In humans, vitamin C is essential to a healthy diet as well as being a highly effective antioxidant, acting to lessen oxidative stress; a substrate for ascorbate peroxidase;
Collagen, carnitine, and tyrosine synthesis, and microsomal metabolism
Ascorbic acid performs numerous physiological functions in human body. These functions include the synthesis of collagen, carnitine and neurotransmitters, the synthesis and catabolism of tyrosine and the metabolism of microsome. Ascorbate acts as a reducing agent (i.e. electron donor, anti-oxidant) in the above-described syntheses, maintaining iron and copper atoms in their reduced states.
Vitamin C acts as an electron donor for eight different enzymes: These reactions add hydroxyl groups to the amino acids proline or lysine in the collagen molecule via prolyl hydroxylase and lysyl hydroxylase, both requiring vitamin C as a cofactor. Hydroxylation allows the collagen molecule to assume its triple helix structure and making vitamin C essential to the development and maintenance of scar tissue, blood vessels, and cartilage.
2 are necessary for synthesis of carnitine. Carnitine is essential for the transport of fatty acids into mitochondria for ATP generation.
The remaining three have the following functions in common but do not always do this:
dopamine beta hydroxylase participates in the biosynthesis of norepinephrine from dopamine.
another enzyme adds amide groups to peptide hormones, greatly increasing their stability.
one modulates tyrosine metabolism.
Antioxidant
Ascorbic acid is well known for its antioxidant activity. Ascorbate acts as a reducing agent to reverse oxidation in aqueous solution. When there are more free radicals (Reactive oxygen species) in the body versus antioxidant, a human is under the condition called Oxidative stress. Oxidative stress induced diseases encompass cardiovascular diseases, hypertension, chronic inflammatory diseases and diabetes The plasma ascorbate concentration in oxidative stress patient (less than 45 µmol/L) measured is lower than healthy individual (61.4-80 µmol/L) According to McGregor and Biesalski (2006). This reaction can generate superoxide and other ROS. However, in the body, free transition elements are unlikely to be present while iron and copper is bound to diverse proteins. thus, ascorbate as a pro-oxidant is unlikely to convert metals to create ROS in vivo.
Immune system
Some advertisements claim that Vitamin C "supports" or is "important" for immune system function. These claims are partially supported by the scientific evidence (see Chandra RK, 1997, "Nutrition and the immune system: an introduction". The American Journal of Clinical Nutrition 66 (2): 460S–463S. PMID 9250133.)
Beta carotene is a member of the carotenoid family belonging to the isoprenoid compounds, which are polyunsaturates with antioxidant properties. The formula for beta carotene is C40H56 and it can exist as cis- or trans-isomers. Most of the naturally-occurring and synthesized forms of beta exists as the all-trans isomer.
Where is beta carotene found?
Beta carotene is produced by plants and microorganisms, with the main sources being yellow or orange and green-leaved vegetables or fruits such as sweet potato, spinach, carrots, pumpkin, butternut squash and apricots.
Beta carotene is also available as supplements, which may be synthetic or derived from palm oil, algae or fungi. When taken as a vitamin or mineral supplement, the dose ranges form 0.4 mg to 20 mg per day.
When used as a medicine to treat vitamin A deficiency, a dose of up to 6 mg/day may be given and in cases of erythropoietic protoporphyria (EPP), up to 300 mg/day may be taken. Beta carotene is also widely used as a yellow colouring agent (EC160a) in food and drink.
Although beta carotene is not classed as an essential nutrient, it is a precursor to vitamin A and the recommended daily intake is expressed as part of the reference nutrient intake (RNI) for vitamin A as retinol equivalents (RE).
Beneficial effects of beta carotene
As a provitamin of vitamin A, the importance of beta carotene in an individual depends on their level of pre-formed vitamin A. It is therefore difficult to define a beta- carotene deficiency. Beta carotene also interacts with other carotenoids during absorption and metabolic processes.
Studies have shown an association between high dietary intake of beta carotene and a reduced risk of heart disease and cancer. This may be due to the antioxidant properties of the molecule.
Properties
The absorption of beta carotene is facilitated by dietary fats and bile salts in the small intestine. Around 10% to 90% of the total dietary beta carotene is thought to be absorbed in the gut, with absorption decreasing, the higher the intake is. Low fat diets also reduce the amount of beta carotene absorbed.
Smokers have a low blood level of beta carotene, as do individuals with a high alcohol intake and those with HIV infection. People with impaired fat absorption from diet due to conditions such as jaundice, liver cirrhosis and cystic fibrosis also have a low blood level of beta carotene. Beta carotene is excreted in the feces and sweat.
What is vitamin D and what does it do?
Vitamin D is a nutrient found in some foods that is needed for health and to maintain strong bones. It does so by helping the body absorb calcium (one of bone's main building blocks) from food and supplements. People who get too little vitamin D may develop soft, thin, and brittle bones, a condition known as rickets in children and osteomalacia in adults.
Vitamin D is important to the body in many other ways as well. Muscles need it to move, for example, nerves need it to carry messages between the brain and every body part, and the immune system needs vitamin D to fight off invading bacteria and viruses. Together with calcium, vitamin D also helps protect older adults from osteoporosis. Vitamin D is found in cells throughout the body.
Table of Contents
What is vitamin D and what does it do?
How much vitamin D do I need?
What foods provide vitamin D?
Can I get vitamin D from the sun?
What kinds of vitamin D dietary supplements are available?
Am I getting enough vitamin D?
What happens if I don't get enough vitamin D?
What are some effects of vitamin D on health?
Can vitamin D be harmful?
Are there any interactions with vitamin D that I should know about?
Vitamin D and healthful eating
Where can I find out more about vitamin D?
Disclaimer
How much vitamin D do I need?
The amount of vitamin D you need each day depends on your age. Average daily recommended amounts from the Food and Nutrition Board (a national group of experts) for different ages are listed below in International Units (IU):
Life Stage Recommended Amount
Birth to 12 months 400 IU
Children 1–13 years 600 IU
Teens 14–18 years 600 IU
Adults 19–70 years 600 IU
Adults 71 years and older 800 IU
Pregnant and breastfeeding women 600 IU
What foods provide vitamin D?
Very few foods naturally have vitamin D. Fortified foods provide most of the vitamin D in American diets.
Fatty fish such as salmon, tuna, and mackerel are among the best sources.
Beef liver, cheese, and egg yolks provide small amounts.
Mushrooms provide some vitamin D. In some mushrooms that are newly available in stores, the vitamin D content is being boosted by exposing these mushrooms to ultraviolet light.
Almost all of the U.S. milk supply is fortified with 400 IU of vitamin D per quart. But foods made from milk, like cheese and ice cream, are usually not fortified.
Vitamin D is added to many breakfast cereals and to some brands of orange juice, yogurt, margarine, and soy beverages; check the labels.
Can I get vitamin D from the sun?
The body makes vitamin D when skin is directly exposed to the sun, and most people meet at least some of their vitamin D needs this way. Skin exposed to sunshine indoors through a window will not produce vitamin D. Cloudy days, shade, and having dark-colored skin also cut down on the amount of vitamin D the skin makes.
However, despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight in order to lower the risk for skin cancer. When out in the sun for more than a few minutes, wear protective clothing and apply sunscreen with an SPF (sun protection factor) of 8 or more. Tanning beds also cause the skin to make vitamin D, but pose similar risks for skin cancer.
People who avoid the sun or who cover their bodies with sunscreen or clothing should include good sources of vitamin D in their diets or take a supplement. Recommended intakes of vitamin D are set on the assumption of little sun exposure.
What kinds of vitamin D dietary supplements are available?
Vitamin D is found in supplements (and fortified foods) in two different forms: D2 (ergocalciferol) and D3 (cholecalciferol). Both increase vitamin D in the blood.
Am I getting enough vitamin D?
Because vitamin D can come from sun, food, and supplements, the best measure of one's vitamin D status is blood levels of a form known as 25-hydroxyvitamin D. Levels are described in either nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL), where 1 nmol/L = 0.4 ng/mL.
In general, levels below 30 nmol/L (12 ng/mL) are too low for bone or overall health, and levels above 125 nmol/L (50 ng/mL) are probably too high. Levels of 50 nmol/L or above (20 ng/mL or above) are sufficient for most people.
By these measures, some Americans are vitamin D deficient and almost no one has levels that are too high. In general, young people have higher blood levels of 25-hydroxyvitamin D than older people and males have higher levels than females. By race, non-Hispanic blacks tend to have the lowest levels and non-Hispanic whites the highest. The majority of Americans have blood levels lower than 75 nmol/L (30 ng/mL).
Certain other groups may not get enough vitamin D:
Breastfed infants, since human milk is a poor source of the nutrient. Breastfed infants should be given a supplement of 400 IU of vitamin D each day.
Older adults, since their skin doesn't make vitamin D when exposed to sunlight as efficiently as when they were young, and their kidneys are less able to convert vitamin D to its active form.
People with dark skin, because their skin has less ability to produce vitamin D from the sun.
People with disorders such as Crohn's disease or celiac disease who don't handle fat properly, because vitamin D needs fat to be absorbed.
Obese people, because their body fat binds to some vitamin D and prevents it from getting into the blood.
What happens if I don't get enough vitamin D?
People can become deficient in vitamin D because they don't consume enough or absorb enough from food, their exposure to sunlight is limited, or their kidneys cannot convert vitamin D to its active form in the body. In children, vitamin D deficiency causes rickets, where the bones become soft and bend. It's a rare disease but still occurs, especially among African American infants and children. In adults, vitamin D deficiency leads to osteomalacia, causing bone pain and muscle weakness.
What are some effects of vitamin D on health?
Vitamin D is being studied for its possible connections to several diseases and medical problems, including diabetes, hypertension, and autoimmune conditions such as multiple sclerosis. Two of them discussed below are bone disorders and some types of cancer.
Bone disorders
As they get older, millions of people (mostly women, but men too) develop, or are at risk of, osteoporosis, where bones become fragile and may fracture if one falls. It is one consequence of not getting enough calcium and vitamin D over the long term. Supplements of both vitamin D3 (at 700–800 IU/day) and calcium (500–1,200 mg/day) have been shown to reduce the risk of bone loss and fractures in elderly people aged 62–85 years. Men and women should talk with their health care providers about their needs for vitamin D (and calcium) as part of an overall plan to prevent or treat osteoporosis.
Cancer
Some studies suggest that vitamin D may protect against colon cancer and perhaps even cancers of the prostate and breast. But higher levels of vitamin D in the blood have also been linked to higher rates of pancreatic cancer. At this time, it's too early to say whether low vitamin D status increases cancer risk and whether higher levels protect or even increase risk in some people.
Can vitamin D be harmful?
Yes, when amounts in the blood become too high. Signs of toxicity include nausea, vomiting, poor appetite, constipation, weakness, and weight loss. And by raising blood levels of calcium, too much vitamin D can cause confusion, disorientation, and problems with heart rhythm. Excess vitamin D can also damage the kidneys.
The safe upper limit for vitamin D is 1,000 to 1,500 IU/day for infants, 2,500 to 3,000 IU/day for children 1-8 years, and 4,000 IU/day for children 9 years and older, adults, and pregnant and lactating teens and women. Vitamin D toxicity almost always occurs from overuse of supplements. Excessive sun exposure doesn't cause vitamin D poisoning because the body limits the amount of this vitamin it produces.
Are there any interactions with vitamin D that I should know about?
Like most dietary supplements, vitamin D may interact or interfere with other medicines or supplements you might be taking. Here are several examples:
Prednisone and other corticosteroid medicines to reduce inflammation impair how the body handles vitamin D, which leads to lower calcium absorption and loss of bone over time.
Both the weight-loss drug orlistat (brand names Xenical® and Alli®) and the cholesterol-lowering drug cholestyramine (brand names Questran®, LoCholest®, and Prevalite®) can reduce the absorption of vitamin D and other fat-soluble vitamins (A, E, and K).
Both phenobarbital and phenytoin (brand name Dilantin®), used to prevent and control epileptic seizures, increase the breakdown of vitamin D and reduce calcium absorption.
Tell your doctor, pharmacist, and other health care providers about any dietary supplements and medicines you take. They can tell you if those dietary supplements might interact or interfere with your prescription or over-the-counter medicines, or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients.
Vitamin D and healthful eating
People should get most of their nutrients from food, advises the federal government's Dietary Guidelines for Americans. Foods contain vitamins, minerals, dietary fiber and other substances that benefit health. Dietary supplements might help in some situations to increase the intake of a specific vitamin or mineral. For more information on building a healthy diet, refer to the Dietary Guidelines for Americansexternal link icon and the U.S. Department of Agriculture's food guidance system, ChooseMyPlateexternal link icon.
Protein is one of the three nutrients found in food that the body requires in large amounts. Along with carbohydrates and fat, protein is essential for the human body.
Proteins are made of small compounds called amino acids. There are hundreds of amino acids that exist in nature, but the human body only utilizes 22 of them.
The human body can produce all but nine of the amino acids that it needs. These nine are called essential amino acids and must be consumed through food.
All foods contain differing combinations of amino acids, making a balanced diet essential. In general, animal proteins like meat, dairy, and eggs contain all the essential amino acids.
Plant-based proteins from foods like beans, grains, nuts, and soy are rich in some amino acids but may be lacking in others. This lack underlines the need for a well-balanced diet with variety.
What does protein do?
Protein is the major building block of the human body. Its main job is to build and maintain tissue.
Food sources containing protein.
Many foods are high in protein, including several that are suitable for vegetarians and vegans.
Periods of growth, such as infancy, childhood, and pregnancy, require more protein for this growth to occur. Protein needs are also increased for the following people:
People who have undergone surgery
Active people who are consistently breaking down muscle during exercise
The total amount of protein that is consumed in a day is not nearly as important as how protein intake is spread out over the day.
Many people will consume a small amount of protein at breakfast, a moderate amount at lunch, and a large amount at dinner.
A typical day's eating might involve 10 grams of protein or less at breakfast (cereal), 25 grams at lunch (sandwich), 5 grams for a snack (granola bar), and 40 grams at dinner (chicken or beef).
However, the body can only absorb and use a certain amount protein at one time. The body uses what it can and then what is left over becomes waste. So, it is better for people to spread 60 grams of protein over three or four meals of 15-20 grams each instead of having 60 grams of protein in one meal.
How much protein is needed each day?
There is a certain amount of protein people can aim for to make sure they are they get the most protein use, muscle generation, and recovery every time they eat. This amount depends on the person's body size and how active they are.
Blocks of tofu.
Half a block of tofu contains 18 grams of protein.
A 6-foot, 250-pound man who strength trains five times a week can absorb and utilize more protein than a 5-foot female who does not exercise much. Studies to date have suggested a 20-30 gram per meal protein goal, but more research is needed.
The Recommended Dietary Allowance (RDA) for protein is 0.8 grams per kilogram of body weight per day. The RDA is the minimum amount of protein needed for meeting nutritional requirements, not the maximum.
Endurance athletes need 1.2 to 1.4 grams per kilogram of body weight. Strength training or power athletes require 1.2 to 1.7 grams per kilogram of body weight. The more physically active a person is, the more protein that they will need to consume.
Some research has recommended as much as 2 grams per kilogram of body weight to prevent muscle loss in athletes who want to lose weight and have reduced the amount of calories they consume.
Amount of protein in common food sources
According to the U.S. Department of Agriculture, the following amounts of protein can be found in common sources of food:
Food Amount Grams of protein
Chicken 3 ounces 20
Ground beef 3 ounces 21
Milk 1 cup 9
Egg 1 6
Black beans ¾ cup 11.43
Peanut butter 2 tablespoons 8
Tofu ½ block 18Risks and precautions for consuming protein
Most studies support an intake of up to 2 grams per kilogram of body weight without any negative or adverse effects (including kidney damage). Consuming more than 2.5 grams of protein per kilogram of body weight can increase the risk of the following:
Dehydration
Fatigue
Taking in too many calories
Passing out higher levels of the nutrient calcium in the urine
Eating more than 200 to 400 grams of protein per day can exceed the liver's ability to convert excess nitrogen to a waste product called urea. This can lead to nausea, diarrhea, and other adverse side effects.
What is vitamin E?
Vitamin E is an antioxidant that occurs naturally in foods such as nuts, seeds, and leafy green vegetables. Vitamin E is a fat-soluble vitamin important for many processes in the body.
Vitamin E is used to treat or prevent vitamin E deficiency. People with certain diseases may need extra vitamin E.
Important information
Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.
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Before taking this medicine
Ask a doctor or pharmacist if it is safe for you to use vitamin E if you have other medical conditions, especially:
anemia (low red blood cells);
a bleeding or blood clotting disorder such as hemophilia;
liver disease;
kidney disease;
any allergies;
an eye disorder called retinitis pigmentosa;
a vitamin K deficiency;
high cholesterol or triglycerides (a type of fat in the blood);
a history of cancer;
a history of stroke or blood clot; or
if you need surgery, or have recently had surgery.
FDA pregnancy category C. It is not known whether vitamin E will harm an unborn baby. Do not use this medicine without a doctor's advice if you are pregnant.
See also: Pregnancy and breastfeeding warnings (in more detail)
It is not known whether vitamin E passes into breast milk or if it could harm a nursing baby. Do not use this medicine without a doctor's advice if you are breast-feeding a baby.
Your dose needs may be different during pregnancy or while you are nursing.
How should I take vitamin E?
Use vitamin E products exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.
Vitamin E works best if you take it with food.
Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.
Artificially sweetened liquid medicine may contain phenylalanine. Check the medication label if you have phenylketonuria (PKU).
The recommended dietary allowance of vitamin E increases with age. Follow your healthcare provider's instructions. You may also consult the Office of Dietary Supplements of the National Institutes of Health, or the U.S. Department of Agriculture (USDA) Nutrient Database (formerly "Recommended Daily Allowances") listings for more information.
If you need surgery or a medical procedure, tell the surgeon ahead of time that you are using vitamin E. You may need to stop using the medicine for a short time.
Store at room temperature away from moisture and heat.
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include stomach pain, nausea, diarrhea, dizziness, headache, tiredness, blurred vision, or tiredness.
What should I avoid while taking vitamin E?
Avoid taking other vitamins, mineral supplements, or nutritional products without your doctor's advice.
If you also take orlistat (alli, Xenical), do not take it within 2 hours before or 2 hours after you take vitamin E.
Vitamin B12 is a nutrient that helps keep the body's nerve and blood cells healthy and helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia called megaloblastic anemia that makes people tired and weak.
Two steps are required for the body to absorb vitamin B12 from food. First, hydrochloric acid in the stomach separates vitamin B12 from the protein to which vitamin B12 is attached in food. After this, vitamin B12 combines with a protein made by the stomach called intrinsic factor and is absorbed by the body. Some people have pernicious anemia, a condition where they cannot make intrinsic factor. As a result, they have trouble absorbing vitamin B12 from all foods and dietary supplements.
Table of Contents
What is vitamin B12 and what does it do?
How much vitamin B12 do I need?
What foods provide vitamin B12?
What kinds of vitamin B12 dietary supplements are available?
Am I getting enough vitamin B12?
What happens if I don't get enough vitamin B12?
What are some effects of vitamin B12 on health?
Can vitamin B12 be harmful?
Are there any interactions with vitamin B12 that I should know about?
Vitamin B12 and healthful eating
Where can I find out more about vitamin B12?
Disclaimer
How much vitamin B12 do I need?
The amount of vitamin B12 you need each day depends on your age. Average daily recommended amounts for different ages are listed below in micrograms (mcg):
Life Stage Recommended Amount
Birth to 6 months 0.4 mcg
Infants 7–12 months 0.5 mcg
Children 1–3 years 0.9 mcg
Children 4–8 years 1.2 mcg
Children 9–13 years 1.8 mcg
Teens 14–18 years 2.4 mcg
Adults 2.4 mcg
Pregnant teens and women 2.6 mcg
Breastfeeding teens and women 2.8 mcg
What foods provide vitamin B12?
Vitamin B12 is found naturally in a wide variety of animal foods and is added to some fortified foods. Plant foods have no vitamin B12 unless they are fortified. You can get recommended amounts of vitamin B12 by eating a variety of foods including the following:
Beef liver and clams, which are the best sources of vitamin B12.
Fish, meat, poultry, eggs, milk, and other dairy products, which also contain vitamin B12.
Some breakfast cereals, nutritional yeasts and other food products that are fortified with vitamin B12. To find out if vitamin B12 has been added to a food product, check the product labels.
What kinds of vitamin B12 dietary supplements are available?
Vitamin B12 is found in almost all multivitamins. Dietary supplements that contain only vitamin B12, or vitamin B12 with nutrients such as folic acid and other B vitamins, are also available. Check the Supplement Facts label to determine the amount of vitamin B12 provided.
Vitamin B12 is also available in sublingual forms (which are dissolved under the tongue). There is no evidence that sublingual forms are better absorbed than pills that are swallowed.
A prescription form of vitamin B12 can be administered as a shot. This is usually used to treat vitamin B12 deficiency. Vitamin B12 is also available as a prescription medication in nasal gel form (for use in the nose).
Am I getting enough vitamin B12?
Most people in the United States get enough vitamin B12 from the foods they eat. But some people have trouble absorbing vitamin B12 from food. As a result, vitamin B12 deficiency affects between 1.5% and 15% of the public. Your doctor can test your vitamin B12 level to see if you have a deficiency.
Certain groups may not get enough vitamin B12 or have trouble absorbing it:
Many older adults, who do not have enough hydrochloric acid in their stomach to absorb the vitamin B12 naturally present in food. People over 50 should get most of their vitamin B12 from fortified foods or dietary supplements because, in most cases, their bodies can absorb vitamin B12 from these sources.
People with pernicious anemia whose bodies do not make the intrinsic factor needed to absorb vitamin B12. Doctors usually treat pernicious anemia with vitamin B12 shots, although very high oral doses of vitamin B12 might also be effective.
People who have had gastrointestinal surgery, such as weight loss surgery, or who have digestive disorders, such as celiac disease or Crohn's disease. These conditions can decrease the amount of vitamin B12 that the body can absorb.
Some people who eat little or no animal foods such as vegetarians and vegans. Only animal foods have vitamin B12 naturally. When pregnant women and women who breastfeed their babies are strict vegetarians or vegans, their babies might also not get enough vitamin B12.
What happens if I don't get enough vitamin B12?
Vitamin B12 deficiency causes tiredness, weakness, constipation, loss of appetite, weight loss, and megaloblastic anemia. Nerve problems, such as numbness and tingling in the hands and feet, can also occur. Other symptoms of vitamin B12 deficiency include problems with balance, depression, confusion, dementia, poor memory, and soreness of the mouth or tongue. Vitamin B12 deficiency can damage the nervous system even in people who don't have anemia, so it is important to treat a deficiency as soon as possible.
In infants, signs of a vitamin B12 deficiency include failure to thrive, problems with movement, delays in reaching the typical developmental milestones, and megaloblastic anemia.
Large amounts of folic acid can hide a vitamin B12 deficiency by correcting megaloblastic anemia, a hallmark of vitamin B12 deficiency. But folic acid does not correct the progressive damage to the nervous system that vitamin B12 deficiency also causes. For this reason, healthy adults should not get more than 1,000 mcg of folic acid a day.
What are some effects of vitamin B12 on health?
Scientists are studying vitamin B12 to understand how it affects health. Here are several examples of what this research has shown:
Heart disease
Vitamin B12 supplements (along with folic acid and vitamin B6) do not reduce the risk of getting heart disease. Scientists had thought that these vitamins might be helpful because they reduce blood levels of homocysteine, a compound linked to an increased risk of having a heart attack or stroke.
Dementia
As they get older, some people develop dementia. These people often have high levels of homocysteine in the blood. Vitamin B12 (with folic acid and vitamin B6) can lower homocysteine levels, but scientists don't know yet whether these vitamins actually help prevent or treat dementia.
Energy and athletic performance
Advertisements often promote vitamin B12 supplements as a way to increase energy or endurance. Except in people with a vitamin B12 deficiency, no evidence shows that vitamin B12 supplements increase energy or improve athletic performance.
Can vitamin B12 be harmful?
Vitamin B12 has not been shown to cause any harm.
Are there any interactions with vitamin B12 that I should know about?
Yes. Vitamin B12 can interact or interfere with medicines that you take, and in some cases, medicines can lower vitamin B12 levels in the body. Here are several examples of medicines that can interfere with the body's absorption or use of vitamin B12:
Chloramphenicol (Chloromycetin®), an antibiotic that is used to treat certain infections.
Proton pump inhibitors, such as omeprazole (Prilosec®) and lansoprazole (Prevacid®), that are used to treat acid reflux and peptic ulcer disease.
Histamine H2 receptor antagonists, such as cimetidine (Tagamet®), famotidine (Pepcid®), and ranitidine (Zantac®), that are used to treat peptic ulcer disease.
Metformin, a drug used to treat diabetes.
Tell your doctor, pharmacist, and other health care providers about any dietary supplements and medicines you take. They can tell you if those dietary supplements might interact or interfere with your prescription or over-the-counter medicines or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients.
Vitamin B12 and healthful eating
People should get most of their nutrients from food, advises the federal government's Dietary Guidelines for Americans. Foods contain vitamins, minerals, dietary fiber and other substances that benefit health. Dietary supplements might help in some situations to increase the intake of a specific vitamin or mineral. For more information on building a healthy diet, refer to the Dietary Guidelines for Americansexternal link icon and the U.S. Department of Agriculture's food guidance system, ChooseMyPlateexternal link icon.