The Status Of Trace Elements And Heavy Metals In Toenails And Their Associations With Insulin Sensitivity Among Vegetarians In Shanghai

BackgroundAt present,there are few reports on the long-term trace element nutritional status and heavy metal accumulation in vegetarians.Examining the concentrations of trace elements and heavy metals in toenails among vegetarians and studying their associations with insulin sensitivity can help provide a scientific evidence for reducing micronutrient malnutrition and heavy metal accumulation in vegetarians,as well as providing nutritional advice on mineral intake to prevent and control insulin resistance and diabetes.Objective:1.To investigate the status of trace elements and heavy metals among Chinese vegetarians.2.To investigate the status of glucose metabolism and insulin sensitivity among Chinese vegetarians.3.To investigate the associations between concentrations of trace elements and heavy metals in nails and insulin sensitivity.MethodsWe recruited 220 vegetarians and 220 omnivores matched by age and sex from Shanghai.Social demographic and lifestyle characteristics were collected using general information questionnaire.Physical examination and dietary survey using 24 h recalled method were implemented to assess basic status and daily dietary intakes of some trace elements.Inductively coupled plasma mass spectrometry(ICP-MS)method was used to examine the concentrations of trace elements including aluminum,chromium,manganese,ferrum,nickel,copper,selenium;and heavy metals including arsenic,cadmium?mercury?lead in toenails of subjects.Elbow vain blood samples were collected to examine fasting blood glucose and fasting insulin concentrations.Insulin secretion index(HOMA-B)and insulin resistance index(HOMA-IR)were calculated to assess insulin sensitivity.Paired t-test and covariance analysis were used to examine the differences on concentrations of trace elements and heavy metals,glucose metabolism and insulin sensitivity indices between vegetarians and omnivores.Then we used multi-linear regression to investigate the association between nail concentrations of trace elements,heavy metals and insulin sensitivity after adjusting for confounders.Results1.The mean concentration of selenium in toenails of Shanghai vegetarians was 0.53±0.16?g/g,which was lower than that of omnivores(0.69±0.53?g/g,P<0.05).Vegetarians had a lower concentration of mercury in toenails at 0.15±0.57?g/g than that of omnivores at 0.16±0.11?g/g.2.The fasting blood glucose of vegetarians was 4.63±0.67 mmol/L,and the fasting insulin of vegetarians was 4.89±2.30 mU/L,which were both lower than those of omnivores(P<0.05).The average HOMA-IR of vegetarians was 1.03±0.59,which was significantly lower than that of omnivores(1.30±0.71,P<0.05).3.In population with dietary intake of selenium at or over recommended nutrient intake level,the concentration of selenium in toenails was positively associated with fasting insulin and HOMA-IR(P<0.05),however no association was observed in population with dietary intake of selenium under recommended nutrient intake level.The concentration of nickel in toenails was positively associated with fasting insulin,HOMA-IR and HOMA-B(P<0.05).Conclusions1.The concentrations of selenium and mercury in toenails were lower in vegetarians than omnivores.2.Vegetarians have lower fasting blood glucose,fasting insulin and HOMA-IR than omnivores.3.In population with dietary intake of selenium at or over recommended nutrient intake level,the concentration of selenium in toenails was positively associated with fasting insulin and HOMA-IR,however no association was observed in population with dietary intake of selenium under recommended nutrient intake level.The concentration of nickel in toenails was positively associated with fasting insulin,HOMA-IR and HOMA-B.