I’ve looked online and haven’t found an answer to this specific question. I feel like it could be a real long time but maybe I’m wrong! Thanks for your knowledge!
Survive? A long ass time. Thrive with no health complications? Probably still a long ass time but as soon as you start pursuing anything like running long distances, sport, training hard, or other stressors you’re probably not going to perform at a very high level on rice and carrots.
if you take b vitamin complex tablets and eat a substantial quantity of calorioes you can survive off this way of eating, but i definitely wouldn’t recommend it.
the truth is, so long as you are getting all your micronutrients at 100%, you can practically survive any diet regardless of what you are eating.
hence why ommitting meat from the diet but sourcing b12 from supplements is a viable strategy
or you could go full carnivore but take vit c tablets
whatever extreme diet you do, supplementing is key, especially b vitamins because they are responsible for metabolism and the nervous system - you can get chronic nerve pain and chronic depression if you dont get enough b vitamins in your diet from a variety of foods
no need to worry about protein really since, if you are going to eat that way, it’s obviously going to be a low protein diet and low protein diets have been shown to improve longevity in rat studies which is interesting.
The was a brilliant doctor named Walter Kempner and he developed the first cure for diabetes, it was called “The Rice Diet.” It was helpful for all kinds of chronic diseases, including kidney disease caused by high blood pressure and for obesity. People lost hundreds of pounds on this diet. It consisted of only white rice and fruit, white sugar, and vitamins. There was no fat, because fat would aggravate the diabetes. It was strictly calorie controlled. The sugar was added to supplement the calories, because if you ate enough rice to meet caloric needs, the protein would be too high, and it would harm the kidneys of these very sick diabetics and high blood pressure patients. You can read about it, it was very famous and the cure was offered until about year 2000, if I recall correctly.
Another diet that was very heavy in rice, was the zen macrobiotic diet out of Japan. Supposedly, some practitioners (mostly monks) at almost nothing but rice, for a very long time, years, but it turned out not to be very good for them (the rice-only version of the macrobiotic diet). Most who ate the rice-heavy diet supplemented it with at least sesame seeds and salt (gomasio). The sesame adds calcium. Usually, the whole grain makes up the majority of the diet, and there is also assorted vegetables, a small amount of beans (traditionally soy or aduki). Miso soup is also available, and a small amount of wheat.
I have a good friend who has been on a version of macrobiotic diet for 50 years, since he was 20, and he is very healthy. He was prescribed it by a naturopathic doctor for his then-severe acne. He eats whole grains, vegetables, steamed or stir-fried, some little bits of beans but mostly tofu, wheat germ, sesame, tamari, and olive oil. I believe he also eats some herbs and spices and vitamins. An occasional apple, oats or toast for breakfast, and about once a week, a single egg, that’s his only animal product. Most days he has no caffeine, but sometimes some black coffee. And he like to drink alcohol occasionally when he goes out.
But he has been eating these exact same simple meals for 50 years, and he works hard, travels, surfs even in his old age, and does yoga.