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| Basic properties | ||||
| Physiological properties | ||||
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Taste, palatability, sweetness
Lactose has a clean and sweet taste without any aftertaste. The sweetness profile resembles that of sucrose. However, the relative sweetness of lactose is small (only 20%) when compared to sucrose (100%). β-lactose appears to be somewhat sweeter than α-lactose, probably due to the fact that β-lactose dissolves somewhat quicker in the saliva of the mouth than α-lactose, hence reaching a higher concentration in the same period of time and thus giving rise to a higher sweetness sensation. Lactose tolerance Lactose is not actively absorbed by the intestines unless it is first split into its two monosaccharide components, i.e. glucose and galactose. This hydrolysis of lactose is effected by the lactase enzyme produced by the epithelial cells in the brush border of the small intestine. Thus, the capacity of mammals to digest lactose depends on the lactase activity in the intestine. The maximum activity of the enzyme occurs shortly after birth and declines during the weaning period, after which it remains at a relatively constant level. Genetically determined factors governing residual lactase activity also exist. Individuals having low lactase activity are called lactose malabsorbers. They may not be able to digest all the lactose ingested. Consequently, remnants of lactose remain in the intestine, which may lead to disturbed water resorption in the small intestine . Lactose that reaches the large intestine (colon) will be fermented by the microbial flora residing there, yielding lactic and other organic acids, hydrogen, carbon dioxide, etc. This causes increased moisture retention in the colon which, in combination with the gas produced, cause symptoms like diarrhoea, abdominal pain and flatulence. Various studies have shown that 80 to 90% of individuals clinically diagnosed as lactose malabsorbers can tolerate 250 ml of milk without any symptoms. This percentage is even greater among children and adolescents. Thus the regular intake of small or medium quantities of milk or corresponding amounts of lactose would give rise to little concern in the majority of consumers. Particularly when, as is more normal, milk or lactose is taken in combination with other foods, thus slowing down in gastric emptying and intestinal passage. Some individuals are extremely sensitive to even small amounts of lactose. As little as 3 gram portions have been reported to cause complaints in some cases. However, in the majority of cases the quantity of lactose in a tablet or a capsule does not exceed 1 g. Therefore no lactose ingestion problems are to be expected after taking a tablet or a capsule , even in individuals who are very sensitive to lactose. Diabetes In the modern treatment of diabetes mellitus, strictly sugar-free diets are no longer advised. The aim of the diet is to obtain normal blood glucose levels throughout the day (and night). This can be perfectly attained by a normal diet, provided it is restricted in energy and the meals are spread evenly throughout the day. A daily basic diet for a diabetes mellitus type I patient may contain up to 255 grams of carbohydrates, accounting for 50% of the total energy consumed. Compared to this amount of dietary sugars, the amount of lactose ingested when taking medicines is very small. Furthermore, lactose is resorbed slowly compared to sucrose and glucose. Hence, there will generally be no restrictions for diabetes patients to take medicines containing lactose. Cariogenicity Milk sugar is hardly cariogenic when compared to sucrose. To explain this it is important to recognise the factors that promote dental caries. The aetiology of dental caries lies in the presence of Streptococcus species bacteria in the oral cavity. These bacteria synthesise adhesive extracellular polymers that assist the bacteria in sticking to teeth and thus promote the colonisation of teeth. On top of that, these difficult-to-remove bacteria ferment carbohydrates, resulting in the formation of organic acids capable of destroying the surface layer of the tooth. The increased acidity in the oral cavity causes calcium from the enamel layer of the tooth to dissolve. Biosynthesis of the adhesive substances occurs largely by the action of microbial enzymes that are highly specific for dietary sucrose. These enzymes are much less capable of using other dietary sugars than sucrose. Therefore other sugars, including lactose, are relatively safe with respect to dental caries. In addition, tablets and capsules are commonly swallowed with water. The rinsing effect leaves hardly any residues of lactose in the oral cavity.However, it is recommended to rinse the mouth with water after using a dry powder inhaler, especially when inhaling shortly before going to sleep. |
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