S. Boyd Eaton

Women's Reproductive Cancers in Evolutionary Context

Reproductive experiences for women in todays affluent Western nations differ from those of women in hunting and gathering societies, who continue the ancestral human pattern. These differences parallel commonly accepted reproductive risk factors for cancers of the breast, endometrium and ovary. Nutritional practices, exercise requirements, and body composition are nonreproductive influences that have been proposed as additional factors affecting the incidence of womens cancers. In each case, these would further increase risk for women in industrialized countries relative to forager women. Lifestyles and reproductive patterns new from an evolutionary perspective may promote womens cancer. Calculations based on a theoretical model suggest that, to age 60, modern Western women have a breast cancer risk as much as 100 times that of preagricultural women.

An evolutionary perspective on human physical activity: implications for health

At present, human genes and human lives are incongruent, especially in affluent Western nations. When our current genome was originally selected, daily physical exertion was obligatory; our biochemistry and physiology are designed to function optimally in such circumstances. However, todays mechanized, technologically oriented conditions allow and even promote an unprecedentedly sedentary lifestyle. Many important health problems are affected by this imbalance, including atherosclerosis, obesity, age-related fractures and diabetes, among others. Most physicians recognize that regular exercise is a critical component of effective health promotion regimens, but there is substantial disagreement about details, most importantly volume: how much daily caloric expenditure, as physical activity, is desirable. Because epidemiology-based recommendations vary, often confusing and alienating the health-conscious public, an independent estimate, arising from a separate scientific discipline, is desirable, at least for purposes of triangulation. The retrojected level of ancestral physical activity might meet this need. The best available such reconstruction suggests that the World Health Organizations recommendation, a physical activity level of 1.75 ( approximately 2.1 MJ (490 kcal)/d), most closely approximates the Paleolithic standard, that for which our genetic makeup was originally selected.

The ancestral human diet: what was it and should it be a paradigm for contemporary nutrition?

Awareness of the ancestral human diet might advance traditional nutrition science. The human genome has hardly changed since the emergence of behaviourally-modern humans in East Africa 100-50 x 10(3) years ago; genetically, man remains adapted for the foods consumed then. The best available estimates suggest that those ancestors obtained about 35% of their dietary energy from fats, 35% from carbohydrates and 30% from protein. Saturated fats contributed approximately 7.5% total energy and harmful trans-fatty acids contributed negligible amounts. Polyunsaturated fat intake was high, with n-6:n-3 approaching 2:1 (v. 10:1 today). Cholesterol consumption was substantial, perhaps 480 mg/d. Carbohydrate came from uncultivated fruits and vegetables, approximately 50% energy intake as compared with the present level of 16% energy intake for Americans. High fruit and vegetable intake and minimal grain and dairy consumption made ancestral diets base-yielding, unlike todays acid-producing pattern. Honey comprised 2-3% energy intake as compared with the 15% added sugars contribute currently. Fibre consumption was high, perhaps 100 g/d, but phytate content was minimal. Vitamin, mineral and (probably) phytochemical intake was typically 1.5 to eight times that of today except for that of Na, generally <1000 mg/d, i.e. much less than that of K. The field of nutrition science suffers from the absence of a unifying hypothesis on which to build a dietary strategy for prevention; there is no Kuhnian paradigm, which some researchers believe to be a prerequisite for progress in any scientific discipline. An understanding of human evolutionary experience and its relevance to contemporary nutritional requirements may address this critical deficiency.

Paleolithic Nutrition: Twenty-Five Years Later

A quarter century has passed since the first publication of the evolutionary discordance hypothesis, according to which departures from the nutrition and activity patterns of our hunter-gatherer ancestors have contributed greatly and in specifically definable ways to the endemic chronic diseases of modern civilization. Refinements of the model have changed it in some respects, but anthropological evidence continues to indicate that ancestral human diets prevalent during our evolution were characterized by much lower levels of refined carbohydrates and sodium, much higher levels of fiber and protein, and comparable levels of fat (primarily unsaturated fat) and cholesterol. Physical activity levels were also much higher than current levels, resulting in higher energy throughput. We said at the outset that such evidence could only suggest testable hypotheses and that recommendations must ultimately rest on more conventional epidemiological, clinical, and laboratory studies. Such studies have multiplied and have supported many aspects of our model, to the extent that in some respects, official recommendations today have targets closer to those prevalent among hunter-gatherers than did comparable recommendations 25 years ago. Furthermore, doubts have been raised about the necessity for very low levels of protein, fat, and cholesterol intake common in official recommendations. Most impressively, randomized controlled trials have begun to confirm the value of hunter-gatherer diets in some high-risk groups, even as compared with routinely recommended diets. Much more research needs to be done, but the past quarter century has proven the interest and heuristic value, if not yet the ultimate validity, of the model.

Estimated macronutrient and fatty acid intakes from an East African Paleolithic diet

Our genome adapts slowly to changing conditions of existence. Many diseases of civilisation result from mismatches between our Paleolithic genome and the rapidly changing environment, including our diet. The objective of the present study was to reconstruct multiple Paleolithic diets to estimate the ranges of nutrient intakes upon which humanity evolved. A database of, predominantly East African, plant and animal foods (meat/fish) was used to model multiple Paleolithic diets, using two pathophysiological constraints (i.e. protein < 35 energy % (en%) and linoleic acid (LA) >1.0 en%), at known hunter-gatherer plant/animal food intake ratios (range 70/30-30/70 en%/en%). We investigated selective and non-selective savannah, savannah/aquatic and aquatic hunter-gatherer/scavenger foraging strategies. We found (range of medians in en%) intakes of moderate-to-high protein (25-29), moderate-to-high fat (30-39) and moderate carbohydrates (39-40). The fatty acid composition was SFA (11.4-12.0), MUFA (5.6-18.5) and PUFA (8.6-15.2). The latter was high in α-linolenic acid (ALA) (3.7-4.7 en%), low in LA (2.3-3.6 en%), and high in long-chain PUFA (LCP; 4.75-25.8 g/d), LCP n-3 (2.26-17.0 g/d), LCP n-6 (2.54-8.84 g/d), ALA/LA ratio (1.12-1.64 g/g) and LCP n-3/LCP n-6 ratio (0.84-1.92 g/g). Consistent with the wide range of employed variables, nutrient intakes showed wide ranges. We conclude that compared with Western diets, Paleolithic diets contained consistently higher protein and LCP, and lower LA. These are likely to contribute to the known beneficial effects of Paleolithic-like diets, e.g. through increased satiety/satiation. Disparities between Paleolithic, contemporary and recommended intakes might be important factors underlying the aetiology of common Western diseases. Data on Paleolithic diets and lifestyle, rather than the investigation of single nutrients, might be useful for the rational design of clinical trials.

Biological and Clinical Potential of a Palaeolithic Diet

Purpose: To explore the possibility that a Palaeolithic diet, i.e. one that corresponds to what was available in any of the ecological niches of pre‐agricultural humans (1.5 million–10,000 years bp), is optimal in the prevention of age‐related degenerative disease.Design: Literature review.Materials and Methods: Between 1985 and December 2002, more than 200 scientific journals in medicine, nutrition, biology and anthropology were systematically screened for relevant papers. Computer‐based searches and studies of reference lists in journals and books provided a vast number of additional papers.Results: Increasing evidence suggests that a Palaeolithic diet based on lean meat, fish, vegetables and fruit may be effective in the prevention and treatment of common Western diseases. Avoiding dairy products, margarine, oils, refined sugar and cereals, which provide 70% or more of the dietary intake in northern European populations, may be advisable. Atherosclerosis is highly dependent on dietary manipulation in a...

Comparison of current radiologic approaches to the diagnosis of pancreatic disease.

Abstract To assess prospective accuracy and clarify indications for diagnostic study, 45 patients suspected clinically of having pancreatic disease were studied by conventional barium examination of the upper gastrointestinal tract, hypotonic duodenography, selective angiography and selenomethionine isotope scanning. Duodenography achieved 78 per cent, isotope scanning 72 per cent, conventional upper gastrointestinal examination 57 per cent, and angiography 55 per cent correct prospective diagnoses. Isotope scanning produced most (19 per cent) false-positive and angiography most (38 per cent) false-negative interpretations (most of those falsely negative on angiography occurred in patients with pancreatitis). Specific diagnostic procedures should be chosen on the basis of the provisional clinical diagnosis. The most appropriate approaches appear to be duodenography and angiography for pancreaticoduodenal cancer, scanning and angiography for cancer of the body and tail, conventional upper gastrointestinal ...

Villous Adenomas of the Duodenum

Six cases of villous adenoma of the duodenum are described and compared to the 6 previously reported in the literature. The overall incidence of malignant degeneration is 46%, which is comparable to the incidence reported for villous tumors arising in the stomach (58%) and colon (34-79%). Duodenal villous adenomas are morphologically similar to their colonic counterparts. The cauliflower-like appearance so characteristic of these tumors is best delineated by hypotonic duodenography.

Evolution, body composition, insulin receptor competition, and insulin resistance.

OBJECTIVE Better understanding of the relationships between body composition and insulin resistance. RESULTS Average human adiposity and sarcopenia have attained unprecedented levels and the resultantly abnormal body composition distorts insulin receptor balance. Compared to evolutionary norms we now have too many adipocyte insulin receptors (in adipose tissue and liver) and too few myocyte insulin receptors. The bodys insulin receptors can be conceptualized as competing for insulin molecules released from the pancreas. When an insulin molecule docks on an adipocyte receptor, substantially fewer glucose molecules are cleared from the blood than when an insulin molecule docks on a myocyte insulin receptor. Populational insulin receptor imbalance would seem to parallel the secular rise in insulin resistance and offers an attractive pathophysiological explanation for the accompanying type 2 diabetes epidemic. CONCLUSION An evolutionary perspective regarding body composition, insulin receptor imbalance, and the consequent impact on carbohydrate metabolism should enhance public acceptance of recommendations to increase physical activity.

PREVALENCE OF DIVERTICULAR DISEASE, HIATUS HERNIA, AND PELVIC PHLEBOLITHS IN BLACK AND WHITE AMERICANS

Phleboliths, and especially diverticular disease and hiatus hernia, are rarer in developing countries than in economically more developed communities, but all three conditions were as common in Black as in White Americans. This finding suggests that they are due to environmental rather than to genetic causes. A deficient intake of dietary fibre may be the common factor predisposing to these three conditions.