The consumption of dairy products is an important part of a balanced healthy diet. Most dietary guidelines recommend two to three servings per day of dairy products.
However, over the past few years, the consumption of dairy products has been a subject of debate in the scientific and public communities. The potential association of dairy product consumption with obesity and metabolic syndrome has been a topic of rising concern.
Metabolic syndrome, characterized by a cluster of cardiometabolic risk factors such as abdominal obesity, insulin resistance, hyperglycemia, dyslipidemia, and hypertension, is a well-known risk factor for diabetes and cardiovascular disease. Therefore, metabolic syndrome is gaining significance as a matter of public health concern.
What we know about dairy products and metabolic syndrome
Previous studies have suggested an association between dairy product consumption and metabolic syndrome. However, the results have been inconsistent.
Although some clinical studies have shown associations between dairy intake and a reduction of several parameters of metabolic syndrome including weight, waist circumference, blood pressure, dyslipidemia, and hyperglycemia, a handful of studies have provided evidence for the harmful effects of saturated fat intake associated with dairy products.
In addition, some studies either found a beneficial effect or no effect of dairy products on metabolic risk factors.
Understanding the role of dairy products on cardiometabolic health
To better understand the role of dairy products and related nutrients on cardiometabolic health, a team of researchers in Baltimore City, Maryland, USA conducted a prospective, population-based study.
The study, published in the British Journal of Nutrition, assessed the association between the consumption of dairy products and obesity and metabolic syndrome using repeated dietary and metabolic parameter measures. The study also examined correlations between sociodemographic factors, race, sex, dairy product consumption, and metabolic disturbances.
A total of 1,371 urban adults with a mean age of 48.4 years completed the study. Initiated in the year 2004, the study used two visits to assess two 24-hour dietary recalls of the participants.
The first visit between 2004-2009 was followed up by the second visit between 2009-2013 with a mean follow-up period of 4.6 years. The average nutrient and food group intake of participants was estimated at each visit.
Anthropometric measures such as body mass index (BMI), waist circumference, blood pressure as well as metabolic risk factors including total cholesterol, HDL-cholesterol, triglycerides, and glucose levels were measured at each visit.
Key dietary exposures that were measured included total dairy product, fluid milk, cheese, and yogurt intake. In addition, researchers also measured dairy-related nutrients such as calcium, phosphate, magnesium, and dairy fat.
They recorded these measures at the start of the study and as an annual rate of change of consumption by the participants.
Dairy products produced mixed outcomes
The important finding of this study was an increased risk of central obesity associated with both cheese and yogurt consumption in the urban adult population.
Dairy fat was positively associated with increased triglycerides and HDL cholesterol in the blood as well as metabolic syndrome. High fluid milk intake, however, was associated with decreased triglycerides in the blood and fewer indicators of metabolic syndrome, although it was associated with increased levels of HDL cholesterol.
In addition, as calcium and phosphorus intake increased markers of metabolic syndrome decreased.
Socio-demographic and sex-specific findings revealed that whites had an increased risk of central obesity due to increased milk intake compared with African Americans. Also, the positive association between dairy product fat intake and metabolic syndrome was found only in whites.
Furthermore, in men, dairy product fat consumption had an inverse relationship with obesity while in women it was positively related to increased HDL cholesterol.
The physiological effects of dairy consumption
It is interesting to note how the various nutritional components of dairy products affect physiology and what are the possible mechanisms leading to metabolic syndrome. For instance, calcium reduces body weight by affecting plasma vitamin D levels.
Calcium is also known to bind to intestinal fatty acids and bile acids leading to the upregulation of LDL receptors and a reduction of LDL-cholesterol levels.
The magnesium from dairy products increases the levels of lipoprotein lipase, an enzyme that breaks down fats, thus reducing the levels of triglycerides and LDL cholesterol while increasing the levels of HDL cholesterol.
Furthermore, the milk proteins whey and casein have been associated with the inhibition of the angiotensin-converting enzyme, and therefore help in the reduction of blood pressure. They also enhance the anti-obesity effects of calcium. Through a complex mechanism involving many factors, dairy product nutrients target the various components of metabolic syndrome.
Dairy products and health outcomes
This study highlights that various dairy products alter the components of metabolic syndrome differently. The consumption of milk lowered the risk of metabolic syndrome while cheese and yogurt consumption increased the risk of metabolic syndrome and its components.
The association between dairy product consumption and metabolic syndrome is an important consideration for nutritional interventions and public health awareness.
The prospective design, long follow-up period, repeated measures of dairy product exposure and outcomes, and two 24-hour dietary recalls are some important strengths of this study.
In conclusion, the study findings suggest that the consumption of fluid milk is inversely related to the risk of metabolic syndrome while cheese and yogurt have a direct relationship with obesity and metabolic syndrome in urban adults. The study is interesting but more research is warranted to better understand the physiological effects of dairy products consumption.
The authors suggest that these findings should be strengthened by future research on the association of dairy products with metabolic disorders.
Reference: Mary A. Beydoun et al. Dairy product consumption and its association with metabolic disturbance in a prospective study of urban adults. British Journal of Nutrition (2018), 119, 706-719
