A ‘sustainable’ diet: Must it all be cereal and cabbage?
Many people want to eat in a way that’s good for their health and also good for the environment. One does not necessarily translate to the other.
For one thing, the word “sustainable” is easy to bandy about but involves a whole medley of considerations: greenhouse gas emissions, how and where a food was grown, how much water was used to grow it, from what distance it was shipped, how much goes to waste and how leftovers are disposed of, whether people can make a living producing it, and more.
For another, simply cutting out animal products -- and their comparatively large carbon footprint -- does not automatically make a diet nutritionally well-balanced (one of my younger brother’s favorite vegetarian dishes as a teen was white rice with a dab of margarine and a sprinkling of MSG).
Scientists at the University of Aberdeen in Scotland tried to tackle one part of the issue -- whether people could still get all their nutrient needs while reducing the greenhouse gas emissions that came from producing the raw materials of their diet.
Here are the nuts and bolts of what they did:
They set out to devise a diet that would fill the nutritional needs of an adult woman, age 19 to 50. Women of that age were chosen because they tend to be deficient in iron, and the scientists needed to be sure that a diet with significantly reduced greenhouse gases (likely to include less meat) would satisfy their iron requirements.
The diet didn’t include soy foods or quorn, a vegetarian protein made from a fungus, because those aren’t broadly eaten by the population that they were studying: the fine residents of the United Kingdom. And data were lacking on what happens in terms of greenhouse gas contributions after the basic ingredients of foods arrived at regional distribution points, so the authors had to do their calculations based on gases emitted up to that point only. It’s estimated that 56% of greenhouse gas emissions are produced by the time a food reaches this point.
The authors used recipe books to figure out how much a processed foodstuff contains of the various ingredients. And they consulted a database of 82 foods, with their greenhouse-gas estimates and nutrient composition, to come up with diets.
They even figured out where different foods consumed in the UK came from and in what proportions -- since a food’s greenhouse gas contribution depends a lot on how it was grown -- and adjusted their calculations accordingly.
On their first go-round, the scientists aimed for a 90% reduction in greenhouse gas emissions based on the average diet consumed by women in 1990 (a reasonable baseline, they said) -- while still fulfilling basic minimums and maximums for proteins, carbs, added sugars, salt and certain vitamins and micronutrients, etc.
Success! Their computer modeling produced a nutritionally balanced diet.
Unfortunately, it consisted of only seven foods: whole-grain breakfast cereal (generally vitamin-fortified), pasta, peas, fried onions, brassicas (cabbage, Brussels sprouts, that kind of thing), sesame seeds and confectionery (a.k.a. candy).
I don’t know whether you’ve ever played the “what five foods would I take to a desert island?” game, but I have, fairly recently. The above would not be my list. (I came up with cabbage, bacon, coffee, potatoes and onions -- and then the exercise unraveled into a debate as to whether garlic could be included among the herbs and spices.)
“The amounts required were large and unrealistic,” the authors wrote of their list. They also pointed to a problem of “a large quantity of breakfast cereal with no milk.”
Back to the drawing board. This time, the scientists relaxed their constraints a little and ended up with a diet that reduced greenhouse gas emissions by 36%. It included 52 foods, among them some milk for the breakfast cereal and enough to be added to three hot drinks a day.
It also contained a little bit of meat -- 60% of what’s eaten by women in the UK today, enough for three meat meals a week of the size eaten today or more meals with smaller portions.
It included the UK’s recommendation of two fish meals a week, one of which should be oily, and enough fruits and vegetables to satisfy the nation’s five-a-day recommendation.
This is only one diet combo of many that could be possible, the authors said. It could be adjusted based on preference.
It cost about the same as what people spend today with groceries, and buying tea and coffee (not included) would not bump up costs by much.
But since the population of the UK has grown from the baseline data from 1990, in today’s terms the greenhouse-gas emission reduction would be about 30%, and by 2050, if the population grows as expected, it would fall to 14%.
You can read the entire study, just published in the American Journal of Clinical Nutrition, as well as an accompanying commentary. The authors also mapped out meals for a week’s diet, including items such as chicken and curry with pita bread, tomato and red pepper soup and egg salad sandwiches.
Even scones and jam and a potato chip or two.
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