Young girls who do not drink milk frequently may have a higher risk of asthma than their peers, particularly if they are overweight. Some past studies have suggested that children who drink little or no milk are more likely than their peers to be overweight, and excess weight has also been linked to a higher asthma risk in children. Researchers at the University of Manitoba in Winnipeg studied 246 children with asthma (diagnosed by an allergy specialist) and 477 non-asthmatic controls at the age of 8–10 years. A link was found between infrequent milk consumption — defined as twice a week or less often — and asthma risk, but only among girls. However, it was also found that low milk levels and excess weight were each by themselves linked to a higher asthma risk in girls. What's more, the combination of the two seemed especially problematic. Asthmatic girls were nearly four times more likely than other girls to be overweight and to drink milk infrequently. This association was still seen after a range of other possible contributing factors were considered, including the children's overall diet, exercise habits and family income. The findings suggest that low milk consumption may directly affect asthma risk, and in a manner unrelated to weight. What that manner might be is not clear. This may be because children who get little milk may be low in vitamin D, especially if they live in colder climates with limited sun exposure. Vitamin D seems to affect the way body's cells respond to the hormone oestrogen. Some research suggests that oestrogen is involved in airway inflammation, and oestrogen influences asthma symptoms in women. Such an effect could potentially be exaggerated in overweight girls, because their oestrogen levels are typically higher than those of normal-weight girls. Further studies are needed to determine the relationship among milk consumption, weight and children's asthma risk.
Allergy,
November 2007