Global Study Challenges Advice To Limit Dairy Foods

“There is a recent increased focus on higher consumption of protective foods for disease prevention. Outside of larger amounts of fruits, vegetables, nuts, and legumes, the researchers showed that moderation is key in the consumption of natural foods,” said first author Andrew Mente, PHRI scientist and assistant professor at McMaster’s Department of Health Research Methods, Evidence, and Impact.

This study published in the European Heart Journal suggests that unprocessed lean cuts of red meat and whole grains can either be included or avoided in a healthy diet. The findings show that diets encouraging the consumption of fruits, vegetables, whole-fat dairy, nuts, legumes, and fish were linked with a lower risk of cardiovascular disease (CVD) and premature death in all world regions. 

"Low-fat foods have taken centre stage with the public, food industry and policymakers, with nutrition labels focused on reducing fat and saturated fat," said study author Dr. Andrew Mente of the Population Health Research Institute, McMaster University, Hamilton, Canada. "Our findings suggest that the priority should be increasing protective foods such as nuts (often avoided as too energy dense), fish and dairy, rather than restricting dairy (especially whole-fat) to very low amounts. Our results show that up to two servings a day of dairy, mainly whole-fat, can be included in a healthy diet. This is in keeping with modern nutrition science showing that dairy, particularly whole-fat, may protect against high blood pressure and metabolic syndrome."

The researchers examined the relationships between a new diet score and global health outcomes. The new healthy diet score was created based on 6 foods that are linked with longevity, deriving the score from the ongoing PURE Study which recommends an average daily intake of: 2-3 servings of fruit; 2-3 servings of vegetables; one serving of nuts; and two servings of whole-fat dairy. The PURE Healthy Diet Scores also includes: 3-4 weekly servings of legumes; 2-3 weekly servings of fish, with possible substitutions including whole grains at one daily serving, and lean cuts of unprocessed red meat or poultry at one serving per day. 

A score of 1(healthy) was assigned for intake above the median or a score of 0 (unhealthy) for intake at or below the median, for a total of 0-6. According to the researchers, those in the top 50% of the population on each of the 6 food components attained the maximum diet score of 6, which they feel is an achievable level. Associations of the score with mortality, stroke, myocardial infarction, and total CVD were tested in the PURE Study which involved 147,642 general population people in 21 countries, and the analysis was adjusted for various potential confounding factors. 

Findings revealed that the average diet score was 2.95, and during a median follow-up of 9.3 years, there were 15,707 deaths as well as 40,764 cardiovascular events. The healthiest diet scores of 5 or more were linked with a 30% lower risk of death, an 18% lower likelihood of cardiovascular disease, a 14% lower risk of myocardial infarction, and a 19% lower risk of stroke compared to the least healthy diets of 1 or less. These associations were replicated and confirmed in five independent studies involving 96,955 people with and without cardiovascular disease in 70 countries. 

"This was by far the most diverse study of nutrition and health outcomes in the world and the only one with sufficient representation from high-, middle- and low-income countries. The connection between the PURE diet and health outcomes was found in generally healthy people, patients with CVD, patients with diabetes, and across economies,” said Dr. Mente.

"The associations were strongest in areas with the poorest quality diet, including South Asia, China and Africa, where calorie intake was low and dominated by refined carbohydrates. This suggests that a large proportion of deaths and CVD in adults around the world may be due to undernutrition, that is, low intakes of energy and protective foods, rather than overnutrition. This challenges current beliefs," said Professor Salim Yusuf, senior author and principal investigator of PURE.

"The new results in PURE, in combination with prior reports, call for a re-evaluation of unrelenting guidelines to avoid whole-fat dairy products. Investigations such as the one by Mente and colleagues remind us of the continuing and devastating rise in diet-related chronic diseases globally, and of the power of protective foods to help address these burdens. It is time for national nutrition guidelines, private sector innovations, government tax policy and agricultural incentives, food procurement policies, labelling and other regulatory priorities, and food-based healthcare interventions to catch up to the science. Millions of lives depend on it,’ said Dr. Dariush Mozaffarian of the Friedman School of Nutrition Science and Policy, Tufts University, Boston, in an accompanying editorial. 

Paper: “Diet, cardiovascular disease, and mortality in 80 countries”