Nonlinearity in the relationship between bone Sr/Ca and diet: Paleodietary implications

Strontium in archaeological human bones is widely, almost paradigmatically, used as a measure of the relative dietary abundances of plants and meat. Quantitative modeling reveals, however, that there is not a simple proportional relationship between bone strontium and the dietary plant/meat ratio. While knowledge of specific foods and their compositions may permit accurate calculation of average bone strontium levels, knowledge of bone strontium does not inversely allow accurate calculation of specific foods. Although bone strontium quantitatively reflects the average dietary Sr/Ca ratio, it is disproportionately sensitive to high-calcium foods and can be easily affected by minor dietary constituents and culinary practices. Bone strontium, and by analogy, barium, should be seen as a reflection of the high-mineral dietary components rather than a quantitative index of trophic position. © 1995 Wiley-Liss, Inc.     

Bone chemistry and prehistoric diet: strontium studies of laboratory rats

Strontium analysis of prehistoric human bone for the reconstruction of past diets is a relatively new technique in anthropology. In order to evaluate certain assumptions of the method, diets with low and high levels of strontium were fed to male, virgin female, and pregnant female laboratory rats. Analysis of the femurs of these rats by inductively coupled plasma/atomic emission spectrometry indicates that dietary intake is directly reflected in levels of strontium in bone ash. When dietary strontium levels were low, the observed ratio for bone:diet in the laboratory rats averaged 0.26, a value similar to that observed by other investigators. Among the groups fed high levels of strontium, pregnant females accumulated the most and virgin females accumulated the least strontium in bone. Males were intermediate. Gender differences in bone strontium among prehistoric human populations are considered in these terms.     

Bone strontium in pregnant and lactating females from archaeological samples

Because plants and animals consume or absorb different amounts of strontium and calcium, anthropologists are able to use strontium/calcium (Sr/Ca) ratios from archaeologically recovered human bone to estimate the relative contributions of meat and plants to paleodiets. Often females exhibit higher Sr/Ca ratios than males, a fact usually attributed to lower meat intake among women. However, in vivo and in vitro experiments with laboratory animals show that pregnancy and lactation elevate maternal bone strontium and depress maternal bone calcium because 1) strontium is discriminated against in favor of calcium in the transport of ions to the placenta and mammary glands and 2) pregnancy and lactation facilitate absorption of alkaline earth metals from the gut. In this study, bone Sr/Ca ratios and strontium concentrations were compared between reproductive-age females, postmenopausal females, and adult males from two late prehistoric Native American sites in Georgia: the King site (N = 43) and the Etowah site (N = 51). At the King site, the mean Sr/Ca ratio of females was over 14% greater than that of males. At Etowah, the mean strontium level of reproductive-age females exceeded that of postmenopausal females by almost 25%. Most of the difference, it is argued, is due to pregnancy and lactation. A dietary preference among pregnant and lactating women for foods high in alkaline earths, particularly nuts and corn, may also be partially responsible. Until we assess the influence variables other than nutrition exert on trace element concentrations, our reconstructions of paleodiets will be suspect.     

Palaenutritional studies on skeletal remains of ancient populations from the Mediterranean area: an attempt to interpretation

As indicators of dietary status, standardised levels of strontium and zinc in specimens of bones from several prehistoric and historic sites in Europe are compared. The bone level of strontium reflects the vegetable intake in the diet, the level of zinc that of foods of animal origin. The large quantities of plants in the diet of palaeolitic hunters gave way in the mesolithic to an almost exclusively vegetarian diet, but then an increase in meat consumption in the neolithic. Agricultural economies characterised classical Greece and Rome, but the big towns were able to maintain a mixed diet. In the early centuries AD there was a decline in agricultural consumption.     

Strontium ranelate--a promising therapeutic principle in osteoporosis

Strontium ranelate (2g/day) appears to be a safe and efficient treatment of osteoporosis (OP), reducing the risks of both vertebral and non-vertebral fractures (including hip) in a wide variety of patients. Thus, the agent can now be considered as a first-line option to treat women at risk of OP fractures, whatever their age and the severity of the disease. A long-term treatment with strontium ranelate in OP women leads to a continued increase in bone mineral density at spine and hip levels, and a sustained antifracture efficacy. The mode of action of strontium ranelate involves a dissociation between bone resorption and formation, as the bone formation rate is increased and not influenced by the antiresorptive action of the agent. Strontium is heterogeneously distributed in bone tissue: it is absent from old bone tissue and is exclusively present in bone formed during the treatment. Total area containing strontium in bone tissue increases during treatment, although the focal bone strontium content is constant. Whatever the duration of treatment and the content of strontium in bone, the degree of mineralization is maintained in a normal range. Furthermore, no change at crystal level is detected up to 3 years of treatment.     

The use of strontium and barium analyses for the reconstruction of the diet of the early medieval coastal population of Gdańsk (Poland): A preliminary study

Barium and strontium analyses yield an important perspective on temporal shifts in diet in relation to social and environmental circumstances. This research focuses on reconstructing dietary strategies of individuals in the early medieval (12-13th century) population of Gdańsk on the coast of the Baltic Sea. To describe these strategies where seafood rich in minerals was included in the diet, levels of strontium, barium, calcium and phosphorus were measured in first permanent molars of adult men and women whose remains were excavated from the churchyard in the city centre. Faunal remains from the excavation were analysed as an environmental background with respect to the content of the above-mentioned elements. The impact of diagenesis on the odontological material under study was also determined by an analysis of the soil derived from the grave and non-grave surroundings. For verification of diagenetic processes, the calcium/phosphorus index was used. Strontium, calcium, phosphorus and barium levels were determined with the spectrophotometric method using the latest generation plasma spectrophotometer Elan 6100 ICP-MS. From the results of the analysis of taphonomic parameters such as the soil pH, potential ion exchange in the grave surroundings and the Ca/P ratio, it can be inferred that diagenetic factors had little impact on the studied material. From this pilot study we can conclude that in the early Middle Ages in the Baltic Sea basin, seafood was included in the diet from early childhood and at the same time the diet contained calcium-rich milk products (also rich in minerals). The lack of sex differences may indicate the absence of a sex-specific nutritional strategy in childhood and early adolescence.     

河南淇县宋庄东周墓地人骨稳定同位素分析——东周贵族与殉人食谱初探

淇县宋庄东周墓地出土贵族和殉人骨骼遗存的稳定同位素分析是国内首例针对东周社会分化背景下不同社会阶层先民开展的食谱研究。稳定碳氮同位素分析结果表明,贵族阶层在主粮和肉食方面与殉人群体明显不同。贵族几乎完全以粟为主粮,食物中肉类含量很高;而殉人阶层整体食肉水平较低,主粮的内部差异显著,大部分个体都不同程度的食用了当时不受青睐的小麦。食谱特征也暗示殉人阶层内部存在地位差异;殉人的食谱特征与同时期城市居民相似,表明他们生前可能跟随贵族居住在城市里,饮食生活状况与普通城市居民相近。这些结果表明东周时期的社会高度分化对先民食物资源分配产生了直接影响。宋庄人群的同位素数据进一步证实小麦在东周时期主要是被社会底层人群食用,为研究古代北方农业结构以及小麦在北方饮食中的扩散过程提供了重要线索。     

Effects of oral supplementation with stable strontium

The biologic effects of stable strontium, a naturally occurring trace element in the diet and the body, have been little investigated. This paper discusses the effects of oral supplementation with stable strontium in laboratory studies and clinical investigations. The extent of intestinal absorption of various doses of orally administered strontium was estimated by determining serum and tissue levels with atomic absorption spectrophotometry. The central observation is that increased oral intake produces a direct increase in serum levels and intracellular uptake of strontium. The results of these studies, as well as those of other investigators, demonstrate that a moderate dosage of stable strontium does not adversely affect the level of calcium either in the serum or in soft tissues. In studies of patients receiving 1 to 1.5 g/d of strontium gluconate, a sustained increase in the serum level of strontium produced a 100-fold increase in the strontium:calcium ratio. In rats, studies indicate that an increase in intracellular strontium content following supplementation may exert a protective effect on mitochondrial structure, probably by means of a stabilizing effect of strontium on membranes. The strontium:calcium ratio in animals receiving a standard diet is higher in the cell than in the extracellular fluid; this may be of physiologic significance.An increase in density that corresponded to the deposition of stable strontium was observed in areas of bone lesions due to metastatic cancer in patients receiving stable strontium supplementation. This suggests the possibility of using strontium to mineralize osteophenic areas and to relieve bone pain. Also, because of reports of an inverse relation between the incidence of dental caries and a high strontium content in drinking water, the use of natural water containing relatively high levels of stable strontium should be considered. In each of these instances it is important to maintain a normal dietary intake of calcium.     

The effects of strontium on skeletal development in zebrafish embryo

The strontium is an alkaline earth metal found in nature as trace element. Chemically similar to calcium, it is known to be involved in the human bone mineral metabolism. The strontium ranelate has been approved in therapy as drug with both anti-resorption and anabolic effects on bone tissues. Since few data in vivo are available, we used Danio rerio as animal model to evaluate the effects of strontium on skeletal development. First, toxicity assay performed on zebrafish embryos estimated the LC50 around 6 mM. Since several zebrafish bones are formed from cartilage mineralization, we evaluated whether strontium affects cartilage development during embryogenesis. Strontium does not perturb the development of the cartilage tissues before the endochondral osteogenesis takes place. About the mineralization process, we evidentiated an increase of vertebral mineralization respect to controls at lower strontium concentrations whereas higher concentration inhibited mineral deposition in dose dependent fashion. Our results evidentiated, in addition, that the calcium/strontium rate but not the absolute level of strontium modulates the mineralization process during embryonic osteogenesis.Zebrafish represents an excellent animal model to study the role of micronutrients in the development of the tissues/organs because the ions are not absorbed by intestine but assumed by skin diffusion.     

Reconstruction of the diet of the Middle Woodland Amerindian population at Abbott Farm by bone trace-element analysis

In order to reconstruct the diet of various occupations of Middle Woodland Amerindians at Abbott Farm, New Jersey, nine different trace-element analyses were performed on bone specimens from the site. Contemporary bone specimens were also used as controls. Specimens of human bone from the site exhibited lower strontium levels and strontium-to-calcium ratios than deer specimens from the same site, reinforcing paleodemographic evidence that the human populations that inhabited this site included substantial amounts of meat in their diets. Strong evidence for diagenetic enrichment of strontium was also found. Copper levels were not affected by diagenesis, but dietary discrimination was not clear for this element. The results for lead were too inconsistent to permit conclusions. Magnesium levels were clearly depleted by diagenesis, suggesting that this element is less useful than others in dietary reconstruction studies. Manganese concentrations were greatly enriched by diagenesis, rendering this element useless in dietary reconstruction. Molybdenum was absent from virtually every specimen. Excellent dietary discrimination was found for sodium, despite significant leaching. Zinc was not affected by diagenesis, but interpretation of results was hampered by its complex metabolism in mammals. The results also suggest that the Middle Woodland aboriginal residents of Abbott Farm ate little seafood and utilized grain or other plants that contain phytate as a food source.     

Dietary intake and bioavailability of trace elements

In order to assess the nutritional importance of trace elements, it is relevant to consider the factors regulating their metabolism. One of the most important factors is the true intake level. Conventional techniques such as diet history and interview studies in conjunction with standard food tables do not provide the true intake levels from prepared meals. Employing the duplicate portion technique, we have investigated the dietary intake of trace elements in prepared meals consumed by children, adults, and elderly in Sweden. The results indicate that the intake of potassium, magnesium, zinc, copper, and selenium is low when compared with the present recommended dietary allowance (RDA) values. It appears that a marginal deficiency of a number of trace elements may exist in the general population of affluent countries. When the dietary intakes are known, it is necessary to consider the bioavailability. This depends on the chemical form as well as the concentration of other dietary constituents such as fiber, phytate, carbohydrates, macrominerals, and vitamins in the diet. Knowledge of these interactions are important to improve the overall nutritional status of the population in general and patients in particuler.     

Effects of the different levels of dietary trace elements from organic or inorganic sources on growth performance,carcass traits,meat quality,and faecal mineral excretion of broilers

ABSTRACT

This experiment was conducted to evaluate the effects of different sources and levels of trace elements on growth performance, carcass composition and mineral excretion levels of broilers. In a completely randomised experimental design, 900 one-day-old male Ross-308 broilers were assigned to 5 treatments, with 6 replicates of 30 birds each. The control group (CITE) was fed with a basal diet containing regular inclusion levels of inorganic trace elements. Treatment groups were supplied with reduced levels (30% and 50% of the regular level) of inorganic (ITE) or organic trace elements (OTE), respectively. Groups 50% ITE, 30% OTE and 50% OTE diets had equivalent average daily gain (ADG), average daily feed intake (ADFI), feed to gain ratio (F/G ratio) and mortality rate compared with group CITE in any phase. However, compared with group CITE chicks in group 30% ITE have lower ADG and ADFI and higher F/G ratio. The carcass yields were not affected by dietary treatments. Compared with group CITE, in groups 30% ITE, 50% ITE, 30% OTE and 50% OTE the shear force values of the breast muscle were only 71.8%, 83.4%, 63.5% and 59.4% (p < 0.05), respectively. Birds received diets containing reduced levels of trace elements had diminished excretions of Mn and Zn throughout the entire period (p < 0.01). In conclusion, the reduced supplementation of trace elements had no or slightly negative impact on growth performance, carcass yield and meat quality, but decreased faecal mineral excretion. Moreover, the trace element supply as OTE played a limited role on performance and excretion and was only partly beneficial for animal performance in case the trace element supply was reduced to 30%.     

Osteoporosis and trace elements--an overview

More than 200 million people are affected by osteoporosis worldwide, as estimated by 2 million annual hip fractures and other debilitating bone fractures (vertebrae compression and Colles' fractures). Osteoporosis is a multi-factorial disease with potential contributions from genetic, endocrine functional, exercise related and nutritional factors. Of particular considerations are calcium (Ca) status, vitamin D, fluoride, magnesium and other trace elements. Several trace elements such as zinc and copper are essential for normal development of the skeleton in humans and animals. Fluoride accumulates in new bone and results in a net gain in bone mass, but may be associated with a tissue of poor quality. Aluminum induces impairment of bone formation. Gallium and cadmium suppresses bone turnover. However, exact involvements of the trace elements in osteoporosis have not yet been fully clarified. Numerous investigators have evaluated the role of medications and supplementations with minerals and trace substances to reverse the progression of this disease. Although bisphosphonates are still the drugs of choice, low-dosed fluoride and strontium salts have shown promise for the future.     

Effect of dietary copper and zinc levels on tissue copper,zinc, and iron in male rats

The interaction between dietary copper and zinc as determined by tissue concentrations of trace elements was investigated in male Sprague-Dawley rats. Animals were fed diets in a factorial design with two levels of copper (0.5, 5 μg/g) and five levels of zinc (1, 4.5, 10, 100, 1000 μg/g) for 42 d. In rats fed the low copper diet, as dietary zinc concentration increased, the level of copper decreased in brain, testis, spleen, heart, liver, and intestine. There was no significant effect of dietary copper on tissue zinc levels. In the zinc-deficient groups, the level of iron was higher in most tissues than in tissues from controls (5 μg Cu, 100 μg Zn/g diet). In the copper-deficient groups, iron concentration was higher than control values only in the liver. These data show that dietary zinc affected tissue copper levels primarily when dietary copper was deficient, that dietary copper had no effect on tissue zinc, and that both zinc deficiency and copper deficiency affected tissue iron levels.     

A high-beef diet alters protein kinase C isozyme expression in rat colonic mucosa

We recently reported that a red meat (beef) diet relative to a casein-based diet increases protein kinase C (PKC) activity in rat colonic mucosa. The purpose of this study was to further elucidate the effects of a high-beef diet on colonic intracellular signal transduction by analyzing steady-state protein levels of different PKC isozymes as well as activities of the three types of sphingomyelinases. Male Wistar rats (n = 12/group) were fed AIN93G-based diets either high in beef or casein for 4 weeks. Rats fed the beef diet had significantly (P < 0.05) higher cytosolic PKC alpha and lower membrane PKC delta protein levels than rats fed the casein diet. The beef-fed rats also had alterations in subfractions of PKC zeta/lambda so that they had a significantly (P = 0.001) lower level of membrane 70 & 75 kDa fraction and a higher (P = 0.001) level of cytosolic 40 & 43 kDa fraction than rats fed the casein diet. Because protein levels analyzed with a PKC zeta-specific antibody were similar, these differences in PKC zeta/lambda were probably due to changes in PKC lambda expression. PKC beta2 levels did not differ between the dietary groups. Diet had no significant effect on the activity of acid, neutral, or alkaline sphingomyelinase. This study demonstrated that consumption of a high-beef diet is capable of modulating PKC isozyme levels in rat colon, which might be one of the mechanisms whereby red meat affects colon carcinogenesis.     

Conformity in diversity? Isotopic investigations of infant feeding practices in two iron age populations from Southern Öland,Sweden

This article presents the results of a study of infant diet at two Iron Age sites on the island of Öland, Sweden. The cemetery at Bjärby contained a large number of subadults who had survived the earliest years of life, whereas most individuals at Triberga had died by 6 months of age. To investigate whether differences in infant feeding could explain the different mortality rates, the carbon, nitrogen, and sulfur stable isotope ratios of bone and tooth dentin collagen from the two sites were analyzed. Twenty‐two samples from Triberga and 102 from Bjärby yielded data that could be included in the carbon and nitrogen analysis. Twelve samples from Triberga and 42 from Bjärby were included in the sulfur analysis. The results for carbon (δ¹³C: Triberga X = –18.8, s.d. = 1.1; Bjärby X = –19.8, s.d. = 0.4), nitrogen (δ¹⁵N: Triberga X = 12.9, s.d. = 1.5; Bjärby X = 13.4, s.d. = 1.4), and sulfur (δ³⁴S: Triberga X = 8.1, s.d. = 1.1; Bjärby X = 5.8, s.d. = 1.3) suggest that diet was broadly similar at both sites and based on terrestrial resources. At Bjärby, females and high‐status individuals consumed higher‐trophic level protein than other males from early childhood onward. There was some indication that the contribution of marine resources to the diet may also have differed between the sexes at Triberga. No consistent differences in breast milk intake were observed between the two sites, but there was substantial variation at each. This variation may reflect an influence of gender and social status on infant feeding decisions. Am J Phys Anthropol 149:217–230, 2012. © 2012 Wiley Periodicals, Inc.     

Effect of crude protein and phosphorus level on growth performance, bone mineralisation and phosphorus, calcium and nitrogen utilisation in grower-finisher pigs

Two experiments in a 2 x 2 factorial arrangement were conducted to evaluate the effect of crude protein (CP) (130 vs. 200 g/kg) and phosphorus (P) (4.0 vs. 6.0 g total P/kg) level in a phytase supplemented diet (500 FTU [phytase units]/kg) in grower-finisher pigs. Owing to the design of the experiment, as dietary P level increased, there was also an increase in dietary calcium (Ca) level in order to maintain a dietary Ca to P ratio of 1.6:1. In Experiment 1, four diets were fed to 56 pigs (n = 14, initial body weight [BW] 36.7 +/- 4.2 kg) to investigate the interaction between CP and P on growth performance, bone mineralisation and digesta pH. Experiment 2 consisted of 16 entire male pigs (n = 4; offered identical diets to that offered in Experiment 1) for the determination of total tract apparent digestibility and nitrogen (N), P and Ca utilisation. There was an interaction between CP and P level on bone ash, bone P and bone Ca concentrations (p < 0.05). Pigs offered low CP-low P diets had a higher bone ash, P and Ca concentrations than pigs offered high CP-low P diets. However, there was no effect of CP level at high P levels on bone ash, P and Ca concentrations. Pigs offered low P diets had a lower ileal pH compared with pigs offered high P diets (p < 0.05). In conclusion, offering pigs a high CP-low P, phytase-supplemented diet resulted in a decrease in bone mineralisation.     

Removal of radioactive strontium from the rat by feeding stable strontium

The effect of administering the stable isotope of strontium (as phos-phate) at different dietary levels to adult rats (fed on a cereal and pulse-based diet containing 0.4% Ca) on the retention of radiostrontium (⁸⁹Sr) and radiocalcium (⁴⁵Ca) in the femur and the whole skeleton was studied for a period up to 6 weeks after an intraperitoneal injection of the two radioisotopes. The ability of strontium to remove⁸⁹Sr under the above dietary conditions was examined. Feeding Sr at 0.5% or 1% levels for 6 weeks had no effect on the skeletal content of⁸⁹Sr or⁴⁵Ca while a dietary regimen of 2% Sr (2000 times the normal content), significantly lowered the⁸⁹Sr and⁴⁵Ca content by about 30% in the femur but not in the whole skeleton. At this Sr level, the urinary excretion of the isotopes increased with a concomitant decrease in their excretion in the faeces. This study underscores the limitations of dietary Sr to mobilise⁸⁹Sr from the bones after it is incorporated in the bone mineral.     

Preservation of Bone Structure and Function by Lithothamnion sp. Derived Minerals

Progressive bone mineral loss and increasing bone fragility are hallmarks of osteoporosis. A combination of minerals isolated from the red marine algae, Lithothamnion sp. was examined for ability to inhibit bone mineral loss in female mice maintained on either a standard rodent chow (control) diet or a high-fat western diet (HFWD) for 5, 12, and 18 months. At each time point, femora were subjected to μ-CT analysis and biomechanical testing. A subset of caudal vertebrae was also analyzed. Following this, individual elements were assessed in bones. Serum levels of the 5b isoform of tartrate-resistant acid phosphatase (TRAP) and procollagen type I propeptide (P1NP) were also measured. Trabecular bone loss occurred in both diets (evident as early as 5 months). Cortical bone increased through month 5 and then declined. Cortical bone loss was primarily in mice on the HFWD. Inclusion of the minerals in the diet reduced bone mineral loss in both diets and improved bone strength. Bone mineral density was also enhanced by these minerals. Of several cationic minerals known to be important to bone health, only strontium was significantly increased in bone tissue from animals fed the mineral diets, but the increase was large (5–10 fold). Serum levels of TRAP were consistently higher in mice receiving the minerals, but levels of P1NP were not. These data suggest that trace minerals derived from marine red algae may be used to prevent progressive bone mineral loss in conjunction with calcium. Mineral supplementation could find use as part of an osteoporosis-prevention strategy.     

An Akt-dependent increase in canonical Wnt signaling and a decrease in sclerostin protein levels are involved in strontium ranelate-induced osteogenic effects in human osteoblasts

Sclerostin is an important regulator of bone homeostasis and canonical Wnt signaling is a key regulator of osteogenesis. Strontium ranelate is a treatment for osteoporosis that has been shown to reduce fracture risk, in part, by increasing bone formation. Here we show that exposure of human osteoblasts in primary culture to strontium increased mineralization and decreased the expression of sclerostin, an osteocyte-specific secreted protein that acts as a negative regulator of bone formation by inhibiting canonical Wnt signaling. Strontium also activated, in an apparently separate process, an Akt-dependent signaling cascade via the calcium-sensing receptor that promoted the nuclear translocation of β-catenin. We propose that two discrete pathways linked to canonical Wnt signaling contribute to strontium-induced osteogenic effects in osteoblasts.