MUNICH — A diet quality score based on the PURE study, which advocates eating more of seven key foods — fruits, vegetables, nuts, legumes, fish, dairy, and nonprocessed red meat — has been linked to lower mortality and cardiovascular events in three independent data sets.
The PURE healthy diet score may be seen as controversial by some as a few elements, namely the inclusion of dairy and meat, differ from most other current dietary advice.
"You need nutrition beyond fruit and vegetables — dairy and red meats both have many nutrients not found in fruits and vegetables. We looked at the whole diet," PURE investigator Andrew Mente, PhD, Population Health Research Institute at McMaster University, Hamilton, Ontario, Canada, told theheart.org | Medscape Cardiology:
"Yes, the inclusion of dairy and unprocessed meat does conflict with current Western guidelines, but we are not suggesting people consume outrageous amounts of these items — three servings of dairy and one and a half servings of unprocessed red meat per day are what our data suggest is beneficial," Mente said.
"Most current guidelines are based on data from high-income countries where there is overnutrition, but our data is based on a global population," he added. "In large parts of the world there is undernutrition, so increasing intake of dairy and unprocessed meats to the levels we recommend is likely to be beneficial on a global level. We propose organizations adopt this score when making global recommendations on diet."
Mente presented data on the new PURE healthy diet score here at the European Society of Cardiology (ESC) Congress 2018.
Commenting on the PURE diet score for theheart.org | Medscape Cardiology, Alice Lichtenstein, PhD, professor of nutrition science at Tufts University, said, "It's a good beginning, but it's probably a bit too simple with some critical components missing."
"I would like to see some distinction between lean and fatty meat, full fat and reduced fat dairy, and refined and nonrefined carbohydrate," she said. "In addition, the characteristics of the populations on which is score is based are also quite different to those of the US, and so I'm not sure how applicable it would be to the US population."
Mente responded that while most of the PURE population came from low- and middle-income countries, 20,000 of the 138,000 people included in the study were from Canada, Sweden, and Poland, "so our results should be applicable to high-income countries as well."
High Fat, Lower Mortality?
The main results of the PURE study, which assessed the link between the diet and mortality and other health outcomes in 138,000 people worldwide, were first presented at the 2017 ESC meeting. Some of the findings caused somewhat of a furor within the cardiology community, in particular the observation that a high fat intake, including saturated fat, was associated with a reduced risk for mortality.
To derive the new PURE diet score, Mente and his colleagues identified seven foods shown in the PURE study to be associated with a lower risk for mortality. Each food was given a score (1 to 5) based on the amount eaten (5 for the top quintile vs 1 for the bottom quintile).
The total PURE diet score was calculated by simply adding up the values for all seven foods and could thus range from 7, the least healthy, to 35, the most healthy.
Table 1. PURE Healthy Diet Score: Foods
|Foods||Least Healthy: Quintile (Number of Servings per Day)||Most Healthy: Quintile 5 (Number of Servings per Day)|
|Fruits and vegetables||1.8||8.4|
|Nuts and legumes||0.7||2.5|
Table 2. PURE Healthy Diet Score: Nutrients
|Nutrients||Least Healthy: Quintile 1 (% of Energy Intake)||Most Healthy: Quintile 5 (% of Energy Intake)|
"Our advice is not so different from other guidelines on the balance of fat, carbohydrate, and protein that should make up the diet, other than we advocate a modest amount of saturated fat," Mente said. "But our score is not based on nutrients. It is based on foods. You don't go into a restaurant and order a specific amount of fat or protein. You order specific foods.
"We have identified seven functional foods, and we are saying that if you eat them in the amounts up to the highest quintiles in our study then you should have optimal health outcomes."
The researchers then validated the score by applying it to three independent study databases in which dietary information and outcome data were collected. These were the ONTARGET trial in patients with heart disease and the INTERHEART and INTERSTROKE case-control studies in healthy individuals.
"We found that in addition to being associated with lower mortality and cardiovascular events in the PURE population, our score also correlated with a protective effect for MI, stroke, and death both in vascular patients and healthy individuals in the other three studies. So there is consistency across four international studies using different designs involving 218,000 people from 50 countries," Mente said.
All results were adjusted for age, sex, education, waist-to-hip ratio, smoking, physical activity, diabetes, and use of statin or antihypertensive drugs.
Table 3. Risk for Mortality, Cardiovascular Events by PURE Diet Score in PURE, ONTARGET, INTERHEART, and INTERSTROKE Studies
|Data Set||Adjusted PURE Diet Score ≤ 11 (Reference)||Adjusted PURE Diet Score > 18||P Value for Trend|
|PURE major cardiovascular disease||1.0||0.91||.0413|
|ONTARGET major cardiovascular disease||1.0||0.86||<.0001|
|INTERHEART myocardial infarction||1.0||0.78||<.0001|
On the causes of mortality prevented, Mente said that the mortality reduction appears to be driven by noncardiovascular deaths.
"We can't really speculate on specific causes of deaths prevented — there appears to be a trend towards a reduction in cancer, but we don't have enough power or follow-up yet to be sure about that," he added. "So far we have 8 years of follow up — we need at least twice as long — and we will continue to follow our population."
Designated discussant of the trial at the ESC Hotline session, Eva Prescott, MD, University of Copenhagen, Denmark, pointed out some caveats with the PURE diet score.
"The score is mainly predictive of all-cause and noncardiovascular mortality, and there is uncertainty on whether it captures all facets of the diet — and whether it is sensitive to changes in the diet."
"We are all impressed with the PURE trial — its large size, global nature, and large variation in food patterns," Prescott said.
But she added that it has some controversial findings, including a decreasing mortality with increasing consumption of saturated fat and no association of cardiovascular disease with saturated fat; a maximum benefit on mortality of fruit/vegetables/legumes at three to four servings per day; and no clear benefit on cardiovascular disease of increasing consumption of fruits and vegetables.
She cited data opposing the idea that unprocessed red meat and dairy products should be included in a healthy diet score.
"A meta-analysis published a few years ago concluded that there was no benefit of eating unprocessed red meat," she noted. "Also studies have shown that if you substitute dairy fat with other sources of energy, then this leads to a reduction in cardiovascular disease."
Prescott also pointed out that ESC guidelines recommend low consumption of salt and no consumption of trans fats, but these were not included in the PURE diet score.
She also questioned the broad applicability and the discriminatory power of the score, noting: "The score had a range of 7 to 35, but most people in the PURE population were lumped towards the lower end, and the difference between the lowest and highest quintiles was only 7 points."
She further pointed out that the mortality data with the PURE score showed good trends, but the associations for cardiovascular events and stroke were not so strong.
"In contrast, the PREDIMED trial of the Mediterranean diet showed no significant effect on mortality but a strong reduction in cardiovascular disease."
She said this leads to the question of whether diet is really not strongly associated with cardiovascular disease or whether the PURE score does not capture the potential impact of diet on cardiovascular disease.
"It would be great if the PURE investigators used their data to validate other diet scores which have been derived from Western populations, but it is possible that it will not be appropriate to use the same diet scores throughout the world as there are such different dietary patterns in different regions," Prescott concluded.
A poll of audience at the ESC Hotline suggested that they were not totally convinced by the PURE data. Asked after the presentation whether they would feel comfortable recommending moderate consumption of saturated fat for the primary prevention of cardiovascular disease, most audience members voted against this idea, saying they would either recommend against eating saturated fat or refrain from giving specific dietary advice altogether.
The PURE study was funded by the Population Health Research Institute, Canadian Institutes of Health Research, Heart and Stroke Foundation of Ontario, unrestricted grants from several pharmaceutical companies, and grants from health agencies or ministries of over 40 countries. Mente has disclosed no relevant financial relationships.
European Society of Cardiology (ESC) Congress 2018. Presented August 28, 2018.
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Cite this: PURE Diet Score Recommends 7 Foods, Including Dairy and Meat - Medscape - Aug 29, 2018.