
Age-related macular degeneration: Some studies show that B12 combined with folic acid and B6 may reduce the risk of macular degeneration, but this is not routinely recommended.
Eczema: One study found that topical B12 cream relieved adult eczema, but large studies have not found a clear link between B12 levels and eczema risk.
Sickle cell anemia: B12 supplements may be ineffective or even harmful for this condition and should be used only after medical evaluation.
Energy and mood: B12 improves energy, concentration, and mood only in people with deficiency; it provides no significant benefit in people with normal levels.
Weight loss: The apparent weight-loss effect of high-dose B12 is largely a placebo effect and is not supported by scientific evidence.
Is High-Dose B12 Safe?
Dr. Wright emphasizes that even high doses of B12 do not pose a serious health risk because it is water-soluble and excess amounts are excreted in urine.
However, certain medications may lower B12 levels, including:
Acid suppressants and stomach medications such as omeprazole (Prilosec) and ranitidine (Zantac)
The diabetes medication metformin (Metformin)
Vitamin C in high doses
The antiseizure medication phenytoin (Dilantin)
The gout medication colchicine (Colchicine)
Cholesterol-lowering medications such as Colestid, Questran, and Welchol
The antibiotic tetracycline (Tetracycline)
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