Folate, Vitamin B6, and B12 Intakes in Relation to Risk of Stroke Among Men
When we think about the people most at risk of a stroke, we tend to think of the elderly or the unfit. Well, if you have a B-vitamin deficiency, you’re in for a shock: you may also be at risk.
It’s now known that deficiencies in folate, B6, and B12 have been linked to elevated blood homocysteine levels. This can pose serious risks of chronic diseases, including stroke.
The Health Professional Follow-up Study was designed to establish just how intakes of folate and vitamins B6 and B12 could influence ischemic and hemorrhagic stroke .
The 14-year study, published in the journal Stroke, involved 43,732 men aged between 40 and 75 who had no history of cardiovascular diseases or diabetes. The men were followed from 1986 to 2000, with dietary assessments taken every four years to calculate their individual nutritional status.
At the end of the study, the participants were divided into quintiles according to their intakes of B vitamins. Their relative risk of stroke was estimated by comparing the incidence of stroke in a particular dietary intake quintile. Elevated risk levels were found with those in the lowest B vitamin intake group.
Results were adjusted to account for other factors that contribute to stroke: cigarette smoking; body mass index (BMI); physical activity; history of hypertension and hypercholesterolemia; aspirin use; and intakes of alcohol, fiber, potassium, vitamin E, and total energy.
The results could have many of us - not just men - rethinking our diet.
When factors such as poor diet, lack of exercise, genetic disorders and other health conditions were accounted for, the risk of stroke was clearly linked to an individual’s intake of folate and B12.
In fact, men in the highest quintile of folate intake had an approximately 30% lower risk of ischemic stroke than those in the lowest quintile.
Intake of vitamin B12 - but not B6 - was also inversely related to risk of ischemic stroke, but not hemorrhagic stroke.
Specifically, it appears that something as simple as a higher intake of folate and vitamin B12 can reduce the risk of ischemic stroke.
But why? And what do these specific B vitamins have to do with stroke?
B-Vitamins and Homocysteine
In recent years, there’s been a lot of research into the link between blood homocysteine levels and stroke.
There is now clear evidence that elevated blood homocysteine concentration increases the risk of stroke, especially among those with high blood pressure.
Prior to the 1986 study, evidence regarding the influence of B vitamins was relatively sparse. Many previous studies also hadn’t distinguished between hemorrhagic and ischemic strokes, which have significantly different causes.
What is a Stroke?
Ischemic strokes occur when blood flow to the brain is blocked by a blood clot. There are two major types of ischemic stroke: Thrombotic (when a blood clot forms in an artery leading to the brain) and embolic (when a clot forms elsewhere in the body — such as the heart or neck — and travels to the brain).
These are the most common types of stroke, comprising about 87 percent of all cases.
A hemorrhagic stroke occurs when a weak blood vessel bursts and bleeds into the brain. Unlike an ischemic stroke, hemorrhagic strokes begin with a sudden onset headache or head pain.
Hemorrhagic strokes are less common, comprising about 15 percent of stroke cases, but they are often fatal. There are two types of hemorrhagic stroke: intracerebral hemorrhage (a weak blood vessel breaking inside the brain) and subarachnoid (a weak blood vessel breaking on the surface of the brain).
Nutritional Status and Stroke
Here’s where the findings of the 1986 study got interesting. The repeated diet assessments allowed the researchers to examine various temporal associations between intakes of these three B vitamins and the risk of stroke.
It was found that men with higher folate intake exercised more, were less likely to be current smokers or overweight, and were more likely to use aspirin regularly. However, they also drank less and had slightly higher proportions of diagnosed hypercholesterolemia.
Men with higher intake of vitamin B6 were very similar to those with higher folate intake, while men with higher intakes of all three B vitamins (folate, vitamin B6, or vitamin B12) were more likely to take vitamin supplements.
When it came to examining men who were older and/or smokers, it was found that those in the highest quintile of folate intake had a significantly lower risk of ischemic stroke than those who were in the lowest quintile.