Articles
dietary factors (ie, nuts, whole grains, seafood, red meat,                 data on fruit and vegetable intake, data on intake of
and processed meat). Third, cost-eﬀectiveness analyses                      specific nutrients such as sodium are scarce. The
of dietary interventions are generally based on a range of                  FAO/WHO Global Individual Food consumption data
simplifying assumptions and do not take into account                        Tool44 aims to address this problem, but several important
the reactions of consumers (eg, substitution eﬀect), the                    gaps will remain. In the absence of reliable biomarkers
food industry (eg, food reformulations and pricing                          or more accurate methods of dietary assessment, the 24 h
strategies), and other stakeholders in the real world.32–35                 diet recall or diet record remains the gold standard
Fourth, despite the growing public and political will for                   method of dietary assessment. However, evidence from
the implementation of some of these policies (eg, trans                     validation studies suggests that it is not highly reliable
fat bans), few countries have successfully adopted and                      for assessment of foods and nutrients due to recall bias
implemented them.36,37 Fifth, many of these policies only                   or potential social desirability.45,46 This evidence highlights
target consumers but not the wide range of interconnected                   the need for development and validation of innovative
factors, such as food production, processing, and                           dietary assessment methods. In the past decade, new
distribution, that exist throughout the food system.                        methods have been developed; however, they have not
Indeed, these factors might aﬀect dietary consumption,                      been widely used and their validity has not been
and it is important to include them to improve diet.38,39                   systematically evaluated.47 Furthermore, accurate estima-
Therefore, in view of the magnitude of the disease                          tion of nutrients (eg, fibre, calcium, and polyunsaturated
burden attributable to diet and the limitations of the                      fatty acids), remains a major challenge. Many countries
existing interventions, development of novel food system                    do not have local food composition tables and rely on
interventions is urgently needed.                                           data from food composition tables from other countries
  Our results show a need for extensive changes in                          (eg, US Department of Agriculture food composition
various sectors of the food system at the global, regional,                 tables). Additionally, the recipes of mixed dishes as well
and national levels to improve diet. Changes in                             as formulation of the food products, particularly their
agricultural practices, if not done properly, might raise                   content of fat, sugar, and sodium, varies across countries
concerns over potential environmental eﬀects on climate                     and over time, which makes estimation of the true intake
change, biodiversity loss, degradation of land and soil,                    of nutrient more challenging.
and freshwater depletion.40–43 A growing body of evidence                     Our systematic evaluation of epidemiological evidence
has emerged in the past decade showing that shifting                        shows several important limitations in existing dietary
diet from unhealthy animal-based foods (eg, red meat                        relative risks. The eﬀect sizes of the dietary risk factors
and processed meat) to healthy plant-based foods                            on disease endpoints were mostly obtained from meta-
(eg, fruits, vegetables, and whole grains) might be                         analyses of prospective observational studies. Although
associated with lower emission of greenhouse gases and                      many of these dietary relative risks have been adjusted
thus might be more environmentally sustainable.40–43                        for the major confounders (eg, age, sex, smoking, and
The few studies evaluating other environmental eﬀects                       physical activity), the possibility of residual confounding
of the shift from animal-based to plant-based diet have                     cannot be excluded. To remove the eﬀect of energy
also demonstrated that this shift might be associated                       intake as a potential confounder and address measure-
with lower land use and water footprint.41 However,                         ment error in dietary assessment tools, most cohorts
because of the variations in the methods and research                       have adjusted for total energy intake in their statistical
questions across these studies and scarcity of reliable                     models. This energy adjustment means that diet
estimates on dietary consumption patterns across                            components are defined as risks in terms of the share of
nations, a comprehensive assessment of environmental                        diet and not as absolute levels of exposure. In other
eﬀects of achieving optimal diet globally has not been                      words, an increase in intake of foods and macronutrients
possible to date. GBD estimates the dietary consumption                     should be compensated by a decrease in intake of other
of key foods and nutrients across 195 nations annually.                     dietary factors to hold total energy intake constant.
These data provide a unique opportunity to quantify the                     Thus, the relative risk of change in each component of
environmental burden of current dietary consumption                         diet depends on the other components for which it is
patterns at global, regional, and national levels in a                      substituted. However, the relative risks estimated from
consistent and comparable way. Additionally, these data                     meta-analyses of cohort studies do not generally specify
could potentially be used to evaluate the eﬀect of various                  the type of substitution. The definition of dietary factors
food system interventions on human health and                               (eg, whole grains) also varies across studies. Additionally,
environment.42                                                              given the intake of healthy dietary factors are generally
  Our study also demonstrates the gaps in nationally                        positively correlated with each other and inversely
representative individual-level data on intake of key                       correlated with harmful dietary factors, the eﬀect size of
foods and nutrients in diﬀerent regions of the world,                       the individual dietary factors might be overestimated.
highlighting the importance of establishing national                        Many of the observational studies used for estimation of
surveillance and monitoring systems for key dietary risk                    the relative risks have not corrected risk estimates for
factors.17,18 For example, although many countries collect                  dietary measurement error, and some have adjusted for
www.thelancet.com Published online April 3, 2019 http://dx.doi.org/10.1016/S0140-6736(19)30041-8                                                     11