Ecology of human nutrition in New Guinea

Food intake in the autochthonous environments of New Guinea is determined primarily by climate and landscape, secondarily by the improvising skills of the inhabitants, their cultural preferences and their isolation.

This has led to accomplished farming techniques, especially in the highlands, but also in one instance to a particular skill in swamp farming.

In the lowlands, it resulted in a subsistence pattern based on the sago palm, supplemented by collecting animal and vegetable products. Only when water is available is there a significant contribution by animal protein. In the hilly interior, taro, yam, sweet potato and bananas in various combinations are the mainstay of diets. In a narrow altitudinal zone in the mountains, where climatic factors determine cultivation, the sweet potato is almost exclusively the staple food.

The diets tend to be monotonous and the absence of cereals is striking. The hand‐to‐mouth subsistence often results in irregular intakes. Diets are mostly composed of cooked starch; protein and fat moieties are small.

The average adult energy intake in the highlands as observed in 14 surveys was 1880 calories per day (7864KJ); 11 surveys in the lower regions indicated an average of 1470 calories per day (6149kJ). The most common limiting factor in lowland diets seems to be calories; in the highlands it is protein.

In the highlands, whether the daily protein intake contains 10 or 30 g per day depends chiefly on the variety of sweet potato consumed. It was the adoption of the sweet potato which made extensive settlement in the highlands possible, but in doing so the settlers preferred quantity above quality.

In evaluating diets, the calories provided by protein are an important factor. In the tuber staples this is only 3–6 per cent. If the needs for essential amino acids are considered at a minimum level, the amount present in a daily portion of 1500 g of food may be sufficient. Qualitatively the S‐amino acids are limiting. The non‐protein nitrogen is probably important.

The potential yields per hectare of the three tubers, the sago palm and bananas cover a similar range of 8–15 tons per hectare. Quantitative surveys show that for adults, intakes of 0.4–0.6 g of crude protein per kg and 30–40 calories per kg (125–167kJ) are the most common.

Tuber diets usually result in very low intakes of sodium and very high intakes of potassium and ascorbic acid. In view of the variable composition of foodstuffs and the importance of even small differences in protein content between varieties of staple foods it is hazardous to rely on nutrient values given in food composition tables. The great diversity of food plants reported by ethnologists should not detract from the fact that very few varieties of plants are present in the daily diet in significant quantities.

Traditional New Guinea diets rarely create malnutrition problems. Physical performance is often excellent.