LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 4B: DIET 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
4. Discussion
The number of studies included in our environmental analysis was limited. Besides, two of the three studies
were from the same author. We found, however, that meals are not a good basis for comparison of the
environmental impact of human diets, as meals are not representative for daily consumption. Because meals
contain a limited number of food products, the amount of quantified nutrients in meals is also more sensitive
to product choice compared to the quantified amount of nutrients in daily or yearly diets.
The protein quality of a food product can be evaluated using the Protein digestibility-corrected amino acid
score (PDCAAS) (Hughes et al., 2011). Because questions were raised concerning the usability of the
PDCAAS method for assessing protein quality at a diet level (FAO/WHO, 1991; Schaafsma, 2000), we did
not account for differences in protein quality between plant and animal based products.
5. Conclusion
Current comparisons of the global warming potential (GWP) of human diets show that diets that have
higher levels of animal-source food products have higher GWP compared to diets that have lower levels of
animal-source food products. However, these comparisons do not account for differences in the nutritional
quality of these diets. The environmental impact of these diets is expressed relative to the functional unit
(FU) ‘day’. In this review, we computed the nutritional quality of diets and evaluated the effect of accounting
for nutritional quality when comparing the environmental impacts of diets that vary in their amount of animal-source
food products.
We concluded that diets with higher levels of animal-source food products have higher (excess) contents
of protein and generally lower composite nutritional quality compared to diets that are lower in animalsource
food products.
We evaluated the effect of using the FUs ‘protein intake’ and ‘composite nutritional quality’. When we
expressed GWP with respect to grams of protein, we found that GWP was lower for diets that had higher
levels of animal-source food products. This lower GWP per gram of protein in diets with higher levels of
animal-source food products was due to the higher (excess) intake levels of total protein in these diets. To
avoid credit for overconsumption, we capped the protein intake levels at 100% of the Daily Recommended
Value and found that GWP per unit ‘protein capped’ was in fact higher for diets that had higher levels of
animal-source food products. When we expressed GWP in terms of the composite nutritional quality, i.e.
using ‘NRD9.3’ as FU, we found that GWP per unit NRD9.3 was higher for diets that had higher levels of
animal-source food products.
Overall, the regression coefficient for the FU ‘day’ was significantly higher compared to the regression
coefficient for the FU ‘protein uncapped’, and was significantly lower compared to the regression coefficient
for the FU ‘NRD9.3’. Not crediting for overconsumption of protein and accounting for overall nutritional
quality thus gives a stronger contrast in the GWP between diets that vary in their amount of animal-source
food products.
6. References
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