Felix Grases

Phytate in foods and significance for humans: Food sources, intake, processing, bioavailability, protective role and analysis

The article gives an overview of phytic acid in food and of its significance for human nutrition. It summarises phytate sources in foods and discusses problems of phytic acid/phytate contents of food tables. Data on phytic acid intake are evaluated and daily phytic acid intake depending on food habits is assessed. Degradation of phytate during gastro-intestinal passage is summarised, the mechanism of phytate interacting with minerals and trace elements in the gastro-intestinal chyme described and the pathway of inositol phosphate hydrolysis in the gut presented. The present knowledge of phytate absorption is summarised and discussed. Effects of phytate on mineral and trace element bioavailability are reported and phytate degradation during processing and storage is described. Beneficial activities of dietary phytate such as its effects on calcification and kidney stone formation and on lowering blood glucose and lipids are reported. The antioxidative property of phytic acid and its potentional anticancerogenic activities are briefly surveyed. Development of the analysis of phytic acid and other inositol phosphates is described, problems of inositol phosphate determination and detection discussed and the need for standardisation of phytic acid analysis in foods argued.

Urinary pH and renal lithiasis

Formation of calcium oxalate crystals, either as monohydrate or dihydrate, is apparently unrelated to urinary pH because the solubilities of these salts are practically unaltered at physiologic urinary pH values. However, a urinary pH <5.5 or >6.0 may induce uric acid or calcium phosphate crystals formation, respectively, which under appropriate conditions may induce the development of the calcium oxalate calculi. We assessed the relationship between the urinary pH and the formation of different types of calculi. A retrospective study in 1,478 patients was done. We determined the composition, macrostructure, and microstructure of the calculi and the urinary pH, 50.9% of calcium oxalate monohydrate unattached calculi were present in patients with urinary pH <5.5. We found that 34.1 and 41.5% of calcium oxalate dihydrate calculi were present in patients with urinary pH <5.5 and >6.0, respectively. Infectious calculi were found primarily in patients with urinary pH >6.0 (50.7%). Only calcium oxalate monohydrate papillary calculi were associated with urinary pH between 5.5 and 6.0 (43.1%). Urine of pH <5.5 shows an increased capacity to develop uric acid crystals, which can act as a heterogeneous nuclei of calcium oxalate crystals. In contrast, urine of pH >6.0 has an increased capacity to develop calcium phosphate crystals, which can act as a heterogeneous nuclei of calcium oxalate crystals. Oxalate monohydrate papillary calculi were associated to pH between 5.5 and 6.0 because the injured papilla acts as a heterogeneous nucleant. Consequently, measurement of urinary pH may be used to evaluate the lithogen risk of given urine.

Phytate inhibits bovine pericardium calcification in vitro

OBJECTIVE The present study examined the inhibitory effects of pyrophosphate, etidronate, and phytate on bovine pericardium calcification in vitro. METHODS Bovine pericardium was glutaraldehyde fixed and then placed in a flow chamber in the presence of a synthetic physiological fluid alone (control) or the fluid plus various concentrations of pyrophosphate, etidronate, or phytate. Following a 96-h incubation, fragments were removed and assayed for calcification by measuring calcium and phosphorus levels. RESULTS The data indicated that both pyrophosphate and etidronate at 1 mg/l (5.75 and 4.95 microM, respectively) inhibited bovine pericardium calcification, whereas neither agent had an effect at 0.5 mg/l (2.87 and 2.47 microM, respectively). Phytate was the most potent inhibitor of calcification, and the effects of this agent were apparent at levels as low as 0.25 mg/l (0.39 microM). CONCLUSIONS While pyrophosphate, etidronate, and phytate were all able to inhibit bovine pericardium calcification in vitro, phytate was found to be the most effective.

A potential role for crystallization inhibitors in treatment of Alzheimer’s disease

Melatonin is a hormone synthesized from the neurotransmitter serotonin and is found mainly in the pineal gland. Melatonin has been suggested to have several properties, acting both as an antioxidant and a neuroprotective agent. Melatonin synthesis decreases with age in all humans, but this decline is more pronounced in Alzheimers patients. In fact, melatonin inhibits the formation of beta-amyloid protein. The mechanism responsible for this decline has not been fully elucidated, although it is known that the human pineal gland calcifies with age. Such calcification necessarily implies the existence of a tissue injury that, if not reabsorbed by the immune system, will act as heterogeneous nucleant for hydroxyapatite and will induce calcification. For this reason, it is hypothesized that a lack of inhibitors of calcium salt crystallization, such as pyrophosphate and phytate, will favor calcification. Therefore, the absence of crystallization inhibitors may be a risk factor for development of Alzheimers disease, and this hypothesis should be evaluated.

Relationship between Urinary Level of Phytate and Valvular Calcification in an Elderly Population: A Cross-Sectional Study

Pathological calcification generally consists of the formation of solid deposits of hydroxyapatite (calcium phosphate) in soft tissues. Supersaturation is the thermodynamic driving force for crystallization, so it is believed that higher blood levels of calcium and phosphate increase the risk of cardiovascular calcification. However several factors can promote or inhibit the natural process of pathological calcification. This cross-sectional study evaluated the relationship between physiological levels of urinary phytate and heart valve calcification in a population of elderly out subjects. A population of 188 elderly subjects (mean age: 68 years) was studied. Valve calcification was measured by echocardiography. Phytate determination was performed from a urine sample and data on blood chemistry, end-systolic volume, concomitant diseases, cardiovascular risk factors, medication usage and food were obtained. The study population was classified in three tertiles according to level of urinary phytate: low (<0.610 μM), intermediate (0.61–1.21 μM), and high (>1.21 μM). Subjects with higher levels of urinary phytate had less mitral annulus calcification and were less likely to have diabetes and hypercholesterolemia. In the multivariate analysis, age, serum phosphorous, leukocytes total count and urinary phytate excretion appeared as independent factors predictive of presence of mitral annulus calcification. There was an inverse correlation between urinary phytate content and mitral annulus calcification in our population of elderly out subjects. These results suggest that consumption of phytate-rich foods may help to prevent cardiovascular calcification evolution.

Non-infectious phosphate renal calculi: Fine structure, chemical and phase composition

Abstract Background. Chemical composition of internally non-homogeneous phosphate stones should be related to the conditions prevailing during the formation of each individual part. Objective. The object of this paper was to provide a detailed study of phosphate stone composition on the micro- and macro-scales. Methods. Fine inner structure, chemical and phase composition of 10 phosphate calculi from different patients were determined by chemical (wet) analysis, observation by scanning microscope, semi-quantitative determination of Ca, Mg, P and C by energy dispersive X-ray and by X-ray diffraction. Results. Eight calculi are formed by amorphous calcium phosphate and two by hydroxyapatite. Magnesium was inversely related to Ca/P ratio. Point chemical composition of solid phase varies in wide limits, i.e. composition of calculus interior is highly inhomogeneous on the microscale. All studied calculi contained an abundance of organic matter incorporated in their volume; the content of carbon was double the calcium content in molar quantities. Conclusions. Phosphate renal calculi with the low Ca/P molar ratio predominantly consist of amorphous calcium phosphate whereas those with a high Ca/P molar ratio are composed of poorly crystalline hydroxyapatite which can be partially carbonated. Magnesium may be an inhibitor of HAP formation from urine. Abundant organic matter incorporated into the calculus volume indicates its decisive role at stone formation. Variable point composition of stones implies widely varying conditions during their development.

Characterization of deposits in patients with calcific tendinopathy of the supraspinatus. Role of phytate and osteopontin.

Calcific tendinopathy of the tendons of the rotator cuff is common in adults. These calcifications tend to be reabsorbed after a period of acute pain. This study evaluated the morphologic characteristics of calcific deposits and the participation of phytate and osteopontin (OPN) in their development. Calcific deposits were removed from 21 patients with calcific tendinopathy by ultrasound‐guided needle puncture under local anesthesia. The removed deposits were evaluated by scanning electron microscopy, X‐ray diffraction and Fourier transform infrared spectroscopy. The amounts of calcium and phosphorus in the deposits were semi‐quantitatively determined by energy dispersive X‐ray analysis. Phytate was determined in 2 h urine samples, and OPN was extracted from a pool of deposits. The calcific deposits consisted of amorphous and poorly crystalline carbonated hydroxyapatite containing molecular water and organic matter. OPN was associated with the hydroxyapatite deposits. Phytate concentrations were significantly lower in the urine of patients with calcific tendinopathy than in healthy controls. The deficit in crystallization inhibitors such as phytate, and the presence of regulators such as OPN, may play important roles in the development of calcific tendinopathy.

Dietary Phytate and Interactions with Mineral Nutrients

For decades phytate has been regarded as an antinutrient, as, during gastrointestinal passage, it may inhibit the absorption of some essential trace elements and minerals, which under certain dietary circumstances leads to calcium, iron and zinc deficiencies. In the last 25 years, however, important healthy beneficial properties of phytate have been observed (antioxidant, anticancer, renal stone prevention, etc.). In this chapter, the effects of phytate on mineral and trace element bioavailability are reported. From the available information it can be deduced that in balanced diets the inhibitory effects of phytate on mineral absorption are low, and little evidence exists from nutritional surveys that in well-nourished population groups,dietary phytate may really affect the status of iron, zinc and calcium. Under malnutrition and non-balanced diets, low in minerals and essential trace elements but high in phytate, however, the situation is different. Vulnerable groups in developing and developed countries, with inadequate intake or deficiencies of minerals and trace elements, need to increase total intake of these elements. This can be accomplishedvia the daily diet or improve their bioavailability, through modification of factors inhibiting or enhancing the bioavailability of the minerals and trace elements in the diet.