The best diet is one based on plant food, with very little animal food. A large portion of that plant food should be starch. By starch I mean … all types of grains (rice, corn, wheat, barley, oats, quinoa), potatoes (all types including sweet potatoes or yams), starchy vegetables (peas, carrots, pumpkins and other squashes), beans, and legumes. But you know that.
If you’re eating this way, you’re eating closer to the way our human ancestors ate a million years ago. That’s what this new report says. (Thank you, Shaun.) What was the real Paleo diet? Cooked starch:
The Importance of Dietary Carbohydrate in Human Evolution, The Quarterly Review of Biology, September 2015
We propose that plant foods containing high quantities of starch were essential for the evolution of the human phenotype during the Pleistocene. … We provide evidence that cooked starch, a source of preformed glucose, greatly increased energy availability to human tissues with high glucose demands, such as the brain, red blood cells, and the developing fetus.
We also highlight the auxiliary role copy number variation in the salivary amylase genes may have played in increasing the importance of starch in human evolution following the origins of cooking. Salivary amylases are largely ineffective on raw crystalline starch, but cooking substantially increases both their energy-yielding potential and glycemia.
Regarding that second paragraph where they talk about “salivary amylase gene copy number variation” … Humans experienced an increase in the number of genes which code for the enzyme amylase right around the time they increased their intake of cooked starch. (We now have more copies of these genes than other primates, who don’t, to date, control fire.) Salivary amylase is secreted into the mouth when we eat. It breaks down starch. It doesn’t work well on uncooked starch, like the starch in raw potatoes. I blogged about this increase in amylase genes when it was reported in the journal Nature Genetics in 2007.
We hypothesize a gene-culture coadaptation scenario whereby cooking starch-rich plant foods coevolved with increased salivary amylase activity in the human lineage.
Here are some kernels I found interesting:
- Brain size increase was observed from about 800,000 years ago, from the Middle Pleistocene onward. That coincided with the increase in amylase genes, and the control of fire.
- “Consumption of meat acted as a buffer against environmental change and to support expansion into unfamiliar environments. However, high-starch plant foods would have been a plentiful, reliable, and important part of the diet.”
- “Humans are the only species that cook food.”
- Starch was found in “roots, tubers, rhizomes, seeds, fruits, nuts, tree bark.”
- Consumption of starch could explain differences in dentition between early hominins and African apes.
- Forage in shallow water promoted bipedality.
- “Postmenopausal females played a central role in foraging for USOs [underground storage organs, e.g. potatoes] and food sharing, which directly enabled younger female relatives to reproduce more frequently.”
- Hunting by early hominins may have been as much to do with status as nutrition, something that has also been proposed for chimpanzees.
- “The reduction in gut size is more likely to have occurred due to a gradual replacement of fibrous plants by higher energy-yielding plant foods, including starchy tubers.”
- “It has been suggested that early Homo acquired the capacity for endurance running, considered essential to exhaust prey or outpace other scavengers in hunting. … The energy source for prolonged high level aerobic activity is an important consideration. Glucose is the only energy source for sustaining running speeds above 70% of maximal oxygen consumption.”
- “There is a limit, considered to be 35–40%, to the amount of energy requirements humans can derive from proteins; above this ceiling protein toxicity can occur, which can cause death quite rapidly.” (Must get rid of protein’s nitrogen/ammonia.)
- In the absence of dietary carbohydrate, or during starvation, gluconeogenesis alone is usually not sufficient. … There remains an absolute requirement for 30–50 g of dietary glycemic carbohydrate per day to fill the gap between gluconeogenic capacity and the brain’s requirement for glucose.
- Tissue protein (muscle) is broken down out of necessity to provide the amino acids for gluconeogenesis.
- “Although a very high fat intake will prevent protein toxicity and provide energy for metabolism, it comes at the cost of high levels ketones in the blood, which can compromise reproductive function.”
- “Glucose is the main energy source for fetal growth.”
- “Fruits and berries may have supplemented the diet depending on climate and seasonality, in particular by providing essential vitamins, but they are unlikely to have provided a consistent contribution to carbohydrate energy requirements.”
I doubt this will change the minds of people who like to eat a lot of meat, and who justify it somehow by saying our ancestors ate a lot of meat. They didn’t. Hunting and meat-eating were about status, or about getting us through hard times … snowy winters or droughts. Man evolved to eat cooked starch.