Date : 05 Dec 2016
Milk and Human Health
This page discusses human health issues that have been positively and negatively linked to dairy product consumption. The effect of diet is only one factor that affects human health. Influences of gender, genetics, and lifestyle patterns such as exercise and smoking are significant factors affecting the health of an individual. There is a considerable amount of variation among individuals and results from different studies on the same nutrient may be contradictory, and thus confusing to the consumer. Scientists continue to refine their study techniques as new information is discovered and scientific tools improve.
Milk and Allergies
A food allergy is an immune response to proteins resulting in inflammatory symptoms involving the skin, respiratory system, and gastrointestinal tract. Some people think they are allergic to milk because they have symptoms of bloating, cramps, flatulence, and diarrhea after consumption of dairy products. This is not an allergic response but is a condition known as lactose malabsorption, which is discussed in a separate section below.
Allergic responses have different mechanisms, and some are mediated by immunoglobulins, specifically IgE. The major food proteins that trigger allergic reactions are milk, eggs, peanuts, tree nuts, fish, shellfish, soy, and wheat. Prevalence of milk allergy in the population is about 2% in children and 1% in adults. Onset of milk allergy may occur within about 1 yr of age and most children outgrow this allergy by 6 yrs of age.
Milk and Arthritis
Arthritis is characterized by damaged joints and leads to physical disabilities. There are many forms of the disease caused by degeneration of the joint (osteoarthritis), autoimmune diseases and inflammation (rheumatoid, psoriatic arthritis), infection (septic arthritis), and others.
It has been suggested that consumption of raw milk helps relieve arthritis. However, there are no studies in the literature that report an effect of drinking milk and relieving arthritis. There are currently no scientifically supported dietary recommendations to help relieve arthritis aside from maintaining a healthy weight and balanced diet.
Milk and Cancer
Cancer is a disease characterized by malignant growth in the body. Different cancers have different causes, modes of progression, treatments, and possible risk factors. The area of cancer research is very active and there is a considerable amount of data in the literature. Because of the variation in cancer types, individual metabolism, and factors evaluated in any given study there may be conflicting results published between studies on the same topic. Factors affecting the risk of cancer include genetics, lifestyle choices such as smoking and exercise, diet and other environmental causes.
Diets high in fat and calories and low in fiber and fruits and vegetables appear to increase the risk of some cancers. Diets high in dairy were thought to increase the risk of breast cancer because of the high fat content of some dairy products. However, there are conflicting research studies on the association between high fat (any type) intake and breast cancer. It used to be thought that dairy product consumption increased the risk of cancer.
Milk and Coronary Heart Disease
Coronary heart disease (CHD) is the leading cause of death in developed countries. Coronary heart disease is characterized by the accumulation of plaque inside the artery walls which narrows the arteries and reduces the flow of blood and oxygen to the heart muscle. There are many risk factors that contribute to CHD. Some risk factors cannot be modified such as being male, getting older, and a family history of CHD, while some risk factors can be modified such as smoking, high blood pressure, obesity, lack of exercise, and high blood cholesterol levels. The positive correlation of high blood cholesterol levels and increased risk of CHD is well-documented.
Milk and Dental Caries
Dental caries occur when the enamel on the teeth loses its mineral content (demineralization) resulting in a pitted surface. Saliva protects teeth from caries by maintaining a balanced pH (approx. 7) in the mouth and by a continuous depositing of calcium and phosphorus on the enamel (mineralization). The formation of dental caries occurs when demineralization is greater than mineralization of the enamel. Fermentation of sugars by the bacteria in the mouth results in the formation of acids which then lower the pH (to 5.5) of the mouth and allows for mineral loss from tooth enamel. It has long been recognized that sugar consumption contributes to dental caries.
Milk and Diabetes
Diabetes is a disease of carbohydrate metabolism. Type I diabetes is caused by an inability to produce insulin and is controlled by insulin injections. Type I diabetes is often associated with childhood onset. Type II diabetes is caused by an inability to respond to insulin that typically occurs in adults, and can be controlled through diet and exercise.
There were some studies that suggested that milk consumption contributed to childhood diabetes. However, these data have not been confirmed in larger studies, and more definitive research on the effects of dairy product consumption on Type I diabetes is needed. There is also a lack of studies that directly evaluate the effects of dairy products in Type II diabetes. Several studies have evaluated the effect of whole diets on diabetes and conclude that people with higher dairy consumption have a lower incidence of Type II diabetes. Although the mechanism of this action is still unknown, it is possible that calcium, which also protects against hypertension, is active in protecting against diabetes.
Milk and Hypertension
Hypertension is characterized by high blood pressure. High blood pressure increases the risk of coronary heart disease, stroke, and kidney disease. Factors that contribute to high blood pressure include obesity, a sedentary life style, and high intake of sodium in some individuals.
Dietary factors that have been studied and shown to reduce blood pressure are adequate intake of calcium, potassium, and magnesium. Calcium and potassium were identified as important nutrients for the reduction of blood pressure in the 1980s. Milk is a good source of calcium, potassium, and magnesium. Lowfat dairy products have been used successfully in dietary intervention studies as a combined source of these minerals to reduce blood pressure.
Milk and Osteoporosis and Bone Health
Osteoporosis is a disease that is characterized by decreased bone mass and deterioration of the bone tissue leading to an increased risk of fracture. Factors in osteoporosis include genetics, gender, race, exercise, and diet, particularly during growth years. Each individual has a genetically determined peak bone mass that is the maximum amount of bone mass that one can possibly have. The higher the bone mass accumulated, the lower the risk of osteoporosis. The majority of bone mass is accumulated by age 20, and continues up to age 30. The size of the skeleton influences the risk of osteoporosis. In general, women are more prone to osteoporosis because they have smaller skeletons than men, and Caucasians and Asians have smaller skeletons than people of African descent, who are less prone to osteoporosis. Estrogen has a protective effect on bone loss and women experience accelerated bone loss during early menopausal years because of decreased estrogen production at this time. Weight bearing exercise throughout life increases the load on the skeleton making it stronger and reducing the risk of osteoporosis.
Milk and Probiotics
Probiotics are defined as live bacteria that provide a health benefit when consumed in adequate amounts. Probiotic bacteria can be consumed as powders, capsules, or as part of foods, which may be called “functional foods.” Many probiotic bacteria are lactic acid bacteria, meaning that they use lactose as an energy source, and hence are associated with dairy products. Yogurt is often associated with probiotics because the bacterial cultures used to ferment milk into yogurt are probiotic cultures, and it is a nutritionally complete food for the maintenance of other probiotics that are added for further health benefits. Most yogurts is made with milk that is pasteurized before fermentation and, therefore, the bacteria are alive at consumption. Some yogurts may be pasteurized after fermentation and this would inactive the probiotic organisms. An important goal of the use of probiotics is that the organisms reach their target location in the body alive and in sufficient numbers to be effective. However, the number of bacteria needed for health benefits is unknown in many cases, because the literature on the survival and persistence of organisms in the human body is sparse and further research is needed. The number of live organisms may or may not be stated on functional foods and probiotic supplements, at the discretion of the producer.
