Lactose intolerance is a condition whereby an individual is lacking the lactase enzyme. This results in an inability to digest lactose, the main sugar in milk. The undigested lactose passes to the colon, where gut bacteria ferment the sugar. This fermentation process results in the production of hydrogen gas, and it is this that causes the bloating and discomfort associated with lactose intolerance. Although some individuals do not produce any lactase, others can produce a limited amount, suggesting that the dose of lactose administered might relate to the severity of symptoms in some individuals. Evidence suggests there may be ethnic variations in the ability to produce lactase and therefore ethnic differences in the ability to digest milk sugar. However, much of the information regarding lactose intolerance has been performed by measuring lactase activity or after a single test dose of milk, equivalent to four large glasses. This is not useful because smaller amounts of milk may more accurately reflect intake and be digestible.
Milk and dairy intolerance appears to be more complicated that a simple inability to produce the enzyme lactase. Studies using milk have shown that lactose intolerant individuals can sometimes consume milk without any symptoms. Consumption of milk with yoghurt also appears to reduce symptoms experienced by lactose intolerant individuals. Studies investigating more moderate amounts of milk have shown that lactose intolerance is not a simple condition, and that it involves more factors that a simple deficiency of lactase. For example, in one study1, researchers administered a lactose free milk drink or an identical drink containing 4.5 % lactose at either 240 mL or 480 mL volumes on 4 consecutive occasions to 110 health teenagers, 67 of whom were lactose intolerant. The results showed that the lactose intolerant and lactose tolerant subjects did not differ in their response to the 240 mL of lactose free or lactose containing milk drink (17 % of all subjects reported symptoms).
Therefore small amounts of milk appear to be tolerated by lactose intolerant individuals, and yet a similar amount of milk caused symptoms in lactose tolerant individual. The authors noted that the symptoms reported by those experiencing them were not consistent with lactose intolerance, but were idiopathic in nature. Increasing the amount of milk ingested to 480 mL caused the number of lactose intolerant subjects experiencing symptoms to increase from 15 with the lactose free milk to 26 with the lactose containing milk. While 24 % of lactose intolerant individuals experienced symptoms with 480 mL of lactose containing milk, only 7 % of lactose tolerant individuals experienced symptoms. Therefore the symptoms experienced from consuming milk cannot be attributed solely to the lactose in the milk. These results support other findings that show that lactose intolerance is a complex phenomenon that is still not fully understood. Following a ‘what works for you’ regimen therefore seems appropriate advice.
RdB
