Remember the experts who said we should drink skim milk? A new large study suggests that full fat milk is healthier. So much for that consensus about saturated fat. There have been signs things were amiss. A few studies recently have shown that milk, yogurt and cheese consumption were associated with a lower incidence of Diabetes Type 2. Dairy didn’t seem to make the heart attacks more likely either. Hmm. So this new study of 26,000 women looked at high fat versus low fat dairy products. Over 14 years the highest consumption (which is 8, crikey, portions of full fat dairy a day) is associated with … a 23% reduction in risk compared to the low fat dairy consumers. Time to eat more Brie? Maybe, maybe not.
I won’t be taking up 8 portions of full fat dairy myself — the 23% figure is not seismic, is based on a modeled estimate (so is open to debate). I suspect it’s not the fat content that is the most important thing here, but something else entirely. The “displacement effect” confounds this sort of study. It might not be that dairy fat is so helpful, just that it is less bad that other things it displaces. Hold onto your hat. Low fat dairy foods are much more likely to also have sugar or artificial sweeteners in them to make up for the flavour lost with lower fat. Coincidentally, also this week, an entirely different study showed that artificial sweeteners appear to have a bad effect, not directly on mammals, but through gut microbes.When mice were fed artificial sweeteners, they developed glucose intolerance. When bacteria in their intestines were transferred to other mice, those mice developed glucose intolerance too. In people, glucose intolerance is described as “the first step on the path to metabolic syndrome and adult-onset diabetes.”
For similar reasons it may also be that the fermented type of dairy matters. Cream was good, but fermented milk (like yoghurt and kefir) was better. Those gut microbes are popping up in study after study.
Confused? Fair enough. But this study, yet again, shows the diet consensus for the last three decades was wrong. Saturated fat, long painted as the enemy, is not necessarily, and artificial sweeteners, long painted as being useful to prevent diabetes, may be helping to create it.
Gut Bacteria, Artificial Sweeteners and Glucose Intolerance
Among other things, says Dr. Eran Elinav of the Weizmann Institute’s Immunology Department, who led this research together with Prof. Eran Segal of Computer Science and Applied Mathematics Department, the widespread use of artificial sweeteners in drinks and food may be contributing to the obesity and diabetes epidemic that is sweeping much of the world.
“The scientists gave mice water laced with the three most commonly used artificial sweeteners – in the equivalent amounts to those permitted by the FDA. These mice developed glucose intolerance, as compared to mice that drank water, or even sugar water. Repeating the experiment with different types of mice and different doses of the sweeteners produced the same results – these substances were somehow inducing glucose intolerance.
“The researchers treated mice with antibiotics to eradicate many of their gut bacteria; this resulted in a full reversal of the artificial sweeteners’ effects on glucose metabolism. Next, they transferred the microbiota from mice that consumed artificial sweeteners to ‘germ-free’ mice – resulting in a complete transmission of the glucose intolerance into the recipient mice. This, in itself, was conclusive proof that changes to the gut bacteria are directly responsible for the harmful effects to their host’s metabolism.
The findings showed that many – but not all – of the volunteers had begun to develop glucose intolerance after just one week of artificial sweetener consumption. The composition of their gut microbiota explained the difference: The researchers discovered two different populations of human gut bacteria – one that induced glucose intolerance when exposed to the sweeteners, the second that had no effect either way. Elinav believes that certain bacteria in the guts of those who developed glucose intolerance reacted to the chemical sweeteners by secreting substances that then provoked an inflammatory response similar to sugar overdose, promoting changes in the body’s ability to utilize sugar.
Consumption of high-fat dairy products associated with lower risk of developing diabetes
[Eureka] New research presented at this year’s annual meeting of the European Association for the Study of Diabetes (EASD) in Vienna, Austria, shows that people with the highest consumption of high-fat dairy products (8 or more portions per day) have a 23% lower risk of developing type 2 diabetes than those with the lowest consumption (1 or less per day). The research is by Dr Ulrika Ericson, Lund University Diabetes Center, Malmö, Sweden, and colleagues.
Dietary fats could affect glucose metabolism and insulin sensitivity and may therefore have a crucial role in the development of type 2 diabetes (T2D). Studies have indicated that replacing saturated fat with monounsaturated and polyunsaturated fats might be favourable in the prevention of T2D. In line with this, plant sources of fat have been suggested to be a better choice compared with animal sources. Indeed, high intakes of red meat and meat products have been shown to increase the risk of T2D. Nevertheless, several epidemiological studies have indicated that a high intake of dairy products may be protective. Subsequently, the importance of dietary fat content and food sources of fat remains to be clarified. In this new study, the authors aimed to examine intakes of main dietary fat sources, classified according to fat content, and their association with risk of developing T2D.
The study included 26 930 individuals (60% women), aged 45-74 years, from the population-based Malmö Diet and Cancer cohort. Dietary data was collected with a modified diet history method. During 14 years of follow up, 2860 incident T2D cases were identified. Modelling was used to estimate hazard ratios (HR) of diabetes incidence in quintiles of energy adjusted dietary intakes. The model included adjustments for age, sex, season, diet assessment method version, total energy intake, BMI, leisure time physical activity, smoking, alcohol consumption and education.
The researchers found that high intake of high-fat dairy products was associated with a 23% lower incidence of T2D for the highest consuming 20% of participants (or quintile) (median=8 portions/day) compared with the lowest consuming 20% (median=1 portion/day).
Concerning intakes of specific high-fat dairy foods, increasing intake of cream (30ml or more a day in the highest consuming 20% versus 0.3ml a day or less in the lowest consuming 20%) was associated with a 15% reduction in risk of developing type 2 diabetes. High-fat fermented milk* consumption also reduced the risk of developing diabetes by 20%, when comparing the highest consumers (180ml/day, the top 10% of consumers), with the non-consumers (60% of participants).
In contrast to these findings, there was no association found between intakes of low-fat dairy products and risk of developing type 2 diabetes.
High intakes of meat and meat products were, regardless of fat content, associated with increased risk, but the increased risk was higher for lower fat meats (increased risk of type 2 diabetes for high fat meats 9%, for low fat 24%), both referring to the risk in the highest-consuming versus lowest-consuming 20%). The highest consuming group for the high-fat meat had 90g or more per day, and for the low-fat meat 80g per day.
Dr Ericson says: “Our observations may contribute to clarifying previous findings regarding dietary fats and their food sources in relation to T2D. The decreased risk at high intakes of high- fat dairy products, but not of low-fat dairy products, indicate that dairy fat, at least partly, explains observed protective associations between dairy intake and T2D. Meat intake was associated with increased risk of developing diabetes regardless of fat content.”
She adds: “Our findings suggest, that in contrast to animal fats in general, fats specific to dairy products may have a role in prevention of type 2 diabetes.”
Consumption of high-fat dairy products associated with lower risk of developing diabetes, Diabetologia (can someone find the actual study? None of the press releases links to it.)
Suez, et al, (2014) Artificial sweeteners induce glucose intolerance by altering the gut microbiota, Nature, doi:10.1038/nature13793