Research released this week has shown a link between folate supplement intake during late pregnancy and the development of asthma in children. The research was conducted at the Adelaide University in Australia and published in the American Journal of Epidemiology. It found that children aged between three and five years were 30 percent more likely to develop asthma if their mothers had taken folate supplements after their first trimester. The link was only found with supplementary folate, not dietary folate intake.

This research is significant as the worldwide incidence of childhood asthma has been increasing. Australia has one of the highest incidences of childhood asthma with up to 1 in 5 children developing the condition.

The researchers of this study have pointed out that sufficient folate intake is important, but that the dose and timing of any supplementary intake is also important. They found no link to the development of asthma in children of women who took folate supplements before conception and then only several weeks into their pregnancy (as is currently advised). The increased incidence of asthma only occurred when mothers continued to take folate supplements into the later stages of their pregnancy.

Folate, or folic acid when it is added to food, is a B group vitamin. An adequate intake of folate during pregnancy is required to prevent neural tube defects such as spina bifida. The neural tube in the unborn baby later becomes his or her brain and spinal cord. As the neural tube is formed during the first four to six weeks of pregnancy, before most women even realize they are pregnant, it is recommended that all women of childbearing age ensure they meet the recommended daily intake of folate prior to conception and during the first trimester. This recommendation may vary slightly from country to country but in the US, Australia and the UK it is generally 400-500mcg per day.

A recent study published in the Journal of Child Psychology and Psychiatryhas also shown that children with mothers whose folate intake is low were at greater risk of developing ADHD. The researchers also found that these children had a smaller head circumference at birth, suggesting a slower rate of prenatal brain growth.

One of the easiest ways of obtaining sufficient folate is by taking a supplement. Women should take comfort in the finding that supplementary folate intake during the early stages of pregnancy, as recommended, has not been shown to result in an increased incidence of childhood asthma. However for women who would rather obtain their required intake through foods naturally high in folate, this can be done easily enough. Excellent sources of folate include:

• Asparagus
• Broccoli
• Chick peas
• Brussels sprouts
• Lentils
• Spinach

Very good sources of folate include:

• Cabbage
• Cauliflower
• Leeks
• Oranges and orange juice
• Parsley
• Peas
• Wholegrain bread

In some countries certain foods (such as breakfast cereals and bread) are fortified with folic acid. If this is the case, it should be clearly indicated on the food's nutritional information label. These foods are another good source of folic acid and do not seem to be linked to the increased incidence of childhood asthma. However further research in this area is needed.

Liver is another good source of folate however it is not recommended for pregnant women due to its high vitamin A content (vitamin A intake over 4,500mcg a day during pregnancy has been found to cause birth defects).