The desert barrier
When we speak of Africa in terms of nutrition, we usually refer to Africa south of the Sahara Desert. The area north of the desert may have its own traits, but nutritionally it belongs more to the Mediterranean world than to the rest of Africa. The area south of the desert is a dry tropical savanna region, succeeded southward and on both sides of the equator by rain forest enclaves, and again by tropical regions further to the south and towards the east.
In earlier times, say around 5000 BC, small bands of people still using stone tools, roamed the savannas of both the northern and southern hemispheres, eating mainly berries, nuts, roots and tubers, like their ancestors for thousands of centuries before them. Meat was available in the savannas, either through hunting or scavenging, but less so in the forested regions around the equator, where the need for protein was probably supplied mainly by a large variety of fresh water fish and crustaceans. In some coastal regions, extensive middens (food remnants) of shellfish are found, but these are mostly recent. The rise in sea level during the last 10,000 years or so, would have naturally concealed or destroyed most earlier evidence.
The grains of this vast region are now maize, sorghums both soft and hard, pearl and bulrush millet, rice, and some other minor cereals of limited significance, like teff, a minute highland grain found mostly in Ethiopia, and Brachiaria deflexa, grown only in the Fouta Djallon region of Guinea. Barley and especially maize are relatively late introductions in the savanna regions. In the forest areas, by contrast, tuber and root plants like various species of yams, manioc, bananas and plantains are the staples, and all but yams and roots are late imports.
Milk is eaten mainly by pastoralists such as the Masai and Samburu of East Africa and the Fulbe (Peul) of the Sahel, but not generally in Africa. In fact, Africans have some of the highest rates of lactose intolerance on the planet. Finally, edible oils came mostly from cultivated palm kernels, the initially imported groundnuts, and mainly cultivated sesame in West Africa.
The staples of a continent
In most of sub-Saharan Africa the basic staple seen today is coarsely ground maize flour boiled to the consistency of a paste. This is called by various names, posho in the Kiswahili of East Africa (actually meaning "daily food rations"), "mealy-meal" in southern Africa, and so on. The maize paste is equivalent to bread, and used to soak up some sauce made out of a variety of local foods or scraps of fish and meat, and perhaps as often as not, some tongue blistering chilies.
But as previously mentioned, maize is a recent arrival in Africa as it is everywhere else outside its original habitat in the Americas. Reports abound about the presence of maize in Africa in pre-colonial days. Be that as it may, it seems that maize as a staple was introduced by Portuguese navigators who brought the plant to Africa for their own use, since the grain required no ploughing, birds did not represent a risk, and the yield was excellent.
So even though in widespread use today, maize cannot really be considered as part of Africa's traditional diet. A large section of the population of Africa, in fact, now eats a staple food with a high glycemic index. This might well have been tolerated, provided the rest of the diet had remained traditional. But this is far from the case nowadays.
The rise of the middle class in Africa from the 1970s on, has created a large group of people who can afford to buy their foods instead of growing them. What they usually buy is attractively packaged and often processed American and European foods or their local equivalents. The esteem that Africans generally have for overseas education, economic prosperity, technological achievement, and unimpeded progress, largely prevents them from seeing that the attractively packaged foods they buy are no more than disguised dietary garbage, depleted of most important nutrients and fiber, and loaded with salt, sugar and saturated fats.
The result of this sudden influx is skyrocketing rates of degenerative disease, with diabetes up to forty percent in some South African townships. Other nutrition related problems are widely known, especially protein-energy malnutrition among children and women of reproductive age, locally vitamin A deficiency, some anemias, and goiter mainly in the Congo Basin and Ethiopia.
Modern slant on old bias
In contrast to such facts, the opinion is often expressed that the chronic degenerative diseases Africans (and the rest of us) now face, spring from our increased longevity and nothing more. This is a modern slant of Thomas Hobbes' view of natural life as "nasty, brutish and short."
On the contrary, four censuses conducted over a ten year period (1964 to 1973) among the !Kung bushmen of the Kalahari, who adhere to their traditional diet, showed ten percent of the population was over sixty. An exceptional figure for hunter-gatherers without state healthcare, or in fact any modern medical care at all. And chronic degenerative diseases among the !Kung, such as high blood pressure among the elderly, etc, are almost unknown. Traditional diets are not a passing food fad.
A traditional African diet, but obviously not of hunters like the !Kung or pastoralists like the Fulbe (Peul), Masai and Samburu, could probably be represented by the food pyramid shown.