Energy
The energy/calorie content of yogurt depends upon the type of yogurt consumed.
Natural yogurts made with semi skimmed or skimmed milks usually have a lower calorie content compared with natural yogurts made with whole milk, due to the lower fat content.
However, flavoured yogurts are usually higher in added sugars than natural yogurts and are consequently higher in calories.
Therefore flavoured, whole milk yogurts tend to have the highest calorie content whilst low fat natural yogurts are lowest.
Protein
The protein in yogurt and milk is of high quality as it provides all of the amino acids the body needs to function correctly. The protein content of yogurt is usually slightly higher than in milk because of the addition of non-fat dry milk during processing.
Interestingly the protein present in yogurt tends to be more readily digested than the proteins present in milk. This is due to the pre-digestion of milk proteins that occurs through the action of the bacteria present in yogurt.
The milk proteins in yogurt also have a higher content of the amino acids proline and glycine compared with milk and these proteins have additional functions in the body including enhancing calcium absorption and boosting the immune system.
It is also important to note that the nutritional value of milk proteins is not affected by the fermentation process.
Carbohydrate
The form of carbohydrate found in yogurt and all dairy products is the sugar known as lactose.
Lactose is digested by the enzyme lactase into glucose and galactose which are then absorbed and used to produce energy.
Before fermentation, the lactose content of yogurt is about 6%. Once the fermentation process begins, lactose is digested by up to 20-30% into its absorbable components, glucose and galactose.
This process lowers the lactose concentration in yogurt compared with milk and partly explains why individuals who have difficulty digesting lactose are able to tolerate yogurt better than milk - see section on lactose intolerance.
Fat
The fat content of yogurts varies depending on the product, ranging from approximately 10% fat for full fat Greek style yogurts, 3% fat for whole milk yogurts, 1.7% fat for low fat yogurts and non-fat varieties containing less than 0.3% fat.
The fat present in milk goes through many biochemical changes during yogurt production. The homogenisation and fermentation processes result in the breakdown of some of the fat into fatty acids which increases the digestion and absorption of the yogurt end product.
Yogurt has also shown to have increased concentrations of conjugated linoleic acid (CLA), a naturally occurring fat, which is believed to boost the immune system and protect against cancers.
