Protein Overconsumption Research Articles

High-Protein Processed Foods: Impact on Diet, Nutritional Status, and Possible Effects on Health.

Proteins are macronutrients with multiple health benefits, but excessive consumption can negatively affect health. This study aimed to evaluate the characteristics of a sample of high-protein processed foods (HPPFs), describe how their consumption affects dietary balance, and acquire knowledge of the consumption patterns of these products in a Spanish population. A sample of HPPFs available in supermarkets and on websites was collected. The contribution to recommended protein intakes was calculated using national and international references and considering the single consumption of the HPPFs and the product plus 150 g of meat. Furthermore, an online survey was conducted among a convenience sample. A total of 36 enriched protein products were evaluated. The percentage of proteins in these products ranges from 10 to 88%. The contribution of the protein recommended intake was within a range of 87.4-306.6% and 66.4-232.8% (women and men, respectively), only considering the additional proteins from 150 g of meat. One hundred thirty-nine participants completed the survey; 67.6% affirmed that they had consumed HPPFs, and half consumed them without following any consumption control. Since these products are accessible to everyone in supermarkets and protein intake is generally higher than the recommended limits, regulating the mass sale of HPPFs is essential to ensure they do not lead to protein overconsumption.

Physiological adaptations to semi‐aquatic habits: the thermogenic macronutrient intake of the Eurasian otter

Abstract Maintaining thermal homeostasis in water is a major challenge for semi‐aquatic mammals, which entails morphological, behavioural and physiological adaptations. Foraging strategies and dietary‐induced thermogenesis (DIT) contribute to regulating body temperature in cold environments. As DIT differs among macronutrients, semi‐aquatic mammals may be expected to regulate their macronutrient ratios to enhance their capability of thermoregulating. We estimated the nutritional intake target of a widespread semi‐aquatic mustelid, Eurasian otter Lutra lutra by reviewing the available literature on otters' diet throughout Europe and assessing the nutritional composition of non‐commercial fish species forming the bulk of otter diet through laboratory analyses. The macronutrient intake target for the otter was assessed as 61% protein and 39% lipid energy ratios. The mean percent protein energy was higher than that reported for typical hypercarnivores and tended to increase with decreasing water temperatures. The additional source of heat provided by the thermogenic effect induced by protein digestion may contribute to balance heat loss, compensating for the costs associated with protein overconsumption. If, as suggested by fossil records, semi‐aquatic habits appeared after the development of otter's ‘fish specialist’ dentition, the thermogenic effect of its fish‐based diet may have promoted the tight relationship occurring between otters and water habitats.

EU consumer awareness of food safety and healthy diets: Are there synergies to benefit a sustainable protein transition?

This paper aims to gain more insight into potential synergies between food safety and healthy diets with a sustainable protein transition (i.e., reducing protein over-consumption and replacing animal protein with plant protein) in the EU. The paper is based on a systematic analysis of the survey on food safety, organized by the European Food Safety Authority (EFSA) as part of Eurobarometer wave 97.2 (Spring 2022). Consumers responded somewhat differently to the survey items on chemical contaminants in food than to those on biological hazards in food, plant health and animal health and welfare. They were somewhat more aware of and concerned about the former than the latter. They also had different ideas on the most important healthy diet items. Cluster analysis identified five clusters who, inter alia, focused on conventional options (e.g., eating fewer calories) or the protein replacement options. Multilevel logistic regression analysis showed that food safety awareness and concern variables, explicitly including farm animal welfare, were somewhat stronger associated with the protein replacement cluster than with the conventional cluster. Hence, synergies between food safety and healthy diet issues may stimulate the replacement (not reduction) aspects of a sustainable protein transition. The Discussion suggests that further research should investigate how improving the quality of a week menu with a high diversity of protein sources can help to promote the reduction of over-consumption.

Energetic and health effects of protein overconsumption constrain dietary adaptation in an apex predator

Studies of predator feeding ecology commonly focus on energy intake. However, captive predators have been documented to selectively feed to optimize macronutrient intake. As many apex predators experience environmental changes that affect prey availability, limitations on selective feeding can affect energetics and health. We estimated the protein:fat ratio of diets consumed by wild polar bears using a novel isotope-based approach, measured protein:fat ratios selected by zoo polar bears offered dietary choice and examined potential energetic and health consequences of overconsuming protein. Dietary protein levels selected by wild and zoo polar bears were low and similar to selection observed in omnivorous brown bears, which reduced energy intake requirements by 70% compared with lean meat diets. Higher-protein diets fed to zoo polar bears during normal care were concurrent with high rates of mortality from kidney disease and liver cancer. Our results suggest that polar bears have low protein requirements and that limitations on selective consumption of marine mammal blubber consequent to climate change could meaningfully increase their energetic costs. Although bear protein requirements appear lower than those of other carnivores, the energetic and health consequences of protein overconsumption identified in this study have the potential to affect a wide range of taxa.

Satiating Effect of High Protein Diets on Resistance-Trained Subjects in Energy Deficit.

Short-term energy deficit strategies are practiced by weight class and physique athletes, often involving high protein intakes to maximize satiety and maintain lean mass despite a paucity of research. This study compared the satiating effect of two protein diets on resistance-trained individuals during short-term energy deficit. Following ethical approval, 16 participants (age: 28 ± 2 years; height: 1.72 ± 0.03 m; body-mass: 88.83 ± 5.54 kg; body-fat: 21.85 ± 1.82%) were randomly assigned to 7-days moderate (PROMOD: 1.8 g·kg−1·d−1) or high protein (PROHIGH: 2.9 g·kg−1·d−1) matched calorie-deficit diets in a cross-over design. Daily satiety responses were recorded throughout interventions. Pre-post diet, plasma ghrelin and peptide tyrosine tyrosine (PYY), and satiety ratings were assessed in response to a protein-rich meal. Only perceived satisfaction was significantly greater following PROHIGH (67.29 ± 4.28 v 58.96 ± 4.51 mm, p = 0.04). Perceived cravings increased following PROMOD only (46.25 ± 4.96 to 57.60 ± 4.41 mm, p = 0.01). Absolute ghrelin concentration significantly reduced post-meal following PROMOD (972.8 ± 130.4 to 613.6 ± 114.3 pg·mL−1; p = 0.003), remaining lower than PROHIGH at 2 h (−0.40 ± 0.06 v −0.26 ± 0.06 pg·mL−1 normalized relative change; p = 0.015). Absolute PYY concentration increased to a similar extent post-meal (PROMOD: 84.9 ± 8.9 to 147.1 ± 11.9 pg·mL−1, PROHIGH: 100.6 ± 9.5 to 143.3 ± 12.0 pg·mL−1; p < 0.001), but expressed as relative change difference was significantly greater for PROMOD at 2 h (+0.39 ± 0.20 pg·mL−1 v −0.28 ± 0.12 pg·mL−1; p = 0.001). Perceived hunger, fullness and satisfaction post-meal were comparable between diets (p > 0.05). However, desire to eat remained significantly blunted for PROMOD (p = 0.048). PROHIGH does not confer additional satiating benefits in resistance-trained individuals during short-term energy deficit. Ghrelin and PYY responses to a test-meal support the contention that satiety was maintained following PROMOD, although athletes experiencing negative symptoms (i.e., cravings) may benefit from protein-rich meals as opposed to over-consumption of protein.

Reducing nitrogen footprints of consumer-level food loss and protein overconsumption in Japan, considering gender and age differences

The agro-food system perturbs the nitrogen (N) cycle through its N loads to the environment. The present study focused on food-related consumer-level N loads in Japan from 1961–2015, with a particular focus on food loss and protein overconsumption. Gender and age differences were also analyzed. Consumer-level food loss was negligible until the 1970s, when it began to slowly increase, accounting for an average of 13.2% of the annual net supply during 2011–2015. Japanese people have consumed more protein than the World Health Organization’s recommended intake since 1961. Protein overconsumption increased until the mid-1990s, when it began to decrease, but it still accounted for an average of 32.3% of total annual protein consumption during 2011–2015. The national mean of food N footprints (total release of reactive N into the environment related to individual food consumption) in the same period was 18.3 kg N capita–1 yr–1, of which food loss accounted for 4% and protein overconsumption for 37%. The food N footprint of each sex/age class varied from 16.0–21.6 kg N capita–1 yr–1, males had a larger footprint in each age class. Seven scenarios to reduce the N footprints were evaluated; a scenario that included halving protein overconsumption, livestock meat consumption, and food loss was estimated to reduce the food N footprint by 31%. Thus, there is room for reducing consumer-induced N loads to the environment. Campaigns aimed at boosting healthy and environmentally friendly diets should consider the diverse consumption patterns of different sex and age classes.

Nutritional Adequacy of Target Pattern in Dietary Guidance System - Dietary Reference Intakes for Koreans 2015 -

2015 한국인 영양소 섭취기준에 제시된 18개의 연령군별 권장식사패턴을 대상으로 영양 적정성을 분석하였다. 권장식사패턴의 식품군별 배정 횟수와 대표영양가표를 활용하여 에너지 함량과 에너지분율의 적정성 여부를 조사하였고, 단백질, 식이섬유, 무기질(Ca, P, Fe, Na, K), 비타민(비타민 A, 티아민, 리보플라빈, 니아신, 비타민 C)의 12가지 영양소에 대하여 영양소 섭취기준 충족 여부를 확인하였다. 조사 대상 12가지 영양소 모두 영양소 섭취기준을 충족시키는 권장식사패턴(MAR=1.0)은 5개뿐으로, 모든 권장식사패턴이 식사구성안의 영양 기대 목표를 만족시키지는 못하는 것으로 나타났다. 권장식사패턴 18개 모두에서 영양소 섭취기준을 충족시켰던 영양소로 단백질과 나트륨이 있었으며, 식이섬유, 칼슘, 칼륨은 미 충족 권장식사패턴이 각각 15개, 10개, 9개나 되었다. 비타민 A의 경우 영양소 섭취기준의 단위는 RAE이고 대표영양가표의 단위는 RE로 되어 있다. 단위의 차이를 무시한 채 비교하였을 때는 18개 권장식사패턴 모두가 비타민 A 권장섭취량을 충족시키는 것으로 조사되었으나, 권장식사패턴의 RE 단위 함량을 RAE 단위함량으로 환산하여 비교하는 경우 3개 권장식사패턴만이 권장섭취량을 충족시키는 것으로 나타났다. 그리고 여성 노인의 권장식사패턴은 MAR이 0.90으로 가장 낮았으며, 영양소 섭취기준을 충족시키지 못하는 영양소가 7가지나 있는 것으로 확인되어 조정이 필요하다. 단백질, 지방, 탄수화물의 에너지분율은 각각 16.04%, 24.35%, 60.91%로 에너지적정비율을 충족시키고 있었다. 권장식사패턴의 에너지 증감을 최소한으로 하면서 영양소 섭취기준에 미달하는 식이섬유, 칼슘, 칼륨, 비타민 A 함량을 증가시킬 수 있는 방안으로 채소군의 배정 횟수 증가가 바람직할 것으로 나타났고, 단백질의 과잉 섭취를 억제하는 방안으로 고기·생선·달걀·콩류군의 배정 횟수감소도 일부 권장식사패턴의 경우 고려해 볼 필요성이 있다. 그리고 양념의 사용은 식단 구성 시 배제하고 있는데, 권장식사패턴에서 양념의 사용에 따른 에너지 배정이 적정 수준으로 확보될 수 있도록 고려하여야겠다.Nutritional adequacy of Target patterns in Dietary Guidance System were evaluated. Study subjects were 18 Target patterns designed for 2 children groups, 4 adolescent and 4 adult male and female groups in Dietary Reference Intakes for Koreans 2015. Nutrients examined were 4 macro-nutrients(protein, fat, carbohydrate, and dietary fiber), 5 minerals(Ca, P, Fe, Na, and K), and 5 vitamins(vitamin A, thiamin, riboflavin, niacin, and vitamin C). Energy and nutrients contents were calculated based upon assigned multiples of single serving in Target pattern and Representative Food Composition Table by Excel program. Among the 18 Target patterns, only 5 were mean adequacy ratio(MAR) of 1.0, fulfilled the expectations of Dietary Guidance System. Protein and Na contents were more than dietary reference intakes(DRI) in all 18 Target patterns. Dietary fiber, Ca, and K were deficient nutrient in 15, 10, and 9 Target patterns, respectively. The units of vitamin A were not same in Target pattern and DRI, retinol equivalent(RE) in Target pattern and retinol activity equivalent(RAE) in DRI. When calculate RE content of vitamin A in Target pattern to RAE content, 15 Target patterns did not reach to DRI of vitamin A. The Target pattern of elderly women showed the lowest mean adequacy ratio(MAR), 7 nutrients were less than DRI, need to be revised. Average energy contribution ratio of protein, fat, and carbohydrate were 16.04%, 24.35%, and 60.91%, respectively, fulfilled the adequate acceptable macro-nutrient distribution range(AMDR). To improve the nutritional inadequacy of dietary fiber, Ca, K, and vitamin A in Target pattern, effective mean may be the increasing vegetable group assignment. Also decreasing the meat·fish·egg·legume group assignment in some Target pattern may be the way of preventing of protein overconsumption. The energy in adequate amount for condiment use also need to be considered.

Diet and Macronutrient Optimization in Wild Ursids: A Comparison of Grizzly Bears with Sympatric and Allopatric Black Bears.

When fed ad libitum, ursids can maximize mass gain by selecting mixed diets wherein protein provides 17 ± 4% of digestible energy, relative to carbohydrates or lipids. In the wild, this ability is likely constrained by seasonal food availability, limits of intake rate as body size increases, and competition. By visiting locations of 37 individuals during 274 bear-days, we documented foods consumed by grizzly (Ursus arctos) and black bears (Ursus americanus) in Grand Teton National Park during 2004–2006. Based on published nutritional data, we estimated foods and macronutrients as percentages of daily energy intake. Using principal components and cluster analyses, we identified 14 daily diet types. Only 4 diets, accounting for 21% of days, provided protein levels within the optimal range. Nine diets (75% of days) led to over-consumption of protein, and 1 diet (3% of days) led to under-consumption. Highest protein levels were associated with animal matter (i.e., insects, vertebrates), which accounted for 46–47% of daily energy for both species. As predicted: 1) daily diets dominated by high-energy vertebrates were positively associated with grizzly bears and mean percent protein intake was positively associated with body mass; 2) diets dominated by low-protein fruits were positively associated with smaller-bodied black bears; and 3) mean protein was highest during spring, when high-energy plant foods were scarce, however it was also higher than optimal during summer and fall. Contrary to our prediction: 4) allopatric black bears did not exhibit food selection for high-energy foods similar to grizzly bears. Although optimal gain of body mass was typically constrained, bears usually opted for the energetically superior trade-off of consuming high-energy, high-protein foods. Given protein digestion efficiency similar to obligate carnivores, this choice likely supported mass gain, consistent with studies showing monthly increases in percent body fat among bears in this region.

The effect of nutritional quality on comparing environmental impacts of human diets

Abstract Several studies support the general conclusion that plant-based diets have a lower environmental impact than animal-based diets. These studies, however, do not account for the nutritional quality of diets. The main objective of our study, therefore, was to explore if accounting for nutritional quality affects the comparison of the environmental impacts of human diets varying in their percentage of animal-source food products (ASFP). We also explored whether meals or daily diets are equally suitable to compare environmental impacts of diets. Fifty peer-reviewed studies were found that examined the environmental impact of diets, generally using life cycle assessment (LCA). Only 12 of these studies were reviewed, based on five criteria: study contains more than one scenario; diet scenarios vary in their percentage of ASFP; the weight of each food product was provided; the study assessed global warming potential and/or land use; diet scenarios are not designed for specific (health) groups. For each diet described in the reviewed studies, we quantified the daily intake of nine qualifying and three disqualifying nutrients. Global warming potential and land use, as provided by the reviewed studies, were expressed in four ways: per day, per daily protein intake capped to the recommended intake level of 57 g; per daily protein intake uncapped; and per NRD9.3 (i.e. a composite nutrient score of a diet). We concluded that the nutrient intake resulting from a meal cannot be used to assess the nutritional quality of a daily diet and, hence, the environmental impact of meals cannot be compared to that of daily diets. Studies on meals were therefore excluded from further analysis. Our results further show that daily diets that had higher percentages of ASFP were associated with higher (excess) intakes of total protein and lower values of NRD9.3. Diets that had higher percentages of ASFP were associated with higher GWPs and LU's per gram protein capped and per unit NRD9.3. Without capping protein to the recommended intake level, GWP and LU per gram of protein were generally lower for diets that had higher percentages of ASFP. Without capping, diets with higher percentages of ASFP are credited for overconsumption of protein. Since overconsumption of protein does not benefit health, we recommend capping to the recommended intake level. The effect of using NRD9.3 rather than day as functional unit was small for GWP. For LU we found no effect. When using NRD9.3 as functional unit, it must be considered that this functional unit requires more data than day or protein. Our analysis is based on a limited number of studies. Although initially a substantial number of studies were found, many of these were excluded because insufficient data were provided about diet composition, only one diet scenario was assessed, or because the studies assessed the environmental impact of meals rather than of diets. We found mainly Western-oriented diets, often designed by the researchers and not representative for actual consumption. For further research on the environmental impact of diets, we therefore recommend analysis on representative daily diets.

Adverse Effects Associated with Protein Intake above the Recommended Dietary Allowance for Adults.

Background. While high-protein consumption—above the current recommended dietary allowance for adults (RDA: 0.8 g protein/kg body weight/day)—is increasing in popularity, there is a lack of data on its potential adverse effects. Objective. To determine the potential disease risks due to high protein/high meat intake obtained from diet and/or nutritional supplements in humans. Design. Review. Subjects. Healthy adult male and female subjects. Method. In order to identify relevant studies, the electronic databases, Medline and Google Scholar, were searched using the terms:“high protein diet,” “protein overconsumption,” “protein overuse,” and “high meat diet.” Papers not in English were excluded. Further studies were identified by citations in retrieved papers. Results. 32 studies (21 experimental human studies and 11 reviews) were identified. The adverse effects associated with long-term high protein/high meat intake in humans were (a) disorders of bone and calcium homeostasis, (b) disorders of renal function, (c) increased cancer risk, (d) disorders of liver function, and (e) precipitated progression of coronary artery disease. Conclusions. The findings of the present study suggest that there is currently no reasonable scientific basis in the literature to recommend protein consumption above the current RDA (high protein diet) for healthy adults due to its potential disease risks. Further research needs to be carried out in this area, including large randomized controlled trials.

Management of protein intake in the fruit fly Anastrepha fraterculus

This work tested if carbohydrates and proteins ingestion is regulated in the South American fruit fly, Anastrepha fraterculus, to optimize survival and reproduction. Adult food treatments were established by providing sugar and hydrolyzed yeast in various combinations either alone or mixed at a standard 3:1 ratio (sugar:hydrolyzed yeast). Individual food consumption was assessed and related to survival patterns. The effects of adult feeding on fecundity and fertility patterns were investigated in groups of flies. Sugar consumption was the lowest in the treatment where it was provided with hydrolyzed yeast at a fixed 3:1 ratio. Consumption of hydrolyzed yeast did not differ between this treatment and the one in which this solution was complemented with one solution of sugar. It seems that a mixture of sugar and hydrolyzed yeast at a fixed ratio of 3:1, respectively, restricts extra ingestion of sugar; most probably because of negative response of the fly to overconsumption of protein. Survival was affected by the treatments, being lower in those cases where protein was at the fixed ratio. Group experiments revealed that protein restriction expanded longevity and decreased egg production. In contrast, egg production was enhanced when flies were kept continuously with a mixture of yeast and sugar plus an extra source of sugar, and this was not in detriment of survival. Our results suggest that fixed sugar-protein ratios in which protein is in excess affects fitness components such as longevity and reproduction. These findings are discussed from a theoretical and applied perspective in the context of pest control by means of the sterile insect technique.

Effects of sodium bicarbonate on diet selection and rumen digestion by growing lambs individually fed whole barley grain and a protein supplement at their choice

A feeding and digestion study was completed to determine whether sodium bicarbonate supplementation modifies diet selection of whole barley grain and a protein supplement by lambs. The underlying hypothesis was that aversion to barley intake to avoid acidosis might explain overconsumption of protein. Sixty weaned lambs (15.1 ± 0.33 kg live weight (LW)) were allocated to one of three dietary treatments in 2 pens of 5 lambs by sex, according to a 3 treatments×2 sex factorial design. Treatments were whole barley grain and a pelleted protein supplement fed at choice either unsupplemented (U) or supplemented with sodium bicarbonate fed by free access on the side (BF) or incorporated into the protein supplement at 15 g/kg dry matter (BI). At the end of the growing period, 7 male lambs from each treatment (24.2 ± 0.13 kg LW) were moved to individual pens and slaughtered after 5 days of individual intake control to characterise rumen fermentation and determine digesta flow and microbial crude protein (CP) contribution to the abomasum, using C 31 alkane and purine bases as flow and microbial markers, respectively. Intake of sodium bicarbonate was higher (P<0.005) when provided free access than when incorporated into the protein pellet (13.9 g/d vs. 5.0 g/d for BF and BI) but it did not affect dry matter intake (797 g/d) or average daily gain (328 g/d vs. 289 g/d for male and female lambs), although barley grain intake tended (P=0.052) to decrease in response to buffer addition. A lower (P<0.05) proportion of organic matter truly digested in the rumen (OMTDR; 0.53 vs. 0.61) and a trend (P=0.098) to increased efficiency of microbial CP synthesis (26.7 gN/kg vs. 21.6 gN/kg OMTDR) ocurred when the buffer was offered free access compared to incorporation into the protein supplement, respectively. Neither rumen fluid pH nor ammonia concentration differed among treatments, but the total concentration of volatile fatty acids and molar proportion of acetate tended (P<0.1) to increase with buffer supplementation (174 mM vs. 200 mM and 46.8 mol/100 mol vs. 52.7 mol/100 mol). Sodium bicarbonate can modify rumen digestion, but failed to buffer rumen fluid pH and reverse the aversion to barley grain.

Estimation of protein requirement for maintenance in adult parrots (Amazona spp.) by determining inevitable N losses in excreta

Especially in older pet birds, an unnecessary overconsumption of protein--presumably occurring in human custody--should be avoided in view of a potential decrease in the excretory organs' (liver, kidney) efficiency. Inevitable nitrogen (N)-losses enable the estimation of protein requirement for maintenance, because these losses have at least to be replaced to maintain N equilibrium. To determine the inevitable N losses in excreta of adult amazons (Amazona spp.), a frugivor-granivorous avian species from South America, adult amazons (n = 8) were fed a synthetic nearly N-free diet (in dry matter; DM: 37.8% starch, 26.6% sugar, 11.0% fat) for 9 days. Throughout the trial, feed and water intake were recorded, the amounts of excreta were measured and analysed for DM and ash content, N (Dumas analysis) and uric acid (enzymatic-photometric analysis) content. Effects of the N-free diet on body weight (BW) and protein-related blood parameters were quantified and compared with data collected during a previous 4-day period in which a commercial seed mixture was offered to the birds. After feeding an almost N-free diet for 9 days, under the conditions of a DM intake (20.1 g DM/bird/day) as in seeds and digestibility of organic matter comparable with those when fed seeds (82% and 76% respectively), it was possible to quantify the inevitable N losses via excrements to be 87.2 mg/bird/day or 172.5 mg/kg BW(0.75)/day. Assuming a utilization coefficient of 0.57 this leads to an estimated protein need of approximately 1.9 g/kg BW(0.75)/day (this value does not consider further N losses via feathers and desquamated cells; with the prerequisite that there is a balanced amino acid pattern).

Stone prevention: why so little progress? *

Despite intensive research the knowledge of stone pathogenesis, which is the basis of every rational stone metaphylaxis, has remained rather scanty. Epidemiology shows that stone formation in most patients is only a sporadic event, probably resulting from a coincidence of different factors. The hypercalciuria, hypocitraturia, hyperuricosuria and hyperoxaluria frequently found in calcium stone formers can be influenced therapeutically and, in affluent societies, seem to be the result of protein over-consumption. These four factors favour crystallization processes in urine. However, urine is normally protected from nucleation, growth and aggregation of calcium minerals by crystallization inhibitors. In urine, crystallization of calcium oxalate can only be induced by an extreme supersaturation, a deficient inhibitor activity and promoters of crystallization. To form a stone, crystals have to be retained in the urinary collecting system. Two mechanisms of retention are discussed: large crystal aggregates trapped in collecting ducts of renal papillae, or a pre-existing calcification of the papilla (mainly calcium phosphate) that may be responsible for growth of an initially fixed particle to a concretion large enough to become symptomatic. An excessive oxalate intake combined with a low calcium consumption can produce marked hyperoxaluria. In the animal model, hyperoxaluria induces not only calcium oxalate crystallization but also papillary damage and incrustations. Hypercalciuria at a low pH favours the aggregation of calcium oxalate, and at a high pH the crystallization of calcium phosphate, a promoter of heterogeneous nucleation of calcium oxalate. All these factors and further complex phenomena mentioned in this paper have to be taken in account to perform rational stone metaphylaxis.

Renal mass and serum calcitriol in male idiopathic calcium renal stone formers: role of protein intake.

To determine whether chronic overconsumption of protein might increase renal mass and cause up-regulation of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D] production, 57 male recurrent idiopathic calcium stone formers (RCSF), 29 with hypercalciuria (HCSF; urinary calcium x V, > 7.50 mmol/day) and 28 with normocalciuria (NCSF), were compared with 15 healthy male controls (C) while consuming a free choice diet. Renal mass in RCSF was measured by the sum of the surface areas of right and left kidneys (square centimeters) on plain films of the abdomen by a computer-assisted sonic stylus; in C, renal mass was assessed sonographically. Serum intact PTH and 1,25-(OH)2D were measured radioimmunometrically. In HCSF, urinary phosphate x V (35.9 +/- 1.2 mmol/day) was higher than that in NCSF (29.3 +/- 1.3 mmol/day; P = 0.0009) or C (28.7 +/- 1.8 mmol/day; P = 0.005); urinary creatinine x V (16.5 +/- 0.5 mmol/day) was also higher in HCSF than in NCSF (15.0 +/- 0.5 mmol/day; P = 0.024) or C (13.8 +/- 0.6 mmol/day; P = 0.002). For identical blood levels of ionized calcium and phosphate, the 1,25-(OH)2D/PTH concentration ratio (an index of regulation of 1,25-(OH)2D production) was higher in HCSF (6.5 +/- 1.0) than in NCSF (4.0 +/- 0.3; P = 0.005). In addition, the sum of the surface areas of right and left kidneys was increased in HCSF (163.4 +/- 2.9 cm2) compared with that in NCSF (140.5 +/- 3.1 cm2; P = 0.0001), and it positively correlated with urinary phosphate x V (r = 0.429; P = 0.001) as well as with urinary creatinine x V (r = 0.294; P = 0.026); no such correlation was noted in C. Calcitriol levels were positively related to renal mass in RCSF (r = 0.316; P = 0.018), but not in C. Finally, urinary calcium x V positively correlated with the serum calcitriol/PTH concentration ratio only in RCSF (r = 0.388; P = 0.003). These findings suggest that protein overconsumption may cause an increase in renal mass and up-regulate calcitriol production in some male RCSF, an effect that would subsequently cause "idiopathic" hypercalciuria.

Turkey feeding regimes with different ages of introduction of a choice of foods

An experiment was carried out to investigate five feeding regimes for the turkey which involve introducing a choice of wheat grain and a higher-protein food at 1, 14, 28, 56 and 77 days of age. Broken wheat grains were used from days 1 to 14, and whole grains thereafter. Protein intakes per bird, calculated from standard tables of feed composition, were 39.1, 43.0, 41.8, 35.5 and 36.0 g/day, respectively, from 14 to 98 days. Further groups of birds on a complete diet regime consumed a significantly lower 33.3 g/day. Only two comparisons were significantly different for body weight at 98 days: birds which received the choice at 14 days had a significantly higher weight (5.7 kg/bird) than those which received the choice at 56 days (5.5 kg) and than those on the complete diet regime (5.5 kg). P resentation of the wheat and higher-protein food during the period of protein over-consumption, according to a fixed ratio schedule, might reduce protein intake.