Going vegan saves roughly 600 gallons of water a day
the verdict
INSUFFICIENT LEANING
refutedsupported
the weight of evidence
3 sources for · 0 against
Peer-reviewed studies indicate that plant-based and reduced-meat diets require significantly less water usage than animal-heavy diets, but the retrieved evidence only partially covers the topic and does not establish the specific figure of 600 gallons of water saved per day.
Demand side interventions, such as dietary change, can significantly contribute towards the achievement of 2030 national sustainable development goals. However, most previous studies analysing the consequences of dietary change focus on a single dimension of sustainability (e.g., environment) using a limited number of indicators and dietary scenarios. A multi-dimension and multi-indicator analysis can identify the potential trade-offs. Here, starting from the current food consumption data (year 2011), we first designed nine alternative dietary scenarios (healthy Swiss diet, healthy global diet, vegetarian, vegan, pescatarian, flexitarian, protein-oriented and meat-oriented diets and a food greenhouse gas tax diet). Next we calculated three nutritional quality (nutrient balance score, disqualifying nutrient score, percent population with adequate nutrition), five environmental (greenhouse gas, water, land, nitrogen and phosphorus use), one economic (daily food expenditure) and one human health indicator (DALYs) for current and alternative diets. We found that transition towards a healthy diet following the guidelines of Swiss society of nutrition is the most sustainable option and is projected to result in 36% lesser environmental footprint, 33% lesser expenditure and 2.67% lower adverse health outcome (DALYs) compared with the current diet. On the other extreme, transition towards a meat or protein oriented diet can lead to large increases in diet related adverse health outcomes, environmental footprint, daily food expenditure and a reduction in intakes of essential nutrients (for Vitamin C, Fibre, Potassium and Calcium). We found that shifting to the vegetarian and vegan diet scenarios might lead to a reduction in intakes of certain micronutrients currently supplied primarily by animal-sourced foods (Vitamin B12, Choline and Calcium). Results show that achieving a sustainable diet would entail a high reduction in the intake of meat and vegetable oils and a moderate
A multi-dimension and multi-indicator analysis can identify the potential trade-offs. Here, starting from the current food consumption data (year 2011), we first designed nine alternative dietary scenarios (healthy Swiss diet, healthy global diet, vegetarian, vegan, pescatarian, flexitarian, protein-oriented and meat-oriented diets and a food greenhouse gas tax diet).
Introduction The food system is highly related to the Sustainable Development Goals (SDGs) involving hunger, nutrition and health, climate change, natural resources, biodiversity and socioeconomics [ 1 , 2 ]. Agriculture is the largest consumer of fresh water and the second largest contributor to greenhouse gas emissions worldwide
Previous studies have found that demand side interventions such as dietary shift (e.g., towards vegan, vegetarian, Mediterranean diets) can have positive consequences for both human health and climate change [ 8 , 9 , 10 , 11 , 12 , 13 ]. However, others have found that shifting from current to vegetarian, vegan or even flexitarian diets carries the risk for deficiency of certain micronutrients that are currently supplied primarily through animal-based products [ 14 , 15 ]. In general, shifting to plant-based diets not only results in greenhouse gas emissions reduction but also other environmental benefits such as water savings [ 16 , 17 , 18 , 19 ].
The Swiss Association of Vegetarians estimates that approximately 3% of the population are vegetarian based on surveys between 1997 and 2013. Rough estimates report that one-tenth of these vegetarians follow a vegan diet and the rest are lacto-ovo vegetarian eating pattern [ 39 ]. More than half (~54%) of the population claim that they eat meat 6 to 7 days a week [ 40 ]. Table 1 shows the average intake of different food groups per capita per day in Switzerland under current and alternative dietary scenarios. 2.2.
For dietary risk factors, under a particular dietary scenario (e.g., current diet, vegan diet, etc.), we assumed that the whole population of a region is subjected to the dietary risk associated with the regional consumption level C f measured in gram per capita per day and that risks began increasing at zero consumption were unbounded [ 44 ]. We adopted standard serving sizes ( c s e r v ) of 100 g for all food groups.
(8) P o v e r w e i g h t = 0.02462 · kcal − 29.67965 (9) P o b e s i t y = 0.01000 · kcal − 14.98936 In Equations (8) and (9), k c a l is the total daily energy intake measured by kilocalorie per capita per day. The weight-related population impact fractions (PIFs) accounted for the weight status of different population fractions and the associated risks.
For example, the current greenhouse gas, water, land, nitrogen and phosphorus footprint of Swiss diet (in per capita per day) are: 2268 gCO 2 eq, 590 L, 4.38 m 2 , 29.03 gN and 5.23 gP, respectively ( Table 4 ). Results show that adoption of RSN diet will reduce these footprints by 54%, 26%, 32%, 33% and 34%, respectively ( Figure 3 ; Table 4 ). The changes in individual environmental footprint varied with the type of scenario.
It can be seen that shifting from current to the meat oriented (MTO) and protein oriented (PTO) diets will increase the cost by 10–20% while adopting a diet based on global (HGD) or Swiss nutrition guidelines (RSN) will decrease the cost by ~35%. See Supplementary Table S6 for cost due to intake of individual food group. nutrients-11-00856-t001_Table 1 Table 1 Food consumption (g capita −1 day −1 ) under different Swiss dietary scenarios.
Five food related environmental footprints (per capita per day) are: greenhouse gas (GHG in kg CO 2 eq), water (WFP in m 3 ), land (LFP in m 2 ), nitrogen (NFP in gN) and phosphorus (PFP in gP). Cost is the daily expenditure on food in Swiss Francs (CHF). nutrients-11-00856-t003_Table 3 Table 3 The ratio of daily nutrient intake amounts and their daily recommended levels under the current Swiss diet (REF) and nine alternative dietary scenarios.
This review utilizes current national dietary guidelines and published databases to evaluate the impacts of reasonable shifts in the amount and type of protein intake in the United States on the intersection of human and environmental health. The established scientific basis and recommendations for protein intake as described in the US Dietary Reference Intakes are reviewed. Data on food availability from both the US Department of Agriculture and the Food and Agriculture Organization of the United Nations and data on consumption from the National Health and Nutrition Examination Survey are used to examine estimates of current US protein consumption. Greenhouse gas (carbon dioxide equivalents, CO2eq) and blue and green water impacts of US protein consumption resulting from US agricultural practices were obtained from previously published meta-analyses. A 25% decrease in protein intake paired with a 25% shift from animal food to plant food protein intake-from an 85:15 ratio to a 60:40 ratio-would best align protein intake with national dietary recommendations while simultaneously resulting in 40% fewer CO2eq emissions and 10% less consumptive water use. The modeling of this strategy suggests a savings of 129 billion kilograms of CO2eq and 3.1 trillion gallons of water relative to current consumption.
A 25% decrease in protein intake paired with a 25% shift from animal food to plant food protein intake—from an 85:15 ratio to a 60:40 ratio—would best align protein intake with national dietary recommendations while simultaneously resulting in 40% fewer CO 2 eq emissions and 10% less consumptive water use. The modeling of this strategy suggests a savings of 129 billion kilograms of CO 2 eq and 3.1 trillion gallons of water relative to current consumption.
There are 3 conditions that would need to be met simultaneously in order to create a need to complement plant-based proteins: total protein intake for the day was low (ie, close to an individual’s protein requirement); very little dietary variety was available or chosen; and no animal proteins were consumed, as in a vegan diet. As will be presented here, most Americans consume a total protein intake that greatly exceeds their requirement. In addition, most Americans have access to and choose a diet comprised of a wide variety of foods. This can also be true for those following a vegan diet.
Another approach to addressing this is to consider using 15% to 16% of energy intake from protein, which has been consistently reported from NHANES analyses, 31 , 39 and apply that to an average caloric intake of approximately 2700 kcal as determined by doubly labeled water studies as noted above, which equals approximately 100 to 110 g of protein per day. A third approach is to consider studies that have used 24-hour urinary nitrogen excretion under weight-stable conditions as a biomarker of protein intake.
Carbon and water footprints of current US protein intake We have used the data presented up to this point to provide an estimate of the total annual greenhouse gas footprint (expressed in CO 2 eq) and water footprint of the foods that contribute to dietary protein consumption in the US. The starting values used were the USDA availability data in Table 3 . Those values were increased by approximately 10% to match the conclusion in summary section on per capita protein intake estimations that Americans consume approximately 90 grams of protein/day (the low end of the 90–100 g/d range).
Those daily values of grams of protein of each food type consumed per day were multiplied by 365 days/year, then multiplied by the greenhouse gas and water footprint per gram of protein of each food type ( Table 5 ) 52 , 62 , 63 and finally were multiplied by 308,827,000 people in the US from the most recent census data. The current consumption of animal food and plant food protein in the U.S. is associated with more than 360 billion kilograms (360 million metric tons) of CO 2 eq greenhouse gas emissions and more than 65 trillion gallons of water per year, or ≈1.2 metric tons CO 2 eq, and greater than 210,000 gallons water per capita/year.
Table 5 Total annual carbon and water footprints of the animal and plant foods that contribute to dietary protein consumption in the United States 52 , 62 , 63 Protein source Greenhouse gases footprint (billion kg of CO 2 eq) Water footprint, blue and green water (billion gallons of water) Beef
Consumption of protein from cattle products accounts for by far the largest amount of carbon emissions and water usage, roughly 70% of the total annual greenhouse gas footprint and 58% of the water footprint of U.S. protein consumption. In contrast, all plant proteins currently contribute to just 4% of the total annual carbon footprint and 23% of the water footprint.
The intent of presenting each plate of food is to illustrate a plausible and familiar set of food types and quantities that would provide all approximately 90 g or all approximately 67.5 g for the entire day (ie, the set of foods is not intended to represent a single meal, nor is it intended to represent a full day of meals and snacks). Therefore, the photos help to demonstrate one possible approach for obtaining either approximately 90 g or approximately 67.5 g of protein from just 6 common animal and plant foods while contributing only 600 to 1100 kcal for the day.
Impacts of reduced protein intake The environmental benefits of reducing protein intake and/or shifting the mix of protein consumed to include a larger share of plant-based protein are significant, particularly in terms of carbon emissions. Under shift scenario 3, US consumption of protein sources would result in 40% fewer CO 2 eq emissions and 10% less blue and green water, representing a savings of 129 billion kilograms of CO 2 eq and 3.1 trillion gallons of water relative to current consumption. Under any scenario of reduced consumption of animal protein, CO 2 eq emissions would be reduced by more than 20%.
<h4>Objective</h4>To compare the use of water, energy, pesticides and fertilizer to produce commodities for two dietary patterns that vary in the content of plant and animal products.<h4>Design</h4>A unique analysis using 'real-world' data was performed, in contrast to previous analyses which applied simulated data. Consumption data from the Adventist Health Study were used to identify two dietary patterns with a markedly different consumption of several plant and animal products. State agricultural data were collected and applied to commodity production statistics. Indices were created to allow a comparison of the resource requirements for each dietary pattern.<h4>Setting</h4>California, USA.<h4>Subjects</h4>None.<h4>Results</h4>The diet containing more animal products required an additional 10 252 litres of water, 9910 kJ of energy, 186 g of fertilizer and 6 g of pesticides per week in comparison to the diet containing less animal products. The greatest contribution to the difference came from the consumption of animal products, particularly beef.<h4>Conclusions</h4>Consuming a more plant-based diet could to an extent alleviate the negative environmental impacts related to food production. As a method to feed ourselves more sustainably, behavioural adjustments appear to be a very important tool.
Keywords Food production Sustainable dietary patterns There is a direct link between dietary preference, agri- cultural production, resource use and
In the USA, food-related energy use increased from 14 % of the national energy budget in 2002 to an estimated 16 % in 2007 (8), of which agricultural production is estimated to account for 14 ·4% (8). Environ- mental impacts associated with the use of fossil fuels include acid rain, air pollution, soil and water con- tamination and greenhouse gas emissions. About 3 million tonnes of pesticides are applied globally every year (9), containing approximately 1600 different chemicals, with a lack of complete toxicity data (10).
Water use Water consumption data for the production of almonds, apples, dried beans, grapes, oranges, peaches and water- melon were obtained from Cost and Return Studies (CRS) published by the University of California Cooperative Extension Service and the University of California Davis Department of Agriculture and Resource Economics (37– 49). For beef products, the water consumed by the animals (obtained from the National Academy of Science (50)) and used in the production of their feed was accounted for.
A feed con- version efficiency of 7 ·0 was assumed (10). Soya in the feed formulations for beef and poultry was excluded. Water consumed directly by chickens grown for meat consumption is generally about twice the weight of their feed (55– 57). Temperature, relative humidity, age of birds and type of watering system are also important (55,57).A n estimated consumption of 0 ·23 kg/bird per d gives an average direct consumption of 227 ·12 litres water/1000 birds per d (55– 57).
An estimated indirect use of 227 ·12 litres water/1000 birds per d relating to the production facility (evaporative cooling, facility sanitation and fire protection) was included (55), giving a total of 454 litres water/1000 birds per d. The production of a 2 ·2 7 k gc h i c k e ni n4 9 dw o u l d require approximately 22 ·0 litres, therefore approximately 9·69 litres of water is required per kilogram of live weight chicken produced.
For egg production, the same average water use was assumed (227 ·12 litres/1000 birds per d) for direct con- sumption and 238 ·48 litres/1000 birds per d for indirect consumption (including egg washing) (55– 57), giving a total water consumption of 465 ·60 litres/1000 birds per d. Assuming average figures (80·6 % hen-day egg production rate and a weight of 60 ·4 g/egg), each hen produces 48 ·7g egg/d(55). Therefore, each kilogram of eggs produced requires approximately 9 ·65 litres of water. Table 2 shows water use data involved in the production of each food item.
Energy use Data for the production of almonds, apples, dried beans, grapes, oranges, peaches and watermelon were obtained from CRS. Original data were reported for gasoline and diesel fuel in gallons per acre and were converted to units of joules of energy used per kilogram of commodity produced using an energy value of 34 828 427 J/litre for gasoline and 38 657 950 J/litre for diesel fuel (58). Data for the production of alfalfa and maize used for animal feed were obtained from CRS. Table 2 shows energy use data for each food item.
The results show a range of water-use ef ficiencies with beef having the least efficient use rate across all food items. From the plant food items, almonds had the least ef ficient water use rate; however, they were still about 1·5 times more efficient than beef. Beef also had the least ef ficient energy and fertilizer use. Almonds had the least ef ficient pesticide use, followed by beef which was about three times more ef ficient. Comparing the diets Table 3 shows the input requirements to produce each food item for each dietary pattern.
Discussion The present findings demonstrate that the production of a diet relatively higher in animal products requires sig- nificantly greater amounts of water, energy, fertilizer and pesticides than a diet containing lower amounts of animal products.
Over the period of one year, the LAP diet would require 515 273 kJ less energy, 9677 g less fertilizer, 294 g less pesticides and 533 102 litres less water compared with the HAP diet. These results are consistent with those reported else- where, for example Horrigan et al. (10) and Leitzmann (75). Considered within a wider context of water use, the average daily indoor and outdoor water consumption per person in the USA is 333 litres (76). Therefore, per day, the LAP diet conserves the equivalent water usage for just over four people in comparison to the HAP diet. The potential savings could be much more substantial when considered in the national context.
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