Does the fat content of dairy products, such as skim milk vs. whole milk, play a role in the development of metabolic syndrome (MetS)?
Metabolic syndrome (MetS) is characterized by abnormalities such as high triglycerides, high blood pressure, high blood sugar, low high-density lipoprotein (HDL) cholesterol, and abdominal obesity. Diet is at the core of diseases associated with MetS. Many cohort studies have shown a relationship between high dairy consumption and risk reduction of MetS, hypertension, and diabetes. Several cohort studies have taken place in North American and Europe, where the diet can vastly differ from other continents.
The Prospective Urban Rural Epidemiology (PURE) study is a prospective epidemiological study whose purpose is two-fold. The Pure study prospectively analyzed the relationship between dairy consumption and the occurrence of hypertension (n=57547 participants without hypertension) and diabetes (n= 131481 participants without diabetes) while also cross-sectionally determining the association between dairy consumption and incidence of MetS (n= 112922). The study spanned over 21 different countries, including Brazil, China, Iran, Sweden, and Zimbabwe. The study participants included individuals from 35 to 70 years of age who were followed for 9.1 years. Participants were categorized into groups based on dairy servings (zero, less than one serving per day, one to two servings per day, and more than two servings a day).
The study standard for having MetS meant that participants must meet three out of the five criteria for having MetS. The first criteria for hypertension were systolic blood pressure (SBP) ≥ 130 mmHg or diastolic blood pressure (DBP) ≥85 mm Hg. High waist circumference was indicated by >80 cm in women and a minimum of 94 cm for men except for Asian and South Americans, where ≥90 cm was used. Low HDL-C levels indicated as 40mg/dL in men and 50 mg/dL in women. High triglycerides were indicated as 150 mg/dL for both men and women. The fifth criteria, diabetes, was suggested as having a fasting glucose of ≥ 5.5 mmol/L or intake of oral hypoglycemic agents. A participant was defined as having hypertension upon follow up if it was self-reported, they were on antihypertensives, or had an SBP >140 mmHg or DBP>90mmHg. Diabetes upon follow-up was defined if the participant self-reported it on oral hypoglycemic medication or had fasting glucose ≥ 7.0 mmol/L.
Validated food frequency questionnaires (FFQs) were used to record the participants’ habitual food consumption, specific to country or region, but with the same format. “Total dairy included: milk, yogurt, yogurt drink, cheese, and mixed dishes prepared with dairy.” The entire dairy list was further divided into whole fat dairy ( whole milk, whole fat yogurt, cheese, yogurt drinks, and mixed dishes with whole-fat dairy products) and low-fat dairy ( 1-2% milk, skimmed milk, low-fat yogurt, cheese, and yogurt drink). Butter intake was not recorded in all countries. Consumption of either whole or low-fat dairy was defined as intake of at least one serving per month. Higher intake includes two or more servings. Standard serving sizes for the products were used. A standardized questionnaire was used to gather medical history, smoking status, prescription medication use, and education level. Physical measurements and fasting blood samples were obtained. Follow up was done every three years through telephone or local interviews.
The consumption of high total dairy (OR 0.76, 95% ci 0.71-0.80, P-trend <0.0001), whole fat dairy alone (OR 0.72, 95% CI 0.66-0.78, P-trend: 0.005) and a combination of whole fat and low fat dairy (OR 0.89, 95% CI 0.80-0.98, p-tend=0.005) were linked to lower MetS prevalence, after covariates adjustment. Low-fat dairy intake alone was not associated with a lower incidence of MetS. High dairy intake was linked to lower hypertension occurrence (HR 0.89, 95% CI 0.82-0.97, P-trend =0.02) and lower diabetes occurrence (HR 0.88, 95% CI0.76-1.02 p-trend=0.01). High intake of low-fat dairy alone showed no association with decreased hypertension or diabetes. The strength of this study is that it is multinational and that it used country-specific FFQs. The study’s weakness includes self-reporting of diet and the inability to assess the incidents of MetS (because waist circumference, blood glucose, and blood lipids were only analyzed in 20% of the population). A large randomized trial should be done to analyze the relationship between whole-fat dairy and the risk of Mets, diabetes, and hypertension.
- Higher intake of whole-fat dairy is associated with lower incidents of MetS, hypertension, and diabetes.
- High intake of low-fat dairy combined with high-fat dairy is associated with lower incidents of MetS, hypertension, and diabetes.
- Low-fat dairy consumption is not associated with lower incidents of MetS, hypertension, and diabetes.
Reference for “Skim Milk vs. Whole Milk: What’s the Healthier Option?”:
Bhavadharini, Balaji, et al. “Association Of Dairy Consumption With Metabolic Syndrome, Hypertension, And Diabetes In 147 812 Individuals From 21 Countries”. BMJ Open Diabetes Research & Care, vol 8, no. 1, 2020, p. e000826. BMJ, doi:10.1136/bmjdrc-2019-000826.
Zahra Hashemy, PharmD. Candidate, USF Taneja College of Pharmacy