October 02, 2006	Monday	Ramazan 8, 1427

DESPITE decades of official neglect, Pakistan remains the fifth largest milk producer in the world. The total value of milk produced is higher than the value of two major crops, wheat and cotton. Milk production was 15,481 million tons in 1990-91, and projected at 29,472 million tons in 2004-05.

Cow milk occupies a special position among foods in being an animal food that has a vegetarian connotation. Milk carries many nutrients which an infant needs for growth and development. For children, adolescent, elderly people pregnant and nursing mothers, milk plays an important role in meeting the requirements of many essential nutrients. It is considered a protective food.

Milk helps to balance human diet by supplementing good quality protein, calcium and vitamins particularly, vitamin A, riboflavin, niacin and folic acid. In addition milk contains several bio-protective molecules which ensure health security to humans. 

In infant and child nutrition, milk fat is of immense benefit. It helps them in meeting their energy requirements by increasing energy density of the diet. A sufficient fat supply is essential for thriving babies, a rosy and smooth skin and also resistance to bacterial infections.

Milk proteins are rich in essential amino acids. The protein efficiency ratio (3.1), biological value (91) and net protein utilization (82) of milk protein are very close to that of egg proteins (3.8, 100 and 94, respectively).

Milk proteins can be added to cereal-based products for increasing their lysine and threonine content. Whey proteins have even better supplementary value and can raise the BV of soy proteins because of their high concentration of sulphur amino acids. Whey obtained as a by-product in cheese manufacture has thus a great potential for incorporation in cereal-based products.

The digestibility of milk proteins is rated higher (96 per cent) than that of plant proteins (74-78 per cent). Because of their high BV, milk proteins are useful in the diet of patients suffering from liver and gall bladder diseases, hyperlipidaemia and diabetes.

Patients with impaired kidney functions rely on protein with high BV for relieving strain on the excretory function of the kidney. The milk proteins are also used in slimming diets. 

Milk proteins have high buffering power; therefore it is useful in the treatment of inflammation of mucous lining of stomach and of stomach ulcers, preventing hyperacidity. Milk and milk products are used as a source of proteins in hyperuricaemia and goat disease.

In contrast to other foods, these do not contain purines, which are precursors in the synthesis of uric acid that causes gout when deposited in the joints or may lead to formation of urinary calculi.

Milk fat has often been implicated in coronary heart diseases (CHD) because of its cholesterol content and composition of its fatty acids. It is however, not correct to judge the implication of milk fat in development of CHD solely on the basis of its fatty acid composition and cholesterol content. The average cholesterol content in cow and buffalo milk is only 2.8 and 1.9 mg/g fat respectively.

Moreover, humans absorb 10-14 per cent of dietary cholesterol, thus only 20-40 mg cholesterol will be absorbed from 50g of dietary milk fat. On the other hand, the body itself synthesizes cholesterol (1-4g daily) in much higher amounts than what is absorbed from the diet.

Protective effect of milk fat against some types of cancer (colon, breast and skin) has recently been reported. Fat in general is regarded as increasing cancer risk, although not for all types of cancer. However, a specific fatty acid has been identified in milk fat, which appears to be an inhibitor of cancerous growth. 

Several studies have shown that milk reduces serum cholesterol levels. Experiments have shown that cholesterol levels do not rise when as much as two litres of milk is consumed daily. On the contrary, the cholesterol level is reduced. Both decreased formation and increased breakdown of cholesterol are responsible for the cholesterol lowering effect of milk. It is suggested that the regular intake of milk keeps blood vessels healthy. 

Milk is a rich source of vitamins not only in terms of their contents but also their better bioavailability. Milk is one of the richest natural sources of vitamin B2. Although milk contains only small amounts of preformed Vitamin B3, nevertheless, it is a good source of this vitamin.

Milk is used as dietary ingredient for patient suffering from pellagra, a niacin deficiency disease. For vegetarian, milk is sole natural source of vitamin B12, as this vitamin is present only in animal foods.

Milk is also a good source of folic acid. Vitamin A deficiency is a major cause of widespread blindness among children. A 250ml serving of cow milk contain vitamin A sufficient to meet 75 per cent daily vitamin A requirement of pre-school child. 

Research has shown that poor nutritional status with respect to calcium is related to diseases like osteoporosis, hypertension and colon cancer. The hypertensive patients have shown significant reduction in blood pressure in response to increased calcium intake.

Introduction of increased dietary calcium through dairy products has been shown to reduce incidences in colon cancer and hyper-proliferation in the colonic mucosa in rodents. Calcium produces these effects by neutralizing de-conjugated bile acids and free acids, thereby removing their mito-enic/ toxic influence.

Milk and dairy products are the most important source of calcium in readily available form. Incorporation of milk in the diet also improves the bioavailability of calcium from vegetable foods. The factors that contribute to better availability of calcium from milk include lactose, protein and phosphorus.

Apart from calcium, milk is associated with phosphorylated casein. The casein phosphopeptides, released in the gastrointestinal tract during digestion, form soluble complex with calcium phosphate salts and improves the diffusion of calcium across the intestine.

Milk is rich in phosphorus that reduces urinary calcium excretion, and counter balances, at least in part, the calciuric effect of dietary proteins. Milk and most dairy products, except some processed cheese, have a near 1:1 calcium to phosphorus ratio considered to be ideal for retention of calcium in the body. 

Lactose, the principal milk sugar, is slowly metabolised and therefore, a considerable portion of it passes into the large intestine where it promotes the growth of lactic acid producing bacteria. Lactic acid creates a desirable condition that inhibits the growth of proteolytic and putrefying bacteria in the intestine and replaces them gradually with acidophilic bacteria.

Several investigations have shown that lactose promotes the utilization of calcium, magnesium and phosphorus. The acidic condition created by fermentation of lactose by intestinal bacteria may increase the solubility and absorption of calcium. Part of the effect may also be due to the ability of lactose to form soluble complex with calcium.

Since lactose is slowly absorbed, it has slight laxative effect. It is due to lowering of the pH that increases the peristalsis of the intestine. The blood glucose does not rise rapidly on lactose diet. Milk consumption, therefore, enables the diabetic person to obtain the biologically highly valuable milk proteins without running the risk of rise in blood glucose levels.