Exposure to cigarette smoke may sap blood levels of folate, the B vitamin thought to protect against birth defects and reduce risk of some cancers, reported researchers in a journal this month.
Both smokers and non-smokers exposed to high levels of secondhand smoke had lower levels of folate in their blood than non-smokers, concluded the US Centers for Disease Control and Prevention study, published in this month's Nicotine & Tobacco Research.
The team tested around 15,500 adults for cotinine, a nicotine byproduct, and folate in both red blood cells and blood serum. They were also asked about their eating and smoking habits.
"Overall, we found that red blood cell folate levels in current smokers were 20 per cent lower than those in our entire group of nonsmokers," said Dr David M. Mannino and colleagues.
Non-smokers exposed to heavy amounts of secondhand smoke also had decreased folate levels, but their folate loss was only 60 per cent of the amount leeched from active smokers.
The researchers suggest that the findings might help explain the increased risk of certain diseases among smokers.
"The finding provides biological support for recent studies linking tobacco smoke exposure to heart disease and breast cancer and provides biological plausibility to examine the role of tobacco smoke exposure in other folate-related diseases such as neural tube defects and colon cancer," write Mannino and colleagues.
While they added that the survey was limited by its cross-sectional nature, the similar findings in both passive and active smokers backs the theory that smoke exposure was behind lower folate levels.