It’s summer time and with summer comes consumption of sweet frozen treats- like ice cream. But before you eat that milky indulgence, let’s consider what clinical trials can tell us about dairy consumption.
The scientific literature on the health affects of dairy, specifically from bovine sources, is incredibly mixed. There are studies showing associations between dairy consumption and an increase in inflammatory diseases, and other studies showing the exact opposite results.1 For example, it is well documented that high saturated fats contribute to an increased inflammatory response, while foods with antioxidants and omega fatty acids have an anti-inflammatory response; milk has both.2 These paradoxical results can make nutrition research difficult to conduct, and the ultimate response from a food is as the whole food, and not by individual constituents, adding another layer of complexity.
So, just what is in dairy and why does consuming it sometimes lead to negative side effects?
Bovine dairy is mostly made up of water- approximately 87%. It also contains 3% protein, 3-4% fat, 4-5% lactose, and less than 1% vitamins and minerals.2
There are many different proteins present in bovine milk and dairy products. Bovine dairy is still considered one of the most concentrated ways to get protein in the diet with 32 g protein/L.2 This protein content contains insoluble proteins, such as casein, and soluble proteins, such as whey. These proteins are rich sources of essential amino acids for the body, have high bioavailability and are highly digestible. Bioactive peptides are also present and have been shown to be antibacterial, antiviral and antifungal among many attributes.2
Saturated fatty acids (SFA) make up most of the fat content in bovine milk with a smaller amount of unsaturated fatty acids. The main SFAs present are palmitic, myristic and stearic acid. While the unsaturated fatty acids include oleic and linoleic fatty acids which are anti-inflammatory. Conjugated linoleic acid is also found in small amounts and has been associated with health benefits for cardiovascular disease and immune function.2, 3
It is well known that bovine milk contains calcium but it also contains other minerals including zinc, magnesium and selenium in small concentrations. Vitamins A, D, and E as well as B complex vitamins such as folate, riboflavin and thiamine are also found in milk.1,2
Excess consumptions of SFAs, which comprise the majority of the fat in milk, are associated with an increased risk for CVD. The mechanisms in which saturated fat increase CVD risk include raising levels of blood lipids such as LDL and total cholesterol.2,3 However the fatty acids found in milk consumed as a whole food may have a protective effect against CVD.2,3 Results from a recent randomized clinical trial (RCT) showed positive or no effect of butter and cheese consumption on cholesterol levels.3 Additional research is needed to better understand this relationship and to examine the variance of fatty acids in milk products. Fatty acids, minerals and vitamins in milk may lower CVD risk as indicated in the Rotterdam study published in 2009 by Engberink examining the relationship between dairy and hypertension showed an antihypertensive effect of milk consumption.5
The impact that milk consumption has on metabolic disorders has not been fully studied and remains unclear. However, some research indicates that there is a protective effect of milk consumption for type 2 diabetes (T2D), which may be due to the high levels of calcium and magnesium that helps regulate insulin sensitivity.2,4 It has also been suggested that the high levels of protein in milk helps with satiety resulting in reduction of food intake.2
Inflammation is a response by the immune system to foreign substances and organisms, which may include intake of foods.1 The immune system can produce either a neutral, pro or anti-inflammatory response to nutrients found in food. Chronic diseases such as obesity and diabetes have been associated with chronic inflammation, which may, in turn, be regulated or induced by specific food intake.2 Understanding the relationship between dairy consumption and the inflammatory response is difficult and there isn’t a definitive answer but current research helps shed light on this complex food. Recent systematic reviews assessing the impacts of dairy products on inflammation indicate, aside from allergies to milk, that there is an overall anti-inflammatory impact from milk consumption. In fact, the studies evaluated in these reviews saw mostly anti-inflammatory or a neutral impact on biomarkers including CRP, IL-6 and TNF-α.1,4
So while we are still waiting to learn more, go ahead and eat that frozen milk treat, but then there’s the matter of all that sugar…
1 Bordoni A, Danesi F, Dardevet D, et al. Dairy products and inflammation: A review of the clinical evidence. Critical Reviews in Food Science and Nutrition. 2015;57(12):2497-2525. doi:10.1080/10408398.2014.967385.
2 Alessandra Bordoni, Francesca Danesi, Dominique Dardevet, Didier Dupont, Aida S. Fernandez, Doreen Gille, Claudia Nunes dos Santos, Paula Pinto, Roberta Re, Didier Rémond, Danit R. Shahar & Guy Vergères (2017) Dairy products and inflammation: A review of the clinical evidence, Critical Reviews in Food Science and Nutrition, 57:12, 2497-2525, DOI: 10.1080/10408398.2014.967385
3 Brassard D, Tessier-Grenier M, Allaire J, et al. Comparison of the impact of SFAs from cheese and butter on cardiometabolic risk factors: a randomized controlled trial. The American Journal of Clinical Nutrition. 2017;105(4):800-809. doi:10.3945/ajcn.116.150300.
4 Labonte M-E, Couture P, Richard C, Desroches S, Lamarche B. Impact of dairy products on biomarkers of inflammation: a systematic review of randomized controlled nutritional intervention studies in overweight and obese adults. American Journal of Clinical Nutrition. 2013;97(4):706-717. doi:10.3945/ajcn.112.052217.
5 Engberink MF, Hendriksen MAH, Schouten EG, van Rooij FJA, Hofman A, Witteman JCM, et al. Inverse association between dairy intake and hypertension: the Rotterdam Study. Am J Clin Nutr 2009;89:1877–83.