I think there are definitely differences between individuals based on gestational, infancy, and childhood microbiome health/harm.
Sure - one can survive on carnivore foods without greens, grasses, seaweed, or berries - but the fact is that such foods when in bioregions or traded were nibbled on and stored by apparently lots of ancient pre-civilizations indigenous & aboriginal peoples. Also, as already pointed out in this here thread, without the nutrients of organ meats (eaten raw, traditionally), raw oysters/fish eggs, and with food harvested from nutrient depleted soils, we are much lacking compared to our ancestors.
I think the key is a healthy gut that supports a healthy mental state. Depression on longer term low-carb/keto can be a thing that is a heavier level than the normal transitory depression we all experience in the ups and downs of life in a stressful society. Bacterial imbalances in the colon can be a thing on longer term zerocarb/keto (as in, 6-7 years). When the good bacteria in the colon are lacking due to overuse of antibiotics since childhood, and excess sugars - it means that our bodies aren’t producing nearly enough butyrate (the good bacteria in the colon produce butyrate). Butyrate in the colon not only fuels ketosis, it also has been found to be protective against colon cancer, apparently. So, theoretically, one can follow a LCHF/keto way of eating and still have gut troubles/excess fermentation, nutrient absorption issues, and cloying depression - because of pre-existing conditions, ie, the after-effects of a childhood in industrial society.
Some folks - myself included - have found that healing the gut (also called the ‘enteric nervous system’ due to its abundant neurons) makes as much sense as LCHF/keto.
Personally, I believe (and it is a central principle of eastern medicine) that the digestive system is the source of all functional health - and that we are meant to be able to tolerate fluctuation in food supply by being both fat-adapted and having enzymatic strength and fortitude. We’re meant to have a “warrior gut” and a largely joyful mental & emotional outlook.
Though supplementing with Ginger has helped me dramatically heal my gut enzyme production and eliminate dairy bloat/phlegm whilst reducing my cortisol-driven midlife belly fat storage, I found that it was after making doubly sure I had veg fiber daily and/or resistant starch from a little (2 tblsp) refried basmati rice, my neurogenesis really had an uptick and emotional outlooks got solidly elevated and way more resilient. There are 4 kinds of resistant starch, and they have different impacts - worth looking into if you are fat-adapted and yet suffer from low emotional stamina, or basic depression on keto. This may be controversial to some, fine! I think it’s critical to acknowledge that most of us in industrial society have had out of whack guts since even infancy - and that unless we’ve healed a ton by eating raw organ meats prebiotics, and probiotics we may need some further protocols and nourishments for a greater experience of ketogenic benefits.
For more on this, see the work of microbiologist Norm Robillard (recommended by cornerstone LCHF physicians the Drs. Eades) and pharmacologist Grace Liu to decide for yourself what your present gut health is and what may help enhance you health as well as healthy longevity.
