In a recently published study, Dr JAMA Network OpenResearchers evaluate the impact of adherence to the Planet Health Diet (PHD) on environmental and human health.
Study: Adherence to a Planetary Health diet, environmental influences, and mortality in Chinese adults. Image credit: Created with assistance from DALL·E 3
Background
PHD is characterized by increased consumption of plant-based foods and reduced consumption of animal food products. The impact of PHD on environmental and mortality outcomes in Asians is unknown.
Previous studies have proposed grading techniques to measure PhD adherence; But there was no agreement. Furthermore, these trials were performed exclusively in Western individuals without considering individual-level caloric consumption and different levels of PHD adherence.
To date, few studies have evaluated the link between PhD, environmental variability, and mortality using individual-level data.
About the study
In the current study, the researchers investigated whether PhD scores were associated with environmental exposure and mortality among Chinese Singaporeans. To this end, a grading system was developed to assess PhD compliance and study benefits related to the environment and human health.
Researchers examined data from Singapore Chinese Health Study (SCHS) participants. Individuals without a history of cardiovascular disease or cancer and permanent residents of Singapore speaking Cantonese or Hokkien dialects were enrolled from 1993 to 1998 and followed up to 2020 using record linkage data. Data was analyzed between September 2022 and April 2023
PHD scores were determined using a standardized food frequency questionnaire recording consumption of 14 dietary components for PHD and individual caloric intake. These surveys were also used to measure the environmental impacts of food. Mortality outcomes including all-cause mortality, respiratory disease, cardiovascular disease, and cancer were ascertained using national registry data.
Total water footprint (TWF), land use and greenhouse gas (GHG) emissions were estimated using the China Health and Nutrition Survey database. These data were used to determine dietary impacts on the environment based on average impacts determined by dividing the environmental impacts by each gram of food item consumed. The amount of GHG emitted was calculated from the period between food production and consumption.
TWF was calculated using the WF Network database for non-aquatic foods, whereas for aquatic food items, TWF was determined using techniques from previous studies. The Food and Agriculture Organization (FAO) database was used to estimate land use.
Professional interviewers conduct offline interviews using standardized questions to obtain data. International Classification of Diseases, Ninth and Tenth Revision (ICD-9 and 10) codes were used to classify deaths.
Linear regression modeling was performed to determine the relationship between PhD scores and environmental influences, including age, sex, body mass index (BMI), educational attainment, physical activity, smoking status, alcohol intake, sleep duration, total caloric intake, diabetes, and hypertension. . Cox proportional regression modeling was performed to determine hazard ratio (HR) values for the relationship between PhD scores and risk of death.
Sensitivity analyzes were conducted by excluding participants with diabetes or hypertension, as well as those who died within five years of enrollment, and using PhD-S calculated using different methods. The researchers eliminated 1,060 individuals who consumed more than 600 or 3,000 kcal per day for women and less than 700 or 3,700 kcal per day for men.
Study results
A total of 57,078 individuals were included in the study, with a mean age of 56 years, of whom 56% were women. During a median follow-up of 23 years, 22,599 deaths were reported.
The average PhD score was 55 points and ranged from 13 to 95 points. PhD adherence was low among participants, with more than 80% reporting good adherence to unsaturated fats, fish and fruit.
The median value of daily food intake to land use, TWF and GHG release was 3.1 m22.5 m3and 2.7 kg of carbon dioxide (CO2) are equivalent, respectively. Higher PhD scores reduced GHG emissions by 7% but increased land use by 10% and TWF by 8%.
Those in the top quintile of PhD scores had a lower risk of all-cause mortality, cardiovascular disease mortality, cancer mortality, and respiratory disease mortality than those in the lowest quintile. Individuals with higher PhD adherence were more likely to be on average 54 years old than 57 years old, female, more educated, non-smokers, non-drinkers and physically fit.
Total grains, fish and red meat contributed the most to GHG emissions at 55%, 11% and 9% respectively. Crops primarily contribute to land use at 34% and TWF at 37%. The corresponding contribution of fruits was 10% and 8.6% respectively.
Red meat, dairy, poultry and fish contribute 11%, 10%, 8.4% and 5.9% of land use respectively. Sensitivity analyzes produced comparable results, thus indicating the robustness of the preliminary results.
Conclusion
Increased PHD adherence was attributed to reduced risk of death from chronic disease. However, the environmental impacts were unknown, as improved adherence to PhDs was associated with lower GHG emissions but greater land use and water footprints.