Vitamin B12 is vital for our nervous and immune systems and is needed to make red blood cells. Many studies link low levels of B12 with depression and tiredness; it’s needed to help the body release energy from food and for cell division.
What happens if I don’t get enough vitamin B12?
Fortunately, most people in the UK get enough vitamin B12 from their diet. But a deficiency causes a form of anaemia, which has symptoms such as yellow-tinged skin, mouth ulcers, pins and needles, muscle weakness, poor memory, impaired vision and irritability.
The absorption of vitamin B12 declines naturally as we get older, so deficiencies become more common, affecting around one in 20 people aged 65 to 74 years and one in 10 people over the age of 75. A simple blood test can identify whether you’re deficient. If needed, treatment options include supplements or regular vitamin B12 injections, depending on the cause (see The link with autoimmune conditions).
How much vitamin B12 do I need each day?
The Nutrient Reference Value (NRV) for vitamin B12, which you’ll see on food labels, is 2.5mcg a day. But the figures below show the more detailed guidelines in the UK for vitamin B12 needs at specific ages and stages in life.
When to supplement
Vitamin B12 isn’t naturally found in plant foods, but a few foods including yeast extracts (such as Marmite), breakfast cereals and soya milks, are fortified with it, so check labels. As a result, people who follow a vegan diet may be at a greater risk of a deficiency, so supplements are recommended. There are no known side effects from very high doses of vitamin B12 in supplement form, but the Department of Health suggests doses below 2,000mcg.
The main sources of vitamin B12
The main sources of vitamin B12 are animal products, including meat, fish, dairy and eggs. ‘Superfoods’ spirulina and algae are often marketed as containing vitamin B12, but the body isn’t able to make use of the nutrient in this form so these foods shouldn’t be relied on to boost intakes.
The most common cause of a vitamin B12 deficiency in the UK is an autoimmune condition called pernicious anaemia, most common in women around the age of 60 and in anyone with a family history or another autoimmune condition. The cause is unknown, but it results in the immune system attacking cells in the stomach that produce a protein called intrinsic factor, which normally combines with vitamin B12 so it can be absorbed into the bloodstream. If you don’t produce any intrinsic factor, then B12 can’t be absorbed and a deficiency results.
Vitamin B12 and fighting depression
Many studies have found a link between vitamin B12 intakes and depression. For example, in one recent study from Canada, elderly men with the highest dietary intakes of vitamin B12 were 68% less likely to be depressed.
Related article: Why we need vitamin C