Palm oil taxes and cardiovascular disease mortality in India: economic-epidemiologic model

Abstract

Objective: To examine the potential effect of a tax on palm oil on hyperlipidemia and on mortality due to cardiovascular disease in India.

Design: Economic-epidemiologic model.

Modeling methods: A microsimulation model of mortality due to myocardial infarction and stroke among Indian populations was constructed, incorporating nationally representative data on systolic blood pressure, total cholesterol, tobacco smoking, diabetes, and cardiovascular event history, and stratified by age, sex, and urban/rural residence. Household expenditure data were used to estimate the change in consumption of palm oil following changes in oil price and the potential substitution of alternative oils that might occur after imposition of a tax. A 20% excise tax on palm oil purchases was simulated over the period 2014-23.

Main outcome measures: The model was used to project future mortality due to myocardial infarction and stroke, as well as the potential effect of a tax on food insecurity, accounting for the effect of increased food prices.

Results: A 20% tax on palm oil purchases would be expected to avert approximately 363,000 (95% confidence interval 247,000 to 479,000) deaths from myocardial infarctions and strokes over the period 2014-23 in India (1.3% reduction in cardiovascular deaths) if people do not substitute other oils for reduced palm oil consumption. Given estimates of substitution of palm oil with other oils following a 20% price increase for palm oil, the beneficial effects of increased polyunsaturated fat consumption would be expected to enhance the projected reduction in deaths to as much as 421,000 (256,000 to 586,000). The tax would be expected to benefit men more than women and urban populations more than rural populations, given differential consumption and cardiovascular risk. In a scenario incorporating the effect of taxation on overall food expenditures, the tax may increase food insecurity by <1%, resulting in 16,000 (95% confidence interval 12,000 to 22,000) deaths.

Conclusions: Curtailing palm oil intake through taxation may modestly reduce hyperlipidemia and cardiovascular mortality, but with potential distributional consequences differentially benefiting male and urban populations, as well as affecting food security.

Fig 1 Change in domestic food consumption of major vegetable oils in India, 2003-12. All other oils are of lower per capita consumption than those shown

Fig 2 Activity diagram for microsimulation model. 10 000 people are simulated from each of 24 cohorts defined by 10 year age groups (20-29, 30-39, …, 70-79 years), sex, and rural versus urban location. Each simulated person is assigned a cardiovascular disease “risk factor profile” based on cohort specific data on six risk factors: systolic blood pressure, total cholesterol, tobacco smoking, diabetes, coronary heart disease, and cerebrovascular disease. Cardiovascular disease mortality from myocardial infarctions and strokes (using a Framingham-like risk equation), as well as all cause mortality, are calculated. Palm oil taxation is simulated by calculating how changes in palm oil consumption (and potential substitution with other oils) affect total cholesterol

Fig 3 Daily saturated and polyunsaturated fat intake from vegetable oils among 20-79 year old adults in India, before and after 20% palm oil tax. “No substitution” refers to scenario in which 20% palm oil tax results only in reduction in palm oil consumption but no substitution with other oils. “Pessimistic substitution” refers to pessimistic scenario in which some palm oil consumption is substituted with major oils (rapeseed, mustard seed, and groundnut) in proportion to their cross elasticities, and proportion of oil substituted from “other oils” category in Indian National Sample Survey (in addition to major oils) goes toward cottonseed oil (least healthy “other oil” in terms of saturated fat per gram). “Optimistic substitution” refers to optimistic case in which “other oil” substitution goes toward soybean oil (most healthy product in “other oil” category). On each box, central mark is median, edges of box are 25th and 75th centiles, and whiskers extend to 1.5 times interquartile range (capturing 99.3% of distribution)

Fig 4 Estimated future mortality averted from myocardial infarctions and strokes among 20-79 year old adults in India (top). See fig 3 for explanation of substitution scenarios. Wide confidence intervals are due more to uncertainty in baseline risk estimates than to uncertainty between simulated tax scenarios; to illustrate this, between group differences in change in mortality from myocardial infarctions and strokes relative to urban men group within each of 10 000 simulations are shown (difference in differences chart) (bottom)