The effect of the vitamin B complex: the most important questions and answers

Die Wirkung des Vitamin B Komplex: Die wichtigsten Fragen und Antworten

Everyone knows how important vitamins are. One of the most popular dietary supplements is probably the vitamin B complex, which contains eight important B vitamins. You may be wondering if this is just a trend, or if a vitamin B complex actually makes a difference.

Vitamin B is indispensable for the functionality of the human organism. In most cases, a deficiency can be compensated for. However, many are afraid of the risks of a vitamin B complex. While some say vitamin overdoses are harmless, others claim they are extremely risky.

In this article we will provide some clarity on the effects of the vitamin B complex so that you can take care of your health with peace of mind. You will also find out how much vitamin B is good or dangerous for you, what it does and how you should take it.

the essentials in brief

  • The B vitamins are important for hormone formation, blood circulation, metabolism and the nerves. However, long-term overdoses of a vitamin B complex can cause great harm in humans.
  • Not only humans, but also animals can suffer from vitamin B deficiency. While the deficiency in dogs only becomes noticeable after years, the consequences in horses appear very quickly.
  • The important B vitamins are only found in animal and plant-based foods. They work together and need to be fed daily because they are water soluble.

The effect of vitamin B complexes: What you should know

In order to be able to take the vitamin B complex without hesitation, you should find out what effect it will have on your body and what side effects it can cause. While not harmful, you shouldn't take a B complex vitamin in arbitrary amounts just for no reason. While overdoses of B vitamins do not cause any adverse effects in some animals, they can cause great harm in humans.

How important is a vitamin B complex?

The vitamin B complex is a blend of eight closely related B vitamins. The vitamins are precursors of important coenzymes. They are indispensable for the functionality of the human organism. The vitamins of the B group are important for hormone formation and influence blood circulation. They are also involved in carbohydrate, protein and fat metabolism.

We need B vitamins for blood formation and for our nerves to function properly.

If you are deficient in B vitamins, it is important to get the vitamins your body needs through diet or supplements. Vitamin deficiency can be caused by malnutrition, the use of certain medications or absorption disorders in the gastrointestinal tract. Vegans and vegetarians, for example, are often deficient in B vitamins because they don't eat many animal products that contain certain B vitamins (5).

different dishes

A balanced diet is important for vitamin intake, but if you avoid certain foods, the daily intake of vitamin B complex is recommended. Image source: Comfreak - Pixabay

B vitamins do not occur individually in nature, which is an indication that they work more together than alone. Each B vitamin has a specific task and supports the effect of the other B vitamins in a complex. Some B vitamins need the other representatives to become active in the first place.

For whom is a vitamin B complex suitable?

People with a balanced diet usually consume enough vitamins.

However, medications or physical disorders can often prevent your body from absorbing certain B vitamins.

If you fall into one of the following categories, getting these vitamins through a vitamin B complex and talking to your doctor is advisable.

  • People with vitamin B deficiency diseases: Symptoms of a deficiency disease can include stress, tiredness, exhaustion, performance deficits, loss of appetite, depressed mood, insomnia, susceptibility to infections, gastrointestinal complaints, pain and sensory disturbances due to damage to the nervous system or inflammation or changes to the skin and the mucous membranes.
  • Vegans, vegetarians: Certain B vitamins, such as vitamin B12, are found almost exclusively in animal products. Since vegans and vegetarians do not get many of these foods into their bodies, a vitamin B12 deficiency usually occurs.
  • People with absorption disorders in the gastrointestinal tract: It is possible that your body does not absorb the vitamins supplied despite a balanced diet. In this case, you should talk to a doctor about what may be the reason and how to solve this problem.
  • People who eat less: Older people often have less appetite and cannot supply their body with the recommended amount of B vitamins. Even people who eat less because of a diet should take care to balance their vitamin B levels.
  • People who take medication: Some medications and the birth control pill are considered vitamin thieves. These can inhibit vitamin absorption and greatly increase the requirement.
  • Pregnant and breastfeeding women: During pregnancy, there is an increased need for nutrients. B vitamins are generally deficient quickly, so intake during pregnancy is even more important. Folic acid, for example, is important for the healthy development of the child (1).
  • Athletes: More B vitamins are needed for strenuous sports, especially if the sport promotes muscle growth.

As previously mentioned, you should always check with a doctor before taking any particular dietary supplement. It is also important to know how severe the deficiency is in order to be able to adjust the dosage of the vitamin B complex.

What do the ingredients of vitamin B complexes do?

The vitamin B complex includes the 8 B vitamins that our body needs to function properly. Although they differ from the vitaminoids, which are produced by the body itself, they can be ingested through food. Each B vitamin has a specific job. This table shows you the effects of these vitamins.

vitamin Effect
Vitamin B1 (thiamine) Thiamine is responsible for energy metabolism, heart function and mental function. This vitamin strengthens nerves and is considered a “mood vitamin” (6).
Vitamin B2 (Riboflavin) Riboflavin reduces signs of fatigue and protects cells from oxidative stress. It is important for the mucous membranes, skin and vision (7).
Vitamin B3 (Niacin) Niacin promotes mental function and reduces fatigue. It is important for memory and concentration and has a vasodilating effect. We also need it for the mucous membrane, the skin and many metabolic processes.
Vitamin B5 (pantothenic acid) Pantothenic acid helps synthesize vitamin D and some neurotransmitters. It promotes mental performance and reduces fatigue. Vitamin B5 is also important for building connective tissue, mucous membranes, hair and nails.
Vitamin B6 (pyridoxine) Pyridoxine stabilizes the immune system and promotes psychological function and hormonal activity (8). When taking the contraceptive pill, there is an increased need.
Vitamin B7 (biotin) Biotin supplies skin and hair and promotes the proper functioning of the nervous system. It is involved in cell growth and a cofactor in energy metabolism.
Vitamin B9 (folic acid, folate) Folic acid can be called a cell vitamin because it supports cell division. Pregnant women need a particularly large amount of folic acid (1).
Vitamin B12 (cobalamin) Cobalamin can be stored in the body. It improves the formation and maturation of red blood cells and the structure of certain nerve cells. It is also something like an “activator” for folic acid. Furthermore, vitamin B12 promotes well-being.

No matter why you need to take the vitamin B complex, as long as you do not exceed the recommended dosage, the combination of B vitamins will certainly not harm you.

What side effects do vitamin B complexes have?

Overdoses and intolerance to vitamin B complexes can lead to side effects. While toxicity is known only for vitamin B6, many B vitamins have side effects that are considered less of a concern. Here you can find out which side effects can occur with the following vitamins.

  • Vitamin B1 (thiamine): High-dose injections into the bloodstream can cause cramps, nausea, headaches, a feeling of heat and cardiac arrhythmia.
  • Vitamin B2 (Riboflavin): The natural coloring of vitamin B2 colors the urine neon yellow. This happens because excess vitamin B2 is excreted this way, but it is not dangerous.
  • Vitamin B3 (niacin): The consequences of an overdose are flushing, reddening of the skin, excessive urination and liver damage.
  • Vitamin B5 (pantothenic acid): Digestive disorders can occur due to an overdose.
  • Vitamin B6 (pyridoxine): Nerve disorders are possible with an overdose of pyridoxine (4).
  • Vitamin B7 (biotin): There are no known side effects or intolerance to vitamin B7.
  • Vitamin B9 (folic acid, folate): Since this vitamin is only found in very few foods, an overdose is almost impossible. Otherwise, sleep problems, gastrointestinal disorders and increased nervousness can occur.
  • Vitamin B12 (cobalamin): A high dose leads to loss of appetite, dizziness, weight loss or forgetfulness. The appearance of acne is also possible. Hypersensitivity can sometimes cause eczema or hives. Long-term intake of vitamin B12 increases the risk of lung cancer in men (3).

A well-known statement related to dietary supplements is, "The more the merrier". Unfortunately, this statement is not entirely true. You should be aware of the side effects before taking a vitamin B complex and avoid overdoses.

What is the daily requirement of vitamin B complex?

Although many believe that extreme overdoses of certain B vitamins are safe, they can have dire consequences. Depending on age and gender, the dosage of a vitamin B complex should be adjusted correctly. The table below shows estimates of the daily requirement of vitamin B for adults.

vitamin Recommended daily requirement for adults
Vitamin B1 (thiamine) 1.0 to 1.3 mg
Vitamin B2 (Riboflavin) 1.0 to 1.4 mg
Vitamin B3 (Niacin) 11 to 16 mg
Vitamin B5 (pantothenic acid) 6 mg
Vitamin B6 (pyridoxine) 1.4 to 1.6 mg
Vitamin B7 (biotin) 30 to 60 µg
Vitamin B9 (folic acid, folate) 300mcg
Vitamin B12 (cobalamin) 4.0 µg

When it comes to dietary supplements, you should definitely pay attention to how high they are dosed.

How and when should I take a vitamin B complex?

Although each B vitamin has its own specific job to do, the vitamins in the vitamin B complex need each other to work optimally. It is therefore important to provide the body with all eight B vitamins on a regular basis.

Before taking a vitamin B complex, one should know how or when to take it and how the B vitamins work together in the body.

B vitamins dissolve in water after ingestion. Unlike fat-soluble vitamins, water-soluble vitamins cannot be stored by the body and must therefore be taken daily. The kidneys excrete excess vitamins in the urine.

Vitamin B tablets

In order to get the vitamin B values ​​in balance, the vitamin B complex should be taken daily. Image source: MasterTux - Pixabay

Only vitamin B12 and vitamin B9 (folic acid) are stored in the liver. Together, these can lower homocysteine ​​levels. Elevated levels of this amino acid (metabolic intermediate) can damage blood vessels. Along with vitamin B12, vitamin B6 facilitates the conversion of folic acid from homocysteine ​​to methionine (2). Vitamin B3 helps certain forms of cobalamin to be converted into bioactive vitamin B12 variants. The organism can use only such species directly.

It is best to take your vitamin B complex on an empty stomach as it is water soluble.

It is recommended to take this either 30 minutes before or about 2 hours after a meal. If this variant upsets your stomach, you can of course also take the vitamins with a light meal. But don't use it at night. B vitamins increase energy and can prevent you from falling asleep. Always store the products in a cool place so that no nutrients are lost.

What does a vitamin B complex do in animals?

Vitamin B complexes are also important for animals. A lack of B vitamins can lead to growth disorders, skin and coat problems and other problems. Here you can find out what advantages and disadvantages a vitamin B complex can have in dogs, horses and cats (10).

The effect of vitamin B complexes in dogs

Basically, B vitamins have a similar effect in dogs as in humans. These are the pros and cons of taking vitamin B complex in dogs:

In dogs, the deficiency symptoms of vitamin B only show up after years, often through tiredness, weakness, an impaired immune system or nervous disorders. Vitamin B deficiency can also show symptoms of dementia.

The effect of vitamin B complexes in horses

Vitamin B is important for all metabolic processes in the horse's body. Here you can find out the advantages and disadvantages of taking vitamin B complexes in horses:

A lack of B vitamins in horses can lead to nerve problems, muscle problems, diarrhoea, watery faeces, jumpiness, poor hoof growth and a dull coat.

The effect of vitamin B complexes in cats

Unlike dogs and horses, a vitamin B complex can cause side effects in cats. Here you can find out how B vitamins work in cats and what you have to take into account:

A lack of B vitamins can lead to nervous disorders with movement disorders and cramps in cats. Diarrhea, vomiting and anemia are also possible. Just like dogs, cats can also develop dementia or a compromised immune system.

What alternatives are there to vitamin B complexes?

Since B vitamins are only found in foods, the only real alternative to taking B complex vitamins is to change your diet.

Depending on which vitamin you need, you should think about how you want to structure your meals in the future.

However, if you suffer from a severe vitamin B deficiency, for example because you suffer from an intestinal disease or are vegan or vegetarian, a vitamin B complex is highly recommended. You can find out here which foods contain the necessary B vitamins.


Vitamin B is found in animal and plant foods and must therefore be obtained through diet or supplements. A vitamin B deficiency can often be compensated for with diet alone. Here you can see which foods you need to eat to compensate for the lack of certain B vitamins.

vitamin Occurrence in food
Vitamin B1 (thiamine) Silver skins (inner shells) and germs of grain
Vitamin B2 (Riboflavin) Eggs, meat and fish, offal, nuts, mushrooms, dairy products
Vitamin B3 (nicotinic acid/niacin) Poultry, meat, fish, dairy products, eggs, brewer's yeast, legumes and fruit
Vitamin B5 (pantothenic acid) in almost all foods
Vitamin B6 (pyridoxine) Liver, Yeast, Fish, Dairy, Corn, Soy, Greens
Vitamin B7 (biotin, vitamin H) Offal, milk, egg yolk, legumes, nuts
Vitamin B9 (folic acid) Spinach, yeast, offal
Vitamin B12 (cobalamin) Meat, milk, eggs (9)

As you can see, there is no need to always turn to supplements. If you pay attention to a balanced diet and look at which vitamins you need to take, you can easily balance your vitamin levels.


Despite the important function of B vitamins, a long-term overdose of a vitamin B complex can have unpleasant consequences. Although we need vitamin B for hormone formation, blood circulation, our metabolism and for our nerves, the side effects and consequences of an overdose should not be underestimated. It can cause nerve damage or even increase the risk of lung cancer in men (3).

As always, you can stick to the following saying: "Everything is good in moderation." Talk to your doctor about whether you suffer from a vitamin B deficiency at all and try to find out how much of it you really need. Then you don't have to worry about the consequences of an overdose.


  1. Annabelle Birkenberger, Wolfgang Henrich, Frank Chen (2019). Folic acid intake in Berlin women as a function of socioeconomic status
  2. K Pietrzik (2006). Homocysteine ​​as a cardiovascular marker and risk factor
  3. J Clin Oncol (2017). High doses of B vitamins: Is there a risk of lung cancer?
  4. Ahmad I, Mirza T, Qadeer K, Nazim U, Vaid (2013). Vitamin B6: deficiency diseases and methods of analysis
  5. Melina V, Craig W, Levin S (2016). Position of the Academy of Nutrition and Dietetics: Vegetarian Diets
  6. Berndt SF, Pflughaupt KW, Holzbach E. (1977). Determination of the vitamin B1 balance with 35S-thiamine
  7. Fuchsluger, T., Geerling, G. (2017). Therapy-associated corneal pathologies
  8. Röckl, H., Pascher, G. (1960). The influence of water-soluble components of the stratum corneum on bacteria
  9. Brouwer-Brolsma EM, Dhonukshe-Rutten RA, van Wijngaarden JP, Zwaluw NL, Velde Nv (2015). Dietary Sources of Vitamin B-12 and Their Association with Vitamin B-12 Status Markers in Healthy Older Adults in the B-PROOF Study
  10. Hanisch F, Toresson L, Spillmann T (2018). Cobalamin deficiency in dogs and cats
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