#### Pages within the "support" section:

- Support home
- Glossary
- Model parameters
- Summary
- 1. Introduction
- 1.1 General framework
- 1.2 Relationship to the BRAFO tiered approach
- 2. Problem formulation
- 2.1 Dietary scenarios
- 2.2 Population
- 3. Common metrics for integration of risks & benefits
- 3.1 DALY versus QALY.
- 3.2 Alternative approaches for calculating DALY/QALYs
- 4. Main elements of the Qalibra framework
- 5. When is use of the Qalibra framework appropriate?
- 6. Calculation of DALYs for quantal health effects
- 7. Calculation of DALYs for continuous health effects
- 8. Calculation of QALYs for quantal and continuous health effects
- 9. Recurrent effects
- 10. Effects on the next generation
- 11. Multiple effects on the same health endpoint
- 12. Calculating the net health impact of a dietary change [current page]
- 13. Direct health loss calculations for a single individual
- 14. Data needed as inputs to the Qalibra framework
- 14.1 Individuals and their attributes
- 14.2 Life expectancy
- 14.3 Health effects to be quantified
- 14.4 Dietary intakes
- 14.5 Probability of quantal effects
- 14.6 Probability and magnitude of continuous effects
- 14.7 Probabilities of recovery and death
- 14.8 Duration of disease
- 14.9 Severity of effect (disease weights)
- 15. Addressing uncertainty in risk-benefit assessment
- 15.1 Qualitative evaluation of uncertainties
- 15.2 Quantitative evaluation of uncertainties
- 15.3 Probabilistic treatment of uncertainty in Qalibra
- 16. Treatment of variability in the Qalibra framework
- 17. Treatment of dependencies in Qalibra framework
- 18. Presentation of results
- 19. Interpretation of results
- 20. Risk management considerations
- 21. Final remarks
- Acknowledgements
- References

# 12. Calculating the net health impact of a dietary change

In a risk-benefit assessment the focus is on evaluating the net health impact of a dietary change or intervention, represented as a change from a reference scenario to an alternative scenario.

The net health impact in DALYs may be calculated as:

_{
}

where

_{
}
= sum of DALY losses for reference scenario

_{
}
= sum of DALY losses for alternative scenario

The summation in these equations is over both health effects (within individuals) and individuals (to provide population totals).

As DALYs represent health loss, a positive result for
_{
}
implies that changing to the alternative scenario has an adverse health impact overall, whereas a negative
_{
}
implies the alternative scenario is beneficial.

Analogous calculations can be done with the QALY losses from Equations (3) and (4), leading to an estimate for
_{
}
. Then as a final step, the net health impact can be expressed as a change in QALYs (rather than QALY losses):

_{
}

As QALYs represent health loss, a positive result for
_{
}
implies that changing to the alternative scenario has an beneficial health impact overall, whereas a negative
_{
}
implies the alternative scenario is adverse.

The results for both DALYs and QALYs are subject to the same limitations as before, that the effects have been considered in isolation. How these uncertainties can be taken into account in interpreting the results is discussed in section 15.1.