Hypercalcemia in Children Using the Ketogenic Diet: A Multicenter Study

The effects of popular diets on bone health in the past decade: a narrative review

Bone health encompasses not only bone mineral density but also bone architecture and mechanical properties that can impact bone strength. While specific dietary interventions have been proposed to treat various diseases such as obesity and diabetes, their effects on bone health remain unclear. The aim of this review is to examine literature published in the past decade, summarize the effects of currently popular diets on bone health, elucidate underlying mechanisms, and provide solutions to neutralize the side effects. The diets discussed in this review include a ketogenic diet (KD), a Mediterranean diet (MD), caloric restriction (CR), a high-protein diet (HP), and intermittent fasting (IF). Although detrimental effects on bone health have been noticed in the KD and CR diets, it is still controversial, while the MD and HP diets have shown protective effects, and the effects of IF diets are still uncertain. The mechanism of these effects and the attenuation methods have gained attention and have been discussed in recent years: the KD diet interrupts energy balance and calcium metabolism, which reduces bone quality. Ginsenoside-Rb2, metformin, and simvastatin have been shown to attenuate bone loss during KD. The CR diet influences energy imbalance, glucocorticoid levels, and adipose tissue, causing bone loss. Adequate vitamin D and calcium supplementation and exercise training can attenuate these effects. The olive oil in the MD may be an effective component that protects bone health. HP diets also have components that protect bone health, but their mechanism requires further investigation. In IF, animal studies have shown detrimental effects on bone health, while human studies have not. Therefore, the effects of diets on bone health vary accordingly.

Persistent hypercalcemia mimicking hypophosphatasia after discontinuation of a ketogenic diet: a case report

OBJECTIVES

Hypercalcemia has been reported as an uncommon complication of the ketogenic diet (KD). Here we present a toddler whose hypercalcemia persisted for 2 months after stopping the KD.

CASE PRESENTATION

A 2 year 11-month-old child with global developmental delay, infantile spasms, neuromuscular weakness with limited mobility, tracheostomy and ventilator dependence, and oropharyngeal dysphagia with G-tube dependence presented with hypercalcemia in the setting of recurrent vomiting. At presentation, the patient was adherent to a KD and taking topiramate since infancy for intractable seizures. His laboratory parameters at presentation showed hypercalcemia (11.9 mg/dL), hypercalciuria, acute renal failure, low alkaline phosphatase (76 IU/L [110-302 IU/L]), parathyroid hormone (PTH) <6 pg/mL (18-80 pg/mL), normal thyroid function, cortisol and vitamin D level. The patient's hypercalcemia persisted post-discontinuation of the KD and topiramate. PTH-related protein was mildly elevated at 15.3 pmol/L. Follow-up laboratory and imaging studies ruled out malignancy. He was managed with calcitonin 4 u/kg/dose Q12H × 1 day and 8 u/kg/dose Q8H × 1 day, hydration and low-calcium formula. Post-discontinuation of the KD, normalization of alkaline phosphatase levels preceded the normalization of calcium on day 55 and PTH on day 85.

CONCLUSIONS

Hypercalcemia may persist for an extended period after weaning from a KD; lab parameters may mimic that of hypophosphatasia as previously described in the literature. Normalization of alkaline phosphatase, a marker of bone turnover, indicates recovery from the adynamic state induced by the KD and typically precedes the normalization of calcium and PTH.

Effects of very low carbohydrate ketogenic diets on skeletal health

PURPOSE OF REVIEW

Very low carbohydrate ketogenic diet (KD) therapy has been associated with skeletal demineralization in children with drug-resistant epilepsy, but the cause of this association is unclear. Recently, interest in the KD has grown owing to its potential benefits for other illnesses including cancer, type 2 diabetes, obesity, and polycystic kidney disease. Summaries of the best available evidence regarding effects of a KD on skeletal health are lacking.

RECENT FINDINGS

Recent rodent studies found that a KD can harm the growing skeleton, which corroborates most but not all studies in pediatric patients. Proposed mechanisms include chronic metabolic acidosis and depressed osteoanabolic hormones. Relative to other weight-reducing diets, a weight-reducing KD for treatment of obesity and/or type 2 diabetes in adults has not been associated with adverse skeletal effects. By contrast, recent evidence suggests that adaptation to a eucaloric KD may impair bone remodeling in elite adult athletes. Discrepancies in the literature may relate to differences between study populations and in diet formulation.

SUMMARY

Attention to skeletal health is warranted when using KD therapy given the uncertainty in the literature and suggestive harms in certain populations. Future research should focus on potential mechanisms of injury.

Breaking the Cycle of Recurrent Calcium Stone Disease

Calcium stones are common and recurrent in nature, yet few therapeutic tools are available for secondary prevention. Personalized approaches for stone prevention have been informed by 24-hour urine testing to guide dietary and medical interventions. However, current evidence is conflicting about whether an approach guided by 24-hour urine testing is more effective than a generic one. The available medications for stone prevention, namely thiazide diuretics, alkali, and allopurinol, are not always prescribed consistently, dosed correctly, or tolerated well by patients. New treatments on the horizon hold the promise of preventing calcium oxalate stones by degrading oxalate in the gut, reprogramming the gut microbiome to reduce oxalate absorption, or knocking down expression of enzymes involved in hepatic oxalate production. New treatments are also needed to target Randall's plaque, the root cause of calcium stone formation.

Hypercalcemia: A Review

IMPORTANCE

Hypercalcemia affects approximately 1% of the worldwide population. Mild hypercalcemia, defined as total calcium of less than 12 mg/dL (<3 mmol/L) or ionized calcium of 5.6 to 8.0 mg/dL (1.4-2 mmol/L), is usually asymptomatic but may be associated with constitutional symptoms such as fatigue and constipation in approximately 20% of people. Hypercalcemia that is severe, defined as total calcium of 14 mg/dL or greater (>3.5 mmol/L) or ionized calcium of 10 mg/dL or greater (≥2.5 mmol/L) or that develops rapidly over days to weeks, can cause nausea, vomiting, dehydration, confusion, somnolence, and coma.

OBSERVATIONS

Approximately 90% of people with hypercalcemia have primary hyperparathyroidism (PHPT) or malignancy. Additional causes of hypercalcemia include granulomatous disease such as sarcoidosis, endocrinopathies such as thyroid disease, immobilization, genetic disorders, and medications such as thiazide diuretics and supplements such as calcium, vitamin D, or vitamin A. Hypercalcemia has been associated with sodium-glucose cotransporter 2 protein inhibitors, immune checkpoint inhibitors, denosumab discontinuation, SARS-CoV-2, ketogenic diets, and extreme exercise, but these account for less than 1% of causes. Serum intact parathyroid hormone (PTH), the most important initial test to evaluate hypercalcemia, distinguishes PTH-dependent from PTH-independent causes. In a patient with hypercalcemia, an elevated or normal PTH concentration is consistent with PHPT, while a suppressed PTH level (<20 pg/mL depending on assay) indicates another cause. Mild hypercalcemia usually does not need acute intervention. If due to PHPT, parathyroidectomy may be considered depending on age, serum calcium level, and kidney or skeletal involvement. In patients older than 50 years with serum calcium levels less than 1 mg above the upper normal limit and no evidence of skeletal or kidney disease, observation may be appropriate. Initial therapy of symptomatic or severe hypercalcemia consists of hydration and intravenous bisphosphonates, such as zoledronic acid or pamidronate. In patients with kidney failure, denosumab and dialysis may be indicated. Glucocorticoids may be used as primary treatment when hypercalcemia is due to excessive intestinal calcium absorption (vitamin D intoxication, granulomatous disorders, some lymphomas). Treatment reduces serum calcium and improves symptoms, at least transiently. The underlying cause of hypercalcemia should be identified and treated. The prognosis for asymptomatic PHPT is excellent with either medical or surgical management. Hypercalcemia of malignancy is associated with poor survival.

CONCLUSIONS AND RELEVANCE

Mild hypercalcemia is typically asymptomatic, while severe hypercalcemia is associated with nausea, vomiting, dehydration, confusion, somnolence, and coma. Asymptomatic hypercalcemia due to primary hyperparathyroidism is managed with parathyroidectomy or observation with monitoring, while severe hypercalcemia is typically treated with hydration and intravenous bisphosphonates.

Fad Diets: Facts and Fiction

The global prevalence of obesity is alarmingly high and is impacting both developed and underdeveloped countries, beyond the borders of ethnicity, sex, and age. On the other hand, the global interest in dieting has increased, and people are obsessed with certain fad diets, assuming them as a magic bullet for their long-term problems. A fad diet is a popular dietary pattern known to be a quick fix for obesity. These diets are quite appealing due to the proposed claims, but the lack of scientific evidence is a big question mark. Such diets are often marketed with specific claims that defy the basic principles of biochemistry and nutritional adequacy. These diets may have protective effects against obesity and certain chronic diseases like cardiovascular diseases, metabolic syndrome, and certain cancers. Limited evidence exists to support the proposed claims; rather certain studies suggest the negative health consequences of long-term adherence to such dietary patterns. Many fad diets have emerged in the previous few decades. This review article will explore the current evidence related to the health impacts of some most popular diets: Atkins diet, ketogenic diet, Paleolithic diet, Mediterranean diet, vegetarian diet, intermittent fasting and detox diet.

Molecular mechanisms altering tubular calcium reabsorption

The majority of calcium filtered by the glomerulus is reabsorbed along the nephron. Most is reabsorbed from the proximal tubule (> 60%) via a paracellular pathway composed of the tight junction proteins claudins-2 and -12, a process driven by sodium and consequently water reabsorption. The thick ascending limb reabsorbs the next greatest amount of calcium (20-25%), also by a paracellular pathway composed of claudins-16 and -19. This pathway is regulated by the CaSR, whose activity increases the expression of claudin-14, a protein that blocks paracellular calcium reabsorption. The fine tuning of urinary calcium excretion occurs in the distal convoluted and connecting tubule by a transcellular pathway composed of the apical calcium channel TRPV5, the calcium shuttling protein calbindin-D_28K and the basolateral proteins PMCA1b and the sodium calcium exchanger, NCX. Not surprisingly, mutations in a subset of these genes cause monogenic disorders with hypercalciuria as a part of the phenotype. More commonly, "idiopathic" hypercalciuria is encountered clinically with genetic variations in CLDN14, the CASR and TRPV5 associating with kidney stones and increased urinary calcium excretion. An understanding of the molecular pathways conferring kidney tubular calcium reabsorption is employed in this review to help explain how dietary and medical interventions for this disorder lower urinary calcium excretion.

3-Hydroxybutyrate administration elevates plasma parathyroid hormone in a pilot human randomized, controlled, cross over trial

CONTENT

Ketone bodies, in particular 3-hydroxybutyrate (3OHB), are known to possess important energetic and signaling capacities. There is a growing block of evidence, that ketogenic dieting (KD), fasting, and sodium glucose transporter 2 inhibitor (SGLT2i) treatment are associated with hyperparathyroidism and negative bone health.

OBJECTIVE

We aimed to study the effect of exogenous 3OHB administration on bone metabolism, specifically the effect on parathyroid hormone (PTH) and calcium/phosphate homeostasis.

DESIGN

A randomized, controlled, cross over study with two arms: i) saline infusion and ii) 3OHB infusion.

SETTING

The study was conducted at Aarhus University Hospital.

PARTICIPANTS

We examined eight healthy human subjects aged 50-70 years.

INTERVENTION

Continuous intravenous DL-3OHB-NaCl infusion or 0.9% NaCl was administered for 390 min.

MAIN OUTCOME MEASURES

The study was designed to test the impact of 3OHB on PTH, calcium-phosphate, C-terminal Telopeptide (CTX), and Procollagen I N-terminal Propeptide (PINP). The study was a post hoc study.

RESULTS

The PTH concentration increased by 25% with a concomitant drop in phosphate of 30% in the 3OHB group. 3OHB infusion increased concentrations of CTX by 5%, without changes in PINP and albumin corrected calcium concentrations.

CONCLUSION

In conclusion, 3OHB administration increases PTH concentration and markers of bone resorption. These findings suggest a possible negative effect on bone health, which needs to be determined in future studies.

[Obesity, inflammation and COVID-19: preventive interest of ketogenic diet?]

Obesity is considered a pandemic responsible for millions of deaths worldwide for many years. At the end of 2019, the Coronavirus disease 2019 (COVID-19) appeared, causing the death of more than a million people in less than a year. Numerous studies suggest that obesity could be defined as key to the onset of severe forms of this emerging disease. Indeed, SARS-CoV2 infects the host by binding to ACE2 receptors present on the surface of the cells and causes excessive secretion of pro-inflammatory cytokines including IL-1, IL-6 and TNF-α, which lead to developing acute respiratory distress syndrome (ARDS). It therefore seems essential to make up effective preventive strategies to protect this part of the population from the risk of developing a severe form of COVID-19. The ketogenic diet, which is low in sugars and high in fat, has interesting properties, both in the fight against obesity but also against severe infections. This article focuses on the latest scientific advances that make it possible to consider the ketogenic diet as a preventive strategy that simultaneously reduces the development of obesity while strengthening the immune system, two key actions in the fight against SARS-CoV2 infections and severe forms of COVID-19.

A Novel Germline Mutation of ADA2 Gene in Two "Discordant" Homozygous Female Twins Affected by Adenosine Deaminase 2 Deficiency: Description of the Bone-Related Phenotype

Adenosine Deaminase 2 Deficiency (DADA2) syndrome is a rare monogenic disorder prevalently linked to recessive inherited loss of function mutations in the ADA2/CECR1 gene. It consists of an immune systemic disease including autoinflammatory vasculopathies, with a frequent onset at infancy/early childhood age. DADA2 syndrome encompasses pleiotropic manifestations such as stroke, systemic vasculitis, hematologic alterations, and immunodeficiency. Although skeletal abnormalities have been reported in patients with this disease, clear information about skeletal health, with appropriate biochemical-clinical characterization/management, its evolution over time and any appropriate clinical management is still insufficient. In this paper, after a general introduction shortly reviewing the pathophysiology of Ada2 enzymatic protein, its potential role in bone health, we describe a case study of two 27 year-old DADA2 monozygotic female twins exhibiting bone mineral density and bone turnover rate abnormalities over the years of their clinical follow-up.

Incidence and Characteristics of Kidney Stones in Patients on Ketogenic Diet: A Systematic Review and Meta-Analysis

Very-low-carbohydrate diets or ketogenic diets are frequently used for weight loss in adults and as a therapy for epilepsy in children. The incidence and characteristics of kidney stones in patients on ketogenic diets are not well studied. Methods: A systematic literature search was performed, using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from the databases’ inception through April 2020. Observational studies or clinical trials that provide data on the incidence and/or types of kidney stones in patients on ketogenic diets were included. We applied a random-effects model to estimate the incidence of kidney stones. Results: A total of 36 studies with 2795 patients on ketogenic diets were enrolled. The estimated pooled incidence of kidney stones was 5.9% (95% CI, 4.6–7.6%, I2 = 47%) in patients on ketogenic diets at a mean follow-up time of 3.7 +/− 2.9 years. Subgroup analyses demonstrated the estimated pooled incidence of kidney stones of 5.8% (95% CI, 4.4–7.5%, I2 = 49%) in children and 7.9% (95% CI, 2.8–20.1%, I2 = 29%) in adults, respectively. Within reported studies, 48.7% (95% CI, 33.2–64.6%) of kidney stones were uric stones, 36.5% (95% CI, 10.6–73.6%) were calcium-based (CaOx/CaP) stones, and 27.8% (95% CI, 12.1–51.9%) were mixed uric acid and calcium-based stones, respectively. Conclusions: The estimated incidence of kidney stones in patients on ketogenic diets is 5.9%. Its incidence is approximately 5.8% in children and 7.9% in adults. Uric acid stones are the most prevalent kidney stones in patients on ketogenic diets followed by calcium-based stones. These findings may impact the prevention and clinical management of kidney stones in patients on ketogenic diets.