Does a vitamin B complex have side effects? Here's what to look out for.

A vitamin B complex is one of the most commonly used supplements and is important for your overall health.

A well-composed vitamin B complex generally has few to no side effects. However, it's important to know that not all supplements are created equal.

Some vitamin B complexes can cause unpleasant side effects . This can have several causes:

• An incorrect ratio of B vitamins
• Low quality ingredients (e.g. synthetic forms)
• Too high doses of certain B vitamins.

In this article, I explain exactly what a vitamin B complex is, which B vitamins can cause side effects, and how to choose a well-composed supplement to prevent these problems.

A vitamin B complex consists of all eight B vitamins:

• B1 (thiamine)
• B2 (riboflavin)
• B3 (niacin / niacinamide)
• B5 (pantothenic acid)
• B6 (pyridoxine / pyridoxal-5-phosphate)
• B7 (biotin)
• B9 (folic acid / folate)
• B12 (cobalamin)

Often, B-complex supplements are supplemented with additional ingredients that enhance the effectiveness of the B vitamins. I'll tell you more about this later in this article!

All these B vitamins work together and are essential for many different processes in your body.

These are the main functions of B vitamins in the B complex:

1. Energy production - B vitamins contribute to the conversion of food into energy.
2. Support of the nervous system - They support the proper functioning of the nervous system.
3. Healthy skin and hair - The B complex contributes to healthy skin and hair growth.
4. Metabolism - B vitamins support important metabolic processes.
5. Fatigue - They contribute to the reduction of fatigue.

In addition, taking a vitamin B complex is better than taking individual B vitamins. All the different B vitamins work together and support each other's function.

Although most people tolerate B vitamins without problems, some vitamins in the B complex can cause side effects.

This can happen when the dosages of certain B vitamins are too high, with incorrectly composed supplements or depending on the form of the vitamin used.

Vitamin B3 comes in two forms: niacin and nicotinamide (also called niacinamide). While both forms are effective sources of vitamin B3, they differ in their effects on the body.

Side effects of too much B3 (Niacin) - High doses of vitamin B3 can lead to the well-known 'niacin flush'.

This manifests as temporary redness and warmth in the face, neck, arms, and chest, sometimes accompanied by mild swelling of the skin and a burning, tingling, or itching sensation. A headache may also occur.

This reaction is caused by dilation of the blood vessels. It can be quite startling and unpleasant, but in most cases it's harmless.

To prevent this - Choose nicotinamide (niacinamide). This form of vitamin B3 doesn't cause flushing and is therefore often better tolerated. Nicotinamide offers the same health benefits as niacin, but without the vasodilating effect.

Tolerable Upper Limit - 10 mg for nicotinic acid and 900 mg for nicotinamide

Vitamin B5 is generally very safe and causes no side effects when used normally. Even at higher doses, it is usually well tolerated.

Side effects of too much B5 - Only at extremely high doses, such as 2000 times the recommended amount, can diarrhea occur.

Tolerable Upper Limit - No tolerable upper intake level for vitamin B5 has been established, which means that the risk of side effects with normal use is very small.

Vitamin B6, often found in supplements as pyridoxine, must be converted by your body into the active form pyridoxal-5-phosphate (P-5-P).

Side effects of too much B6 - With prolonged use of more than 21 mg per day, your body cannot keep up with this conversion, which can lead to a build-up of B6 and peripheral neuropathy (tingling, numbness or pain in the hands and feet).

To prevent this - Is it better to take P-5-P directly, which can be used immediately by the body? Research from Maastricht University confirms that pyridoxine in high doses is harmful to nerve cells, while P-5-P is safe.(1)

Tolerable Upper Limit - 12 mg per day

Because a vitamin B6 excess is relatively common, we have written an extensive article about what you can do in case of a vitamin B6 excess.

Folic acid is considered both vitamin B9 and B11. It's the synthetic form often used in supplements and can cause problems if taken in high doses.

Folate is the natural form of this vitamin found in our food.

Side effects of too much B9 - A dose of more than 1000 mcg (1 mg) of folic acid per day may mask symptoms of vitamin B12 deficiency, which can cause neurological problems.

In addition, these side effects of too much folic acid can occur:

• Sleep disorders
• Concentration disorders
• A bitter taste in the mouth
• Despondency
• Confusion
• Irritability
• Hyperactivity

To prevent this - To avoid side effects of folic acid, it is wise to choose active forms such as 5-MTHF folate (Quatrefolic®).

This biologically active form can be used directly by the body, without the need for conversion, which is especially beneficial for people with a deficiency of the MTHFR gene (which is essential for the conversion of folic acid).(2)

This reduces the chance of accumulation of unused folic acid, which can cause side effects.

Tolerable Upper Limit - 1000 mcg per day

There are also B vitamins in the B complex that have no side effects:

Vitamin B1 has no established upper limit for intake, which means that the chance of side effects from too much B1 is very low.

On the other hand, a deficiency of this vitamin is rare, except in severe alcoholics. In this group, a B1 deficiency due to alcohol consumption can lead to Korsakoff's disease.

There is also no upper limit set for vitamin B2, and with normal use there are no side effects.

Biotin has no established upper limit and is generally well tolerated.

Most people tolerate vitamin B12 well, and there are no known negative effects from long-term use. Therefore, there is no established tolerable upper intake level for B12.

Excess B12 is primarily excreted in urine, as your body regulates its absorption based on needs. This means your body ensures it doesn't absorb more B12 than is needed.

However, it is important to pay attention to the different forms of B12 in supplements, as they are not all equally effective.

• Synthetic form - The synthetic form, cyanocobalamin , must be converted to active forms and is rapidly excreted because it is not well retained by the body. This can make conversion and absorption less effective.(3)(4)
• Natural and active forms - Therefore, I recommend choosing natural active forms, such as adenosylcobalamin and methylcobalamin . These forms are readily usable and are absorbed more efficiently.(4)

When choosing a safe vitamin B complex, it is important to pay attention to several aspects on the label, such as the composition, dosages and the forms of the vitamins used.

This may help prevent B-complex side effects.

Follow these steps:

Check if it contains niacin or nicotinamide. If the label doesn't say anything, it's often niacin, which is usually cheaper.

The best choice - Nicotinamide, because it is gentler on the body and has fewer side effects.

Check the form of vitamin B6 and the dosage. Avoid pyridoxine (HCL).

The best choice - Pyridoxal-5-phosphate (P-5-P) at a dose of less than 5.0 mg per day, because this active form is absorbed more efficiently.

Check which form of folic acid it contains. Folic acid and regular folate are fine, provided they are taken in doses of less than 500 mcg per day.

The best choice - Quatrefolic® 5-MTHF, the active form that is better utilised by the body.

Check if the complex contains additional ingredients, such as half-vitamins (PABA, choline, inositol). These ingredients strengthen the B complex and ensure that your B vitamins work better.

Why are they important? They support various bodily functions and enhance the effectiveness of other vitamins, contributing to your overall health and well-being.

You now know what to look for when choosing a good and safe vitamin B complex supplement.

Our vitamin B complex meets all these criteria. It contains all the B vitamins in their most active form, ensuring rapid and effective absorption. We've also added all the essential vitamins, such as PABA, choline, and inositol, along with organic vitamin C.

These additional ingredients enhance the effect of the B complex and optimally support your health.

Sources used

1. Vrolijk, M. F., Opperhuizen, A., Jansen, E. H., Hageman, G. J., Bast, A., & Haenen, G. R. (2017). The vitamin B6 paradox: Supplementation with high concentrations of pyridoxine leads to decreased vitamin B6 function. Toxicology in Vitro , 44 , 206–212. https://doi.org/10.1016/j.tiv.2017.07.009 
2. Selhub, J., & Rosenberg, I. H. (2016). Excessive folic acid intake and relation to adverse health outcome. Biochimie, 126, 71–78. https://doi.org/10.1016/j.biochi.2016.04.010 
3. Vasavada, A., Patel, P., & Sanghavi, D. K. (2024, January 31). Cyanocobalamin . StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK555964/ 
4. Paul, C., & Brady, D. M. (2017, February 1). Comparative Bioavailability and Utilization of Particular Forms of B12 Supplements with Potential to Mitigate B12-related Genetic Polymorphisms. https://pmc.ncbi.nlm.nih.gov/articles/PMC5312744/