A few weeks ago I discussed the pros and cons of folic acid (folate) fortification of bread. Now here’s one more possibly negative effect of fortifying our food with folic acid: if you have vitamin B12 deficiency, too much folate in your blood can make it worse.

Researchers at Tufts University analysed data from surveys before and after folic acid fortification in the USA. They found that people with low B12 and normal folate levels were one and a half times more likely to show cognitive impairment compared to people with normal B12 and folate levels. But people with low B12 and high folate were almost 5 times more likely to show cognitive impairment. These interactions between high folate and vitamin B12 were seen only in people surveyed after folic acid fortification in 1998, not before.

Vitamin B12 is important for healthy nerves, red blood cells and making DNA. Our body stores enough vitamin B12 to last 3-5 years so it takes a while for a deficiency shows up. When it does it leads to anaemia and cognitive impairment, and it is likely a risk factor for dementia.

Hydrochloric acid in our stomach releases vitamin B12 from foods. It then combines with a substance in our stomach called ‘intrinsic factor’ which allows it to be absorbed. Some older people have a mild inflammation of the stomach that reduces hydrochloric acid which means B12 isn’t so well absorbed. Vitamin B12 deficiency affects somewhere between 15-40% of people over 65 years of age.

So what can we do about this? Eat vitamin B12 rich foods (animal foods) such as meat, chicken, fish, milk, yoghurt and eggs.

This could make you a little wary of folic acid fortification but so long as you keep your vitamin B12 levels up, you should still be able to thrash the grandchildren at crosswords and cards!