The between nutrition and cardiovascular risks on a

The study of Dehghan et al. (2017) “Associations of fats and carbohydrate intake
with cardiovascular disease and mortality in 18 countries from five continents
(PURE): a prospective cohort study” 1 is a part of a large-scale
epidemiological study Prospective Urban Rural Epidemiology (PURE), which an
ultimate aim was to examine the relationship between societal influences,
lifestyle behavior, and cardiovascular risks in human population 2. In the
recent study, Dehghan et al. (2017) examine the association between
carbohydrate and fat consumption with cardiovascular risks and related
mortality. The study included about 135 000 individuals aged 35-70 years in 18
countries on 5 continents followed for 7.4 years on average. The general
conclusion of the study is that high carbohydrate consumption, but not total
fat or different types of fat, were associated with higher cardiovascular
risks. For these reasons, the authors propose that current “dietary guidelines
should be reconsidered” 1. Although the study has a few weaknesses, being one
of the largest observational studies to the association between nutrition and cardiovascular
risks, it can significantly contribute to the future public health measures and



To better understand the relation between nutrition
and the burden of cardiovascular diseases in low- and middle-income countries,
the authors searched for relevant articles in PubMed in the last 50 years. Justifying
their study by the lack of evidence about the association between nutrition and
cardiovascular risks on a global scale, with most of the studies from European
and North American countries, the authors included 18 countries classified as
high-income, middle-income, and low-income countries and measured a number of parameters
to strengthen the study. By now, it is one of the most comprehensive studies pointing
out that high carbohydrate intake is harmful while total fats, as well as
saturated and unsaturated fatty acids, have no adverse effects on mortality
related to cardiovascular diseases.

The study included more than 130 000 participants in
different countries. Information about demographic factors, socio-economic
status, lifestyle, health history, physical activity, and food intake was collected
using 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 those
countries that did not have questionnaires available, new ones were developed using
a standard method. They also adjusted models for sex, gender, and education and
categorized countries into seven regions due to different culture-dependent
dietary patterns. Furthermore, they maximize the significance of the results
within regions by taking into consideration the differences in food intake that
might occur, such as the difference in carbohydrate intake between Asian and
non-Asian countries, with higher intake in Asian countries. Based on the
nutrition intake, they even categorized participants into region-specific

The results of this comprehensive study are clearly
presented especially considering the number of countries involved, number of
participants with wide variability in diet, lifestyles, and disease incidence,
different parameters measured, and the time period of the study. The main
results clearly state that higher carbohydrate intake is associated with an
increased risk of cardiovascular risks and mortality unlike higher total fat
and/or different types of fat, which were not associated with cardiovascular risks
and mortality. Consequently, their results do not support the recommended
guidelines of total fat and saturated fat intake proposed by the World Health Organization
(2018) 3 and suggest the revision of
current dietary guidelines. This, however, opens a lot of questions since a
single study, even with impressive numbers of participants and researchers
involved such as the reviewed one, is not enough to change global guidelines.

Despite being a large and detailed study, a few
weaknesses can be observed and some of them are even noted by the authors
themselves. Namely, the food frequency questionnaires used for the study did
not measure absolute intake and the nutrient database used for these
questionnaires was not the same for all the countries with most of them based
on the United States Department of Agriculture food composition database.
Further, food intake was measured only at baseline and possible changes in
dietary habits or lifestyles were not taken into consideration. For the latter
one, the authors did not expect to affect the results although daily lifestyle
habits are associated with cardiovascular risks 4,
5. As authors also mentioned, they were unable to quantify different types of
carbohydrate and to measure trans-fat intake. Despite the fact they
proposed ApoliproteinB-to-ApoliproteinA1 ratio as strong lipid predictor of
cardiovascular risk, the measurements of the ratio were not observed in this
article, though the results are presented in the associated article 6 from the PURE study. One of the limitations of
the study is using questionnaires in data collection since questionnaires may
not be very accurate as they depend on subjective interpretation, which could
affect the assessment of the real association between nutrients and
cardiovascular risks. Yet, they are still commonly used in studies with a great
number of participants. As Ramsden and Domenichiello (2017) point out, it seems
that there are a lot of questions open for the future research. They suggest
further research that will observe the effects of different animal products
rich in saturated and unsaturated fatty acids, micronutrient deficiency, and
different types of carbohydrates (refined sugar or whole grain) intake on
cardiovascular risks and mortality 7. Furthermore, the information
about the dominant fat types of the food, as well as the food habits in
different regions of the countries included in the study is not reported and
for the future research, it may be interesting to involve this information as



The comprehensive study
of Dehghan et al. (2017) offers
valuable insights into the relationship between nutrition and cardiovascular
risks. It is one the largest observational study that included more than 100
000 participants in 18 different countries and about 200 researchers. Together
with the associate study 6, its results
will certainly contribute to the public health and maybe even influence the current
dietary guidelines. Still, future research on this topic is necessary and the
authors themselves are aware of some of the weaknesses and limitation of their
study. Overall, this is one impressive large-scale study that opens a lot of
questions about the effects of macronutrients in chronic diseases. It should incite
further research in this area and include more countries and more relevant parameters,
especially before reconsidering the global dietary guidelines as proposed by
the authors.