Eating Dairy Every Day Linked to Lower Risk of Developing Diabetes and High Blood Pressure

Eating dairy every day has been linked to a lower risk of developing high blood pressure, diabetes and lower rates of metabolic syndrome—a condition associated with heart disease—according to a study. However, the authors stress their findings should not be seen as a green light to eat unlimited amounts of products like butter.

Metabolic syndrome is characterized by a person having five health problems at once: high blood pressure, abdominal obesity, high levels of triglycerides, low levels of so-called "good cholesterol," and high blood sugar levels. It is linked with a higher risk of developing heart disease, and type 2 diabetes.

Most studies on the health effects of consuming dairy have focused on North American and European participants, where diets are "substantially" different to those in other parts of the world, said the authors of a paper published in the journal BMJ Open Diabetes Research & Care.

For their paper, they looked at data collected on 112,922 people as part of the Prospective Urban Rural Epidemiology (PURE) epidemiological study. Participants were aged between 35 and 70-years-old from 21 countries on five continents. These were Argentina; Bangladesh; Brazil; Canada; Chile; China; Colombia; India; Iran; Malaysia; Palestine; Pakistan; Philippines, Poland; South Africa; Saudi Arabia; Sweden; Tanzania; Turkey; United Arab Emirates; and Zimbabwe.

At the start of the study, the participants filled out a questionnaire on how often they ate certain foods in the past year, including milk, yoghurt and yoghurt drinks, cheese, and meals containing dairy products. They were also asked whether they ate full or low fat foods.

Participants provided demographic, health and lifestyle information like their blood pressure levels, as well as a blood sample.

The team used "standard serving sizes" when considering the products, with a glass of milk or cup of yogurt at 244g, a slice of cheese at 15g, and a teaspoon of butter at 5g. On average, participants consumed 179 g of dairy, at 124.5g in full fat versus 65g low fat products.

The researchers followed up with the participants after about nine years, and found that a higher intake of whole fat, but not low fat, dairy was linked with a lower incidence of high blood pressure and diabetes. In epidemiology, incidence refers to new cases of a disease or condition in a population. They also found whole fat dairy was linked to a lower prevalence of metabolic syndrome, or how many people had the condition.

Eating at least two servings of dairy per day was on average linked to lower blood pressure, waist circumference, body mass index, triglycerides, the ratio of triglycerides to good cholesterol, and blood sugar, compared with those who did not.

Triglycerides are the form that most fats take in food and our bodies. When calories consumed are not immediately used by fats, they are turned into triglycerides, sent to fat cells and stored as energy.

Total dairy intake and whole fat, but not low fat, dairy was also linked with a lower prevalence of metabolic syndrome, including high blood pressure, as well as elevated waist circumferences, blood glucose and triglycerides.

People in Europe, North America, the Middle East, and South America consumed the most dairy on average, while people in South Asia, China, Africa and Southeast Asia consumed the least. Low fat products were more likely to be consumed in North America and Europe. BMI was the highest in the Middle East and South America.

While the link between dairy intake and metabolic syndrome were consistent across areas with high and low dairy intake, the magnitude was strong in areas where people ate less dairy overall.

Next, large randomized trials of the effects of different types of dairy products on long term blood pressure and diabetes should be carried out to shed further light on the links highlighted in the study, the team said.

The authors acknowledged the patterns they noticed may be down to participants' overall diet, although they adjusted for this in their analysis. They concluded: "If our findings are confirmed in sufficiently large and long term trials, then increasing dairy consumption may represent a feasible and low cost approach to reducing [metabolic syndome], hypertension, diabetes, and ultimately cardiovascular disease events worldwide."

Co-author Andrew Mente, associate professor of nutrition and epidemiology at Canada's McMaster University told Newsweek. "Dairy products are a major source of saturated fats, which have been presumed to adversely affect blood lipids and increase cardiovascular disease and mortality. Using this framework, dietary guidelines recommend minimizing consumption of whole-fat dairy products for cardiovascular disease prevention in populations.

"However, dairy foods also provide high-quality protein and a wide range of essential vitamins and minerals including calcium, magnesium, potassium, zinc, phosphorus, and vitamins A, B12, and riboflavin. Additionally, recent studies have shown that whole-fat dairy is not associated with higher risk of heart disease and might even be protective against stroke. Therefore, the potential impact of dairy on health cannot be projected from its saturated fat content and its minimal impact on blood cholesterol."

Robert H. Eckel, a past-president of the American Heart Association and Clinical Professor Emeritus at the University of Colorado School of Medicine who did not work on the study told Newsweek the findings are limited because the researchers relied on the participants accurately reporting what they ate.

Also the study was was observational, where scientists did not change the conditions of the participants but look for certain outcomes, so the data needs to be validated in other similar epidemiological trials, and in randomized clinical trials in a smaller number of participants, he said.

The study was also unable to show that dairy was the cause of the outcomes, only that there was a link.

"The American Heart Association continues to recommend a heart healthy dietary pattern, e.g. DASH, Mediterranean-style with lots of fruits and vegetables, whole grains, lean poultry and fish, legumes, nuts," he said .

Victoria Taylor, senior dietician at the U.K.-based charity the British Heart Foundation who did not work on the study told Newsweek: "The effect of milk and dairy products on heart and circulatory diseases and their risk factors is an interesting, and growing, area of research. However, this type of study only shows an association. More research is needed to give us a clearer picture of whether it is the dairy itself that is behind the effects seen, or other factors amongst the people studied. We also need more information about the effects of different types of dairy products and what it is about them that is potentially beneficial."

Taylor said the research alone cannot be used as the basis for dietary guidelines. She pointed out the same limitations as Eckel, and said it is "necessary to take the data about butter with caution—the data was not collected across everyone involved in the study, and the overall butter intake was low."

"We now need to better understand how dairy could positively affect other risk factors for heart and circulatory diseases such as high blood pressure and type 2 diabetes, as well as the effects of different types of dairy and the optimal amounts that we should be consuming of each."

She also warned eating more saturated fat than is recommended can lead to raised cholesterol levels, which can put a person at greater risk of heart and circulatory diseases. "Choosing low and reduced fat dairy is one easy way to cut down on saturated fat intake to help lower cholesterol levels. Milk and plain yogurt may be better sources of dairy as cheese will have added salt, and flavoured yogurts can also come with a lot of added sugar."

Matt Petersen, vice president of medical information and professional engagement for the American Diabetes Association who did not work on the paper, told Newsweek: "The study suggests that full-fat dairy is probably a safe component of an overall healthy diet. There is substantial evidence that a wide range of diets can support long-term health—e.g., from vegan to Mediterranean to low carb, and this study doesn't provide the kind of data that would suggest that full fat dairy should necessarily be added to an existing healthy diet."

This article has been updated with comment from Andrew Mente and Matt Petersen.

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