In our house we have made the decision to strictly limit cow's dairy products, after reading some scientific research and doing our own Biblical studies.
I will give you the facts that we based our decision on, and then you can decide what is right your family.
The Bible compares an immature understanding of the Word of God to milk and a mature understanding to meat (but, don't go eating loads of meat!). The idea here is that milk is for infants (immature), and meat is for when we get older (mature) and can chew/handle it.
In Exodus, Israel is described as a land flowing with milk and honey. This is speaking about of rich, fertile land for agriculture (honey = bees and livestock = milk).
The Bible never tells us we should drink cow's milk. The tribes of Israel drank sheep's milk (Deuteronomy 32:14; 1 Corinthians 9:7) and goat's milk (Proverbs 27:27). Goats were reared principally for their milk and for good reason, goat's milk avoids most of the problems associated with cow's milk (click on the highlighted text & scroll to bottom of page for more info on goat's milk).
Calcium: According to the Physician's Committee For Responsible Medicine, milk’s main selling point is calcium, and milk-drinking is touted for building strong bones in children and preventing osteoporosis in older persons. However, clinical research shows that dairy products have little or no benefit for bones.
A 2005 review published in Pediatrics showed that milk consumption does not improve bone integrity in children. Similarly, the Harvard Nurses’ Health Study, which followed more than 72,000 women for 18 years, showed no protective effect of increased milk consumption on fracture risk.
You can decrease your risk of osteoporosis by reducing sodium & animal protein intake in the diet, increasing intake of fruits and vegetables, exercising, and ensuring adequate calcium intake from plant foods such as kale, broccoli, and other leafy green vegetables and beans.
Cancer: Prostate and breast cancers have been linked to consumption of dairy products, presumably related to increases in a compound called insulin-like growth factor (IGF-I).
IGF-I is naturally found in cow’s milk and has been shown to occur in increased levels in the blood of individuals consuming dairy products on a regular basis.
Ovarian cancer may also be related to the consumption of dairy products. The milk sugar lactose is broken down in the body into another sugar, galactose. Research suggests that the dairy sugar galactose might be toxic to ovarian cells. In a study conducted in Sweden, consumption of lactose and dairy products was positively linked to ovarian cancer. A similar study, the Iowa Women’s Health Study, found that women who consumed more than one glass of milk per day had a 73 percent greater chance of ovarian cancer than women who drank less than one glass per day.
Hormones: Milk naturally contains hormones and growth factors produced within a cow’s body. In addition, synthetic hormones such as recombinant bovine growth hormone (rBGH) are commonly used in dairy cows to increase the production of milk. Because treated cows are producing quantities of milk nature never intended, the end result can be mastitis, or inflammation of the mammary glands. Treatment of this condition requires the use of antibiotics, and antibiotic traces have occasionally been found in samples of milk and other dairy products. Pesticides, polychlorinated biphenyls (PCBs), and dioxins are other examples of contaminants found in milk. These toxins do not readily leave the body and can eventually build to harmful levels that may affect the immune and reproductive systems. The central nervous system can also be affected. Moreover, PCBs and dioxins have also been linked to cancer.
Cholesterol: Dairy products - including cheese, ice cream, milk, butter, and yogurt - contribute significant amounts of cholesterol and saturated fat to the diet. Diets high in fat and saturated fat can increase the risk of heart disease, among other serious health problems.
Diabetes: Insulin-dependent (Type 1 or childhood-onset) diabetes is linked to consumption of dairy products. A 2001 Finnish study of 3,000 infants with genetically increased risk for developing diabetes showed that early introduction of cow’s milk increased susceptibility to Type 1 Diabetes.
Intolerance: Lactose intolerance is common among many populations. Up to two-thirds of the world's population are lactose-intolerant, according to the Surgeon General's 2004 report on Bone Health: approximately 95% of Asian Americans, 74% of Native Americans, 70% of African Americans, 70% of Jewish descent, 53% of Hispanic, and 15% of Caucasians. We personally do not think God designed us to drink cow milk. Sure, some people can "tolerate" it but Jesus, Moses, Noah, Abraham, etc. were probably lactose intolerant.
Vitamin D: Individuals often drink milk in order to obtain vitamin D in their diet, unaware that they can receive vitamin D through other sources. The natural source of vitamin D is sunlight. Five to fifteen minutes of sun exposure to the arms and legs or the hands, face, and arms can be enough to meet the body’s requirements for vitamin D. Other good vitamin D sources can be found here.
Lobbyists: New York University professor Marion Nestle writes extensively in Food Politics how lobbyists have influenced the government’s nutritional guidelines. It’s the profit motive, as Nestle explains in her book “Food lobbyists, therefore, are people who ask government officials to make rules or laws that will benefit their clients’ companies, whether or not they benefit anyone else.” So, if a particular type of food gets the governments’ stamp of approval, then it's likely that sales will increase. The dairy industry spends millions promoting consumption, such as in the “Got Milk” ad campaign.