Irish researchers have debunked claims that having high blood levels of folate-folic acid-increases the risk of poor brain function in older adults, especially in those with low levels of vitamin B12.
The study, published today in the British Journal of Nutrition, was led by researchers from The Irish Longitudinal Study on Ageing (TILDA) at Trinity College Dublin.
Both vitamin B12 and folate are essential vitamins for the nervous system and healthy blood cells.
Deficiency of folate in early pregnancy can lead to neural tube defects (NTDs) in new-born babies. This is the reason for mandatory fortification of the food supply with folic acid in the US and other countries-but not Ireland or Europe. While fortification is proven to reduce NTDs, several influential publications in the US suggest that very high folate levels in older persons, if coupled with low vitamin B12, leads to poorer brain function and a faster rate of cognitive decline.
The researchers pointed out that largely because of such fears, no country in Europe has implemented mandatory folic acid fortification, although the NTD rates have not declined in two decades and may be rising in Ireland.
Using blood samples from over 3,700 Irish older adults aged 50 and over, the study compared cognitive health in individuals grouped by their combinations of vitamin B12 and folate blood levels.
It found no evidence that having high blood levels of folate affected the risk of cognitive decline in those with low levels of vitamin B12.
Moreover, having higher folate seemed to be associated with better cognitive function in these older adults.
Cognitive performance was not worse in older people with low vitamin B12 combined with high folate (representing 1.5pc of older adults in Ireland).
Those with normal vitamin B12 levels and high folate levels (7.6pc of older adults) performed better cognitively than the others.
The use of folic acid - containing supplements was uncommon, with higher rates among women than men but less than 4pc overall taking supplements
TILDA has previously reported high rates of deficiency: 1 in 8 older adults are deficient in vitamin B12, while 1 in 7 are deficient in folate. Vitamin B12 deficiency is associated with cognitive impairment and nerve damage. Older adults can have difficulty in absorbing vitamin B12 due to diminished digestive function or medications. Folate deficiency causes anaemia and is associated with heart disease, stroke, and possibly certain cancers.
Folate is critical to the healthy development of the brain and spinal cord in the growing foetus, and deficiency can cause NTDs, such as spina bifida. Consequently, public health authorities world-wide recommend that women of childbearing age consume folic acid from fortified foods and/or supplements.
Voluntary food fortification is permitted in Ireland but is not effective in this regard. Ireland has one the highest rates of NTDs in Europe but does not have mandatory fortification largely because of concerns detailed above.