In almost all baby mammals, including humans, milk is fed through breastfeeding. Milk consumption is the primary way for infants to obtain energy and nutrients, but humans are the only ones who continue to drink it well beyond weaning into adulthood.
People often question as to whether or not milk and dairy products should be eliminated from the diet altogether. After all, several studies suggest there are both pros and cons of milk and dairy intake. The truth is that dairy foods—preferably low-fat and taken in moderation— offer many health benefits that can’t be ignored.
Milk, for example, is a very important protein source as it contains essential amino acids that are easily digestible and readily available for absorption. It is also a good source of vitamins, such as vitamins A, D, E, and B-complex. It contains several important minerals including calcium, phosphorus, magnesium, zinc, and selenium. Milk has antibacterial, antiviral, and antimicrobial properties, which can help defenseless newborns fight off potential infections. There has also been a lot of research evaluating the role milk and dairy intake plays when it comes to fighting chronic diseases.
Milk, Dairy and Cancer Prevention
Depending on the type of cancer, studies have shown that milk and dairy products may have protective effects against cancer. The World Cancer Research Fund and the American Institute for Cancer Research have both stated that incorporating milk into your diet can likely reduce your risk of colorectal cancer; however, there is limited support for bladder cancer.
In a 2009 study, it was found that participants who consumed the highest amounts of dairy in their diets had a reduced risk of developing colorectal cancer—15% among men and 30% among women, respectively. A meta-analysis that incorporated 19 different studies found that milk and total dairy intake was associated with a lower risk of colorectal cancer. However, when evaluating specific dairy products, cheese was not found to reduce overall risk, likely due to its high fat content. Calcium, which is largely abundant in milk and dairy products, may be the compound that helps reduce the risk of colorectal cancer in individuals.
When it came to other cancer types, the effects of dairy intake and risk differed. For instance, some studies found an association between increased milk intake and a reduced risk of bladder cancer, but other studies found no significant effects. One review study that evaluated twelve prospective cohort studies found that dairy intake had no association with ovarian cancer risk.
Some studies found that high dairy consumption was associated with an increased risk of prostate cancer. However, several other cohort studies found no such evidence. Other studies found that diets high in calcium likely increased the risk of prostate cancer, whereas the evidence linking milk and dairy intake with an increased risk of prostate cancer was limited.
When evaluating dairy intake and its association with breast cancer risk, a meta-analysis that included twelve prospective cohorts found that increased dairy intake was associated with a decreased risk of breast cancer. There were stronger associations among premenopausal women and participants who consumed low-fat dairy options. Keep in mind that other studies demonstrated an increased risk of breast cancer with increased dairy consumption.
Perhaps the increased risk could be attributed to increased intakes of high-fat dairy options. High-fat intake affects the production of sex hormones, such as androgens and estrogens. These hormones contribute to the development of prostate and breast cancer.
In general, studies have demonstrated that there is an association between consuming dairy products and a reduced cancer risk, especially when incorporating low-fat options into the diet. Protective effects have not been demonstrated by including high-fat dairy foods.
Dairy Intake and Bone Health
The major structural component of the bone is protein, with calcium being the most abundant mineral. Therefore, it is essential for proper bone health to ensure you are consuming an adequate intake of both protein and calcium. The highest risk for deficiencies of both protein and calcium is found among the elderly population, putting them at even greater risk of falls, fractures, and osteoporosis.
Previously it was thought that too much protein might actually put you at an increased risk of bone loss, fractures and osteoporosis. Protein is associated with increased calcium excretion; however, it may not actually affect calcium balance and bone metabolism. In fact, it may actually increase the body’s ability to absorb more calcium, which can improve bone health. Therefore, higher protein intake may actually be beneficial.
One study found that within a weight loss program, individuals maintaining a moderate weight loss over six months had reduced bone mineral density, whereas those maintaining moderate weight loss over one year had significantly reduced bone mineral density, especially on the spine and hip bones. With adequate intakes of calcium and protein, there was a reduced risk in bone mineral density. Therefore, it is recommended to incorporate several servings of dairy each day since dairy is an excellent source of calcium. In combination, protein will help maximize calcium absorption, improve bone mineral density and overall bone health.
Dairy and Diabetes Prevention
Dairy intake may play a role in improving insulin sensitivity and blood-glucose regulation. Some cross-sectional studies demonstrated a decreased incidence of impaired fasting blood-glucose levels and type 2 diabetes with increased dairy intake. However, no cause and effect from these studies can be determined. Findings from a systematic review that assessed dairy intake and its effect on controlling blood-sugar levels did reveal that higher dairy consumption might improve insulin sensitivity. Perhaps the combination of calcium and magnesium consumed through foods as opposed to supplements may demonstrate improved insulin sensitivity and glucose tolerance. Several studies haven’t found any association between dairy consumption and improved blood sugar levels.
Another study found that a high protein diet that incorporates milk protein provides long-term benefits on insulin sensitivity and blood-sugar regulation compared to a diet that incorporates soy protein. Furthermore, individuals who consumed a dairy snack (i.e. milk or yogurt) compared to individuals who consumed a carbohydrate-rich snack two hours prior to a mixed meal experienced reductions in blood sugar spikes.
While dairy may play a role in reducing the risk of type 2 diabetes, improving insulin sensitivity, and blood-sugar regulation, further research is warranted as evidence is currently inconclusive.
As you can see, there are several health benefits of incorporating low-fat milk and dairy options into a healthy diet. The key is to keep your diet balanced and consume a variety of different foods in moderation.
Sources for Today’s Article:
Abid, Z., et al., “Meat, dairy, and cancer,” The American Journal of Clinical Nutrition 2014; 100(suppl):386S-93S.
Pasiokos, S.M., “Metabolic advantages of higher protein diets and benefits of dairy foods on weight management, glycemic regulation, and bone,” Journal of Food Science 2015; 80(S1):A2-A7.
Pereira, P.C., “Milk nutritional composition and its role in human health,” Nutrition 2014; 30(2014):619-627.