Lactose intolerance

Lactose is a milk-sugar found in milk, and (in varying levels) in milk-derived dairy products, and is added (as an additive or in the form of whey etc) to various foods stuffs (bread, cereals, processed meats, potato chips, cake mix, soft drinks and lagers), but very often not labelled on the product. [1]). Lactose intolerance may, besides bloating and cramping, sometimes cause itchy rashes, eczema, diarrhea, nausea, sickness, asthma, irritable bowel syndrome and osteoarthritis.[2][3] [4] Intolerance prevalence across all functional gastrointestinal disorders is 60% to fructose, 51% to lactose and 33% to both.[5]

Lactic acid in humans

Lactase (lactic acid) in the small intestine breaks down lactose into glucose and galactose. If dietary lactose is not sufficiently enzymatically broken down (by lactase), bacterial decomposition may cause bloating, gasses, cramps and nausea. Naturally, as humans age, their lactase level decreases, resulting in some level of lactose maldigestion, the levels differing individually. Most humans loose 75 to 90% of the capacity to produce lactase within a few years of weaning.[6][][7]

Decrease in lactase activity

Lactose maldigestion (caused by relative lactase deficiency) can be shown by laboratory tests. Lactose intolerance is the name of the clinical syndrome, in which lactase activity has decreased to 5 to 10% of birth levels. In northern Europe nearly 5% of the adult population is lactose intolerant, compared to more than 90% in some Asian and African countries and the far middle-east. (75% worldwide) [8] 82% of African-American adolescent girls had lactose maldigestion, but were not considered lactose intolerant.[9] Daily ingestion of less than 240 mL of milk (up to 10 - 11 g. lactose) is well tolerated by most lactose-intolerant adults.[10] Lactose maldigesters may be able to tolerate foods containing 6 g lactose or less per serving, such as hard cheeses.[11]

Lactococcus in milk (products)

Lactose is broken down during ripening of cheese by lactic acid. Lactic acid (from glucose fermentation) is produced by lactic acid bacteria (Lactococcus). In raw milk produced in Normandy 38 different strains of Lactococcus were identified. 97% of these strains fermented lactose.[12]

Lactose levels in cheese

Lactose levels in cheese may differ depending on the conditions of processing and ripening (pH, glucose concentration, and Lactococcus nutrient limitation). The lactic acid (lactate) consumption rate in Camembert cheese was 2.9 times higher when temperature was 16°C rather than 8°C, during ripening.[13] Lactose levels in Gouda, Edam and Cheddar cheese may vary from insignificant to significant. Cheese produced in one area of England where the manufacturing process is standardised and guaranteed, may have guaranteed lactose levels of below 0.003%.[14]

Average lactose contents of various food stuffs

Food	Lactose in %
dried whey (whey powder)	68.2
dried skimmed milk (milk powder)	50.5
coffee creamer	45.0
dried butter milk	44.2
dried milk, whole (milk powder)	35.1
condensed milk (skimmed)	12.8
condensed milk (min. 10% fat)	12.5
condensed milk (sweetened)	10.2
condensed milk (min. 7.5% fat)	9.2
human milk	7.0
human milk, transitional (6-10th day post partum)	6.6
mare's milk (horse milk)	6.2
donkey milk	6.1
icecream	6.0
buffalo milk	4.9
camel milk	4.8
cow's milk (skimmed milk; 0.07% fat)	4.8
whey	4.7
cow's milk (1.5 to 1.8% fat)	4.6
cow's milk (3.5% fat consumers milk)	4.6
ewe's milk (sheep milk)	4.6
cow's milk (whole, raw)	4.5
goat's milk	4.2
cream (min. 10% fat)	4.1
buttermilk	4.0
fresh cheese (50% fat in dry matter)	3.4
cream (min. 30% fat)	3.3
yoghurt, reduced fat (1.5 - 1.8% fat)	3.3
Cottage cheese	3.3
yoghurt (min. 3.5% fat)	3.2
quark, fresh cheese (from skimmilk)	3.2
Ricotta cheese	3.0
quark, fresh cheese (20 - 40% fat in dry matter)	2.7
fresh cheese (60 - 85% fat in dry matter)	2.6
Mozzarella cheese	2.0
Emmentaler cheese	1.5
sherbet	1.5
butter	0.6
Apenzeller cheese	0.6
Gruyere cheese	0.6
Filsitter cheese	0.6
Feta cheese (45% fat in dry matter)	0.5
Cheddar cheese	0.3
Camembert cheese (50% fat in dry matter)	0.1
Edam cheese	0.1
Brie cheese	0.1
Parmesan cheese	0.06