- Consumption of low-fat dairy lowers the odds of developing type 2 diabetes by about 10% for each additional serving per day.
- High-fat dairy products, as a group, show no significant association with type 2 diabetes, although some studies suggest that cheese may be preventative.
- Whey protein and vitamin K2 may provide protection against type 2 diabetes.
Type 2 diabetes describes a condition where cells that would normally respond to insulin by absorbing glucose from the blood stop doing so, allowing blood glucose to rise to unhealthy levels. It is closely associated with obesity. Various studies link the regular consumption of low-fat dairy products to reduced odds of developing type 2 diabetes. Not every study finds this effect, but in those that do, the question is: why?
Funny enough, the answer is whey, at least in part. Dairy proteins contain two main categories of protein, caseins and whey proteins.
Typically during the development of type 2 diabetes, the number of functional insulin receptors sitting on the surface of fat and muscle cells decreases over time. Therefore, the signal these cells receive for any given amount of circulating insulin slowly wanes.
Experiments with both mice  and people  show that eating whey protein stimulates the insulin-producing cells in the pancreas to work harder than they normally would. They simply make greater amounts of insulin. In other words, the body’s internal message relaying that it’s time to remove glucose from the blood gets communicated more loudly. And this counteracts the lessened ‘listening’ ability of those cells whose job it is to pick up blood sugar.
One study  on type 2 diabetics reported that when whey protein is added to a meal of easy-to-digest carbohydrates, blood insulin levels are hiked by 57%. More importantly, the blood glucose levels of the diabetics in the study were 21% lower than they were after they ate a control meal.
Whey’s benefits are also implied by studies that link the consumption of dairy products to an overall lower likelihood of developing diabetes. Many studies have looked for this effect; some have found one, others have not.
A meta-analysis  conducted in 2011 by researchers at Soochow University in Suzhou, China, brought the results of seven cohort studies together. They report a 14% reduction in the risk of type 2 diabetes in people with high dairy consumption compared to people with very low diary consumption. This dose-dependent effect implies a 10% reduction in the odds of getting type 2 diabetes with each additional daily serving of low-fat dairy.
Perhaps the most instructive individual cohort study is the one that followed its participants for the longest time. The Nurses Health Study involves some 120,000 female registered nurses. They began enrolling in the study in 1989 and have filled in biennial lifestyle questionnaires ever since. These women have also been asked to recall their dairy intake during high school .
The results are intriguing. They confirm that consuming dairy products as an adult offers modest protection against type 2 diabetes. However, the really significant benefit comes from eating lots of dairy as an adolescent. This suggests the mixed results from other cohorts might boil down to when and for how long the researchers tracked the participants.
Whey is not the only constituent of diary that could help prevent diabetes. Another component was brought into the spotlight by a closer analysis of the particular kinds of dairy products that are good for diabetics. The place to study such a topic is Europe, where high dairy consumption is combined with strong national preferences. The French, for example, eat a lot of cheese, meanwhile the Swedes and Dutch get through large quantities of yogurt.
Eight European countries, 340,000 people in total, are taking part in EPIC InterAct, a study that aims to unpick the genetic and lifestyle factors that contribute to type 2 diabetes risk. The researchers running EPIC InterAct have not found any statistically significant anti-diabetic benefit to drinking lots of milk . But, after statistically correcting for all sorts of risk factors, including obesity, they have reported that a diet rich in fermented dairy products, including cheese, is protective.
Why fermented dairy? No one is completely sure. But one explanation is that a vitamin called K2 is causing the effect . K2 is not made in mammalian bodies, so it isn’t present in all dairy. It is manufactured, however, by the bacteria used to seed the dairy fermentation process. K2 reduces inflammation, which, it is thought, raises insulin sensitivity.
Although many questions remain unanswered, this research is heartening, particularly for people with a family history of type 2 diabetes. Like obesity, diabetes can have devastating medical consequences over time—indeed, it is the primary non-traumatic cause of blindness and kidney failure in developed countries. As a result of these consequences, diabetes is also an expensive burden on society.
The University of South Australia, Adelaide, has put numbers on this. Researchers James Doidge and colleagues  asked how much increasing the consumption of dairy in Australia could cut the national healthcare bill. For the financial year 2010-2011, they came up with the figure AUD $2.0 billion (USD $2.1 billion), an amount slightly greater than total public health spending in the country the year before. Whether they are correct or not, the ballpark their calculation landed in is surely worthy of attention.
1. Salehi A, Gunnerud U, Muhammed SJ, Ostman E, Holst JJ, Björck I, Rorsman P. (2012) The insulinogenic effect of whey protein is partially mediated by a direct effect of amino acids and GIP on β-cells. Nutr Metab (Lond) 9:48.
2. Petersen BL, Ward LS, Bastian ED, Jenkins AL, Campbell J, Vuksan V. (2009) A whey protein supplement decreases post-prandial glycemia. Nutr J 8:47.
3. Frid AH, Nilsson M, Holst JJ, Björck IM. (2005) Effect of whey on blood glucose and insulin responses to composite breakfast and lunch meals in type 2 diabetic subjects. Am J Clin Nutr 82:69-75.
4. Tong X, Dong JY, Wu ZW, Li W, Qin LQ. (2011) Dairy consumption and risk of type 2 diabetes mellitus: a meta-analysis of cohort studies. Eur J Clin Nutr 65:1027-1031.
5. Malik VS, Sun Q, van Dam RM, Rimm EB, Willett WC, Rosner B, Hu FB. (2011) Adolescent dairy product consumption and risk of type 2 diabetes in middle-aged women. Am J Clin Nutr 94:854-861.
6. Sluijs I, Forouhi NG, Beulens JW, van der Schouw YT, Agnoli C, Arriola L, Balkau B et al. (2012) The amount and type of dairy product intake and incident type 2 diabetes: results from the EPIC-InterAct Study. Am J Clin Nutr 96:382-390.
7. Struijk EA, Heraclides A, Witte DR, Soedamah-Muthu SS, Geleijnse JM, Toft U, Lau CJ. (2012) Dairy product intake in relation to glucose regulation indices and risk of type 2 diabetes. Nutr Metab Cardiovasc Dis Epub ahead of print.
8. Doidge JC, Segal L, Gospodarevskaya E. (2012) Attributable risk analysis reveals potential healthcare savings from increased consumption of dairy products. J Nutr 142:1772-1780.
Professional science writer & editor