Dietary magnesium intake in type 2 diabetes

Hypomagnesemia and Cardiovascular Risk in Type 2 Diabetes

Hypomagnesemia is tenfold more common in individuals with type 2 diabetes (T2D), compared to the healthy population. Factors that are involved in this high prevalence are low Mg2+ intake, gut microbiome composition, medication use and presumably genetics. Hypomagnesemia is associated with insulin resistance, which subsequently increases the risk to develop T2D or deteriorates glycaemic control in existing diabetes. Mg2+ supplementation decreases T2D associated features like dyslipidaemia and inflammation; which are important risk factors for cardiovascular disease (CVD). Epidemiological studies have shown an inverse association between serum Mg2+ and the risk to develop heart failure (HF), atrial fibrillation (AF) and microvascular disease in T2D. The potential protective effect of Mg2+ on HF and AF may be explained by reduced oxidative stress, fibrosis and electrical remodeling in the heart. In microvascular disease, Mg2+ reduces the detrimental effects of hyperglycemia and improves endothelial dysfunction. Though, clinical studies assessing the effect of long-term Mg2+ supplementation on CVD incidents are lacking and gaps remain on how Mg2+ may reduce CVD risk in T2D. Despite the high prevalence of hypomagnesemia in people with T2D, routine screening of Mg2+ deficiency to provide Mg2+ supplementation when needed is not implemented in clinical care as sufficient clinical evidence is lacking. In conclusion, hypomagnesemia is common in people with T2D and is both involved as cause, probably through molecular mechanisms leading to insulin resistance, and consequence and is prospectively associated with development of HF, AF and microvascular complications. Whether long-term supplementation of Mg2+ is beneficial, however, remains to be determined.

The effects of magnesium supplementation on obesity measures in adults: a systematic review and dose-response meta-analysis of randomized controlled trials

Previous studies reported inconsistent findings regarding the effects of magnesium supplementation on obesity measures. This study was done to quantify the effect of magnesium supplementation on body weight, Body Mass Index (BMI), Waist Circumference (WC), Body Fat (BF) percentage and Waist to Hip Ratio (WHR). Four online databases (Scopus, PubMed, Google Scholar and Cochrane library) were searched until March 2020 using relevant keywords. Random-effects model was used to pool effect sizes; Cochran's Q-test and I2 index assessed heterogeneity. Sensitivity analysis and Egger test were used to check the robustness of findings and the possibility of publication bias, respectively. Thirty-two RCTs including different dosage of magnesium (48-450 mg/d), and duration (6-24 weeks) were entered to this study. Magnesium supplementation resulted in a great reduction in BMI [Weighted Mean Difference (WMD): -0.21 kg/m², 95% CI: -0.41, -0.001, P = 0.048, I² = 89.5%, n = 22], which was mainly driven by the effect among those with magnesium deficiency, insulin resistance related disorders, and obesity at baseline. No significant change was observed in bodyweight, WC, BF percentage and WHR as compared to controls. However, the change in body weight, and WC was significant in subgroups of participants with insulin resistance related disorders, hypertension, obesity, magnesium deficiency at baseline, and females. We found a significant reduction in BMI following magnesium supplementation. The change in body weight and WC were evident in certain subgroups.

Amelioration of thyroid dysfunction by magnesium in experimental diabetes may also prevent diabetes-induced renal impairment

Background

Diabetes mellitus has been reported to cause thyroid dysfunction, which may also impair renal function. Magnesium has been reported to exert ameliorative effects in diabetes mellitus. This study investigated thyroid and renal functions in experimental type-2-diabetic Wistar rats.

Methods

Experimental type-2-diabetes was induced using short duration high-fat (30%) diet feeding followed by single-dose streptozotocin (35 mg/kg i.p.). Fifty rats were randomly divided into five equal groups consisting of control, diabetes untreated, diabetes treated with either magnesium (250 mg/kg) or metformin (250 mg/kg) and diabetes treated with both metformin and magnesium simultaneously.

All treatments were carried out orally for 14days post-diabetes induction. Body weight and blood glucose was monitored using the tail tipping method before diabetes induction and thereafter on days 1,7,14 post-treatment respectively. Thereafter, blood samples were collected by cardiac puncture after light anesthesia into plain and EDTA sample bottles. Total protein, albumin, globulin (plasma) and insulin (serum) were assayed in all samples obtained. Thyroid stimulating hormone (TSH), triiodothyronine, thyroxine was also evaluated (n = 5/group) in serum while blood urea nitrogen (BUN), creatinine was assessed (n = 5/group) in plasma. Kidney homogenates were obtained per group and analyzed for renal superoxide dismutase (SOD), reduced glutathione (GSH) and lipid peroxidation (MDA). Kidney histology was also evaluated per group using both Haematoxylin and Eosin and periodic acid Schiff stains.

Results

Body weight, blood glucose, insulin, renal MDA was increased in diabetic untreated compared to other groups. Reductions (P < 0.05) in TSH, triiodothynine, Renal SOD and GSH levels where observed in diabetic untreated compared to other groups. Renal histology in diabetic untreated showed glomerula sclerosis, fused messengial cells and either collapsed tubular lumen or lumen with eosinophilic renal cast. These pathologies where partially reversed in the other experimental groups.

Conclusion

This study suggests that thyroid and renal impairment may be present in experimental type-2-diabetes. Treatment with oral magnesium may cause a partial restoration of thyroid function that may impede the development of renal dysfunction.

Effect of magnesium supplementation on endothelial function: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

Findings of past studies are inconsistent regarding the effects of magnesium (Mg) supplementation on endothelial function (EF). We performed this meta-analysis to examine the effects of magnesium supplementation on flow-mediated dilation (FMD) and carotid intima media thickness (CIMT) as markers of EF.

METHODS

Literature searches of English publications in MEDLINE and EMBASE databases were conducted up to November 2017. Results are reported as weighted mean difference (MD) with 95% confidence intervals (CI) using random effects model (DerSimonian-Laird method). Cochrane's Q test and I-squared (I²) were used to determine heterogeneity among included studies. To determine potential sources of heterogeneity, subgroup analysis was conducted for pre-defined criteria. Funnel plot and Egger's regression test were used to assess publication bias.

RESULTS

Seven RCTs with 306 participants were included. Mg supplementation significantly increased FMD (MD: 2.97; 95% CI: 0.23 to 5.70%, p = 0.033). Between studies heterogeneity was high and subgroup analysis could not identify the sources of heterogeneity. Magnesium supplementation had no significant effect on CIMT (MD: -0.13 mm; 95% CI: 0.27, 0.01; p = 0.077) with high heterogeneity. Mg dose, duration of treatment, healthy status, baseline CIMT and sample size were the potential sources of heterogeneity. Mg supplementation could decrease CIMT to a greater extent in hemodialysis (HD) patients; lower doses of Mg, higher sample size and follow up duration and subjects with higher baseline CIMT also reduced the heterogeneity to some degree (p < 0.001).

CONCLUSIONS

Magnesium supplementation may improve endothelial function without affecting carotid intima media thickness.

Association among dietary magnesium, serum magnesium, and diabetes: a cross-sectional study in middle-aged and older adults

BACKGROUND

A number of studies have reported the association between magnesium (Mg) and diabetes. However, the various conclusions were inconsistent and the data on the Chinese population was limited. The objective of this study was to evaluate the association among dietary Mg, serum Mg, and diabetes in Chinese adults.

METHODS

A cross-sectional study that contained 2904 subjects was conducted. Biochemical test results and dietary intakes of subjects were collected for analysis. The adjusted odds ratios (ORs) and the corresponding 95 % confidence intervals (95 % CIs) were used to determine the relationship between Mg status and diabetes by logistic regression.

RESULTS

The prevalence of diabetes of the investigated population was 10.1 %. Dietary Mg intake was not significantly correlated with diabetes (P > 0.05). The significant negative association between serum Mg and diabetes existed, and the multivariate adjusted OR was 0.34 (95 % CI 0.24, 0.49) in model 3 for the highest quartile of serum Mg compared with the lowest. The P values for trend were all less than 0.001 for the relationship between serum Mg and diabetes. Dietary Mg intake and serum Mg were not significantly correlated in the diabetes population (P = 0.936).

CONCLUSIONS

Dietary Mg was not significantly correlated with diabetes, while serum Mg was inversely correlated with diabetes in the Chinese population. Meanwhile, dietary Mg intake and serum Mg were not significantly correlated in the diabetes population.

Protective effect of magnesium on renal function in STZ-induced diabetic rats

Background

Diabetic nephropathy is a serious complication of T1D (type one diabetes mellitus). Persistent hyperglycemia and subsequent hypomagnesemia is believed to develop kidney damage by activation of oxidative stress. We conducted this study to investigate the renoprotective effect of magnesium sulfate (MgSO₄) on renal histopathology and oxidative stress in diabetic rats.

Methods

The study included 70 male rats. The animals were divided into seven groups: control (CRL), control receiving MgSO₄ (CRL + Mg1 & CRL + Mg8), diabetic (DM1 & DM8) and diabetic receiving MgSO₄ (DM + Mg1 & DM + Mg8). Rats were given 20 mg/kg (i.p) Streptozocin (STZ) for 5 consecutive days in (MLD) multiple low doses to induce T1D. At day 10 treatment groups were received MgSO₄ (10 g/l) in drinking water, for 1 or 8 weeks. The blood glucose, BUN and creatinine levels were measured. Renal tissue levels of malondialdehyde (MDA) were measured by thiobarbituric acid (TBA) method to evaluate the oxidative stress. Renal histopathology was done using H & E staining method.

Results

Treatment with MgSO₄ significantly decreased the blood glucose in DM + Mg1 and DM + Mg8 groups as compared with DM1 and DM8. Magnesium treatment also decreased serum BUN and tissue level of MDA significantly in both short and long term treatment. The body weight loss and kidney weight to body weight ratio was improved by MgSO₄. Histological results showed there were no differences between DM and DM + Mg groups.

Conclusion

Our findings showed that diabetic nephropathy is associated with high blood glucose level and oxidative stress (significant increase in MDA level). The renal dysfunction and oxidative stress can be improved by magnesium sulfate administration. It is suggested that protection against development of diabetic nephropathy by MgSO₄ treatment involves changes in the blood glucose and oxidative stress.

Association between magnesium : iron intake ratio and diabetes in Chinese adults in Jiangsu Province

BACKGROUND

The intake of iron is positively related to the risk of diabetes, whilst magnesium intake is inversely related. However, it is unknown whether there is an interaction between dietary magnesium and iron expressed as a ratio and diabetes.

METHODS

This is a cross-sectional household survey carried out in 2002 in Jiangsu Province, China. A total of 2849 men and women aged >or = 20 years participated (participation rate 89.0%). Iron and magnesium intake was assessed by 3-day weighed food records. Fasting plasma glucose, serum ferritin and haemoglobin were measured.

RESULTS

The mean intake of iron and magnesium was 25 mg/day and 332 mg/day, respectively. The prevalence of diabetes was 3.0% in men and 2.6% in women. Magnesium intake was negatively associated with diabetes when adjusted for age and sex, but not in a fully adjusted model. A strong inverse association between magnesium : iron intake ratio and diabetes was observed. In the fully adjusted model, the odds ratios of diabetes across quartiles of magnesium : iron intake ratio were: 1.0, 0.63 [95% confidence interval 0.32-1.25], 0.36 (0.16-0.81) and 0.48 (0.20-1.14) (P for trend 0.038). There was an interaction between central obesity and magnesium : iron ratio.

CONCLUSION

Magnesium : iron intake ratio is an independent risk marker for diabetes in Chinese adults. As this is a cross-sectional study, we cannot establish any causal relationship.

Nutritional deficiencies in morbidly obese patients: a new form of malnutrition? Part B: minerals

Even though in the Western world there is almost no limitation to a wide variety of food supply, nutritional deficiencies can be found in both normal-weight population and in the obese population. In this review, we examine the prevalence and manifestations of various mineral deficiencies in obese patients.

Magnesium and diabetes mellitus: Their relation

The aim of this review was to elaborate a synthesis about the discussions on magnesium and diabetes mellitus, in the last 14 years. The magnesium deficiency has been associated with chronic diseases, amongst them, diabetes mellitus. Epidemiological studies had shown low levels of magnesium ingestion in the general population, as well as a relation between the ingestion of food rich in magnesium and the reduction of diabetes installation and its complications. Hypomagnesemia is frequently present in diabetic patients, however there is not an exact elucidation of the mechanism of magnesium deficiency in diabetes mellitus. On the other hand, in the presence of this illness, it is observed that inadequate metabolic control can affect the corporal concentrations of magnesium, developing hypomagnesemia, which may be still directly related with some micro and macrovascular complications observed in diabetes, as cardiovascular disease, retinopathy and neuropathy. This way, the chronic complications of diabetes can appear precociously. Based on this, the supplementation with magnesium has been suggested in patients with diabetes mellitus who have proven hypomagnesemia and the presence of its complications.

Effects of administration of oral magnesium on plasma glucose and pathological changes in the aorta and pancreas of diabetic rats

1. Magnesium deficiency has recently been proposed as a novel factor implicated in the pathogenesis of the complications of diabetes. The purpose of the present study was to determine the relationship between oral Mg supplementation and changes in plasma glucose, calcium, haemoglobin, Ca/Mg ratio, blood pressure and the histology of the pancreas and vascular system in streptozotocin-induced diabetic rats. 2. Ten days after the induction of diabetes in male Wistar rats, half the diabetic animals were divided into six groups, receiving 0, 1, 3, 10, 30 or 50 g/L MgSO4 added into the drinking water for 8 weeks. Plasma glucose and Mg were measured at days 1, 2, 3, 5, 7, 14 and 21 to find the optimum dose of Mg and the time-course of its effect. In addition, histological observations were undertaken. Eight weeks later, all animals were decapitated, the pancreas and thoracic aorta were removed carefully and immersed immediately in 10% formaldehyde for histological study. 3. To evaluate the effects of Mg on plasma glucose, calcium, haemoglobin, Mg and blood pressure, another group of animals was divided into four experimental groups, as follows: (i) non-diabetic controls received tap water for 8 weeks; (ii) acute diabetics received tap water for 10 days; (iii) chronic diabetic controls received tap water for 8 weeks; and (iv) Mg-treated chronic diabetic rats received 10 g/L MgSO4 added into the drinking water 10 days after the induction of diabetes for 8 weeks. 4. Magnesium dose dependently affects plasma glucose levels. The peak effect was reached during the first 24 h following oral administration. Administration of 10 g/L MgSO4 results in the return of normal structure in the diabetic pancreas and aorta. Moreover, this concentration of MgSO4 causes glucose, haemoglobin, calcium, the Ca/Mg ratio and blood pressure to reach normal levels. Although the Mg level increases slightly following the administration of 10 g/L MgSO4 to diabetic rats, it never reaches control levels. 5. On the basis of the results of the present study, it may be concluded that chronic Mg administration may have beneficial effects on diabetes.

Urinary excretion of an intravenous 26Mg dose as an indicator of marginal magnesium deficiency in adults

BACKGROUND

Measurement of magnesium (Mg) status is problematic because tissue Mg deficiency can be present without low serum Mg concentrations.

OBJECTIVE

To evaluate a modified version of the Mg retention test using stable isotopes for the assessment of Mg status in general, and the detection of marginal Mg deficiency in particular.

DESIGN

A modified version of the Mg retention test using a small dose of (26)Mg was evaluated for assessment of Mg status in 22 healthy subjects. Muscle Mg concentration was used as reference for Mg status. A muscle biopsy was taken from the lateral portion of the quadriceps muscle from each subject. After 2 to 4 weeks, 11 mg of (26)Mg (as MgCl(2) in 14 ml water) were injected i.v. over a period of 10 min and all urine was collected for the following 24 h. Excretion of the isotopic label was expressed as percentage of the administered dose excreted in urine within 24 h.

RESULTS

Mean +/- s.d. Mg concentration in muscle was 3.85 +/- 0.17 mmol/100 g fat-free dried solids. Mean +/- s.d. excretion of the injected dose within 24 h was 7.9 +/- 2.1%. No correlation was found between muscle Mg concentration and excretion of the isotopic label (r (2 ) = 0.061, P = 0.27).

CONCLUSIONS

In this study, urinary excretion of an intravenous Mg tracer was not influenced by muscle Mg concentration and its usefulness for the detection of marginal Mg deficiency could therefore not be demonstrated.

SPONSORSHIP

Swiss Foundation for Nutrition Research and Swiss Federal Institute of Technology, Zurich, Switzerland.

Nutrition and prevention of type 2 diabetes

In recent years, the prevalence of type 2 diabetes has increased alarmingly worldwide, giving diabetes the dimension of an epidemic. Striking parallel increases in the prevalence of obesity reflect the importance of body fatness as a contributing factor to diabetes incidence. Moreover, it has been estimated that up to 75% of the risk of type 2 diabetes is attributable to obesity. Recent clinical trials and observational epidemiologic studies demonstrate the efficacy of lifestyle changes, including decreased energy intake, decreased fat intake, and weight loss, as well as regular participation in physical activity, in improving insulin sensitivity (SI) and reducing the risk of diabetes. This review evaluates evidence of the effect of diet on insulin resistance, insulin secretion, and glucose tolerance, and reflects on directions for future work toward primary prevention of type 2 diabetes.

Measurement of magnesium absorption and retention in type 2 diabetic patients with the use of stable isotopes

BACKGROUND

Magnesium deficiency has been associated with type 2 diabetes and may reduce insulin sensitivity and impair glucose tolerance. The etiology of magnesium depletion in diabetes is unclear. Animal studies suggest that diabetes may impair magnesium absorption; however, there are no published data on magnesium absorption in humans with diabetes.

OBJECTIVE

Magnesium absorption from a test meal and the excretion and retention of magnesium were compared between patients with type 2 diabetes and healthy control subjects.

DESIGN

A meal labeled with 10 mg (26)Mg isotopic label was administered, and stool and urine samples were collected for 10 and 6 d, respectively. Apparent absorption was calculated as the difference between the oral dose of (26)Mg isotopic label and the total amount of the isotopic label excreted in the feces. Magnesium retention was calculated from the apparent absorption and urinary excretion of (26)Mg isotopic label in the 6 d after administration.

RESULTS

Mean (+/- SD) values for fractional magnesium absorption in the diabetic patients and the control subjects were 59.3 +/- 7.0% and 57.6 +/- 8.5%, respectively (NS). Mean (+/- SD) urinary magnesium excretion values in the diabetic patients and the control subjects were 11.2 +/- 2.6% and 11.7 +/- 3.8%, respectively (NS); retention values were 54.2 +/- 7.1% and 51.4 +/- 6.1%, respectively (NS).

CONCLUSION

Dietary magnesium absorption and retention are not impaired in patients with reasonably well-controlled type 2 diabetes.

Oral magnesium supplementation improves insulin sensitivity and metabolic control in type 2 diabetic subjects: a randomized double-blind controlled trial

OBJECTIVE

To determine whether oral magnesium supplementation (as magnesium chloride [MgCl(2)] solution) improves both insulin sensitivity and metabolic control in type 2 diabetic subjects with decreased serum magnesium levels.

RESEARCH DESIGN AND METHODS

This study was a clinical randomized double-blind placebo-controlled trial. A total of 63 subjects with type 2 diabetes and decreased serum magnesium (serum magnesium levels </=0.74 mmol/l) treated by glibenclamide received either 50 ml MgCl(2) solution (containing 50 g MgCl(2) per 1,000 ml solution) or placebo daily for 16 weeks. Chronic diarrhea, alcoholism, use of diuretic and/or calcium antagonist drugs, and reduced renal function were exclusion criteria. Homeostasis model assessment for insulin resistance (HOMA-IR) was used as the parameter of insulin sensitivity and glucose and HbA(1c) as parameters of metabolic control.

RESULTS

At the end of the study, subjects who received magnesium supplementation showed significant higher serum magnesium concentration (0.74 +/- 0.10 vs. 0.65 +/- 0.07 mmol/l, P = 0.02) and lower HOMA-IR index (3.8 +/- 1.1 vs. 5.0 +/- 1.3, P = 0.005), fasting glucose levels (8.0 +/- 2.4 vs. 10.3 +/- 2.1 mmol/l, P = 0.01), and HbA(1c) (8.0 +/- 2.4 vs. 10.1 +/- 3.3%, P = 0.04) than control subjects.

CONCLUSIONS

Oral supplementation with MgCl(2) solution restores serum magnesium levels, improving insulin sensitivity and metabolic control in type 2 diabetic patients with decreased serum magnesium levels.