What human should eat to stay healthy and strong is very much controversial. Research yet have understood that eating the right foods in a right amount and taking break from foods can help you in many health benefits.
Many suggest to have vegan diet for some specific reason. Because of higher amount of human population, animals are killed in a higher rate and using drugs to make them grow faster. This ain't the things which our ancestors used to eat to stay strong and healthy even in those rough conditions.
The fast growing population and obesity with so many chronic infection/disease, always take to the mark of bad living habits. Research believe that, only bad choice of food can only hamper your body and brain by 80%, and it's true as well. All the medicines are made from plants or animals only, on early days people have to drink medicine which aren't taste good for sure and converted them to small tablet which are easy.
Easy living life for human making them lazy, also with foods as well. Pre cooked packed foods, or instant cooking foods isn't the right choices.
We aren't getting the right quality food into our body. If we eat a green fresh food also, those food also have a lot of chemical inside it.
So, isn't their anything we can eat and stay healthy. Their are foods and scientists believe that their is nothing like having only vegetables and stop eating animals.
Surely our teeth are designed like chewing or munching the food and not for tearing the flesh like teeth that lion does. But it's wrong to be said that we don't have to eat flesh. Our ancestors eat both animals and plants, and always eat low glycemic foods and foods which are naturally occurring. They eat sugar like honey not refined one.
Our closest living relatives such as chimpanzees and gorillas live on a diet of foods overwhelmingly derived from plants. We ignore our evolutionary past at our peril, with the growing epidemics of killer diseases such as cancer, heart disease, obesity and diabetes now occurring in almost every corner of the planet.
We Munch Not Tear.
Okay as discussed above, we don't have teeth like lions or any carnivorous animals to tear the meat. Our teeth are designed like herbivores animals.
From growing from child to adult we know that, we can't even swallow those whole, but must chew them finely and mix them with saliva before the ball of food will slide down the oesophagus. In contrast, carnivorous animals such as lion tear off chunks and swallow them almost immediately without even chewing them.
Our teeth are so designed that it open and close and have no space between it. Out teeth are made to crush the food and not to tear them. But on carnivorous animals have lower jaws have very limited side-to-side motion. They are fixed only to open and close, which adds strength and stability to their powerful bite.
Before getting into the digestion process, out mouth digest the food about 50% before going into the stomach mixing with Saliva. Carnivorous animals don't have this saliva thing, check the cat's mouth their mouth are soo dry. They gulp the food no matter it's a fish or it's Fish bone they eat them all.
Getting inside the stomach, the stomach juices of meat-eating animals are highly acidic then the plant eaters or herbivores. They have to be, so that they can break down the large quantities of muscle and bone materials they eat. Much lower concentrations of stomach acid are needed to digest starches, vegetables and fruits. So our stomach take 8-24hours to digest the meat we eat, or some even cannot able to digest milk as well, that's because due to low concentration of stomach acid in humans.
The human intestine is long and coiled, much like that of cows and horses etc. This makes digestion slow, allowing time to break down and absorb the nutrients from foods. In contrast, the intestine of a carnivore, such as a cat, lion is short, straight and tubular which don't take enough time to make the food pass away.
We cannot make vitamin C by our own, we have to consume them from diet. But carnivorous animals make them internally.
How About Ancestors
This all things always described that our body is well structured to eat only plants but not animals. So our ancestors also eat animals then how are they so stong?
One studies have done with tribal community in a jungle who have similar diet and habits like ancient peoples (link)
And it makes a twist, their is no single human diet which Best for human health.
Some of them get most of the nutrition from carbohydrates and some are mostly relying on meat. Almost all of them eat a mix of meat, fish and plants, consuming foods that are generally packed with nutrients.
It was also found that they eat a lots of fiber then normal human beings. Most of their carbohydrates are from plants contains higher fibers and have low glycemic index. It means that they eat, which do not spike blood sugar levels rapidly.
Though it's concluded that their is no exact diet for humans to eat. If you eat all plants then you will not get vitamin B12.
The findings suggest that there is no one “true” diet for humans, who “can be very healthy on a wide range of diets,” said the lead author of the study, Herman Pontzer, an associate professor of evolutionary anthropology at Duke University. “We know that because we see a wide range of diets in these very healthy populations.”
So they eat the right food, means they don't have to suffer?
It might happen not sometimes it fails as well, It might help that genetics and other factors can fight you from chronic disease but studies shows that when people born into hunter-gatherer societies move to large cities and adopt Western lifestyles, they develop high rates of obesity and metabolic disease just like everyone else.
The Tsimane get most of their calories from complex carbohydrates high in fiber like plantain, corn, rice and bananas, and animals and fish. Dr. Gurven has published detailed studies showing that they have exceptional cardiovascular health and almost no diabetes.
But after they shift to cities they are developing and drying because of type 2 diabetes by getting into the traditional diet.
It was so clear shows that getting into the diet with fries, soda and junk foods with less to no activity making them into type 2 diabetes. Where no sign of this before in their entire life. Eating carbohydrates which have no nutrition like soda, ice cream, cake can be so harmful for human body that can convert the life of a healthy one to sluggish.
The True Human Diet.
As you understand that their is nothing specific true diet for human but human have to choose their lifestyle to become health. Our body need nutrients to work and function properly, having fries, soda, instant cooked food like Maggie pasta, junk foods like pizza, burger are not the foods which should be included in our diet because they are nutritional less. Providing most of the fruits and vegetables with some animal's flesh will help one to stay healthy. Including intense physical activity with good healthy and nutritional food can only the true human diet.
Our body never understand the chemicals which are added to the junk foods and stop metabolic response, which make us lazy. Junk food or Western foods are only the reason for obesity and death due to several diseases.
Junk foods are so made with chemicals and preservatives with correct sweet and salt combination that they always taste good. Don't fool yourself, stick to natural and be healthy.
Conclusion:
The only true human diet is naturally occurring green vegetables, fruits and very few animals with some intense workout and be active all day to stay physically fit. Say no to bad foods and simple suger.