Milk is a healthy drink that should be consumed on a regular basis
Milk is produced by cows, goats and some other animals as food for their young and used as a drink by humans. Perhaps as early as 8000 BC, the ancient man learned to domesticate certain species of animals to consume their milk. These included buffaloes, sheep, goats, and camels, all of which are still raised in various parts of the world for the production of milk. Fermented milk products such as cheese, yogurt, concentrated milks, butter, and even ice-cream have also been used for many centuries.
Technological advances have only come about very recently in the history of milk chemistry and consumption, and our generation will be the one who’d be given the credit for having turned milk processing from an art into a science. The availability and distribution of milk and its products in the modern era are a blend of centuries old knowledge of traditional milk products with the application of modern science and technology. The role of milk in the traditional diet has varied greatly in different regions of the world. In the northern regions of the world, Europe and North America, people traditionally consumed more milk and milk products in their diet than the African and Asian races. In tropical countries like Pakistan where high temperatures prevail and lack of refrigeration has led to the inability to produce and store fresh milk, it has traditionally been preserved through means other than refrigeration, including immediate consumption of raw milk after milking, or by conversion into more stable products such as fermented milk and sweets (paneer, dahee, lassee, makhan, kholya, barfee and some other traditional products).
Milk is regarded as a complete food. It contains protein, fat, carbohydrates, all the known vitamins, various minerals and all the food ingredients considered essential for sustaining life and maintaining health. Milk protein is of the highest biological value and it contains all the amino acids essential for body building and repair of body cells. A litre of milk provides all the calcium needed by an individual for one day, practically all the phosphorus, a liberal amount of vitamins A and C, one-third or more of protein, one-eighth or more of iron, at least one-fourth of energy, and some of vitamins B, E and D. Milk ranks high in digestibility. Its fat is 99 per cent digestible, its protein 97 per cent and its carbohydrates 98 per cent. It is said to require about one-and-a-half hour for digestion. It curdles almost immediately after it reaches the stomach. The organic salts and water begin to be absorbed immediately, while the solid matters are passed on to the intestines where fat is quickly absorbed by the lacteals.
In the modern era of scientific and technological developments, a better understanding of the link between diet and health has raised the awareness and demand for functional food ingredients from milk and its products. Many biologically active peptides have been identified from milk proteins and other dairy products by proteolysis with digestive enzymes or microbial enzymes or by fermentation; they have shown various bioactivities such as opioid, anti-hypertensive, mineral-binding, anti-thrombotic, and immunomodulatory activities.
Hypertension, a silent killer, is a dangerous condition where blood pressure is persistently higher than normal. Hypertension is a risk factor for cardiovascular diseases, including coronary heart diseases, peripheral arterial diseases, stroke and kidney failure. In the vast majority of cases no direct cause of hypertension is known. Certain factors are known to increase the risk of developing the disease. These include a sedentary lifestyle, drinking alcohol, and smoking.
The renin-angiotensin system is an important regulator of blood pressure. Therefore, substances that inhabit the renin-angiotensin system, either by inhabiting the angiotensin-converting enzyme (ACE) or by blocking angiotensin receptors, are widely used in the treatment of hypertension. ACE inhibitors have a dual effect on the renin-angiotensin system: they inhibit the production of the vasoconstrictor angiotensin II and inhabit the degradation of the vasodilator bradykinin. In addition, ACE inhibitors have other beneficial effects in hypertensive patients, for example, in those with cardiac or renal insufficiency or diabetes. Through fermentation, peptides that have an ACE-inhabiting and thus a blood pressure lowering effect can be derived from milk proteins. Some of these peptides have also been found to have opioid receptor binding properties.
Fermented milk products (paneer, dahee and lassee) with biologically active peptides valyl-prolyl-proline (Val-Pro-Pro) and isoleucyl-prolyl-proline (IIe-Pro-Pro) were shown to lower blood pressure in hypertensive cases. It’s suggested that small peptides are absorbed from the gastrointestinal tract without being decomposed by digestive enzymes. Two other peptides (Tyr-pro and Lys-Val-Leu-Pro-Val-Pro-gIn) that were purified and characterized from fermented milk were also shown to have ACE-inhibitory activity in hypertension laboratory animals. It was recently shown that a-lactablumin reduced blood pressure in hypertension. The blood pressure reducing effects of complex systems such as fermented milk drinks and milk protein hydrolysates many only be in part due to ACE inhibition. These products contain a complex mixture of peptides that many also have opioid binding capabilities. Furthermore, the hypotensive effects of fermented milk drinks may also be in part due to the high levels of biologically available calcium present in these products. The hypotensive effects of high calcium, low fat dairy product diets have been well documented in literature.
The application of specific foods or food components in the prevention and/or treatment of disease are of a particular relevance to the management of cardiovascular diseases. High blood pressure or hypertension is a controllable risk factor in the development of a range of cardiovascular conditions. Therefore, any food component that on ingestion has the ability to reduce blood pressure is a potential candidate competent in the prevention/treatment of cardiovascular diseases.
A high level of serum total cholesterol is generally considered to be a risk factor for coronary heart diseases and atherosclerosis all over the world. Reducing the level lowers the incidence and mortality of an ischemic heart disease and atherosclerosis. Many studies have been conducted in experimental animals and humans to elucidate the effect of dairy products on serum cholesterol. The mechanisms of the hypocholesterolemic activity of lactic acid bacteria (in yogurt) have been proposed to involve inhibition of exogenous cholesterol absorption from the small intestine by the binding of cholesterol and bile acids with bacterial cells, assimilation of cholesterol, as well as suppressing bile acid resorption by deconjugation as a function of the bacteria bile salt hydrolase activity. The low fat diary fermented drinks (lasee after removing butter fat) could be recommended to hypertensive patients to reduce the occurrence of cardiovascular diseases.
Consumption of skim or low-fat milk is associated with a reduced risk of cancer. They hydrolysis in the digestive tract, releasing long chain bases, may protect the intestines from cancer formation. There is a growing consensus on the beneficial effects of fermented need diary products on cancer. Both epidemiological and experimental studies indicate that yogurt reduces the risk of certain types of cancer, and inhibits the growth of certain experimental tumours. Cheese contains conjugated dienoic derivatives of linoleic acid, which have been shown to have potent anti-tumour activity in animals. Consumption of fermented milk containing lactobacillus acidophilus significantly reduces the count of fecal putrefactive bacteria, suggesting a beneficial effect on intestinal micro-ecology.
Total body calcium increases with age up to age 20, with a sharp increase in puberty. In women, bone loss begins prior to menopause, with loss increasing rapidly for about five years after menopause. On an average, women lose 30-40 per cent of their bone mass by the age of 70. The incidence of bone fractures is inversely proportional to bone mineral content in females and to calcium intake. In the gastrointestinal tract, milk protein is digested into smaller peptides, some of which have physiological effects. These bioactive peptides can be formed by enzymatic hydrolysis with digestive enzymes, and also by fermentation of milk with starter cultures as previously mentioned. These bioactive peptides, for example, caseinphosphopeptides, in milk support bone mineral density in animal models and increase calcium absorption in postmenopausal women and thus lower the chances of bone fracture.
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 gout disease. In contrast to other foods, these do not contain purines, which are the precursor to the synthesis of uric acid that causes gout when deposited in the joints or may lead to formation of urinary calculi.
The substances in milk which have an antimicrobial effect are immunoglobulins, lactoferrin, lysozyme, lactoperoxidase and vitamin B12-binding protein. The immunoglobulins, mainly IgA are not broken down by digestive enzymes. Thus, they not only act against the microorganisms in the intestine, but also prevent the absorption of foreign proteins. Lactoferrin is an iron binding glycoprotein that occurs in cow milk at a level of 0.2 mg/ml. Lactoferrin play an important role in the resistance against intestinal infection, particularly escherichia coli. Lactoferrin has both bacteriostatic and bactericidal properties.
A number of enzymes are also involved in the milk immune system. These are lactoperoxidase, xanthin oxidase and lysozyme. Lysozyme has a direct effect by breaking down the cell wall of gram-positive bacteria. The lactoperoxidase-thiocyanate-H20 system is an anti-bacterial system. Lactoperoxidase and thiocyantate are found in milk, and H2O is produced by lactic acid bacteria or by the action of xanthin oxidase.
Milk is produced by cows, goats and some other animals as food for their young and used as a drink by humans. Perhaps as early as 8000 BC, the ancient man learned to domesticate certain species of animals to consume their milk. These included buffaloes, sheep, goats, and camels, all of which are still raised in various parts of the world for the production of milk. Fermented milk products such as cheese, yogurt, concentrated milks, butter, and even ice-cream have also been used for many centuries.
