Nutritional characteristics of wild primate foods: do the diets of our closest living relatives have lessons for us?

Evolution of dietary antioxidants

Oxygen is vital for most organisms but, paradoxically, damages key biological sites. Oxygenic threat is met by antioxidants that evolved in parallel with our oxygenic atmosphere. Plants employ antioxidants to defend their structures against reactive oxygen species (ROS; oxidants) produced during photosynthesis. The human body is exposed to these same oxidants, and we have also evolved an effective antioxidant system. However, this is not infallible. ROS breach defences, oxidative damage ensues, accumulates with age, and causes a variety of pathological changes. Plant-based, antioxidant-rich foods traditionally formed the major part of the human diet, and plant-based dietary antioxidants are hypothesized to have an important role in maintaining human health. This hypothesis is logical in evolutionary terms, especially when we consider the relatively hypoxic environment in which humans may have evolved. In this paper, the human diet is discussed briefly in terms of its evolutionary development, different strategies of antioxidant defence are outlined, and evolution of dietary antioxidants is discussed from the perspectives of plant need and our current dietary requirements. Finally, possibilities in regard to dietary antioxidants, evolution, and human health are presented, and an evolutionary cost-benefit analysis is presented in relation to why we lost the ability to make ascorbic acid (vitamin C) although we retained an absolute requirement for it.

Nutrition and the extremes of life: dilemmas and enigmas of advanced old age

Pre-term infants born four months before term have a very low birth weight; in an evolutionary sense, they were never 'meant' to survive through the evolutionary period preceding the technological age. In the same way, evolution failed to contemplate survival to ages 50, 60, 70 and beyond. Because peak reproductive performance comes before the vagaries of a given individual's survival is determined, and the fact of that survival conveys no advantage to disseminating the genetic make-up, natural selection cannot select for advantages related to longevity. Moreover, in the larger context of species survival and biodiversity, the crowding of the human ecosphere with older persons would seem to have had more liabilities than assets over evolution. We cannot learn from nature how to feed and nourish the oldest old. The lessons, if any, would be cruelly averse to our humanitarian values. However, we do have values and they guide us to the goal for quality of life for the assorted conditions of the extremely old. The choices are laissez faire or laissez aller. If we are ignorant about how to achieve the goals, perhaps the 'first do not harm' principle should be operative. Should we decide that prescription of diet and adjustment of nutritional stores are required, hypothesis-based research to provide evidence-based practices is required. We may be facing a true Heisenberg principle. The fact that ageing leads to the greatest heterogeneity among individuals complicates the generation of universal principles for prescriptive actions. Another quandary could be the fact that insufficient individuals within the age groups of interest are available for outcome research in any given area to provide statistically robust findings. Shifting once again to the lowest extreme of human survival, we know that what is good for the full-term infant is not the formula for the 600 g premature neonate. Failing to heed the distinction can be lethal. My suspicion is that what is good dietary practice for the younger adult is also not what is best for octogenarians. I would predict that a new intergenerational confrontation is in the offing as we recognise and raise the issues of alimentation of the extremely old. It is the tyranny of the preventive regimens of assorted guidelines to be imposed across the whole population that may exacerbate the tension between young and old, although the young's consuming a more healthful diet will presumably allow more of them to eventually reach the status of advanced age, and hopefully with greater health, vigour and function.

Estimation of the net acid load of the diet of ancestral preagricultural Homo sapiens and their hominid ancestors

BACKGROUND

Natural selection has had < 1% of hominid evolutionary time to eliminate the inevitable maladaptations consequent to the profound transformation of the human diet resulting from the inventions of agriculture and animal husbandry.

OBJECTIVE

The objective was to estimate the net systemic load of acid (net endogenous acid production; NEAP) from retrojected ancestral preagricultural diets and to compare it with that of contemporary diets, which are characterized by an imbalance of nutrient precursors of hydrogen and bicarbonate ions that induces a lifelong, low-grade, pathogenically significant systemic metabolic acidosis.

DESIGN

Using established computational methods, we computed NEAP for a large number of retrojected ancestral preagricultural diets and compared them with computed and measured values for typical American diets.

RESULTS

The mean (+/- SD) NEAP for 159 retrojected preagricultural diets was -88 +/- 82 mEq/d; 87% were net base-producing. The computational model predicted NEAP for the average American diet (as recorded in the third National Health and Nutrition Examination Survey) as 48 mEq/d, within a few percentage points of published measured values for free-living Americans; the model, therefore, was not biased toward generating negative NEAP values. The historical shift from negative to positive NEAP was accounted for by the displacement of high-bicarbonate-yielding plant foods in the ancestral diet by cereal grains and energy-dense, nutrient-poor foods in the contemporary diet-neither of which are net base-producing.

CONCLUSIONS

The findings suggest that diet-induced metabolic acidosis and its sequelae in humans eating contemporary diets reflect a mismatch between the nutrient composition of the diet and genetically determined nutritional requirements for optimal systemic acid-base status.

Fermenting fruit and the historical ecology of ethanol ingestion: is alcoholism in modern humans an evolutionary hangover?

In the field of addiction research, the possibility of ancestral exposure to psychoactive compounds has generally been excluded. A paleobiological approach to the human diet, however, illustrates the potential utility of historical data in interpreting modern-day addictive behaviors. Low-level dietary exposure to ethanol via ingestion of fermenting fruit has probably characterized the predominantly frugivorous anthropoid lineage for about 40 million years. Potentially adaptive primate behaviors associated with the natural occurrence of ethanol include the olfactory use of ethanol plumes to localize fruit crops, the use of ethanol as an appetitive stimulant to facilitate rapid consumption of transient nutritional resources, and the physiological exploitation of the caloric benefits of ethanol. Such behavioral and energetic advantages probably pertain to all animal taxa that consume fermenting fruit, and may have been retained in modern humans in spite of considerable dietary diversification over the last several million years. In contemporary human environments, excessive consumption of ethanol would then represent maladaptive cooption of ancestrally advantageous behaviors given essentially ad libitum access to a compound otherwise found only within scarce nutritional substrates. Epidemiologically demonstrated health benefits of low-level alcohol consumption are consistent with an ancient and potentially adaptive exposure of primate frugivores to this most common of the psychoactive substances.

Expression of type 2 cystatin genes CST1-CST5 in adult human tissues and the developing submandibular gland

Type 2 cystatins comprise a class of cysteine peptidase inhibitor presumed to mediate protective functions at various locations, including the oral cavity. Seven cystatin genes are clustered within a 300-kb region of human 20p11.2. "Salivary" cystatins, encoded by CST1, 2, 4, and 5, are present in saliva at significant levels but have also been reported in other secretions, such as tears, suggesting that during their evolution, these genes have acquired mechanisms directing differential tissue-specific expression. However, their patterns of expression, which might also provide additional clues to their individual functions, have not been determined. Gene-specific RNase protection assays were used to examine the qualitative and quantitative distribution of expression of these seven genes within a collection of 23 adult human tissues. The CST3 gene, encoding cystatin C, was expressed at modest levels in all tissues examined. The presumptive pseudogenes CSTP1 and CSTP2 were not expressed at detectable levels in any tissue. The CST1, 2, 4, and 5 genes were expressed in differential, tissue-specific patterns. Expression of CST2 and CST5 was restricted to the submandibular and parotid glands, while CST1 and CST4 were expressed in these tissues and in the lacrimal gland. Immunohistochemistry studies localized expression to the serous-type secretory end pieces. Coexpression of CST1 and CST4 was also observed in the epithelial lining of the gallbladder and seminal vesicle. The CST1 product was detected in the tracheal glands and CST4 in the kidney and prostate. Despite their different adult patterns of expression, analysis of CST1, 2, 4, and 5 mRNA levels in infant submandibular glands demonstrated a coordinate upregulation of expression of between 3.5 and 9 months of age. The patterns of cystatin gene expression are consistent with several proposed oral functions of the salivary cystatins but also suggest they are important in other locations and that, despite their close sequence similarity, they are individually specialized.

Limits to human locomotor performance: phylogenetic origins and comparative perspectives

Studies of human exercise physiology have been conducted from a largely ahistorical perspective. This approach usefully elucidates proximate limits to locomotor performance, but ignores potential sources of biomechanical and physiological variation that derive from adaptation to ancestral environments. Phylogenetic reconstruction suggests that multiple hominoid lineages, including that leading to Homo sapiens, evolved in African highlands at altitudes of 1000–2000m. The evolution of human locomotor physiology therefore occurred under conditions of hypobaric hypoxia. In contrast to present-day humans running on treadmills or exercising in otherwise rectilinear trajectories, ancestral patterns of hominid locomotion probably involved intermittent knuckle-walking over variable terrain, occasional bouts of arboreality and an evolving capacity for bipedalism. All such factors represent potential axes of locomotor variation at present unstudied in extant hominoid taxa. As with humans, hummingbirds evolved in mid-montane contexts but pose an extreme contrast with respect to body size, locomotor mode and metabolic capacity. Substantial biomechanical and physiological challenges are associated with flight in hypobaria. Nonetheless, hummingbird lineages demonstrate a progressive invasion of higher elevations and a remarkable tolerance to hypoxia during hovering. Upregulation of aerobic capacity and parallel resistance to hypoxia may represent coupled evolutionary adaptations to flight under high-altitude conditions.

Human obesity: an evolutionary approach to understanding our bulging waistline

The unique worldwide spread of the human species and the remarkably long post-reproductive survival show that our genome permits excellent adaptation to vastly different environments. Moreover, the main scourges of later age, namely malignant growths and atherosclerosis, appear in humans later than in shorter-living animals. In recent years, excess weight and obesity have become mass phenomena with a pronounced upward trend in all developed countries. However, despite the detrimental effects of being overweight, these populations live longer than ever, which in part may be explained by the availability of better medical treatment. The prevalence and predicted further spread of obesity can be understood in the light of evolution. In all animal species energy metabolism is asymmetric with energy accumulation ('thrifty genotype') being the necessary condition of survival during hard times. For humans, which are no different to other animals in this respect, this genetic programming was necessary for survival because during the course of history, including the recorded history in the more developed Middle East, Europe or China, there was never a long period of uninterrupted food abundance, whereas famines were regular and frequent. Therefore fat accumulation, when food was available, meant survival at times of shortage, while the possible detrimental effects of overindulgence in food and being overweight expressed in unrealistically old age were irrelevant. It is the central, mostly intra-abdominal fat (in both humans and animals) that is more medically important than the subcutaneous truncal fat, and the accumulation of both types of fat is conditioned by high food consumption; therefore it is a historic novelty for human populations. In contrast, lower-body fat in human females is unique in the animal kingdom: it is much less metabolically active, it is of much lower pathologic significance than central fat, and it is programmed to be mobilized mostly during pregnancy and lactation. In view of all this, norms of desired weight should be based on hard mortality and morbidity statistics and not on theoretical, esthetic or fashion considerations. By this criterion, the upper limit of desirable weight is likely to be body mass index (BMI) 27 or 28, but specified for different populations (sex, race, ethnic origin); moreover, with aging, the detrimental effects of obesity diminish and finally disappear. Risks of other pathologies related to obesity (e.g. diabetes, hypertension and coronary disease) are also population-specific. However, total fatness, measured by BMI, is insufficiently sensitive as a risk factor, and fat distribution (upper-body versus low-body type, as reflected by waist circumference and waist:hip ratio) plays at least as prominent a role. Therefore the detailed norms, not yet available, should take into account both general obesity and fat distribution and be specific for different populations. Since long-term weight loss in adults is rarely achievable, public health measures should be aggressively directed at the prevention of obesity from childhood.