A recent study investigated whether increasing the consumption of fat-free milk would affect metabolic syndrome in individuals with type 2 diabetes.
Favouring glycemic control and weight loss, dairy products are a great source of nutrients and bioactive compounds with the potential for reducing inflammation and oxidative stress. In particular, low-fat products such as fat-free milk are a great source of vitamins and minerals such as vitamin D, calcium, zinc, magnesium, and phosphate which have been associated with lowering the risk of type 2 diabetes and cardiovascular disease. An increase in the consumption of calcium has also been associated with beneficial effects on body weight, blood pressure, and type 2 diabetes.
How Do Dairy Products Impact Metabolic Syndrome?
Previous studies have shown an inverse association between the consumption of low-fat dairy products and factors such as inflammation and oxidative stress, which play pivotal roles in the development and onset of metabolic syndrome. Metabolic syndrome is a combination of conditions that occur simultaneously including excess body fat around the waist, high blood pressure (hypertension) and blood sugar, and abnormal cholesterol levels which lead to an increase in the risk of heart disease, stroke, and type 2 diabetes.
Studies have also shown a link between a higher consumption of dairy products and a lower incidence of metabolic syndrome and type 2 diabetes. However, the association between dairy and cardiovascular disease remains controversial despite evidence that dairy products may play a role in modulating cardiovascular risk factors such as inflammation, insulin response, and abnormalities in cholesterol levels and blood pressure.
Given that milk proteins (such as whey protein) appear to have anti-inflammatory and anti-hypertensive effects, further research was necessary. It has been proposed that in combination with energy-restrictive, or low-calorie diets, the consumption of low-fat dairy such as fat-free milk could be effective in reducing body weight and fat mass, waist circumference, and blood pressure. This may be especially true in comparison to whole dairy and non-energy restrictive diets.
What is the Impact of Fat-free Milk?
To date, research has focused on investigating the association between the consumption of dairy products and its subsequent effects on body weight and glycemic control. Therefore, a recent randomised, cross-over clinical trial conducted by Brazilian researchers investigated whether increasing the consumption of calcium from fat-free milk along with an energy-restricted diet in adults with type 2 diabetes would result in beneficial effects on metabolic syndrome. They also determined whether there would be effects on cardiometabolic outcomes such as insulin resistance, impaired glucose tolerance, and hypertension. The results were recently published in the British Journal of Nutrition.
The trial included fourteen adults between the ages of 20–59 years with type 2 diabetes, an average body mass index (BMI) of 29.4 kg/m2 (classifying them as overweight to obese), low habitual calcium consumption, low level of physical activity, and adhering to an energy-restrictive diet. The participants underwent two 12-week phases with a washout period in between of eight weeks. They were prescribed an energy-restrictive diet of 500 kcal per day with 800 mg of dietary calcium, and randomly assigned to either a high-calcium fat-free milk phase or the low-calcium control phase, where they received breakfast shakes containing 700 mg or 6.4 mg of calcium, respectively.
The researchers assessed each patients waist circumference, fasting glucose, blood pressure, fasting total cholesterol, fasting LDL (low-density lipoprotein or “bad” cholesterol) and HDL (high-density lipoprotein or “good” cholesterol), LDL:HDL ratio, and fasting triglyceride levels (type of fat in your blood) at baseline and after each 12-week phase.
Higher Dietary Calcium Led to Increased Weight Loss
Total calcium consumption for the high-calcium phase was approximately 1200 mg per day, including 700 mg from fat-free milk and 500 mg from other dietary sources, as opposed to 525 mg per day in total for the low-calcium or control phase. The high-calcium fat-free milk phase resulted in a greater reduction in waist circumference, LAP index (lipid accumulation product e.g. fats and triglycerides) and blood pressure when compared to the results from the low-calcium phase. Furthermore, an increase in HDL:LDL ratio (i.e. an increase in good vs bad cholesterol) and a reduction in LDL-cholesterol, blood pressure and total cholesterol decreased was only observed in participants in the high-calcium phase.
While the randomised, controlled cross-over design of the study and inclusion of an energy-restricted diet helped reduce between-subject variability to strengthen the study, one limitation noted by the researchers was the increase in dietary fibre observed for the high-calcium phase participants only. However, they explain that this increase was unlikely to significantly influence the results as daily consumption of at least 40 g of fibre is required to improve blood glucose levels. Hence, 10 g of dietary fibre is unlikely to increase weight loss.
The results indicate the increase in daily consumption of calcium from fat-free milk in combination with at least 700 mg of dietary calcium and an energy-restricted diet over a 12-week period promotes a greater decrease in waist circumference, blood pressure, and other metabolic indicators such as LAP index. Given the relevance of dietary treatments for individuals with type 2 diabetes and metabolic syndrome, these outcomes show there are indeed beneficial effects of increasing the daily consumption of calcium on some metabolic syndrome and cardiometabolic conditions compared to a low-calcium diet.
Written by Lacey Hizartzidis, PhD
Reference: Gomes JMG, Costa JDA, Alfenas RCG. Effect of increased calcium consumption from fat-free milk in an energy-restricted diet on the metabolic syndrome and cardiometabolic outcomes in adults with type 2 diabetes mellitus: a randomised cross-over clinical trial. Br J Nutr. 2018 Feb;119(4):422-430. doi:10.1017/S0007114517003956.