Are you deficient in vitamin B 12? Hopefully not, because you wouldn’t want your brain to shrink

New research has shown that vitamin B 12 deficiency promotes brain atrophy (shrinkage) and impairs cognitive function, potentially leading to dementia.

Vitamin B 12 deficiency is quite common, particularly in older people and people with digestive or immune system problems or vegetarians. B 12 is mainly found in animal foods such as seafood, poultry, red meat, eggs and dairy products. Some vegetarian foods are fortified with vitamin B 12, such as breakfast cereals. Its presence in mushrooms and yeast is controversial. Symptoms of vitamin B 12 deficiency include fatigue, pale skin, depression, anaemia, poor appetite, a sore tongue and tingling in the arms or legs. These are not uncommon symptoms.

What causes vitamin B 12 deficiency?

It is not easy to absorb B 12 through food; you really need good digestion to achieve the task. You need good levels of stomach acid and your stomach must also produce adequate levels of a substance called intrinsic factor. This is vital for proper absorption. People with the autoimmune disease pernicious anaemia cannot make intrinsic factor in their stomach and therefore they must receive B 12 injections. People with other autoimmune diseases also commonly do not absorb B 12 well and they must be tested for deficiency.

B 12 deficiency is extremely common in people over the age of 60, largely because the ability of our stomach to secrete hydrochloric acid declines with age. Many older people take medication that blocks stomach acid and this is a huge problem. Acid blocking drugs reduce your ability to absorb all nutrients from food and it has been known for some time that they increase the risk of dementia. Anyone with poor digestion, bloating, irritable bowel syndrome or celiac disease may be B 12 deficient and should be tested. Metformin is the most commonly used drug for type 2 diabetes and it causes B 12 deficiency. This is bad news for diabetics, who are already at increased risk of dementia due to high blood sugar.

Testing for vitamin B 12 deficiency

Your doctor can order a blood test for vitamin B 12 and this is useful. However, it is more effective to get a blood test for a substance called homocysteine. This is a type of protein found in the bloodstream that is a more reliable indicator of how well your body absorbs and utilises vitamin B 12. It’s also an indicator of your B 6 and folate levels. You want your homocystein level to be as low as possible.

What did the research show?

A study published in the journal Neurology compared markers of B 12 deficiency with brain MRI scans (to measure brain shrinkage) as well as neuro-psychological tests to measure brain function. The study lasted five years. Researchers discovered that low levels of vitamin B 12 were associated with brain shrinkage as well as poorer memory and cognitive function. Interestingly it was the blood homocysteine level that predicted these symptoms, rather than blood B 12 level.

How to correct B 12 deficiency

If, despite eating animal foods regularly, your B 12 levels are too low and/or homocysteine is too high, you need to take a B 12 supplement. Tablets usually aren’t very effective because they don’t overcome the problems of low stomach acid and low levels of intrinsic factor. Sublingual (under the tongue) supplements exist, as well as injections. It is certainly worthwhile making sure you obtain adequate levels of vitamin B 12; your brain will thank you for it.

Tangney CC, Aggarwal NT, Li H, Wilson RS, DeCarli C, Evans DA, Morris MC (2011) Vitamin B12, cognition, and brain MRI measures - A cross-sectional examination. Neurology 77:1276-1282