Recent media reports on new research suggest taking B Vitamins (B6, B12, Folic Acid) can prevent the mental decline in Alzheimer’s. This piqued my interest so I decided to find out more. The original research is here (full text behind paywall). Reports in the popular media are here and here. But they are, unsurprisingly, a bit too upbeat and as we shall see the study does not look at the impact on Alzheimer’s. The excellent NHS Choices site has a much better report here and I would urge anyone wondering about a popular media health report to check NHS Choices. There are a couple of problems with that though.
So, what’s the story? 270 men and women over 70 with mild cognitive impairment were randomly split into two groups. One group got high dose B Vitamins (B6, B12, Folic Acid) while the other got a placebo. As NHS Choices says this is the best experimental design for this study. They took those B Vitamins or the placebo for 2 years and their brains were scanned at the start and end of the study. This is a secondary study, the first looked at whole brain shrinkage while this one used the same data to look at which brain regions were most affected. Brain shrinkage is associated with the mental decline seen in dementias and Alzheimer’s in particular. This study looked particularly at grey matter, cells rather than axon tracts (in electronic terms transistors not the wires that connect them). They found that the B Vitamin treated group had smaller shrinkages in brain regions associated with Alzheimer’s symptoms than the placebo group. It’s important to note that the vitamins did not stop the shrinkage, they just slowed it. They further found that patients with high homocysteine levels had the biggest effects in terms of shrinkage reduction. The brain regions the shrinkage was found in are those that shrink and are affected most in Alzheimer’s.
So now we need to take a diversion and look at homocysteine, and B Vitamins. Homocysteine is a metabolite of the amino acid methionine. High levels are associated with Cardiovascular Disease in particular and increasingly in at least a sub population of Alzheimer’s patients. Vitamins B12 and Folic Acid are necessary co-factors to help your body turn homocysteine back into methionine where it can be used to make new proteins. Vitamin B6 is a cofactor for turning it into cysteine, another useful amino acid. If your B Vitamin status is low your homocysteine levels will tend to be high. The elderly are often deficient in B Vitamins because their ability to absorb them in the gut decreases.
So this is why B Vitamins and homocysteine levels are being looked at in terms of Alzheimer’s.
The study also looked at the test subject’s mental performance and found this correlated with the reductions in the various brain regions studied and they declined by less in the Vitamin treated group with high homocysteine levels. There was no significant difference in either brain shrinkage or cognitive scores in Vitamin treated subjects with low homocysteine.
This figure from the paper shows the result of a Bayseian statistical analysis of the causal pathway, which shows that B12 acts to reduce homocysteine levels which lowers the rate of brain shrinkage and cognitive decline.
The NHS choices report claims there was no analysis of cognitive impairment but I think they were misled by the way those data are presented in the study: correlated with the decline in brain regions and not delineated separately. You really need to read the first paper to get this. Though to be fair and absolutely strict they did not show B Vitamins, lowered homocysteine and reduced rates of brain region shrinking had an effect on Alzheimer’s. But then the paper doesn’t claim that and neither does the title. But from reading the popular press that will have passed you by. It’s unclear if the distinction was missed by the journalists, missed by the university press office or just simply hyped. It does show you need to be careful with popular media reports of individual science papers.
So why do these people with low homocysteine levels have Mild Cognitive Impairment and brain shrinkage? The answer is that there is more than one way to get to that point. One way is through being Type II diabetic or on the threshold of it: having peripheral insulin resistance (where the muscles refuse to take up glucose from the blood in response to insulin). Increasingly specialists in the area are calling Alzheimer’s ‘Type III Diabetes’. It seems that chronic high insulin has nasty feedback effects on the brain.
After all this you probably just want to know if you should take B Vitamins to stave off Alzheimer’s. Well that depends. IF you are not overweight, don’t have Type II, are sufficiently physically active and eat a good diet (low GI, rich in fruit and veg but also containing some meat and fish) and don’t abuse alcohol (regularly) then you probably don’t have high homocysteine levels.
If you do none or few of those things then you may have high homocysteine levels which leaves you open to heart disease and stroke as well as dementia. B Vitamins are not a magic pill allowing you to abuse your body and get off free though as their effects are only mild. The NHS Choices report says you should eat well, exercise, lose weight and not abuse alcohol. But we all know how few people pay attention. So their sniffiness about this study on that basis is from an unrealistic stand point. It’s also unhelpful to those who cannot exercise for whatever reason.
Hat-tip to my youngest R for the full text of the paper provided so promptly