Phil, I too wonder if the mother's diet can influence the nutrient composition but if Mark Sissom's recent article is of any validity than it appears it does not matter much.
http://www.marksdailyapple.com/nursing-primal-blueprint-diet/
While Mark started out by downplaying the effect of diet on mother's milk, towards the end he writes: "A lot of babies have reflux, and it can sometimes be related to food sensitivities. If it’s a significant or ongoing problem, it’s worth eliminating certain food groups for a couple weeks at a time to see if it makes any difference. Although gluten and dairy get the most attention and warrant initial test runs, you might want to consider doing the same test runs with nuts, nightshades, eggs, citrus and any remaining soy in your diet." So even he appears to recognize that there can be important differences in mother's milk due to differences in mother's diets. I also recall reading studies that found that undigested protein peptide fragments from wheat and other toxic foods, can be passed on to the fetus from the mother, and the mother's immune system can be triggered by these fragments in her own body and her immune system can then attack the fetus as well as her own body, due to the phenomena known as molecular mimicry and autoimmunity. Given those differences I, like you, still wonder if there might be subtle differences in the macronutrient ratios also.
It is still quite puzzling that human breast milk contains so much carbohydrate (the most among mammals?)
Are you sure it's the most among all mammals? So far you've only mentioned cheetahs and cows, what about nonhuman primates? Data on pig, bear and canid mother's milk would also seem more relevant than cow's milk. Humans do seem to handle carby foods like fruits better than cats and canids, so it doesn't suprise me that human mother's milk would be more carby than that of cats, but it does surprise me that it's more carby than bovine milk--though I think I have read that before. Why would calves not need as much carbs as human infants, I wonder? Is it because the bovine diet is fiber-rich, instead of fruit-rich? If so, that would suggest that mountain gorilla mother's milk would be lower carb also and we should expect frugivorous chimp mother's milk to have more carbs than mtn gorilla milk.
This still leaves protein at a low amount - just 1g/100ml where as cow milk is 3.5g/100ml. The best way I can explain this is that humans grow so much slower than most(every?) other mammals. At least this shows that growth can take place with quite low amounts of protein - just 7g/day.
Interesting idea, but calves are fast-growing and bovine milk is lower in carbs. Wouldn't fast-growers need carbs as well as protein? Or are protein and fat actually more important for fast growth?
Also interesting - in one of the comments from the sissom article it states that additional calcium and magnesium supplements might be needed if the diet is too high in animal protein. Well this matches up with the inland inuit who experienced early onset bone loss, perhaps with a diet too high in protein. hmmm...
Yes, and the alternative would be to eat a lot of blood, organs and soft bones from animals pastured on soils as rich in minerals and iodine as Stone Age soils (which is very rare these days) or from wild seafood (which would be quite expensive). In part for this reason, and despite Tyler's warnings against supplementation, I take Mg and low-dose Dr. Ron's multi-vit/mineral supplement and I eat pasture-fed meats, fats and organs, kelp, seafood, sea salt, and young greens. I also have residual mineral deficiencies left over from my SAD days, so I probably need more supplementation than most.
Also, can anyone give an explanation as to why our protein needs would change from such a low amount - 5 percent - to 10-20% range for adulthood??
Good question. I know the needs change from infancy to adulthood, but I don't know the details of the changes.