Is dairy deadly?
The long-held belief that dairy products increase the risk of heart disease still persists, even though evidence suggests otherwise
Studies have shown meat is associated with an increased risk of heart disease, whereas dairy is not.
Is dairy bad for our health? Or are milk and butter the new superfoods?
The link between milk and mortality is complicated.
A recent conference held in Seville, Spain, looked at the role of dairy in sustainable diets, and more specifically, the impact of dairy consumption on overall health. Dr Ian Givens, professor of food-chain nutrition at Reading University, was there to discuss his research on whether dairy products increase the risk of death from any cause and from either serious heart problems or cardiovascular disease.
“There’s been a lot of publicity over the last five to 10 years about how saturated fats increase the risk of cardiovascular disease and a belief has grown up that they must increase the risk, but they don’t always,” said Dr Givens.
Several major reviews of the evidence linking dairy and cardiometabolic diseases, namely cardiovascular disease and diabetes, have been published in recent years, several of which Prof Givens has been involved in writing. “Broadly speaking, these tell us that the relative risk of all-cause mortality in cardiovascular disease in relation to milk consumption overall is neutral,” he tells The Irish Times.
“There is no evidence of an increased risk, and on the other hand, one study looking at cheese and its relation to cardiovascular risk saw a significant reduction in risk. We have seen this over the past 10 years, with negative associations observed between milk consumption and stroke, as well as cheese and stroke, although the latter is not as significant.”
In Givens’ opinion, the most interesting, and possibly the most important, piece of evidence is that which shows a direct association between yoghurt consumption and diabetes. “Fermented dairy products seem to be associated with a reduced risk of diabetes. I think this is an area that we should probably bring more emphasis on, whether we try to use yoghurt more in a preventive role, or whether it can also be beneficial in a treatment role, but it is something that we should be capitalising on,” he says.
Givens also sought to shed some light on the image of saturated fat as the real enemy in the war against heart disease. He says this belief stems from studies carried out in the mid-20th century, which showed saturated fat elevated blood cholesterol. As high levels of cholesterol were known to be associated with an increased risk of cardiac disease, scientists and food researchers thus assumed that saturated fat was a direct route to heart disease. Hastily drawn up dietary guidelines urged people to cut down on sources of saturated fat – a belief that still persists to this day.
“For many people, dairy products are still the biggest source of saturated fats in their diets,” says Givens.
Yet, the evidence suggests the source of saturated fat may play a bigger role – studies have shown meat is associated with an increased risk of heart disease, whereas dairy is not. “This suggests dairy and saturated fat may not always have the effect you might predict from the old data,” he says.
Another area that has received a lot of attention is that of the so-called “dairy matrix effect”. The food scientist explains that this was a “very real effect”, whereby reductions in cholesterol are observed in people after consumption of butter or cheese.
“It seems to be an effect of calcium actually reducing the amount of fat that arrives in the gut and is absorbed, and that is probably one of the factors influencing this cholesterol response we see, although it is thought that this only explains about 50 per cent of this effect.”
The public perception of saturated fat clogging the arteries still persists. Why hasn’t this narrative changed?
Givens blames the media. “Years and years of being told that saturated fats increase cholesterol, and that increases the risk of heart disease, will not be wiped out overnight. It’s not completely untrue, but what the public haven’t been made aware of is that there are situations where it is untrue. The media hasn’t spent the time explaining the more complicated areas – for example, there is good cholesterol and bad cholesterol but that has not been made clear.”
Givens believes the focus should not be on our consumption of saturated fat, but rather what has replaced it in our diets. The PURE study, which made headlines over the world in summer 2017, looked at the association between different fats and carbohydrate intake in relation to the risk of heart disease.
“What stands out from the study is the effect of increasing the amount of energy from carbohydrate. It showed if you replace saturated fatty acids with carbohydrates, the risk increases, and this is particularly the case with more refined carbohydrates. Over the past 20 to 30 years, there has been a decline in saturated-fat consumption, but it has probably mainly been replaced by carbohydrates,” Givens explains. “In dietary guidelines, less emphasis on fat and probably a little more emphasis on restricting carbohydrate might improve health. This message is not fully appreciated.”
Indeed, the recent trend towards focusing on the sustainability of different diets is not welcomed by Givens. “So-called sustainable diets must be assessed for functionality, which goes beyond traditional nutrients composition, because you can’t predict the effect on blood pressure, or arterial stiffness, or on blood glucose, simply from nutrient composition.
“There should be some recognition that trade-offs need to be made, in terms of sustainability from a health point of view and sustainability from an environmental point of view.”