The actual amount of carbohydrates required by humans for health? ZERO.

You may find this hard to believe - but it is documented fact that the Yupik, Inuit and Aleut (formerly known as Eskimos) consume very low levels (close to zero) of carbohydrates during winter.
For 6-9 months every year they subsist entirely on caribou, reindeer and whale meat. That's a lot of animal-based protein and an enormous amount of fat.
Surprisingly, they don't succumb to heart disease, diabetes, obesity, high BP, or any of the other ills of the modern age we're so familiar with.
Instead, they happily live to a ripe old age. In fact they have an extremely low mortality rate from heart disease.
And they have the same exact biochemistry and physiology we do!

The Canadian Arctic explorer and ethnologist Vilhjalmur Stefansson was among the first to document in his book "The Friendly Arctic" that the Inuit would often go 6-9 months every year living on nothing but meat and fish.

Arctic explorer Vilhjalmur Stefansson

Stefansson himself spent 11 years exploring the Arctic. He lived almost exclusively on meat for 9 years, consuming very low levels of carbohydrates as the Inuit do, while remaining perfectly healthy.
Interestingly, in 1927 William A. Thomas reported that he found no incidence of scurvy (a disease resulting from vitamin C deficiency) or rickets (softening of bones in children because of deficiency or impaired metabolism of vitamin D, phosphorus, or calcium) among the Inuit who "lived off the land". However, he reported a high incidence of these diseases among those Inuit who subsisted on canned food, flour, dried potatoes and cereals.

A similar finding has been described in a blog post by Dr. Michael R. Eades, MD, author of Protein Power and The Protein Power Lifeplan.
Claire Cassidy, Ph.D., the author of the study* described in Dr. Eades' post compared hunter-gatherers with agriculturists who likely shared the same genetic heritage, but lived in different times. She found that the former had better bones, no signs of iron-deficiency anemia or infection, few (if any) dental cavities, fewer signs of arthritis and were generally larger and more robust than their agricultural contemporaries.
Clearly, human health took a nosedive when we switched from a hunter-gatherer lifestyle to agriculture; and grains and other forms of carbohydrates became a large part of our diet.

In 1929-30, Stefansson and Danish explorer Karsten Anderson undertook a study under the auspices of the Journal of the American Medical Association to show they could eat a 100% meat diet - with no carbohydrates - in a closely-observed laboratory setting for an entire year.
Their diet included muscle, liver, kidney, brain, bone marrow, bacon and fat from beef, veal, pork, lamb, and chicken. Carbohydrates were limited solely to glycogen from these meat sources.
This came out to 100-140 grams of protein, 2-300 grams of fat and 7-12 grams of carbohydrates, making up a total of 2-3000 calories per day, mostly derived from fat.
A typical day's diet might look like this:
Breakfast - lean beef, 190 grams; fat, 100 grams.
Dinner -  liver, 200 grams; fat, 75 grams.
Supper - lean beef, 200 grams; marrow, 70 grams.
(Not a very varied or appetizing menu, I must admit).

At the end of an entire year on this diet without carbohydrates, vitamin supplementation or any other additives, both men were perfectly healthy and reported to be "in good physical condition, mentally alert and physically active".
They'd lost a little weight, but they had normal cholesterol and blood chemistry values; and their physiological functions were normal.

It is relevant to point out here that the meat and fish consumed by the Inuit and by these explorers came from wild game that lived freely and ate their own natural foods. They were not farmed or force-fed things they normally wouldn't - and shouldn't - eat.
Also, the Inuit and the explorers also led a physically demanding life, not least because living in those conditions requires a lot of energy expenditure.
I would definitely NOT recommend eating the meat of today's farmed animals that are force-fed a diet of hormones, antibiotics and ground-up animal parts for even a single day, much less every day for a year to the tune of 2-3,000 calories/day!

I only wish to use this very real example of an entire ethnic group of people - although old traditions are dying fast, even among them - and the experiment with Stefansson and Anderson to convey the concept of the relative unimportance of carbohydrates in our diet.

*Cassidy CM. Nutrition and health in agriculturalists and hunter-gatherers: a case study of two prehistoric populations. in Nutritional Anthropology. Eds Jerome NW et al. 1980 Redgrave Publishing Company, Pleasantville, NY pg 117-145.

You can read about these revolutionary nutritional ideas and the very real health benefits of a diet that is rich in protein, contains moderate amounts of healthy fat and low carbohydrates in these groundbreaking, must-read books by Drs. Michael and Mary Dan Eades: