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A guide to B-complex vitamins

Are B-complex vitamins really energy-boosting stress busters? Dietitian Katrina Pace finds out.

Feeling stressed? Maybe you’re tired, lacking energy or busy at work? It’s tempting to reach for those B-complex vitamin supplements, especially when they have names like ‘Executive B Stress’ and ‘Stress B-Complex’.

What are B-complex vitamins?

B vitamins, with the exception of vitamin B12, come from mainly plant sources. Vitamin B12 is only found in animal products, a fact vegans and vegetarians need to be aware of.

B vitamins work on many of the enzyme processes involved in how our cells work, meaning they play an important role in the generation of energy and building different molecules (such as neurotransmitters and hormones). It’s their role in energy production that has led to B-complex supplements being promoted for more energy and preventing fatigue.

Why put the B vitamins together in a ‘complex’? One or more of each B vitamin is involved in the energy production process so if one is running low, the whole system is affected.

When might I need extra B vitamins?

  • Pregnant and breastfeeding women may need extra vitamin B9 and B12, especially vegetarian or vegan women. Discuss with your doctor or midwife whether you might need these supplemented.
  • Older adults are particularly at risk of low vitamin B12, B6 and B9 levels. Your GP can test your levels with a simple blood test.
  • If you have a malabsorption condition, such as coeliac disease, inflammatory bowel disease, hypothyroidism or have had weight loss surgery, you might need to top up.
  • Proton pump inhibitor medications (eg, omeprazole), which lower stomach acid levels, may reduce B12 levels.
  • The oral contraceptive pill may reduce your levels of vitamin B6.
  • Ongoing high intake of alcohol may reduce your levels of vitamin B1.
  • A diet low in fresh fruit, vegetables, whole grains and legumes may mean you’re not getting enough B vitamins.
  • It’s important for vegans to take a vitamin B12 supplement as they won’t get any from their diet.

What’s in B-complex supplements?

vitamin B1 (thiamin)
vitamin B2 (riboflavin)
vitamin B3 (niacin)
vitamin B5 (pantothenic acid)
vitamin B6 (pyridoxine)
vitamin B7 (biotin)
vitamin B9 (folic acid)
vitamin B12 (cobalamin)

Some supplements may also contain other vitamins or herbal compounds.

What’s the evidence around B-complex supplements?

Different research studies have investigated different formulations of B-complex vitamins, with or without other vitamins or minerals present. The variation in formulations can make it difficult to build a picture of whether taking a B-complex supplement is likely to have any benefit or not.

Individual B vitamins play an important role in energy production, neurotransmitter synthesis and oxygen transport.

A limited number of small studies suggest B-complex supplements may help mood, mental performance, focus and mental fatigue and, when taken alongside antidepressants, they may also improve mood and anxiety.

Can’t I get enough B vitamins from food?

Yes. Unless you have a specific medical condition and have been advised to take a supplement by your dietitian or doctor, you can get plenty of B vitamins from your diet.

The only exception is for vegans, who definitely need to take a vitamin B12 supplement.

Having a diet that includes a range of wholegrain carbohydrates, legumes, fresh fruit and vegetables, meat, fish, poultry and dairy foods will ensure you’re getting enough B vitamins.

Side effects

B-complex supplements are water soluble, which can cause bright yellow urine as your body gets rid of the excess.

B-complex vitamins are generally well tolerated because any excess is taken out of the body in urine rather than stored.

However, it’s important not to have more than the upper limits, which:

  • for vitamin B3, may cause flushing, nausea, vomiting and diarrhoea
  • for vitamin B9, may mask a vitamin B12 deficiency
  • for vitamin B6, taken in excess for long periods, can cause nerve damage.

Daily upper limits for adults are:

vitamin B3 – 35mg
vitamin B6 – 50mg
vitamin B9 – 1000mcg

First published: May 2019

Article sources and references




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