The researchers from the Pennsylvania State University in the US said older adults exposed to heat were less able than younger people to increase skin blood flow meaning there was a greater risk of heart attacks and strokes during hot weather.
This was partly due to older blood vessels that produced less nitric oxide. Previous research by the same team suggested nitric oxide production could be upped if older adults were given tetrahydrobiopterin (BH4), which helped the enzymes involved in this process.
Folic acid increases the bioavailability of BH4 and this paper found that it also increased cutaneous vasodilation in older adults via nitric oxide-dependent mechanisms.
Vasodilation can refer to the widening of blood vessels as a reaction to heat, meaning the body can move the ‘hot blood’ to the skin where heat can be released more easily.
They said folic acid supplementation could be a cheap way of helping older adults cope during heat waves.
The study, published in the journal Clinical Science, looked at 11 healthy older adults (with an average age of 71) and 11 younger adults (average age of 22) without cardiovascular diseases in two sub-studies.
The first looked at the impact of localised heat treatment and local delivery of 5 mM (millimolar) of the folic acid metabolite 5-MTHF to the blood vessels in the skin compared to a placebo treatment.
The Europe Food Safety Authority (EFSA) has rejected two folic acid (vitamin B9) health claims relating to healthy arteries and vessels and the promotion of heart health as well as a similar claim for Endothjelial (L-5-methyltetra-hydrofolic acid, calcium salt; Vitamin B9) and Metafolin due to a lack of evidence.
The second study looked at whole-body heating and the impact of a five milligram supplement of folic acid or a placebo once a day for six weeks.
Skin temperature was controlled in a lab using a water-perfused suit that covered the whole body except for the head, hands, feet and forearms.
Both folic acid supplements and locally administered 5-MTHF improved cutaneous vasodilation in the elderly group.
The folic acid supplement group’s nitric oxide-dependent vasodilation increased in older but not younger subjects.
Since the localised treatment did not further improve vasodilation compared to the supplement group, they suggested a “ceiling effect” for the ability of the aged cutaneous vessels to vasodilate during hyperthermia.
Future research should focus on the impact of such supplementation for people with cardiovascular disease as well as life-long supplementation and vascular health, the researchers from the university’s Department of Kinesiology said.
Source: Clinical Science
Published online ahead of print, doi:10.1042/CS20140821
“Folic acid supplementation improves microvascular function in aged humans through nitric oxide-dependent mechanisms”
Authors: A. E. Stanhewicz, L. M. Alexander and W. L. Kenney