The public has a negative perception of drinking animal milk, precisely cow’s milk, with many critics citing that no other mammal, besides humans, continue to drink milk into adulthood. Milk has also gained a bad reputation for containing hormones. The natural assumption that has followed, is that milk is not healthy or beneficial for humans. Cow’s milk has been associated with possibly causing increased risks for developing Cardiovascular disease, Diabetes, and certain cancers, but what exactly is in milk, and is drinking milk good for you?
What is milk?
Given the concerns over consuming cow’s milk, non-mammalian sourced alternatives have arisen. Though substance resembling or used as substitutes for milk are called milk they are not truly milk. “Soy milk” and “almond milk”, should rather be referred to as beverages and not milk. Milk, is the fluid produced by the mammary glands of female mammals for the nourishment of their young. It’s secretion is preceded by the colostrum; colostrum however is not included in the milk that is used for human consumption. Sheep and goat’s milk are other sources of milk, but cow’s milk is the most common type of milk that humans consume. So, for simplicity, this article will refer solely to cow’s milk.
History of Milk Production
In the United States, cow’s milk was produced locally and on a small scale throughout the 19th century. In the late 1800‘s pasturization made it possible for milk to be stored longer, transported further, and safe to drink. Pasturization kills of pathogens using high heat sustained for a certain amount of time. Rural milk production eventually gave way to commercial farming as large quantities of milk was first produced for growing urban populations, and marketed as a substitute for breast-milk.
The quantity of milk wasn’t the only change in milk production, but the constitution of milk also changed. Traditionally whole milk was produced from grass fed cows that were only milked during the lactation period -after giving birth to calves. Today cows are milked nearly year round, and most of our milk comes from pregnant cows. This means there has been an increase in the amount of animal sex hormones present in milk. Estrogens and progesterone are present in milk at concentrations that are significantly higher than in human and non-pregnant cow milk. These hormones are not removed by pasturization, however cream seperation introduced in 1871, allows the fat content of milk, where estrogens are solublized to be removed, in the production of skim and reduced-fat milk. The removal of fat from milk, alters its consistency and taste, but through the process of homogenization, milk fat that has been removed can be broken up and redistributed evenly back into the fluid milk, for improved appearance and taste. Vitamin’s A and D were also added to fortify reduced-fat milk, in the 1920s. During that time the bone disorder, Rickets, caused by a deficiency in Vitamin D, was common.
Milk production is now a global industry with millions of tons of cow’s milk produced annually. In comparison to increasing production of milk worldwide, the consumption of milk by individuals in the United States has actually declined. The type of milk consumed has also changed. people have moved away from whole milk, and embraced reduced-fat milk and milk-substitutes, like soy and almond beverages. Some of the reasons for this, are concerns over the health dangers of saturated fat, growing awareness of food allergies and intolerance to lactose.
What’s in milk?
Almost 90% of the content of milk is water. The remainder is composed of proteins, fats, sugars, and vitamins and minerals. The composition of milk is influenced by various factors, including, species, genetics, health and nutrition of the animal, environment, and season.
Milk Proteins & Peptides – Curds & Whey
The curds and whey that little Ms. Muffet ate were full of protein. In fact, milk is a major source of high quality protein; containing all of the amino acids that are required by humans. These proteins are easily digestible making them readily available for use by the body. The proteins in milk are divided into two categories; soluble and insoluble. Soluble milk proteins or whey proteins make up 20% of the protein content of milk, with insoluble casein proteins making up the other 80%.
Whey proteins consist mainly of lactoferrin, beta-lactoglobulin, and alpha-lactoalbumin. Lactoferrin allows for the absorption of iron, while B-lactoglobulin is a carrier for vitamin A, both act as antioxidants. In combination with a-lactoalbumin, they act as tumor suppressors.
Caseins (from the curd portion) function to bind and carry minerals. Alpha, Beta, and kappa- caseins assist in the digestion of calcium and phosphorus. These proteins are capable of acting as pain-relievers and tranquilizers in the the central nervous system. In the cardiovascular system, they protect against disease, by preventing hypertension and blood-clots from forming. They even help to guard the intestinal tract, through the production of mucin, which coats the intestinal wall, preventing the adhesion and motility of pathogenic organisms.
Milk fat contains mostly triglycerides, which are esters of glycerol and three fatty acids. Seventy percent of the fatty acids in milk are saturated, and the rest are unsaturated. Milk also contains cholesterol, which makes up less than 0.5% of the lipids present in milk. Some fat in necessary in the diet, as fat aids in the digestion of lipid-soluble vitamins. Not all fat is bad for you either, unsaturated fatty acid, conjugated linoleic acid for instance, has cardiovascular health benefits, anticancer properties, and immune function, and helps reduce fat. Also, included in milks fat are many bioactive compounds; lipid-soluble vitamins, sphinogmyelin, and gossypol. The amount of fat in cow’s milk varies denpending upon the type of feed, environment, lactation stage,etc.
Whole milk on average contains about 3 to 5% fat, but can contain more or less. Homogenization makes it able for producers to remove the fat from, the milk, and reintroduce it at whatever quantity they desire. The left-over fat, could then be used to make other dairy products. While the preception and consumption of dairy milk has declined, the intake of cheese, butter and yogurt have not. These products however are generated from the fat content of milk, and consequentially contain the highest concentrations of animal estrogens.
Vitamins and Minerals
It’s common knowledge that cows milk is abundant in Calcium, but it is full of many other important vitamins and minerals. Milk is rich in phosphorus, supplies almost one-third of our daily required dietary intake of magnesium, and a good source of fat-soluble vitamin’s A, D, and E – Although, skim and low-fat milks, having lower fat content, lack these, and need to be fortified. Vitamin A is needed for proper growth and development, supports immunity, and eye health. Vitamin D in involved with calcium absorption, bone development, and cardiovascular health.
Aside from fat-soluble vitamins, milk also offers micro-elements – those that we need in minute quantities – Zinc and Selenium. Water-soluble B complex vitamins function as enzymatic cofactors, and are involved in energy production and hormone synthesis.
Thiamine (vitamin B1) is required for proper aerobic metabolism, nerve impulse transmission, and synthesis of acetylcholine. Thiamine deficiency results in Beriberi, a syndrome characterized muscle wasting, neuritis (painful inflammatory of nerves with loss of function), and cardiac failure. Thiamine deficiency may also result in lactic acidosis.
Riboflavin (B2) is involved in glucose oxidation and amino acid deamination, although rare its deficiency causes, fissures in the mouth, inflammation of the tongue, opthalmic keratosis, and dermatitis.
Cyanocobalamin (B12), is essential for hematopoiesis, nucleic acid synthesis, and neuronal myelin synthesis. Deficiency is rare, but results in pernicious anemia. Vitamin B12 is not found in plants, but is present in meat and dairy.
Lactose makes up 4 to 5 percent of milks chemical composition. Lactose is a disaccharide made up of the simple sugars, glucose and galactose. It’s metabolized by the enzyme lactase and a deficiency in this enzyme is responsible for lactose intolerance.
Adverse Reactions to Milk
Everyone is familiar with lactose intolerance and it is a common reason for aversion to drinking milk. Lactose intolerance is more common in some ethnic groups than others, particularly Asians and African-Americans. People who are lactose intolerant cannot properly digest the milk sugar lactose, due to a lack of the necessary enzyme responsible for its metabolism. Since, the lactose cannot be digested, it stays in the gut where it ferments, causing bloating, cramps, and gas. in some cases, it may even cause nausea, vomiting, and diarrhea. People who are lactose intolerant, should avoid milk, but can eat other dairy products, which have lower lactose content, such as, cheese and yogurt.
Cow Milk Protein Allergy
A less familiar and rare adverse reaction to milk is Cow Milk Protein Allergy. It is not clear, but the allergy seems to be both an immediate IgE mediated and delayed non-IgE mediated reaction. Immediate IgE mediated allergies are the type that can cause anaphylaxis. Delayed non-IgE mediated response affects the skin, gastrointestinal tract, and lungs, causing atopic dermatitis, chronic diarrhea, and pulmonary disease. This response is mostly due to the beta-lactoglobulin protein. Person who have this allergy must avoid cow milk products, but can consume milk from other animals, such as goats or sheep.
Estrogens and Progesterone
Milk and dairy products are the main sources of animal estrogens (there are plant estrogens known as phyto-estrogens) in the human diet. The primary estrogen found in modern cows milk is estrone sulfate, and progesterone is present also. Estrogen and progesterone are lipid-hormones, derived from cholesterol, that are soluble in fat. It is debatable whether the presence of these hormones in milk is biologically harmful. Based on criteria provide by the U.S. Food and Drug Administration (FDA), the amount of estrogen ingested from milk is within the range of the accepted daily intake (ADI); having no physiological effect. In regards to Progesterone, only a tenth of what is ingested of it, is available in the body. However, consumption of whole milk was correlated with reduced sperm function and increased risk of prostate cancer. These effects were more so attributed to eating cheese, again, being a consequence of the fat content.
In recent years drinking cows milk has come to be viewed unfavorably my many adults. The fact that it comes from an animal, contains hormones, and that no other animal is said to drink milk into adulthood, and lactose intolerance are amongst the main reasons why people believe milk may not be good for consumption. Milk has also been associated with possibly causing increased risk of cardiovascular disease, diabetes, and even cancer, due to its saturated fat content and the presence of insulin-like growth factors (IGf-1).
Saturated fat, increases blood lipids (cholesterol and low density lipoproteins) and thereby contributed to poor cardiovascular health. The fat content of milk can also influence the production of sex hormones, androgen and estrogen. This as well as IGF-1 may increase the risk of developing breast and prostate cancer.
However, these health-risk associations are related to whole milk, and drinking reduced-fat milk is actually a good way of preventing weigh gain. Milk whey proteins, help you to feel satiated; decreasing the amount of food you eat. Milk whey proteins also help control the bodies glucose levels, and decrease ghrelin which plays a role in the body’s response to insulin and the development of diabetes. Speaking of diabetes, the calcium and magnesium, abundant in milk, also play a role in maintaining sensitivity to insulin and glucose tolerance. In addition, calcium and magnesium protect against osteoporosis.
Drinking milk is healthy, and 2 to 3 servings of dairy a day is recommended as part of a balanced diet. Drinking reduced fat milk instead of whole milk, resolves most of the potential deleterious aspects attributed to cows milk. In cases of lactose intolerance, lactose-free milk is available, and has has the same consistency and flavor of ordinary milk, minus the lactose.