Food and Behaviour Research

Donate Log In

16 January 2017 - Nutraingredients - Vitamin B6 deficiency linked to cognitive decline

Eliot Beer

FAB RESEARCH COMMENT:

For details of the associated research, see:
The significant associations reported here between cognitive decline and low vitamin B6 in older adults cannot be taken as evidence of a causal link, as the study was purely observational; although the use of a follow-up design (whereby B vitamin status had been measured 4 years earlier) strengthens that possibility.

In this study, links between cognitive decline and other B vitamins were not significant - although as the authors note, very few participants in this sample of 155 showed clinical deficiencies in these nutrients, while 11% did for vitamin B6.  

Many previous association studies have reported links between cognitive decline and/or dementia and low B12 and folate (which like B6, are important for reducing the build-up of homocysteine, a toxic by-product of normal metabolism).

See for example:  And for information on randomised controlled treatment trials of B vitamin supplementation for age-related cognitive decline and dementia (a study design which can provide evidence of causality), see also:

Low vitamin B6 intake may contribute to cognitive decline in older adults, while other B vitamins do not show the same effects, according to a new follow-up study in Northern Ireland.

Researchers from Northern Ireland and Ireland contacted participants aged 60 and over from a previous study into B vitamin intake, with 155 out of 255 potential subjects, all of whom showed normal cognitive function in the original study, able to participate in the new research.

In the original study participants over the age of 60 completed a cognitive function test – Folstein’s Mini Mental State Examination (MMSE) – in order to test their competence in recalling food intake. The new study compared these results to new MMSEs, along with blood tests and dietary surveys.

Participants had a mean age of 70 years, were predominantly female, well-educated and had a low rate of depression. The majority of participants were regular consumers of foods fortified with B vitamins (75%). "Dietary intakes compared favourably with current UK dietary recommendations as reflected in good overall B vitamin biomarker status."

Biomarkers & surveys show link

Our results showed that participants with lower status of vitamin B6 [PLP; the measure of active vitamin B6] at baseline were 3.5 times more likely to have a greater rate of cognitive decline over a [four year] follow-up period,” wrote the researchers in their paper, published in Nutrients.

The decline affected participants not only with deficient vitamin B6 levels, but also some with clinically sufficient levels of B6. The researchers suggested this showed that optimal vitamin B6 levels might be important for cognitive health in ageing.

No link for other B vitamins

In contrast to vitamin B6 (pyridoxine), the researchers did not find any links between other B vitamin status and cognitive decline in the subjects.

Whilst elevated plasma homocysteine, low folate and, to a lesser extent, vitamin B12 [cobalamin] status have been frequently associated with cognitive decline there was no evidence of significant associations for these biomarkers in the current study,” wrote the researchers.

The findings in the current study may be explained to some degree by the fact that vitamin B6 seemed to be the limiting nutrient within the cohort. There was a greater incidence of deficiency of vitamin B6 (11% clinical deficiency) compared with folate [vitamin B9, 3%] or vitamin B12 (0%),” they added.

They noted other studies support the idea that correcting sub-optimal levels of a B vitamin deficiency has a greater impact than providing additional B vitamins to people with optimal levels.

The researchers said they believed their study was the first longitudinal study to look at both dietary intake and biomarker status of B vitamins and their effect on cognitive health in ageing. But they highlighted a range of other studies which showed links between vitamin B6 deficiency and cognitive decline.