Lactose intolerance is caused by a deficiency of the enzyme lactase, which is responsible for its digestion. In sufferers undigested lactose is transformed into lactic acid, acetic acid, hydrogen and carbon dioxide in the intestine, resulting in symptoms such as abdominal pain, bloating, flatulence and diarrhoea.
In addition, people with a clinical condition called galactosaemia have three different genetic enzyme defects in the metabolism of galactose – and if untreated this may lead to potentially fatal impairment of hepatic and renal function. Newborns and young infancts may develop cataracts that are reversible once dietary glalactose is removed.
According to the European Food Safety Authority’s (EFSA) panel on dietetic products, nutrition and allergies (NDA), which was asked for its opinion on lactose thresholds, there is scientific evidence that most people with lactose intolerance can cope with up to 12g in a single dose, and 20-24g spread throughout the day. But 24g in a single sitting usually brought on symptoms, and 50g almost always did.
Some studies reported symptoms with as little as 6g, however.
“The Panel concludes that the vast majority of subjects with lactose maldigestion will tolerate up to 12 g of lactose as a single dose with no or minor symptoms. Higher doses may be tolerated if distributed throughout the day.”
The findings are useful for the free-from segment of the food industry, which seeks to supply pleasant and palatable foods to people who have an intolerance or allergy to certain foodstuffs. This niche has been growing in recent years, especially as mainstream supermarkets have realised that a good offering is a draw for families with one member that has an intolerance.
However it added that there is limited information on the compositional changes resulting from technological processes to remove lactose from products. It found evidence that the changes may result in lower carbohydrate content and that ultrafiltration or chromatographic separation may mean some small, insignificant decrease in mineral content.
No conclusions could be drawn on the possible effect of lactose on calcium absorption.
However in nutritional terms, it seem there would be little ill effect if the only difference is lactose content.
On the other hand, the panel said: “The avoidance of conventional dairy products without supplementation or appropriate adaptation of dietary habits may result in low intakes of calcium, vitamin D and riboflavin.”
The EFSA panel concluded that people suffering from galactosaemia should avoid lactose “as much as possible”, but that most can cope with a limit of around 25mg per 100kcal. Labelling of any levels of lactose higher than this on infant formula and follow-on formula is helpful for managing this condition in young children.
However EFSA added: “Milk (beverages) in which lactose is (partially) enzymatically hydrolysed to glucose and galactose and from which the latter is not removed are not suitable for patients with galactosaemia regardless of the residual lactose content.”