Type: Research Essays
Sample donated: Tonya Osborne
Last updated: September 21, 2019
The study of Dehghan et al. (2017) “Associations of fats and carbohydrate intakewith cardiovascular disease and mortality in 18 countries from five continents(PURE): a prospective cohort study” 1 is a part of a large-scaleepidemiological study Prospective Urban Rural Epidemiology (PURE), which anultimate aim was to examine the relationship between societal influences,lifestyle behavior, and cardiovascular risks in human population 2. In therecent study, Dehghan et al.
(2017) examine the association betweencarbohydrate and fat consumption with cardiovascular risks and relatedmortality. The study included about 135 000 individuals aged 35-70 years in 18countries on 5 continents followed for 7.4 years on average. The generalconclusion of the study is that high carbohydrate consumption, but not totalfat or different types of fat, were associated with higher cardiovascularrisks. For these reasons, the authors propose that current “dietary guidelinesshould be reconsidered” 1. Although the study has a few weaknesses, being oneof the largest observational studies to the association between nutrition and cardiovascularrisks, it can significantly contribute to the future public health measures andstudies. DiscussionTo better understand the relation between nutritionand the burden of cardiovascular diseases in low- and middle-income countries,the authors searched for relevant articles in PubMed in the last 50 years. Justifyingtheir study by the lack of evidence about the association between nutrition andcardiovascular risks on a global scale, with most of the studies from Europeanand North American countries, the authors included 18 countries classified ashigh-income, middle-income, and low-income countries and measured a number of parametersto strengthen the study.
By now, it is one of the most comprehensive studies pointingout that high carbohydrate intake is harmful while total fats, as well assaturated and unsaturated fatty acids, have no adverse effects on mortalityrelated to cardiovascular diseases.The study included more than 130 000 participants indifferent countries. Information about demographic factors, socio-economicstatus, lifestyle, health history, physical activity, and food intake was collectedusing questionnaires at the individual levels, household, and community. Even though dealing with this number of participants,they succeed to overcome some methodological problems. For instance, for thosecountries that did not have questionnaires available, new ones were developed usinga standard method.
They also adjusted models for sex, gender, and education andcategorized countries into seven regions due to different culture-dependentdietary patterns. Furthermore, they maximize the significance of the resultswithin regions by taking into consideration the differences in food intake thatmight occur, such as the difference in carbohydrate intake between Asian andnon-Asian countries, with higher intake in Asian countries. Based on thenutrition intake, they even categorized participants into region-specificcategories.The results of this comprehensive study are clearlypresented especially considering the number of countries involved, number ofparticipants with wide variability in diet, lifestyles, and disease incidence,different parameters measured, and the time period of the study.
The mainresults clearly state that higher carbohydrate intake is associated with anincreased risk of cardiovascular risks and mortality unlike higher total fatand/or different types of fat, which were not associated with cardiovascular risksand mortality. Consequently, their results do not support the recommendedguidelines of total fat and saturated fat intake proposed by the World Health Organization(2018) 3 and suggest the revision ofcurrent dietary guidelines. This, however, opens a lot of questions since asingle study, even with impressive numbers of participants and researchersinvolved such as the reviewed one, is not enough to change global guidelines.Despite being a large and detailed study, a fewweaknesses can be observed and some of them are even noted by the authorsthemselves. Namely, the food frequency questionnaires used for the study didnot measure absolute intake and the nutrient database used for thesequestionnaires was not the same for all the countries with most of them basedon the United States Department of Agriculture food composition database.
Further, food intake was measured only at baseline and possible changes indietary habits or lifestyles were not taken into consideration. For the latterone, the authors did not expect to affect the results although daily lifestylehabits are associated with cardiovascular risks 4,5. As authors also mentioned, they were unable to quantify different types ofcarbohydrate and to measure trans-fat intake. Despite the fact theyproposed ApoliproteinB-to-ApoliproteinA1 ratio as strong lipid predictor ofcardiovascular risk, the measurements of the ratio were not observed in thisarticle, though the results are presented in the associated article 6 from the PURE study. One of the limitations ofthe study is using questionnaires in data collection since questionnaires maynot be very accurate as they depend on subjective interpretation, which couldaffect the assessment of the real association between nutrients andcardiovascular risks. Yet, they are still commonly used in studies with a greatnumber of participants.
As Ramsden and Domenichiello (2017) point out, it seemsthat there are a lot of questions open for the future research. They suggestfurther research that will observe the effects of different animal productsrich in saturated and unsaturated fatty acids, micronutrient deficiency, anddifferent types of carbohydrates (refined sugar or whole grain) intake oncardiovascular risks and mortality 7. Furthermore, the informationabout the dominant fat types of the food, as well as the food habits indifferent regions of the countries included in the study is not reported andfor the future research, it may be interesting to involve this information aswell. ConclusionsThe comprehensive studyof Dehghan et al. (2017) offersvaluable insights into the relationship between nutrition and cardiovascularrisks. It is one the largest observational study that included more than 100000 participants in 18 different countries and about 200 researchers.
Togetherwith the associate study 6, its resultswill certainly contribute to the public health and maybe even influence the currentdietary guidelines. Still, future research on this topic is necessary and theauthors themselves are aware of some of the weaknesses and limitation of theirstudy. Overall, this is one impressive large-scale study that opens a lot ofquestions about the effects of macronutrients in chronic diseases. It should incitefurther research in this area and include more countries and more relevant parameters,especially before reconsidering the global dietary guidelines as proposed bythe authors.