Meat Protein Intake Research Articles

Dietary Protein Intake and Type 2 Diabetes Among Women and Men in Northeast China.

We conducted a comprehensive and in-depth assessment of different dietary protein sources related to type 2 diabetes (T2D) and determined whether the association is mediated by insulin resistance (IR) and β-cell dysfunction in a population-based cross sectional study of 4,427 women and 2,394 men aged 20–74 years in northeast China. We observed that the intake of total protein, animal protein, and red meat protein was positively associated with T2D prevalence in women. Comparing the women in the highest quintile of protein intake with those in the lowest quintile, the multivariable-adjusted odds ratios of T2D were 2.13 [95% confidence interval (CI): 1.18–3.81] for total protein, 2.27 (95% CI: 1.18–4.35) for animal protein, and 1.75 (95% CI: 1.14–2.68) for red meat protein. Mediation analyses indicated that these associations were mediated mainly by the IR as measured by the homeostasis model (HOMA-IR). The proportions via the mediation of HOMA-IR were 29.0% (95% CI: 10.3%–55.5%), 35.0% (95% CI: 12.9%–83.3%), and 17.2% (95% CI: 5.2%–44.8%) for total protein-, animal protein-, and red meat protein–T2D associations, respectively. These findings support the notion that modifying the sources of dietary protein may be potentially applied to prevent T2D.

Meat, dairy and plant proteins alter bacterial composition of rat gut bacteria.

Long-term consumption of red meat has been considered a potential risk to gut health, but this is based on clinic investigations, excessive intake of fat, heme and some injurious compounds formed during cooking or additions to processed meat products. Whether intake of red meat protein affects gut bacteria and the health of the host remains unclear. In this work, we compared the composition of gut bacteria in the caecum, by sequencing the V4-V5 region of 16S ribosomal RNA gene, obtained from rats fed with proteins from red meat (beef and pork), white meat (chicken and fish) and other sources (casein and soy). The results showed significant differences in profiles of gut bacteria between the six diet groups. Rats fed with meat proteins had a similar overall structure of caecal bacterial communities separated from those fed non-meat proteins. The beneficial genus Lactobacillus was higher in the white meat than in the red meat or non-meat protein groups. Also, rats fed with meat proteins and casein had significantly lower levels of lipopolysaccharide-binding proteins, suggesting that the intake of meat proteins may maintain a more balanced composition of gut bacteria, thereby reducing the antigen load and inflammatory response in the host.

Abstract P037: 24-hour Urinary Amino Acid Excretion And Blood Pressure: The Intermap Study

Background: Available data indicate inverse relations to blood pressure (BP) of dietary vegetable protein and its main amino acid, glutamic acid, also direct relations to BP of meat and animal protein intakes. Data on association of urinary amino acids (UAAs) with BP are limited. Objective: To assess the relationship between UAAs and BP. Methods: This study assessed relations to BP of 21 urinary amino acids among 4,677 men and women ages 40-59 (17 population samples in China, Japan, UK, USA) from the International Study on Macro/Micronutrients and Blood Pressure (INTERMAP). Urinary amino acid excretion was expressed as log transformed value of each urinary amino acid (μmol/24 h), and as % dietary total protein (based on urinary urea nitrogen excretion). Results: In multivariate analyses with all 21 UAAs considered together, independent inverse relations to BP were found for serine, glycine, and lysine, and independent direct relations to BP for threonine, cystine, and 3-methylhistidine, controlling for possible non-dietary and dietary confounders (including body mass index and each of the other UAAs). For example, with log urinary serine at 75th compared to the 25th percentile, SBP/DBP was lower by 2.4/1.8 mm Hg and 2.2/1.7 mm Hg on average without and with adjustment for body mass index in multivariate models. With log urinary 3-methylhistidine at 75th compared to the 25th percentile, SBP/DBP was higher by 3.8/2.7 and 1.6/1.4 mm Hg. Conclusions: These significant new findings on relations to blood pressure of urinary amino acids need to be verified by additional - including prospective - data.

Plant and animal protein intakes are differently associated with nutrient adequacy in French adults

The objective was to study the relations between animal and plant protein intake and the diet quality, as captured by an integrated index of nutrient adequacy. Using data from the French national dietary survey, INCA2 (2006–2007) for 1912 adults, we assessed diet quality with the PANDiet, based on the 35 probabilities of having adequate nutrient intakes. We used multiple regression analysis to study the relation with the intakes of plant, animal, and related food sources proteins. Plant protein intake was positively associated with the PANDiet, irrespective of gender (β=0.50; P<0.0001). In contrast, animal protein intakes were differently associated with the PANDiet, positively in women (β=0.08; P<0.0001) and negatively in men (β=−0.05; P<0.005). Relations between the PANDiet and intakes of animal food proteins were varied. Red meat and poultry protein intakes were negatively associated with the PANDiet in men but not in women. Furthermore, irrespective of gender, we found positive associations for fish, milk and yoghurt protein intakes and negative associations for eggs, offal, processed meat and cheese protein intakes. These findings show that plant protein is a robust marker of a high‐quality diet, whereas total animal protein hides different subtypes of animal food protein that display very contrasted relations with diet quality. These data could help to refine proteins recommendations.

Identification of biomarkers for intake of protein from meat, dairy products and grains: a controlled dietary intervention study

In the present controlled, randomised, multiple cross-over dietary intervention study, we aimed to identify potential biomarkers for dietary protein from dairy products, meat and grain, which could be useful to estimate intake of these protein types in epidemiological studies. After 9 d run-in, thirty men and seventeen women (22 (SD 4) years) received three high-protein diets (aimed at approximately 18% of energy (en%)) in random order for 1 week each, with approximately 14 en% originating from either meat, dairy products or grain. We used a two-step approach to identify biomarkers in urine and plasma. With principal component discriminant analysis, we identified amino acids (AA) from the plasma or urinary AA profile that were distinctive between diets. Subsequently, after pooling total study data, we applied mixed models to estimate the predictive value of those AA for intake of protein types. A very good prediction could be made for the intake of meat protein by a regression model that included urinary carnosine, 1-methylhistidine and 3-methylhistidine (98% of variation in intake explained). Furthermore, for dietary grain protein, a model that included seven AA (plasma lysine, valine, threonine, α-aminobutyric acid, proline, ornithine and arginine) made a good prediction (75% of variation explained). We could not identify biomarkers for dairy protein intake. In conclusion, specific combinations of urinary and plasma AA may be potentially useful biomarkers for meat and grain protein intake, respectively. These findings need to be cross-validated in other dietary intervention studies.

Dietary protein in relation to bone stiffness index and fat-free mass in a population consuming relatively low protein diets

Dietary protein has a mixed effect on skeletal health and the effect may differ by amount or source of protein. The purpose of this study was to investigate dietary protein in relation to bone density and fat-free mass in rural Korean residents consuming relatively low protein diets. Between 2008 and 2010, 3,330 participants were recruited for a baseline examination of a community-based study in Kangwha. Of those, 1,182 men and 1,393 postmenopausal women were eligible for the present study. Diet was assessed using a food-frequency questionnaire developed for Korean adults. Calcaneal bone density measured by ultrasound was expressed as the stiffness index (SI). Fat-free mass index (FFMI) was defined as fat-free mass in kilograms divided by the height in meters squared. The mean ages of men and women were 59.5 and 60.0years, respectively. The median daily intakes of total and meat protein were 52.3 and 6.7g in men and 45.0 and 3.0g in women, respectively. After controlling for potential confounders, SI and FFMI showed an increasing trend with a higher meat protein intake in men (P for trend=0.017 and 0.033, respectively), but not in women. No positive association was observed for other food sources of protein. In conclusion, our findings suggest that meat protein contributes to skeletal health in men consuming relatively low protein diets.

Eating patterns and use of nutritional information in breast cancer survivors treated with radiation therapy in South Korea

The purposes of this study were 1) to investigate eating behaviors and patterns in breast cancer patients using a newly developed food frequency questionnaire and 2) to examine perception and use of nutritional information about breast cancer treatment among cancer patients treated with radiation therapy. Sixty breast cancer patients (case group) undergoing radiation therapy in Ajou University Hospital, Suwon, South Korea and 79 healthy women (control group) participated in this study. Mean age of subjects in the control group was 46.00 ± 7.88 years and BMI was 23.12 ± 2.85 kg/㎡, and that of the case group was 50.06 ± 11.64 years and 22.32 ± 3.24 kg/㎡. The results of eating behaviors showed several significant differences between control and case groups. Breast cancer patients ate meals on a more regular basis, on time, and more frequently compared to control subjects. In addition, they preferred more salty or spicy and bland food compared to healthy women. According to answers from the food frequency questionnaire, breast cancer patients consumed significantly lower amounts of boiled white rice, meats and processed food, fish and shellfish, coffee, milk, and cheese, whereas they consumed a significantly large amount of boiled multigrain rice, vegetable, seaweeds, soybean and processed food, and yoghurt compared to healthy women. This study also observed the way in which cancer patients and healthy control subjects obtain information about breast cancer treatment and its reliabilities. Results showed that healthy women did not hesitate to obtain information from mass media, while breast cancer patients would obtain nutritional information from specialists rather than mass media. Results of this survey confirmed that breast cancer patients avoided intake of red meat protein, even though they already recognized the importance of dietary protein intake for recuperation and treatment of the disease. These results could be used for future diet and nutrition guidelines for breast cancer patients.

Sources of Dietary Protein in Relation to Blood Pressure in a General Dutch Population

BackgroundLittle is known about the relation of different dietary protein types with blood pressure (BP). We examined whether intake of total, plant, animal, dairy, meat, and grain protein was related to BP in a cross sectional cohort of 20,820 Dutch adults, aged 20–65 y and not using antihypertensive medication.DesignMean BP levels were calculated in quintiles of energy-adjusted protein with adjustment for age, sex, BMI, education, smoking, and intake of energy, alcohol, and other nutrients including protein from other sources. In addition, mean BP difference after substitution of 3 en% carbohydrates or MUFA with protein was calculated.ResultsTotal protein and animal protein were not associated with BP (ptrend = 0.62 and 0.71 respectively), both at the expense of carbohydrates and MUFA. Systolic BP was 1.8 mmHg lower (ptrend<0.01) in the highest (>36 g/d) than in the lowest (<27 g/d) quintile of plant protein. This inverse association was present both at the expense of carbohydrates and MUFA and more pronounced in individuals with untreated hypertension (−3.6 mmHg) than in those with normal (+0.1 mmHg) or prehypertensive BP (−0.3 mmHg; pinteraction<0.01). Meat and grain protein were not related to BP. Dairy protein was directly associated with systolic BP (+1.6 mmHg, ptrend<0.01), but not with diastolic BP (ptrend = 0.24).ConclusionsTotal protein and animal protein were not associated with BP in this general untreated Dutch population. Plant protein may be beneficial to BP, especially in people with elevated BP. However, because high intake of plant protein may be a marker of a healthy diet and lifestyle in general, confirmation from randomized controlled trials is warranted.

A randomized controlled trial on the efficacy and safety of a food ingredient, collagen hydrolysate, for improving joint comfort

Introduction Current options to promote joint comfort are limited to medicines that can reduce pain but can also have adverse effects. Collagen, a major component of joint cartilage, is found in the diet, particularly in meat. Its hydrolysed form, collagen hydrolysate (CH), is well absorbed. CH may stimulate the joint matrix cells to synthesize collagen, so helping to maintain the structure of the joint and potentially to aid joint comfort.Methods In a randomized, double-blind, controlled multicentre trial, 250 subjects with primary osteoarthritis of the knee were given 10 g CH daily for 6 months.Results There was a significant improvement in knee joint comfort as assessed by visual analogue scales to assess pain and the Womac pain subscale. Subjects with the greatest joint deterioration, and with least intake of meat protein in their habitual diets, benefited most.Conclusion CH is safe and effective and warrants further consideration as a food ingredient.

Early protein intake and later obesity risk: which protein sources at which time points throughout infancy and childhood are important for body mass index and body fat percentage at 7 y of age?

A high early protein intake has been proposed to increase obesity risk. We examined whether a critical period of protein intake for later obesity may exist early in childhood and investigated the relation between protein intake from different sources and body mass index SD score and body fat percentage (BF%) at 7 y of age. The study population included 203 participants of the Dortmund Nutritional and Longitudinally Designed Study with information on diet at 6 mo, 12 mo, 18-24 mo, 3-4 y, and 5-6 y. Life-course plots were constructed to assess when protein intake (% of energy) was associated with body mass index SD score and BF% at 7 y. Mean values were then compared among tertiles (T1-T3) of protein from different sources at the important time points. The ages of 12 mo and 5-6 y were identified as critical ages at which higher total and animal, but not vegetable, protein intakes were positively related to later body fatness. In fully adjusted models, animal protein intake at 12 mo was associated with BF% at 7 y as follows [x (95% CI) BF%]: T1, 16.20 (15.23, 17.25); T2, 17.21 (16.24, 18.23); T3, 18.21 (17.12, 19.15); P for trend = 0.008. With respect to food groups, dairy, but not meat or cereal protein intake, at 12 mo was related to BF% at 7 y (P for trend = 0.07). Animal protein at 5-6 y yielded similar results (P for trend = 0.01), but food group associations were less consistent. A higher animal, especially dairy, protein intake at 12 mo may be associated with an unfavorable body composition at 7 y. The age of 5-6 y might represent another critical period of protein intake for later obesity risk.

Dietary protein intake and bone mineral content in adolescents—The Copenhagen Cohort Study

Data indicate that various protein sources may exhibit a differential effect on bone metabolism. We investigated associations of milk and meat protein intake with bone mineral content (BMC) in adolescents. Milk, but not meat, protein intake was positively associated with size-adjusted BMC. Milk-derived protein may be beneficial for bone mineralization. Milk and meat protein intake has been reported to exhibit a differential effect on serum insulin-like growth factor-I (IGF-I). IGF-I plays a key role in bone metabolism. Therefore, we investigated associations of different protein sources with BMC and bone area (BA) in adolescents. This was a cross-sectional study of 17-year-old girls (n = 63) and boys (n = 46) participating in the second follow-up of The Copenhagen Cohort Study. We measured dietary intake (7-day food record), BMC and BA (dual-energy X-ray absorptiometry), serum markers for bone turnover and serum IGF-I (immunoassays). The mean total protein intake ( approximately 1.2 g/kg) was modestly higher than that recommended. Total and milk ( approximately 0.3 g/kg) protein intake, but not meat protein intake ( approximately 0.4 g/kg), was positively associated with size-adjusted BMC (P <or= 0.05). The positive association between milk protein intake and size-adjusted BMC remained significant after correction for energy, calcium, and physical activity (P <or= 0.01) and did not seem to be mediated via current serum IGF-I. None of the analyzed protein sources was significantly associated with size-adjusted BA. Our results suggest that some components of milk protein may promote bone mineralization. Further studies are needed to elucidate this phenomenon.

Associations of Total, Dairy, and Meat Protein with Markers for Bone Turnover in Healthy, Prepubertal Boys

We previously reported that high intake of milk, but not meat, equal in protein content, increased serum insulin-like growth factor-I (sIGF-I) in prepubertal boys. sIGF-I plays a key role in bone metabolism. Therefore, the aim of this cross-sectional study was to investigate associations of total, dairy, and meat protein intake with markers for bone turnover and sIGF-I in prepubertal, healthy boys (n = 81). We measured bone turnover (enzyme-linked immunoassay) in serum osteocalcin (sOC), bone-specific alkaline phosphatase (sBAP), and C-terminal telopeptide of collagen type-I (sCTX); dietary intake was estimated from a 3-d weighed food record. sIGF-I and its binding protein-3 were assessed (immunoassay) in a subgroup of 56 boys. All statistical models included effects of age, BMI, and energy intake. Dairy protein was negatively associated with sOC (P = 0.05) but not significantly associated with sBAP and sCTX. Further analyses showed that dairy protein decreased (P = 0.05) sOC at a high meat protein intake (>0.8 g/kg), whereas meat protein increased (P = 0.03) sOC at a low dairy protein intake (<0.4 g/kg). Total and meat protein intake was positively associated with sBAP (P ≤ 0.04) but not significantly associated with sOC and sCTX. Free sIGF-I was positively associated with total (P < 0.01) and dairy (P = 0.06) protein but not with meat protein. Our results indicate that dairy and meat protein may exhibit a distinct regulatory effect on different markers for bone turnover. Future studies should focus on differential effects of dairy and meat protein on bone health during growth.

An NMR-based metabonomic investigation on effects of milk and meat protein diets given to 8-year-old boys

The objective of the study was to investigate the ability of an NMR-based metabonomic approach, applied to biofluids, to explore and identify overall exogenous and endogenous biochemical effects of a short-time high intake of milk protein or meat protein given to prepubertal children, the aim being to compare relative differences and not an absolute quantification. A total of twenty-four 8-year-old boys were asked to take 53 g protein as milk (n 12) or meat daily (n 12). At baseline and after 7 d, urine and serum samples were collected and high-resolution 1H NMR spectra were acquired on these using a 800 MHz spectrometer. The milk diet reduced the urinary excretion of hippurate, while the meat diet increased the urinary excretion of creatine, histidine and urea. The NMR measurements on serum revealed minor changes in the lipid profile, which most probably should be ascribed to an increase in the content of SCFA in the blood after consumption of the milk diet. The meat diet had no effect on the metabolic profile of serum. The study for the first time demonstrates the capability of proton NMR-based metabonomics to identify the overall biochemical effects of consumption of different animal proteins. The urine metabolite profile is more susceptible to perturbations as a result of short diet interventions than the serum metabolite profile. The milk diet-induced reduction in urinary excretion of hippurate suggests alterations in gut microflora, which may be useful information for further studies elucidating the effects of bioactive components in milk.

Meat as a First Complementary Food for Breastfed Infants: Feasibility and Impact on Zinc Intake and Status

This study was undertaken to assess the feasibility and effects of consuming either meat or iron-fortified infant cereal as the first complementary food. Eighty-eight exclusively breastfed infants were enrolled at 4 months of age and randomized to receive either pureed beef or iron-fortified infant cereal as the first complementary food, starting after 5 months and continuing until 7 months. Dietary, anthropometric, and developmental data were obtained longitudinally until 12 months, and biomarkers of zinc and iron status were measured at 9 months. Mean (+/-SE) daily zinc intake from complementary foods at 7 months for infants in the meat group was 1.9 +/- 0.2 mg, whereas that of the cereal group was 0.6 +/- 0.1 mg, which is approximately 25% of the estimated average requirement. Tolerance and acceptance were comparable for the two intervention foods. Increase in head circumference from 7 to 12 months was greater for the meat group, and zinc and protein intakes were predictors of head growth. Biochemical status did not differ by feeding group, but approximately 20% of the infants had low (<60 microg/dL) plasma zinc concentrations, and 30% to 40% had low plasma ferritin concentrations (<12 microg/L). Motor and mental subscales did not differ between groups, but there was a trend for a higher behavior index at 12 months in the meat group. Introduction of meat as an early complementary food for exclusively breastfed infants is feasible and was associated with improved zinc intake and potential benefits. The high percentage of infants with biochemical evidence of marginal zinc and iron status suggests that additional investigations of optimal complementary feeding practices for breastfed infants in the United States are warranted.

Determinants of endogenous calcium entry into the gut

In addition to food sources, calcium enters the gut by way of digestive secretions and shed mucosa. In health, such entry is as large as or larger than urinary calcium excretion. Because calcium absorption is inefficient, most of this endogenous intestinal calcium is excreted. Our aim was to determine the dietary, anthropometric, and physiologic determinants of calcium entering the digestive stream from endogenous sources. Multiple regression modeling of intake and excretion data was used with 553 metabolic balance and kinetics studies performed in 190 midlife, white women. Endogenous intestinal calcium averaged 3.29 +/- 0.83 mmol/d. Multiple regression models explaining variation in this endogenous intestinal calcium were developed with use of dietary intake, anthropometric, and serum mineral variables. All 3 groups of predictor variables individually explained up to 22% of the variation in measured values for endogenous intestinal calcium. A composite model, incorporating all 3 groups explained 29% of the variation, with phosphorus and meat protein intakes, height, weight, and serum calcium and phosphorus concentrations all independently entering the model. Phosphorus intake dominated over all the other predictors, explaining 20% of the variance all by itself, with endogenous intestinal calcium rising by 0.037 mmol for every 1 mmol of phosphorus ingested. Meat protein (but not nonmeat protein) was the only other significant dietary contributor, exhibiting a negative coefficient. As a first approximation, the amount of endogenous calcium entering the digestive stream rises with body size and with the amount of phosphorus-rich food consumed.

Sensitivity to meat protein intake and hyperoxaluria in idiopathic calcium stone formers

High protein intake is an accepted risk factor for renal stone disease. Whether meat protein intake affects oxaluria, however, remains controversial in healthy subjects and in stone formers. This study was designed (1) to test the oxaluric response to a meat protein load in male recurrent idiopathic calcium stone formers (ICSFs) with and without mild metabolic hyperoxaluria (MMH and non-MMH, respectively), as well as in healthy controls, and (2) to seek for possible disturbed vitamin B(6) metabolism in MMH, in analogy with primary hyperoxaluria. Twelve MMH, 8 non-MMH, and 13 healthy males were studied after five days on a high meat protein diet (HPD; 700 g meat/fish daily) following a run-in phase of five days on a moderate protein diet (MPD; 160 g meat/fish daily). In both diets, oxalate-rich nutrients were avoided, as well as sweeteners and vitamin C-containing medicines. Twenty-four-hour urinary excretion of oxalate was measured on the last day of each period, along with 4-pyridoxic acid (U(4PA)) and markers of protein intake, that is, urea, phosphate, uric acid, and sulfate. Serum pyridoxal 5' phosphate (S(P5P)) was measured after protein loading. Switching from MPD (0.97 +/- 0.18 g protein/kg/day) to HPD (2.26 +/- 0.38 g protein/kg/day) led to the expected rise in the urinary excretion rates of all markers of protein intake in all subjects. Concurrently, the mean urinary excretion of oxalate increased in ICSFs taken as a whole (+73 +/- 134 micromol/24 h, P = 0.024) as well as in the MMH subgroup (+100 +/- 144 micromol/24 h, P = 0.034) but not in controls (-17 +/- 63 micromol/24 h). In seven ICSFs (4 MMH and 3 non-MMH) but in none of the healthy controls (P = 0.016, chi square), an increment in oxaluria was observed and considered as significant based on the intra-assay coefficient of variation at our laboratory (8.5%). There was no difference in S(P5P)nd U(4PA)etween the groups after protein loading. Approximately one third of ICSFs with or without so-called MMH are sensitive to meat protein in terms of oxalate excretion, as opposed to healthy subjects. Mechanisms underlying this sensitivity to meat protein remain to be elucidated and do not seem to involve vitamin B(6) deficiency.

Sensitivity to meat protein intake and hyperoxaluria in idiopathic calcium stone formers

Sensitivity to meat protein intake and hyperoxaluria in idiopathic calcium stone formers

Blood cholesterol and apolipoprotein B levels in relation to intakes of animal and plant proteins in US adults

Few studies have examined the association between specific sources of protein and blood lipids in a national sample of adults. We examined this relationship in a sample of adults 20 years and older who participated in phase 1 (1988-91) of the Third National Health and Nutrition Examination Survey, a representative sample of the United States non-institutionalized population. After excluding those participants who reported having been told they had high blood cholesterol concentrations, the final sample size was 6228. Mean intakes of different sources of proteins, as a percentage of total protein, were compared in quartiles of blood lipids. Intakes were adjusted for age, sex and race. Additional adjustments were made for other dietary variables, recall day, BMI, smoking, and income. We observed a lower percentage meat, fish and poultry (MFP) protein intake, including a lower percentage of beef and pork protein, among persons in the lowest quartile of serum total cholesterol and apolipoprotein B (ApoB) concentrations than among persons in the higher quartiles. The percentage of plant protein intake was higher in the lowest quartile than in the highest quartile of serum cholesterol. We also observed a higher percentage of fruit protein intake with lower serum cholesterol and ApoB concentrations. We conclude that in this cross-sectional sample, consumption of MFP proteins was consistently higher among persons with higher cholesterol concentrations while consumption of plant proteins was consistently higher among persons with lower cholesterol concentrations. Our findings support the importance of assessing intake of specific protein sources, especially in studies that address dietary intake in relation to blood lipids.

Effects of a ‘Common Sense Diet’ on Urinary Composition and Supersaturation in Patients with Idiopathic Calcium Urolithiasis

Objectives: To test whether dietary advice as the only treatment is able to reduce urinary supersaturation in patients with idiopathic calcium urolithiasis. Methods: By means of EQUIL 2, we calculated relative supersaturations of calcium oxalate (RS_CaOx), brushite (RS_Brushite), apatite (RS_Apatite) and uric acid (RS_UA) of 24-hour urine samples of 68 healthy male controls as well as of 47 male idiopathic calcium stone formers (ICSF) before and after individualized dietary advice (DA). Main goals of DA were (1) to keep urine volume > 2,000 ml/day, and (2) to reduce meat protein intake to 1 g/kg body weight per day. Compliance was judged from changes in urine volume and U_Urea×V. Results: In the whole group of ICSF, DA did not alter supersaturations. Only in those 9 ICSF (19%) with good compliance (increase in volume and decrease in U_Urea×V), RS_CaOx and RS_UA fell by 26 and 49%, respectively. Besides poor compliance, these findings can be explained by positive correlations between changes in volume and U_Urea×V in ICSF (r = 0.319, p = 0.037) or U_Na×V (r = 0.342, p = 0.019). For instance, ICSF with volumes ≧ 2,000 ml/day had evidence of elevated protein and salt intake; thus, DA mainly focused on protein and salt intake, but not on volume. This resulted in decreases in U_Urea×V and U_Na×V, but also in volume; thus, RS_CaOx remained unaltered. Conclusions: DA is able to significantly lower RS_CaOx; however, because intakes of fluid and protein are directly and positively linked to each other, this only can be achieved if high fluid and lower meat protein intake are equally stressed in all ICSF.

Pathophysiology of idiopathic hypercalciuria: the current concept

During past decades it became fashionable to address individual facets of idiopathic hypercalciuria selectively and independently in the laboratory, thus preparing for the almost impossible conciliation of these fragments in the future. In this review a unifying concept is presented, which places excessive meat protein intake at the centre of the scheme and links it to other facets of the phenotype of the disease, such as the genetic component of bone demineralization, fasting hypercalciuria and excessive production of 1,25-dihydroxyvitamin D, as well as of various cytokines.