Nutrition Epidemiology Highlights Review

Male longevity in Sardinia, a review of historical sources supporting a causal link with dietary factors

Abstract

The identification of a hot spot of exceptional longevity, the Longevity Blue Zone (LBZ), in the mountain population of Sardinia has aroused considerable interest toward its traditional food as one of the potential causal factors. This preliminary study on the traditional Sardinian diet has been supported by the literature available, which has been carefully reviewed and compared. Up to a short time ago, the LBZ population depended mostly upon livestock rearing, and consumption of animal-derived foods was relatively higher than in the rest of the island. The nutrition transition (NT) in urbanized and lowland areas began in the mid-1950s, fueled by economic development, whereas in the LBZ it started later owing to prolonged resistance to change by a society organized around a rather efficient pastoral economy. Even nowadays a large proportion of the population in this area still follows the traditional diet based on cereal-derived foods and dairy products. The LBZ cohorts comprising individuals who were of a mature age when NT began may have benefited both from the high-quality, albeit rather monotonous, traditional diet to which they had been exposed most of their life and from the transitional diet, which introduced positive changes such as more variety, increased consumption of fruits and vegetables and moderate meat intake. It could be speculated that these changes may have brought substantial health benefits to this particular aging group, which was in need of nutrient-rich food at this specific time in life, thereby resulting in a decreased mortality risk and, in turn, life-span extension.

Introduction

Among the populations bordering the Mediterranean Sea, the one living in the central-eastern mountain area of Sardinia occupies a special place because it harbors a hot spot of exceptional longevity known as the ‘Longevity Blue Zone’ (LBZ), which displays one of the highest concentrations of centenarians in the world, whose ages have been thoroughly validated. The longevity of this population shows a noticeable gender equality, instead of the usual women's advantage, a finding that prompted intensive research aimed at identifying the underlying causes.1 Beyond the potential role of inherited traits of the population and physical environment, considerable interest has grown to evaluate whether modifiable factors, such as nutrition and lifestyle,2 may have had a role in the LBZ longevity and particularly in its surprising bias toward men. In a recent ecological study based on historical data,3 we emphasized that the main economic activity in the LBZ was animal husbandry, whereas in the rest of the island it was agriculture. This finding raises the question of whether the superior longevity recorded in the LBZ may be linked in some way to the high proportion of shepherds and whether their lifestyle could be healthier compared with other occupational groups. Unfortunately, most studies conducted so far on the potential relationships between nutrition/lifestyle and longevity in Sardinia have been limited to the analysis of the current diet of sporadic long-lived subjects4 and have largely ignored the dietary differences in specific population subgroups, as well as dietary changes over a wide period of time. In particular, the nutrition transition (NT), which for the whole of Sardinia started in early 1950s while in the mountain area a few decades later, was not adequately explored apart from a few exceptions.5, 6

The aim of this contribution is to review the scientific literature on the traditional nutrition habits in Sardinia and their changes during NT based on works published over a century (Table 1). Research carried out by Silla Lissia,7 Tore,8 Tivaroni,9 Fermi10 and Peretti11 provides a quite reliable picture of nutrition in Sardinia before NT, whereas the works of Peretti,12 Brotzu,13 Carbini14 and Tessier5, 6 allow us to reconstruct the diet during NT, as well as the differences between population subgroups characterized by distinct occupation and lifestyle who later showed remarkable survival differences. In particular, four issues will be addressed: (i) the overall pretransition dietary pattern in Sardinia; (ii) the possible association of NT with the recent rise of longevity in the mountainous area of the island; (iii) the dietary differences within population subgroups according to occupation, gender and geographic location; and (iv) the potential role of specific aspects previously related to longevity and their relevance in the traditional Sardinian diet as determinants of health improvement and, in turn, of the increased life expectancy among the male population.

Table 1 Historical sources of information about nutrition in Sardinia

Methods

This review is a structured search of any historical publication on nutrition found in the main Sardinian libraries, including the ones from the University of Sassari and Cagliari. Research was conducted from early 19th century up to the 1950s by two independent reviewers. Chapters containing descriptions of food habits in Sardinia written in several languages were selected. Initial selection was based on title screening, followed by full-text reading of potentially relevant nutrition information. Table 1 displays the historical sources of information selected in this review. The merit of this compilation of historical data lies in the fact that it is the first attempt to compare the material of these valuable sources of information about the traditional Sardinian population to elucidate the influence of nutritional factors in male longevity in the LBZ of Sardinia.

History of Sardinian food culture in pretransition era

The island of Sardinia is located in the western Mediterranean basin 120 km off the Italian coasts. Over several centuries, it experienced nearly complete isolation and remained sparsely populated owing to a concurrence of factors including poor sanitation, endemic malaria and failure to exploit effectively the territory's resources.15 Although several foreign people attempted to colonize the island, they were never able to penetrate much beyond the coastal areas. A substantial proportion of indigenous people was forced to find refuge in the central mountains, the future LBZ, and to develop a unique culture and diet (the latin diæta means literally ‘a way of living’).16 This mountain population, considered as ‘barbarian’ by the ancient Romans (hence the name of Barbagia given to this inner part of the island), remained relatively independent and developed its own food traditions—primarily based on livestock raising, which has lasted until now. In contrast, the inhabitants of plains and coasts continued the agricultural traditions of the Roman Empire, for which the island was famous for many centuries as an important cereal supplier to the Italian peninsula.17 Until the mid-19th century, little is known about the staple diet in Sardinia, except for sparse accounts found in legal documents (‘Condaghes’) drawn up in monasteries18 or included in the reports of the Spanish viceroys.19 Although a first detailed description of the diet among the Sardinian population can be found in mid-19th century in the work of Angius,20 it is only in the first half of the 20th century that nutritional reports using good scientific standards were available.7, 8, 9, 10, 11, 12, 21

Overall, the Sardinian diet until half a century ago followed the Mediterranean diet model, although there were large internal variants depending on local economy and use of land. In Figure 1, the Sardinian food consumption in pre-NT era, according to the nutritionist Peretti,11 is compared with the overall average food availability in the Data Food Networking (DAFNE) project.22

Figure 1
figure1

Deviation (%) of the daily individual food availability in Sardinia before NT from the overall mean in Mediterranean countries. The reference circle of radius 100% indicated in the figure corresponds to the total DAFNE mean22 and the spikes represent the deviation of specific food group means.

As mentioned by the French geographer Maurice Le Lannou,21 the traditional Sardinian diet has always been ‘remarkably frugal’, and in rural areas it reflected the diffuse poverty of the population and scarcity of market exchanges. Up to the NT, the traditional economy largely favored the consumption of self-produced food. Main foods were derived from cereals (wheat, barley and more rarely corn), legumes, potatoes and dairy products. Two vitally important foods were widely consumed throughout the island, that is, sourdough-leavened bread and vegetable soup (minestrone) that contained fresh vegetables (onions, fennels, carrots, celery) and pulses (beans, fava beans, peas). In the mountain area (Ogliastra), that soup also included some tubers (potatoes) and pork stock.20 Honey was generally used as a sweetener. As a rule, before NT, fresh fruit was consumed almost everywhere in modest amounts, because fruit crops were not extensively cultivated up to the post-war era. However, wild fruits such as cactus pear (Opuntia ficus-indica) and arbutus (Arbutus unedo L.), endemic throughout the island, were occasionally consumed by shepherds and field workers.19 In addition, they would integrate their daily diet with native herbs, the knowledge of which was handed down from father to son, as was customary in many Mediterranean countries.23 The consumption of chestnuts and walnuts was typical of the population of highland villages and provided a substantial calorie intake, as well as monounsaturated fatty acids and minerals, during the winter period.21 Seasonal fruit (figs, grapes) was frequently dried so that it could be consumed throughout the year. On the basis of reports from the mid-19th to mid-20th century, meat consumption by the rural population rarely exceeded 2–4 servings per month,20 and most often it consisted of sheep and pork among shepherds, and sheep and poultry among peasants.11 The consumption of dairy products, both from goats and sheep, was higher in the mountains;20 however, rather than mature cheese, mostly intended for sale, people made extensive use of ricotta (whey cheese, dried curd) and a sort of fresh sour cheese called casu ajedu, which was rich in Lactobacilli. Food intake exceeding the usual moderation was limited only to the greatest religious or civil feasts such as sheep shearing.8 The consumption of fish and seafood in Sardinia before NT was surprisingly low in the inland parts of Sardinia, because of the diffuse communication barriers between the coast and the mountains, as well as because of the widespread lack of refrigeration devices.24 Fish consumption was almost exclusively limited to the villages along the rivers, to the coastal population where fishermen communities existed13, 25 and to the well-off population in main cities and monasteries.8, 18 Wine consumption in Sardinia before NT was quite below the Italian average in the same period (80 vs 100 lt/person/years),3, 26 with a slightly higher, but not significant, consumption in lowland areas3, 11 (Figure 1). In addition, gardening, rearing domestic pigs and sheep (‘mannalitha’) and extensive hunting often complemented the average food intake of families.8 According to Peretti,11 the major discrepancy between the lowland areas, where peasants were the majority of the population, and the mountain areas, essentially pastoral, was the relatively superior consumption of animal-derived foods in the latter (Table 2).

Table 2 Everyday consumption of food in 28 peasant and 17 shepherd families in the Barbagia district in the pre-WWII era11

In the urban areas, the energy intake was higher. Although average energy intake was 10.04 MJ (2400 kcal) per person/day for the whole Sardinia population,9 as reported by Tivaroni in 1924, in the city of Sassari in 1929 the intake ranged between 11.73 MJ (2802 kcal) per person/day and 13.16 MJ (3144 kcal) per person/day among the working class and the upper class, respectively.13 In 1938, Brotzu reported values ranging from 9.81 to 13.39 MJ (2344–3201 kcal) per person/day among the craftsmen and from 11.47 to 16.99 MJ (2740–4058 kcal) per person/day among the well-offs of Cagliari, the island's largest city.27 In the latter study, the average caloric intake for the whole population was 10.24 MJ (2445 kcal) per person/day, very close to that reported by Tivaroni in 1924 and slightly lower than the Italian average of 10.89 MJ (2600 kcal) per person/day in the same period,9 and it could actually be explained by the smaller body size of Sardinians compared with mainland Italians.3

NT in sardinia

The NT is defined as a sequence of dietary and nutritional patterns resulting from large shifts in the global structure of the diet, related to changing economic, social, demographic and health factors.28 Although in the first half of the last century Sardinia was considered an underdeveloped region compared with the rest of Italy, after WWII it recovered slowly and benefited from the marked economic and social advancement of the mainland. Yet, compared with the other Italian regions, Sardinia experienced modernity later, around the mid of 1950s,5 and in some internal areas such as the LBZ it is still ongoing. In 1952, about 45% of the active Sardinian population still owed their livelihood to agriculture and animal farming, and only 28% to industry (in 1936, the percentages were 57 and 20%, respectively).

The changes in the overall Sardinian dietary structure were influenced by various socioeconomic factors: (i) a rapid increase of the average family income, also owing to the return of emigrants with enhanced spending power; (ii) a progressive reduction of self-produced foods resulting from the decreased population directly involved in agropastoral activities; (iii) changes in the role of women who entered the work market for the first time and had to face the reduced availability of time for domestic tasks, including food preparation; and (iv) pressure by the media to adopt non-Mediterranean diet dietary models.14 The population living in urban areas and in the lowland villages were the first to experience the effects of increased food choice. The major modifications in their diet in the 1950s entailed the following: (i) generalized overeating and replacement of pulses soup with higher-calorie foods (meat, pasta) in the everyday diet; and (ii) progressive rise in the consumption of fresh fruits and vegetables (+60%), olive oil (+56%), beef meat (+55%) and fish (+50%) and reduction of the consumption of lard (–80%), potatoes (–45%) and pulses (–42%).5 Although in 1947 the total energy intake per capita had dropped to 7.54–8.37 MJ (1800–2000 kcal) per person/day reflecting the immediate post-war food insecurity,13 in 1952 it returned to the pre-war levels of 10.05 MJ (2400 kcal) per person/day and in 1959 it ranged from 11.04 to 16.39 MJ (2637–3915 kcal) per person/day.29

Overall, during the NT, there has been a remarkable increase in protein intake, an increase of 13–25% in the percentage of fats and a decreased intake of carbohydrates. It is noteworthy that the lipid contribution to the Sardinian energy remained quite low (13–16%) during the early stages of NT. Table 3 illustrates these changes. The consumption per capita of some high-energy foods was still lower than in the other Italian regions. In particular, the overall intake of meat was only 77% of the Italian average, although in the LBZ the figures were much higher owing to the consumption of sheep and goat meat not registered in official statistics. The same could be said about milk and its derivatives, as Tivaroni in 1921 estimated a 79% higher dairy intake in Sardinia as a whole compared with the Italian mainland.9

Table 3 Nutrient intake in Sardinia and Italy in 195229

In the LBZ and, more in general, in the mountain area, geographical isolation, strong cultural resistance to change and persistence of nomadic shepherding determined a considerable forward time shift of NT compared with the rest of the island. As a consequence, the LBZ generations born at the end of the 19th century may have experienced a prolonged exposure to the traditional diet, as they were already aged between 60 and 80 years when NT began. Even though the population of the LBZ followed the traditional lifestyle for a longer time, however, some changes have been documented here as well, such as the increased consumption of vegetables, olive oil and meat, with a prevalence of chicken over beef meat, as well as a reduction in the consumption of milk (–18%) in favor of soft cheese, cottage cheese and yoghurt.5

Nutritional differences in Sardinia according to the traditional occupation and gender

Shepherds vs peasants

The population living in the central mountains of Sardinia, and particularly in the LBZ, exhibits a lifestyle that is rather different from the rest of the island. As the cereal-based agriculture inherited by the Roman Empire was quite incompatible with the mountain soil, these people tried to maintain the pre-Roman traditions up to WWII.21 Being essentially a community of nomadic shepherds,30 over the centuries they adopted eating patterns that differed from the Mediterranean diet, therefore a comparison between their food habits and those of lowland peasants is worthwhile. As shown in Table 2, in both populations, the major contribution originated from carbohydrates, that is, 61.2% among shepherds compared with 68.0% among peasants, whereas protein intake was 19 and 16%, respectively.11, 14 According to the survey of Peretti in 1938, the pastoral population showed a higher (>20%) consumption of animal protein.11 Although animal-derived foods were a forced choice for Sardinian shepherds in the pre-NT era, owing to the constraints inherent to transhumant shepherding, it nearly always implied a higher consumption of dairy products rather than meat and meat products, the intake of which was below the average of other Mediterranean countries10, 21 (Figure 1). Despite the large intake of dairy products, the energy from fats was quite low, both among shepherds and peasants (19 and 14%, respectively). The superior quality of nutrients among shepherds compared with peasants may have had an impact on the overall LBZ population health, and it is likely to reflect the difference in body parameters observed historically between the two groups (Table 4). Indeed, body height among male shepherds was more than 3 cm higher than among peasants, whereas body weight was 7 kg heavier in favor of shepherds.11 The data show that already in the 1930s shepherds in the mountainous area clearly exhibited indicators of a more nutritious diet, such as muscle mass and amount of adipose tissue, compared with peasants living in the plains. However, in the normal range, the body mass index was higher in shepherds (23.5 kg/m2) than in peasants (21.5 kg/m2). This is not in contrast with recent studies suggesting that shorter people live longer.31, 32 As Sardinians are on average shorter than their Italian peers, it has been suggested that a lower body size may have had some role in their longevity.33 Although acknowledging that in genetically predisposed individuals short stature may indicate the potential for greater longevity, we emphasize that in the case of Sardinians it did not arise from undernourishment.

Table 4 Differences in nutritional status and body composition in Sardinian shepherds and peasants in 1938 according to Peretti11

Gender differences in nutrition

As exceptional longevity in central Sardinia affects mainly the male population, it is worthwhile to examine the role of the diet according to gender. In this region, 77% of women have never worked outside the home and could devote more time to self-production of food.5 Differences between the diet of men and women in traditional Sardinia have been mentioned already in the work of Peretti11 who reported that the diet of women was closely related to their social background and especially to the occupation of the family head. According to this author, the nutritional status of women was significantly better in the pastoral than in the agricultural setting (Table 4). In particular, he noticed that the nutritional status of shepherd women was substantially similar compared with shepherd men (P=0.555), whereas it was significantly better than that of peasant women (P=0.013). In addition, some indicators of body fitness, such as body height and muscle mass, were also better in women who lived within a shepherds' household. However, body fitness may not have been entirely dependent on nutritional factors but on physical activity as well, as body dimorphism decreases if men and women are allowed the same opportunities to exercise.34 Although direct evidence is no longer available, the traditional pastoral setting, which traditionally implied the absence of men for 6–9 months of the year, may have implied a stronger constraint to practice extra outdoor physical activity for shepherd women compared with peasant women, although lower than that performed by men engaged in nomadic shepherding.2 These data are consistent with the findings of our recent ecological study that revealed a strong correlation between body robustness, diet quality and longevity among men.3

The work of Peretti also revealed that shepherd women carried relatively more adipose tissue than peasant women (Table 4), implying a greater-than-zero energy balance attributable to the pastoral setting. Hence, the same author inferred the higher nutritional quality of the average shepherd’s diet over that of peasants. In addition, he provided evidence of a greater prevalence of tooth decay among peasant women, which might indicate a gender-related deficiency of calcium during pregnancy and lactation, from which shepherd women were exempted. The finding of an association between a better nutritional status among male shepherds with a significant life-span extension in this population group does not necessarily imply causation. Notwithstanding, it is reasonable that such a nutritious diet, both qualitatively and quantitatively, could have acted at least as a health-promoting factor in the presence of other predisposing factors such as physical activity, low stress levels and strong community support. As for women, it can be postulated that they may have gained in terms of health and fitness from their nearness to an environment providing a healthier diet, yet their gain in longevity appears to have been lower than in men, perhaps because of interference with specific anthropological factors acting at the local level.2 Indeed, the remarkable gender equality in survival observed nowadays in the LBZ is clearly owing to an advantage of men and may have been modulated by complex interactions of a wide spectrum of factors and not only on dietary ones. In addition, a healthier nutrition among fertile shepherd women may have had positive consequences, as in utero conditions related to mother's nutritional status have been reported to have a role in the later risk of developing nontransmissible diseases in adult life.35 According to this hypothesis, shepherds' wives might have benefited from extra dietary resources, allowing them to give birth to offspring inherently more resistant and less susceptible to developing chronic degenerative diseases in adulthood. This hypothesis is supported by recent epigenetic studies. Finally, a gender-related issue, which would deserve further research, is the fact that the women residing in the LBZ before NT were the custodians of their culinary culture and self-production of food, and could have transmitted this knowledge to other family members, especially daughters.5, 6

Specific role of some dietary factors in Sardinian longevity

Specific dietary factors such as calorie restriction,36 low meat and fat consumption,37 drinking red wine38 and the widespread use of fermented foods,39 which have been previously linked to increased longevity in other populations, are briefly discussed as to what extent they may have influenced Sardinian longevity.

As for calorie restriction, although it is true that up to the turn of 19th century the nutrition of the Sardinian population was rather precarious, with diffuse malnutrition in the poorest plain areas and suburbs, the food availability has always been wider in the pastoral highlands, which relied on a more secure traditional economy. In addition, the calorie intake in the Sardinian diet had risen in the first quarter of the 20th century (Table 2), and it has progressively approached the level of other Italian regions so that, in 1924, the average energy intake in Sardinia was only 7% lower than in Italy in the same period: 10.04 vs 10.87 MJ (2400 vs 2600 kcal) per person/day.9, 13 Thus, we believe that the energy intake was appropriate for maintaining a smaller-than-average body size in relation to the level of energy expenditure.

A diet high in animal proteins has been considered to be harmful until now,40 as it may increase the incidence of CV disease41 and some types of cancers,42 as well as the overall mortality risk. In addition, regimes implying moderate or low intake of animal proteins have been described in other longevity areas such as Loma Linda (USA),43 which favors a vegetarian diet, Okinawa,44 Ikaria45 and Nicoya.46 We found that among Sardinian highlanders, the generations that were in their old age during NT experienced an increased capability for the acquisition of animal proteins, which might have contributed to delaying the onset of sarcopenia and osteopenia.47 These findings are consistent with the results of NHANES III study recently reported by Levine et al.48 showing that higher protein intake is associated with significantly increased risks of mortality only among people aged 50–65 years, whereas this effect is no longer observed among adults over the age of 65 years.

As for the role of antioxidants, red wine consumption has been postulated as one of the possible factors involved in longevity of LBZ Sardinians because of its content in resveratrol and proanthocyanidins.38, 49 Actually, resveratrol shows antioxidant properties only in vitro and is not capable of extending the life span of Caenorhabditis elegans50 or of rodents51 under conditions of oxidative stress, and therefore it is hardly probable that it can do this in humans. Moreover, in the ecological study, we have shown that the average intake of red wine was the same in the Sardinian LBZ as in the rest of the island, and the spatial distribution of wine consumption in the municipalities of the island does not exhibit a direct relationship to the longevity index.3 Awaiting further data, no scientific evidence of any benefit of red wine consumption on Sardinian longevity is currently available.

With regard to fermented foods, bread has for long formed a part of the staple diet of the Sardinian population, and its daily consumption before NT could have exceeded 500 g (Table 2). The potential proinflammatory effect of this high-carbohydrate diet was likely counterweighted by the intense physical activity of the majority of subjects, especially the ones involved in long-distance transhumance. Traditionally, bread was prepared from whole grains with ‘homemade’ microbial starters containing Lactobacilli. This type of traditional bread had chemical and physical characteristics that were rather different from bread bought from bakeries, where leavening is carried out with baker's yeast. We have demonstrated that this type of bread is able to reduce postprandial glucose and insulin blood levels by 25%, thereby being potentially able to preserve the function of pancreatic insulin-secreting cells and prevent obesity and diabetes.52 However, in the past 40 years, nearly everywhere in Sardinia, even in the LBZ, sourdough bread was replaced with bread leavened with baker's yeast containing Saccharomyces cerevisiae, the nutritional value of which is inferior. As already mentioned, in Sardinia, grain farming was traditionally accompanied by a significant production of barley, more suitable for the land,53 which continued to be sown, especially in marginal mountain lands, even when in the rest of Sardinia its production had already decreased. Barley bread has a lower glycemic index and reduces cardiovascular disease risk.54

As for dairy products, in the LBZ, they were mostly from sheep and goats rather than cows, and included lactic acid-fermented varieties such as ‘casu ajedu’. Compared with the latter, goat's milk has a higher nutritional value55 and is more similar to human milk. Because of their reduced size and wider surface, fat globules of goat's milk are more easily digested by intestinal lipases; therefore, a diet based on goat's milk can improve lipid metabolism, especially by decreasing triglycerides. Owing to an increased biliary secretion of cholesterol, and its mobilization from deposits, goat's milk shows a hypocholesterolemic effect56 and may protect against cardiovascular disease. Goat's milk also has a high level of short- and medium-chain saturated fatty acids, such as butyric (C4:0), caproic (C6:0), caprylic (C8:0) and capric (C10:0), which are protective in regard to colon carcinogenesis.57, 58 The high content of carnitine in goat milk also permits optimum utilization of fatty acids into mitochondria, thereby limiting the availability of substrates for lipid peroxidation and ultimately improving the overall cell metabolism.59, 60

The higher content in calcium and phosphorus of goat's milk may have preserved the LBZ population from the loss of bone tissue and consequently the risk of fractures during senescence, and it is consistent with the higher vitamin D levels and lower frequency of bone fractures among Sardinian centenarians.61 Goat's milk is also rich in zinc and selenium, which are essential for optimal immune system activity and promote healthy aging.62

All these beneficial effects of goat's milk and derivatives could explain why a population, such as that living in the LBZ, traditionally consuming large amounts of this product may have been favored in escaping major age-related diseases. Nevertheless, further research is necessary to clarify the role of goat's milk as a source of health and especially in survival to advanced age.

Conclusion

The population living in the mountainous area of Sardinia, the ‘Longevity Blue Zone1 is known for having one of the highest concentrations of oldest olds in the world. Its longevity is likely a multifaceted phenomenon that requires a research approach designed with a multidisciplinary strategy.2

From a broader perspective, a thorough in-depth analysis of Sardinian data and well-designed prospective studies are needed to address the classic dilemma of nature vs nurture. In this review, we have considered the available historical data on nutrition in Sardinia, explored the temporal changes in food patterns (that is, the NT), compared occupation and gender differences on nutritional status and discussed the possible role of diet as causal factor on the longevity of its population, whereas genetic, socioeconomic and environmental factors were beyond the objectives of this work. Despite certain caveats due to the scarcity of the literature consulted and to the outdated scientific standards of the oldest works, this review gives an overview of the virtues of the nutrient-rich, traditional LBZ diet. However, negative aspects were also present in the LBZ diet, such as the low food variety and the excess of carbohydrate intake. Undeniably, the diet greatly improved during NT (for example, higher food availability, increased consumption of olive oil, fruits and vegetables and—outside the LBZ—fish), but the NT also contributed to a gradual process of ‘westernization’ of the Sardinian diet albeit slower than in other Mediterranean islands.5 However, during the early stages of NT, the two models were overlapping and complemented each other, probably resulting in health improvement and even life extension. Consequently, we conjecture that the cohorts that were at the ripe of old age during the early stage of epidemiological and nutritional transition have been in the unique position to take full advantage from both the traditional and the changing diet. Under these circumstances, this may have resulted in a rapid improvement of nutritional status of the population and, in the long run, of their global health. In particular, easier access to animal products provided by the NT may have allowed an increasing proportion of aging Sardinians to escape from the aged-related loss of skeletal muscle mass (sarcopenia), thereby reducing the incidence of physical disability later in life. The importance of higher protein intake in the elderly has been previously underlined.63

If this hypothesis is true, it implies that the health benefits of the diet during NT are inherently a transient phenomenon that primarily has affected the generations born at the end of the 19th century, but not necessarily those born earlier or later. When compared with the population of the LBZ, those living in the rest of Sardinia had experienced the NT earlier, and their actual diet could have already been burdened with unhealthy aspects, which might explain—at least partly—the fact that people living on coasts, lowlands and in cities attain exceptional longevity less frequently. Yet, it is possible that a unique combination of nutritional factors resulting from a delayed NT in the LBZ may have produced a significant life-prolonging effect in a genetically predisposed population. Of course additional modifying elements such as improvements in food preservation, sanitation, availability of vaccines, effective medical treatment, population screening for nontransmissible diseases and decreased smoking habits eventually determined a high quality of health in the LBZ. At the moment what can be cautiously said is that this unique population exposed for most of their life to a less varied but high-quality diet could have found in the NT the additional health-promoting factors to prolong their life span. We still need to wait for further research, including an individual assessment of the dietary habits of LBZ long-lived inhabitants, to look for any shared pattern.

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Acknowledgements

We are grateful to Dr Maria Rosaria Manunta of the Sassari University Library for her assistance in retrieving historical documents.

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Pes, G., Tolu, F., Dore, M. et al. Male longevity in Sardinia, a review of historical sources supporting a causal link with dietary factors. Eur J Clin Nutr 69, 411–418 (2015). https://doi.org/10.1038/ejcn.2014.230

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