Soy
"The first principle is that you must not fool yourself, and you are the easiest person to fool."
- Richard Feynman
I am vegetarian by choice, and would be pure vegan if that was healthy, practical, and non-confrontational. However, "pure" is usually a formula for confrontation, and I have more important battles to fight. Vegetarian is more healthy overall, but difficult in an unhealthy, wasteful, high-meat-consumption culture stupified by mass advertising.
Many insist that fish is needed for a healthy diet. If so, the stark choice is between a peaceful planet, and some fish for the wealthy for another decade or two. We are already harvesting most fish species to extinction, and battles over fishing grounds in the South China Sea may evolve into World War Three. I'll revisit the fish option when fish farming drastically improves, perhaps reservoir-farmed Tilapa, bred and fed for high omega-3 content and high food conversion efficiency. However, I expect more efficient results from gene-engineered algae in smaller reservoirs, so I don't think I will ever face the inefficient and uncomfortable choice of killing and eating fish.
"Sustainability" is a label applied to the notion that if we use our planet up more slowly, it might last long enough for our grandchildren. Those brandishing the sustainability label rarely calculate thousand-year effects. I think about billion-year timescales: life on the Earth must survive long enough to replicate in other star systems, which will take a very long time to accomplish. Let's use another term, "Perpetuality", for the very long term perpetuation of life, by natural and artificial means. Perpetuality means "make more than you (and others) use up", i.e. "make more, use less".
Humans are a significant fraction of the animal biomass on the planet, but our food animals (mostly cows, pigs, and chickens) greatly outweigh us. In small numbers, these animals can maintain grasslands, renew the soil, and control insect pests. In their current vast numbers, vast acreages of cropland are used to feed them, halving the food available for humans, while destroying wilderness and filling the oceans with fertilizer and toxic microbes.
All this suggests a near-vegan diet, with some dairy cattle to consume (some of) the grass that we cannot. Frankly, I have not calculated the amount of grassland this is, or the optimum amount of grazing. Numbers needed! It is possible (but seems unlikely) that the optimal amount of grazing is zero - perhaps perpetuality demands a vegan diet. If so, our next decision is about protein sources.
Why Not Soy?
Soy is among the highest protein legumes, and seems a likely source. Sedentary humans need fewer calories per gram of protein, and lupin beans offer the highest ratio of protein grams per calorie. They are also laced with toxic alkaloids, and must be carefully prepared before eating. This is an important clue. Unmodified plants produce seeds for propagation, not animal consumption, and protect their seeds from insects with hard husks or toxic chemicals. How does soy protect itself?
According to some researchers, the phytoestrogens genistein and daidzein in soy beans interfere with growth and reproduction of insects. A biochemist friend says they do the same thing in humans, interfering with the formation of axons and dendrites in the brain. The Honolulu-Asia Aging Study, focused on the effects of the Asian diet on heart health, found that moderate midlife tofu consumption reduced the average age of onset for dementia. This 2000 paper brought a halt to my previously high soy consumption. In my 40's, this may have been closing the barn door after the horses escaped, but perhaps a few nags remain inside.
Soy protein isolate offers very high protein to carbohydrate ratios, but does not remove the phytoestrogens. At 0.9 g/kg, soy protein is more like a pharmaceutical than a food (a dose of estradiol is about 2 milligrams per day).
Before the 20th century, the east Asian diet was meager, almost all vegetables. Soy tofu was a food for the rich, and for celebrations; not consumed in kilogram-per-month quantities. Few people ate enough soy for long enough to match the "moderate" levels observed in the Honolulu study. High soy consumption is a 20th century invention.
My biochemist friend told me that before the 1960s, soy was grown for ink and animal feed. Humans pay more for food, so soy marketing companies like Archer Daniels Midland created the notion that soy was a health food, and fostered the myth of high historical levels of Asian soy consumption.
In my ideal world, we would develop methods to remove the phytoestrogens from soy protein isolate (probably a microbe that gobbles them up, or producing an enzyme that degrades them). It might be possible to genetically engineer soy without the phytoestrogens, but that will lower the insect resistance and increase the need for pesticides. However, the soy protein advocacy community includes many anti-bioengineering zealots, and is easily manipulated by myths created by marketers seeking to isolate and overcharge them. The meat-advocate "carno-paleo" community (note 1) shuns soy and bioengineering.
Perhaps there are enough science-loving environment-loving realists out there to create a market for "ZP-O3-SPI" - Zero-Phytoestrogen Omega-3 Soy Protein Isolate. Given that, I would stop consuming dairy and whey, and move closer to pure vegan. Until then, I will continue to consume some grass-fed milk and whey, sacrificing surplus calves for my dairy-consuming sins (note 2). I will continue to consume a lot of lower-protein beans, with enough exercise to burn off the carbs.
In the long term, I expect we will gene-engineer individualized "manna" plants - a few superefficent, pathogen-invulnerable, digitally-connected artificial plants in our personal kitchen garden that make food and medicines ("nutraceuticals") specifically adapted to us as individuals, producing ideal edibles right-now-only. Pizza flowers for breakfast, burger fruit for dinner, sap that tastes exactly like Domaine de la Romanee-Conti wine, or A&W root beer if preferred. With a wee bit of valacyclovir to fight herpes virus, perhaps.
What's for dinner tonight? Look at the plant's website!
It's all bio-molecules. Why not make plants with DNA that makes the specific molecules we both want and need? Nature did not evolve to feed us, and our appetites did not evolve for the food options now available. We can learn to do better.
note 1: Roundly reviled by carno-paleos, "Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live " by Marlene Zuk (University of California–Riverside), punctures the myth of the meat-rich ancestral diet. Yes, our prehistoric ancestors ate meat. Not very often; our dentation (modern and fossil) and our intestines (long) attest to our mostly-plant-food diet. Meat was a status item, a welcome gift for the folks back home, but before bows and arrows, hunters often did not survive lethal animal encounters and did not make it back home. The high meat ancestry myth comes from the same marketing machine as the high soy Asian diet myth.
note 2: Cows lactate to feed calves, and eventually stop making milk until they birth another calf. So, the cows are artificially inseminated to make calves, and most of the calves are killed for veal soon after birth. For a few years, I lived next to a dairy pasture; the cows moo (loudly) for their missing calves for weeks.
Yet I still drink milk and eat cheese. I am surely a heartless bastard, but not as bad as the anti-science zealots who block the development of safe soy. They can still eat "natural" phyto-soy, and turn their brains into the cheese they won't let me have.