Evidence continues to mount suggesting a link between various stages of depression and low blood levels of the B vitamin folate, according to research funded by the Agricultural Research Service in the US.
Epidemiologist Martha Savaria Morris and colleagues studied data based on a questionnaire given to 3,000 people aged 15 to 39 years. The data showed that individuals with either major or mild forms of depression had lower blood levels of folate than did those who had never been depressed.
The researchers noted that low folate levels are known to be common in psychiatric patients and may hamper the effectiveness of antidepressant therapy.
Morris is with the Nutritional Epidemiology Program at the Jean Mayer USDA Human Nutrition Research Center (HNRCA) on Aging at Tufts University in Boston. The HNRCA is funded by ARS, the US Department of Agriculture's chief scientific research agency.
Folate is a family of related compounds that are naturally present in many foods, such as beef liver, green leafy vegetables and kidney beans. Its synthetic form, folic acid, is used by food processors to fortify enriched grain products, such as breakfast cereals, bread, pasta, flour and rice.
Significantly, different folates are absorbed by the body at different rates, and not all folate consumed is absorbed by the body. Alcohol, certain medications and anaemia can reduce the body's ability to absorb and use folate.
This US study is the latest in a series to look at the potential health benefits of folate. Earlier this year new findings compounded current evidence that suggests folic acid and other related B-vitamins, B6 and B12, can prevent the accumulation of high blood levels of the amino acid homocysteine, thought to be a risk factor for heart disease and strokes.
The study, carried out over 14 years by researchers in Illinois, US, found that men with the highest intake of folic acid were almost 30 per cent less likely to develop an ischaemic stroke than men with the lowest folic acid intake (less than 260 micrograms). Ischaemic stroke accounts for almost 80 per cent of all strokes and is caused by a blocked artery leading to the brain.
In Europe there are around 650,000 stroke deaths each year. Smoking, obesity, high cholesterol and physical inactivity are all controllable risk factors for the event, which is more common at younger ages in men.
The recommended dietary allowance for folic acid in adults is 400 micrograms daily. Europe's Scientific Committee for Food has advised an upper safe level of 1000 micrograms daily although it has not yet set limits for vitamin B12.
While the US, Canada and Chile have mandatory folic acid fortification of grains, Europe appears more hesitant to implement such a programme. Recent research by the UK's food safety organisation, the Food Standards Agency, found that folic acid could mask deficiency of B12 in the elderly.
Folic acid has also been shown to significantly reduce risk of birth defects.