In recent years, the incidence of kidney stones has increased in a number of nations[13]. Most stones were mainly composed of calcium oxalate, calcium phosphate, and uric acid[14]. Inherited conditions, drug use, obesity, and other disorders all contribute to an increased chance of developing stones. There is an association between certain dietary and lifestyle variables and an increased risk of kidney stones. Dietary consumption, in particular, plays a significant role in the pathogenesis of kidney stones[15]. Vitamins cannot be synthesized by the body and must be taken in, as inadequate or slight vitamin deficiency is a risk factor for many chronic diseases[16]. Because some vitamins are related to the metabolism of oxalic acid, uric acid and calcium and phosphorus in the body, they may have a certain impact on the pathological process of urinary stone formation. Currently, vitamins known to be closely related to urolithiasis are vitamin A, vitamin B6, vitamin C, vitamin D, and vitamin K [11, 12, 17, 18]. In addition, there is less evidence of a connection between levels of vitamin B12 and kidney stones, and there is a dearth of large-scale cross-sectional studies that are typical of the population.
In our research, which was a cross-sectional one, we discovered a connection between the amount of vitamin B12 consumed and the likelihood of developing kidney stones. In this cross-sectional study that enrolled 4599 participants, we demonstrated that higher Vitamin B12 intake levels were negatively associated with kidney stone prevalence. This association remained statistically significant after we adjusted for all covariates, including age, sex, BMI, serum calcium, serum uric acid, total serum cholesterol, race, diabetes, and hypertension.
For all participants, the average vitamin B12 level in stone patients was significantly higher than in regular participants. According to the results of an uncorrected logistic regression model, there was an inverse correlation between the occurrence of kidney stones and a quarter of vitamin B12. Interestingly, in the subgroup analysis, after controlling for confounding variables, we discovered that there was an association with ORs for kidney stones that exhibited a U-shaped pattern in the 20–34 age group. This was a finding that we considered to be quite interesting. Research shows that vitamin B12 levels decrease and the incidence of kidney stones increases with age [19, 20]. This is consistent with our results. In the subgroup analysis, we found a negative correlation between vitamin B12 levels and stone incidence in male and female groups after adjusting for confounding factors. And we found the best vitamin B12 intake was 5.84–62.71 mcg/day for men and 3.5–5.84 mcg/day for women.
It was found that plasma vitamin B12 levels were lower in patients with type 2 diabetes taking metformin, and vitamin B12 levels were negatively correlated with obesity and blood pressure[21–23]. In addition, research shows that people with diabetes, hypertension or obesity are more likely to develop kidney stones[24, 25], which is consistent with our results. Based on our current data, perhaps this phenomenon may be related to vitamin B12.
Vitamin B12 is essential in the kidneys; although the glomeruli do not filter it, it needs to be reuptake in the proximal tubules to prevent urine loss [19]. B vitamins are involved in synthesising purine biosynthesis, and excessive administration can increase uric acid, the end product of purine metabolism[26, 27]. Increased excretion of uric acid in the urine can lead to microcrystals of uric acid in the renal tubules or urinary system, which are clinically manifested as kidney stones[28]. And research shows that as serum uric acid concentration increases, the risk of new stone formation increases[29]. In our study, patients with kidney stones had higher serum uric acid levels than non-kidney stone patients, but their vitamin B12 intake was lower. The reason for this phenomenon needs to be further explored because we can not exclude the effect of other factors on serum uric acid concentration.
The current research has several strong points. First, to the best of our knowledge, this research is the first time that the biggest sample size possible that is representative of the whole country has been utilized to investigate the connection between a person's vitamin B12 consumption and their risk of developing kidney stones. Second, this is the first research of its kind to indicate that higher consumption of vitamin B12 is associated with a lower risk of kidney stones in both men and women. Third, in order to acquire more trustworthy findings, we made several modifications to the potential confounding variables. Despite this, there are a number of restrictions that apply to this research. Because this is cross-sectional research, we are unable to draw any conclusions about the nature of the causal association or the timing of events between the formation of kidney stones and the use of vitamin B12. Second, the NHANES database is based on self-report, which means that there is a possibility of memory bias when analyzing the questionnaire "Ever experienced kidney stones?" and 24-hour food intake recalls. Even though we took into account the most important potential confounding variables, it is possible that there are still some that we have missed.