Dairy consumption could lower risk of heart disease - study

Moderate consumption of dairy produce – particularly whole-fat dairy – could reduce risk of heart disease, according to new research.

Dairy consumption of around three servings a day is associated with lower rates of cardiovascular disease and mortality, compared to lower levels of consumption, an observational study of over 130,000 people has found.

The international Prospective Urban Rural Epidemiological (PURE) study – which included people from 21 different countries, aged between 35 and 70 – was published in The Lancet yesterday (Tuesday, September 11).

It was also found that people who consumed three servings of whole-fat dairy per day had lower rates of mortality and cardiovascular disease compared to those who consumed less than a half-serving of whole-fat dairy per day.

The findings are consistent with previous meta-analyses of observational studies and randomised trials, according to the researchers.

However, they conflict with current dietary guidelines which recommend consuming two to four servings of fat-free or low-fat dairy per day and minimising consumption of whole-fat dairy products for cardiovascular disease prevention, authors note.

Findings

One standard serving of dairy was equivalent to a glass of milk at 244g, a cup of yoghurt at 244g, one slice of cheese at 15g, or a teaspoon of butter at 5g.

In their conclusions, researchers said that the consumption of dairy should not be discouraged and should even perhaps be encouraged in low-income and middle-income countries where dairy consumption is low.

Lead author of the study Dr. Mahshid Dehghan, McMaster University, Canada, commented to scientific publication EurekAlert! saying: “Our findings support that consumption of dairy products might be beneficial for mortality and cardiovascular disease, especially in low-income and middle-income countries where dairy consumption is much lower than in North America or Europe.”

Dietary intakes were recorded at the start of the study using country-specific validated food questionnaires. Participants were followed up for an average of 9.1 years. During this time, there were 6,796 deaths and 5,855 major cardiovascular events.

Servings

One standard serving of dairy was equivalent to a glass of milk at 244g, a cup of yoghurt at 244g, one slice of cheese at 15g, or a teaspoon of butter at 5g.

Dairy consumption was highest in North America and Europe (368g/day or above four servings of total dairy per day) and lowest in south Asia, China, Africa and southeast Asia (147, 102, 91 and 37g/day respectively – less than one serving of total dairy per day).

Participants were grouped into four categories: no dairy (28,674 people), less than one serving per day (55,651), one to two servings per day (24,423), and over two servings per day (27,636).

Compared to the no intake group, the high intake group (mean intake of 3.2 servings per day) had lower rates of total mortality (3.4% vs 5.6%), non-cardiovascular mortality (2.5% vs 4%), cardiovascular mortality (0.9% vs 1.6%), major cardiovascular disease (3.5% vs 4.9%), and stroke (1.2% vs 2.9%).

There was no difference in the rates of myocardial infarction between the two groups (1.9% vs 1.6%).

Among those who consumed only whole-fat dairy, higher intake (mean intake of 2.9 servings of whole fat dairy per day) was associated with lower rates of total mortality (3.3% vs 4.4%) and major cardiovascular disease (3.7% vs 5.0%), compared to those who consumed less than 0.5 servings whole-fat dairy per day.

Intake

Higher intake of milk and yoghurt (above one serving per day) was associated with lower rates of the composite outcome, which combines total mortality and cardiovascular disease (milk: 6.2% vs 8.7%; yoghurt: 6.5% vs 8.4%), compared to no consumption.

The differences in the composite outcome for butter and cheese were not significant as intake was lower than for milk and yoghurt.

It was also noted that more research into why dairy might be associated with lower levels of cardiovascular diseases is now needed.

The common recommendation to consume low-fat dairy is based on the presumed harms of saturated fats on a single cardiovascular risk marker (LDL cholesterol).

However, it was noted that evidence suggests that some saturated fats may be beneficial to cardiovascular health, and dairy products may also contain other potentially beneficial compounds, including specific amino acids, unsaturated fats, vitamin K1 and K2, calcium, magnesium, potassium, and potentially probiotics.

The effect of dairy on cardiovascular health should therefore consider the net effect on health outcomes of all these elements.

However, commentators from University of Hong Kong and University of Sydney conclude that dairy dietary guidelines do not need to change just yet, urging caution on such findings at present.