What Are B Vitamins? 8 Types, Functions, Foods, Deficiency & Supplement Guide

“What exactly are B vitamins?” “How are B1, B2, B6 and B12 different?” “Which foods contain them?” “And what should you look for in a B-complex supplement?”

The term B vitamins does not refer to one single vitamin. It describes a group of eight different water-soluble vitamins, each with its own roles in the body.

The eight B vitamins are: vitamin B1, vitamin B2, niacin, pantothenic acid, vitamin B6, biotin, folate and vitamin B12.

Together, they are involved in many processes, including carbohydrate, fat and protein metabolism, amino acid metabolism, DNA synthesis and normal red blood cell formation.

However, saying that B vitamins are involved in energy metabolism does not mean that taking more B vitamins automatically gives you more energy.

Their role is to support the normal biochemical reactions the body uses every day.

In this guide, we explain what B vitamins are, the functions and food sources of all eight types, daily intake, factors linked with low intake or poor absorption, vitamin B12 and plant-based diets, folate and pregnancy, B-complex supplements, different ingredient forms, supplement selection and safety.

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Contents

• What are B vitamins?
• Why are they called the vitamin B group?
• The 8 B vitamins: functions and food sources
• How much do we need each day?
• Vitamin B1: thiamin
• Vitamin B2: riboflavin
• Niacin: vitamin B3
• Pantothenic acid: vitamin B5
• Vitamin B6
• Biotin: vitamin B7
• Folate: vitamin B9
• Vitamin B12
• Foods rich in B vitamins
• When can B-vitamin intake or status become low?
• Vitamin B12 and vegetarian or vegan diets
• Folate and pregnancy
• What is a B-complex supplement?
• Different forms of B6, B12, folate and niacin
• How to choose a B-complex supplement
• Safety: B6, niacin, folate and biotin
• Summary

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What are B vitamins?

The vitamin B group is made up of eight individual nutrients:

• Vitamin B1 — thiamin
• Vitamin B2 — riboflavin
• Niacin — commonly called vitamin B3
• Pantothenic acid — commonly called vitamin B5
• Vitamin B6
• Biotin — commonly called vitamin B7
• Folate — commonly called vitamin B9
• Vitamin B12 — cobalamin

All eight are classified as water-soluble vitamins.

What does “water-soluble” mean?

Water-soluble vitamins dissolve in water and, in general, are not stored in the body in the same way as fat-soluble vitamins.

Some excess can be excreted in urine.

However:

water-soluble does not mean unlimited amounts are always safe.

Vitamin B6 and niacin, for example, can cause adverse effects when taken in high supplemental doses over time.

Vitamin B12 is also unusual because, despite being water-soluble, the body can store relatively large amounts of it.

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Why are they called the vitamin B group?

Early nutrition researchers originally thought vitamin B was a single substance.

As research progressed, scientists discovered that what had been called “vitamin B” actually consisted of several different compounds.

These were gradually classified as individual vitamins.

They are still grouped together because many of them act as coenzymes or precursors to coenzymes and participate in related metabolic pathways.

Did you know? Why are there no vitamins B4 or B8?

Early vitamin research assigned B numbers to several substances that were thought to be essential vitamins.

Later research showed that some of these compounds did not meet the definition of an essential vitamin, while others were reclassified.

That is why the modern B-vitamin numbering system contains gaps.

Many B vitamins work as coenzymes

The body uses thousands of enzymes to break down nutrients and build new compounds.

Some enzymes require additional molecules called coenzymes to function normally.

Many B vitamins are converted into coenzymes or become part of coenzymes involved in carbohydrate, fat, protein and amino acid metabolism.

So rather than thinking of B vitamins as “energy-producing ingredients”, it is more accurate to think of them as nutrients that participate in the reactions that allow the body to use food.

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The 8 B vitamins: functions and food sources

Each B vitamin has its own functions, but several B vitamins may participate in the same metabolic pathway.

That is why it often makes more sense to think about getting a varied range of B vitamins from food rather than focusing on only one B vitamin in isolation.

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How much do we need each day?

Japan's Dietary Reference Intakes (2025 edition) set different intake values for each B vitamin.

As an example, the values for adults aged 30–49 are shown below.

These are example values for adults aged 30–49. Requirements vary by age, sex, pregnancy and breastfeeding status.

Do not confuse mg with mcg

B-vitamin labels use both milligrams (mg) and micrograms (mcg).

1 mg = 1,000 mcg.

For example, vitamin B12 at 4 mcg and vitamin B6 at 1.2 mg cannot be compared simply by looking at the size of the number.

This is especially important when reading international supplement labels.

How much do adults in Japan actually get from food?

According to Japan's 2024 National Health and Nutrition Survey, average daily intake among adults aged 20 and over was approximately 0.94 mg of B1, 1.16 mg of B2, 31.1 mg NE of niacin, 1.17 mg of B6, 5.9 mcg of B12, 277 mcg of folate and 5.58 mg of pantothenic acid.

These are population averages.

They do not show whether every individual meets their own requirement, because dietary reference values differ by age and sex.

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Vitamin B1: thiamin

Vitamin B1 is also known as thiamin.

In the body, it is converted into coenzyme forms that participate in reactions involved in carbohydrate and energy metabolism.

Pork is a particularly well-known source, while whole grains, legumes, nuts and seeds can also contribute.

One important distinction is:

“B1 is involved in energy metabolism” does not mean “more B1 automatically gives you more energy.”

Vitamin B1 is one of the nutrients required for normal metabolic reactions.

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Vitamin B2: riboflavin

Vitamin B2 is also called riboflavin.

It forms part of the coenzymes FAD and FMN, which participate in many oxidation-reduction reactions, including those involved in energy metabolism.

Food sources include liver, eggs, dairy products and fish.

Did you know? Why can B-complex supplements make urine bright yellow?

Some people notice that their urine becomes noticeably brighter or more fluorescent after taking a B-complex supplement.

Riboflavin is one reason.

Riboflavin itself has a yellow colour, and some excess riboflavin can be excreted in urine.

This colour change alone does not necessarily indicate a problem.

Riboflavin is also sensitive to light, which means food storage conditions can affect riboflavin content.

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Niacin: vitamin B3

Niacin is commonly called vitamin B3.

The term includes compounds with niacin activity, including nicotinic acid and nicotinamide.

In the body, niacin is used to form NAD and NADP, two important coenzymes involved in many metabolic and oxidation-reduction reactions.

The body can also make some niacin from tryptophan

Niacin does not come only from food.

The body can produce some niacin from the essential amino acid tryptophan.

This is why Japanese dietary reference values use the unit mg NE, or niacin equivalents.

Food sources include fish, meat, peanuts and mushrooms.

Nicotinic acid and nicotinamide are not identical

Supplements commonly contain either nicotinic acid or nicotinamide.

High supplemental intakes of nicotinic acid can cause niacin flushing, which may involve redness, warmth or tingling of the skin.

Nicotinamide is generally much less likely to cause this type of flushing.

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Pantothenic acid: vitamin B5

Pantothenic acid is commonly called vitamin B5.

It forms part of coenzyme A, or CoA, which is involved in the metabolism of fatty acids and many other compounds.

The name “pantothenic” comes from a word meaning “from everywhere”, reflecting how widely distributed it is in food.

Sources include meat, eggs, mushrooms, legumes and whole grains.

Because it is found in so many foods, isolated pantothenic acid deficiency is uncommon in people eating a varied diet.

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Vitamin B6

Vitamin B6 is not just one compound.

It refers to several related compounds, including pyridoxine, pyridoxal and pyridoxamine.

In the body, vitamin B6 functions mainly in coenzyme forms such as pyridoxal 5'-phosphate (PLP).

It participates in many enzymatic reactions, particularly those involving amino acids and protein metabolism.

Food sources include fish, poultry, potatoes and bananas.

If you eat more protein, do you automatically need large amounts of B6?

Vitamin B6 requirements are influenced in part by protein intake.

However, this does not mean that anyone eating a high-protein diet needs a high-dose B6 supplement.

It is more useful to consider the whole diet and to check how much B6 is already present in multivitamins, B-complex products and other supplements.

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Biotin: vitamin B7

Biotin is commonly called vitamin B7.

It acts as a coenzyme for several carboxylase enzymes involved in carbohydrate, fat and amino acid metabolism.

Food sources include eggs, nuts, soybeans and liver.

Biotin is often marketed in beauty supplements, but it is better understood first as a vitamin involved in normal metabolic processes, rather than as an ingredient with one single cosmetic purpose.

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Folate: vitamin B9

Folate is commonly called vitamin B9.

It participates in DNA and RNA synthesis, amino acid metabolism and normal cell division.

Food sources include leafy green vegetables, broccoli, legumes and liver.

The name “folate” itself is connected historically with leafy vegetables.

Food folate and folic acid are not exactly the same

The term “folate” is often used broadly, but naturally occurring folates in food and folic acid used in supplements and fortified foods differ in chemical form and bioavailability.

In some countries, food and supplement labels may use DFE, or Dietary Folate Equivalents, to account for these differences.

When comparing international supplements with food-based folate values, it is useful to look beyond the number alone.

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Vitamin B12

Vitamin B12 refers to a group of compounds called cobalamins.

One of their unusual features is that they contain cobalt at the centre of the molecule.

Vitamin B12 participates in DNA synthesis, normal red blood cell formation and normal nervous-system function.

Natural food sources are mainly animal-derived foods, including shellfish, fish, meat, eggs and dairy products.

B12 absorption is more complicated than it looks

Vitamin B12 in food is usually bound to protein.

To be absorbed efficiently, food-derived B12 generally goes through several steps:

1. it is released from food protein in the stomach
2. it binds to a protein called intrinsic factor
3. the B12–intrinsic factor complex is absorbed in the final part of the small intestine

Vitamin B12 in supplements is already in a free form, so it does not need to be released from food protein first.

Did you know? B12 is water-soluble but can still be stored for years

Most B vitamins are described as having relatively limited storage in the body.

Vitamin B12 is different.

The body can store relatively large amounts, which means it may take several years for low intake or poor absorption to lead to markedly reduced B12 stores.

Why do some B12 supplements contain 500 mcg or 1,000 mcg?

International vitamin B12 supplements often contain 500 mcg or even 1,000 mcg, far above Japan's adult adequate intake of 4.0 mcg per day.

One reason is that the percentage of B12 absorbed falls as the dose increases.

Human data suggest that approximately 2% of a 500 mcg dose and about 1.3% of a 1,000 mcg dose may be absorbed.

In other words, the amount written on the label is not the same as the amount absorbed.

This is why large label numbers should not automatically be interpreted as a better product.

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Foods rich in B vitamins

There is no single food that provides large amounts of every B vitamin.

Different B vitamins are distributed across different food groups.

Cooking can affect some B vitamins

Because many B vitamins are water-soluble, some can move into cooking water during boiling.

Different B vitamins also vary in their sensitivity to heat and light.

This does not mean that foods need to be eaten raw.

Using a variety of cooking methods, including steaming, stir-frying and dishes where the cooking liquid is consumed, can help retain nutrients while keeping meals practical.

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When can B-vitamin intake or status become low?

B vitamins are widely distributed across food, so people who eat a varied diet are not necessarily at high risk of deficiency in any one B vitamin.

However, intake or status can become more relevant when:

• certain food groups are avoided for long periods
• overall food intake is low
• the diet is very restrictive
• alcohol intake is high
• digestive conditions affect absorption
• ageing changes food intake or absorption
• pregnancy or breastfeeding changes nutritional requirements
• certain medicines are used long term

The effects of low B-vitamin status differ depending on the specific vitamin.

Changes involving appetite, the skin or mouth, blood or nerves may occur in some deficiency states, but these signs can also have many other causes.

For that reason, symptoms alone should not be used to self-diagnose a B-vitamin deficiency and start high-dose supplementation.

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Vitamin B12 and vegetarian or vegan diets

Vitamin B12 is one of the B vitamins most strongly influenced by dietary pattern.

Reliable natural sources are mainly animal-derived foods such as fish, shellfish, meat, eggs and dairy products.

Plant foods generally contain little reliable naturally occurring vitamin B12.

For people following vegan diets, it is therefore important to consider B12 intake from fortified foods or supplements.

Older adults and people with certain stomach or intestinal conditions may also absorb food-bound B12 less efficiently.

This is why vitamin B12 is unusual: how much you eat and how well you absorb it can both matter.

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Folate and pregnancy

Folate is especially important to understand around pregnancy.

Japan's Dietary Reference Intakes (2025 edition) set an adult recommended intake of 240 mcg per day.

During the second and third trimesters of pregnancy, an additional 240 mcg per day is recommended.

There is also specific public-health guidance for women who are planning pregnancy, may become pregnant or are in early pregnancy.

Japanese guidance recommends obtaining an additional 400 mcg per day of folic acid from sources other than ordinary foods in addition to folate from the usual diet, as part of measures associated with reducing the risk of neural tube defects.

This is a public nutrition recommendation and should not be interpreted as a therapeutic claim for any particular commercial supplement.

What is the difference between folic acid and 5-MTHF?

Supplement labels may list:

• folic acid
• 5-MTHF, also called methylfolate

5-MTHF is one biologically relevant form of folate.

However, the long-established public-health evidence for reducing neural tube defect risk is based primarily on folic acid.

If you are planning pregnancy or are pregnant, it is sensible to follow current public-health guidance and discuss supplement choices with a healthcare professional when needed.

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What is a B-complex supplement?

A B-complex supplement combines several B vitamins in one product.

However, the term “B-complex” does not guarantee a standard formula.

Different products may:

• contain all eight B vitamins
• contain only selected B vitamins
• provide some B vitamins in much larger amounts than others
• include vitamin C or other ingredients
• use different forms of B12 or folate

What do “B-50” and “B-100” mean?

International products sometimes use names such as “B-50” or “B-100”.

These names are often used for formulas containing several B vitamins at around 50 mg or 100 mg, but they do not mean that every B vitamin is present in exactly the same amount.

B12, folate and biotin, for example, are often listed in micrograms rather than milligrams.

Always check the actual Supplement Facts panel rather than relying on the product name alone.

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Different forms of B6, B12, folate and niacin

The same vitamin can appear under different ingredient names on supplement labels.

Are “active” or “methyl” forms always better?

Ingredient form can be useful when comparing products.

However, terms such as “active” or “methylated” should not automatically be interpreted as meaning that a product is always better absorbed or superior for everyone.

For example, vitamin B12 supplements may contain cyanocobalamin or methylcobalamin, but current evidence does not establish that one form is universally better absorbed for the general population.

It is more useful to consider form, amount, daily serving and overall formula together.

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How to choose a B-complex supplement

1. Start by looking at your usual diet

B vitamins are distributed across meat, fish, eggs, dairy, legumes, grains, vegetables, nuts and seeds.

Before choosing a supplement, consider which of these food groups are regularly part of your diet.

Supplements are best viewed as a way to complement the diet rather than replace it.

2. Check which of the eight B vitamins are included

A product labelled “B-complex” may not contain the same ingredients or amounts as another B-complex.

Check for B1, B2, niacin, pantothenic acid, B6, biotin, folate and B12, and compare the amount of each.

Some products contain all eight, but more ingredients does not automatically mean a better product.

3. Do not choose based only on the biggest numbers

Large amounts such as 100 mg or 500 mcg may look impressive.

But recommended intakes and safety considerations differ substantially between individual B vitamins.

A higher number is not automatically more useful.

4. Check mg, mcg and ingredient form

B12, folate and biotin are commonly listed in micrograms.

B6, B12, folate and niacin can also appear in different forms.

Compare both the unit and the ingredient name when reading labels.

5. Look for overlap with other supplements

Multivitamins, beauty supplements and energy-focused formulas may already contain B vitamins.

When adding a B-complex product, consider the total daily amount from all supplements combined.

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Safety: B6, niacin, folate and biotin

It is sometimes said that because B vitamins are water-soluble, any excess simply leaves the body in urine.

That is an oversimplification.

Vitamin B6: high doses over long periods matter

Excess vitamin B6 from ordinary foods is not usually a concern.

However, prolonged high supplemental intake has been associated with peripheral nerve effects.

In Japan's 2025 dietary reference values, the tolerable upper intake level for adults aged 30–49 is 60 mg/day for men and 45 mg/day for women.

This is particularly worth checking when comparing high-dose international B-complex supplements.

Niacin: upper levels differ by form

Japan sets upper intake levels for supplemental niacin from sources other than ordinary foods.

For adults aged 30–49:

• Men: 350 mg/day for nicotinamide and 85 mg/day for nicotinic acid
• Women: 250 mg/day for nicotinamide and 65 mg/day for nicotinic acid

This is a useful reminder that even within the same vitamin category, different forms can have different safety considerations.

Folate: the upper level mainly applies to folic acid from non-food sources

For adults aged 30–49, Japan's tolerable upper intake level is 1,000 mcg/day for folate from sources other than ordinary foods.

This figure is not intended to discourage consumption of naturally folate-rich foods such as leafy vegetables and legumes.

Biotin: high-dose supplements can interfere with some laboratory tests

Japan does not set a tolerable upper intake level for biotin.

However, high-dose biotin supplements can interfere with certain laboratory tests.

Depending on the testing method, some thyroid-related tests and other blood tests can produce results that do not accurately reflect the person's true status.

Some beauty supplements contain amounts of biotin far above ordinary nutritional intake.

If you use a high-dose biotin supplement and are having blood tests, tell your doctor or healthcare provider that you are taking biotin.

No upper level does not mean unlimited intake is proven safe

Japan has not established tolerable upper intake levels for B1, B2, B12, pantothenic acid or biotin.

This does not mean that unlimited intake has been proven safe.

In some cases, there is simply not enough evidence to establish a numerical upper level.

When using supplements, it is sensible to compare the amount provided with normal dietary requirements rather than looking only at whether an official upper limit exists.

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Summary

The vitamin B group consists of eight water-soluble vitamins.

Key points include:

• there are eight recognised B vitamins
• they are B1, B2, niacin, pantothenic acid, B6, biotin, folate and B12
• gaps in the numbering reflect the history of vitamin research and reclassification
• many B vitamins act as coenzymes or coenzyme precursors
• they participate in carbohydrate, fat, protein and amino acid metabolism
• being involved in energy metabolism does not mean supplements automatically increase energy
• food sources differ between individual B vitamins
• B12 is found mainly in animal-derived foods and has a relatively complex absorption pathway
• B12 can be stored in the body despite being water-soluble
• the percentage of B12 absorbed falls as supplemental doses become very large
• food folate and supplemental folic acid differ in form and bioavailability
• public-health guidance recommends additional folic acid around conception and early pregnancy
• B-complex products vary considerably in ingredient profile and dose
• terms such as “methylated” or “active” do not automatically mean superior
• water-soluble vitamins are not automatically safe in unlimited amounts
• B6, niacin and folate deserve particular attention when comparing high-dose supplements
• high-dose biotin can interfere with some laboratory tests

B vitamins are sometimes described simply as “energy vitamins” or “beauty vitamins”, but that is far too narrow.

Each of the eight vitamins has its own functions, while many of them also work within interconnected metabolic pathways.

A varied diet containing foods such as meat, fish, eggs, dairy products, legumes, whole grains, vegetables, nuts and seeds is the foundation.

If you choose a supplement, check which B vitamins are included, the daily amount, whether the units are mg or mcg, the ingredient forms and whether the same nutrients are already present in other supplements.

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Main References

• Dietary Reference Intakes for Japanese (2025 edition), Ministry of Health, Labour and Welfare
• National Health and Nutrition Survey 2024, Ministry of Health, Labour and Welfare
• Standard Tables of Food Composition in Japan
• NIH Office of Dietary Supplements: Thiamin – Fact Sheet for Health Professionals
• NIH Office of Dietary Supplements: Riboflavin – Fact Sheet for Health Professionals
• NIH Office of Dietary Supplements: Niacin – Fact Sheet for Health Professionals
• NIH Office of Dietary Supplements: Vitamin B6 – Fact Sheet for Health Professionals
• NIH Office of Dietary Supplements: Vitamin B12 – Fact Sheet for Health Professionals
• NIH Office of Dietary Supplements: Folate – Fact Sheet for Health Professionals
• NIH Office of Dietary Supplements: Pantothenic Acid – Fact Sheet for Health Professionals
• NIH Office of Dietary Supplements: Biotin – Fact Sheet for Health Professionals
• U.S. Food and Drug Administration: Biotin Interference with Lab Tests

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Important Information

This article is intended to provide general nutrition and health information about B vitamins.

It is not intended to diagnose, treat, cure or prevent disease, and it does not claim that any particular food or supplement has therapeutic effects.

If you have a medical condition, are pregnant or breastfeeding, are receiving medical treatment or take medication, speak with a doctor, pharmacist or other qualified healthcare professional before adding a high-dose B-vitamin supplement to your routine.