it is well recognized that the mealtime insulin requirement in type 1 diabetes ( t1 dm ) patients is driven mostly by carbohydrate content and that monitoring it can improve glucose levels . the american diabetes association recommends meal plans based on carbohydrate counting as a key strategy to achieve glycemic control . an impact of protein containing food on glycemia in diabetes has been studied for many decades ; however , it is unclear whether or not the calculation of other food components can also be used to optimize glucose levels [ 3 , 4 ] . some studies have suggested that counting the amount of fat and protein ( using fat / protein exchanges ) may be beneficial for reaching glycemic control in t1 dm children . such an approach could be particularly feasible in t1 dm patients treated with continuous subcutaneous insulin infusion ( csii ) via insulin pump . one of the features implemented in some personal insulin pumps is the dual - wave bolus ( dwb ) option , which delivers the combination of an instant standard premeal insulin bolus followed by a square bolus ( sb ) infused over several hours , helping to tailor prandial insulin delivery to the composition of a meal . this pump option may be particularly useful for mixed , fat-/protein - rich meals since such food seems to modify postmeal glucose patterns with a less rapid and more prolonged increase in plasma glucose concentration . it has recently been shown among a cohort of pediatric patients with long - lasting t1 dm , using pump therapy , that for mixed meals insulin dosing based on both carbohydrate and fat / protein counting leads to lower postprandial glycemic levels than the conventional counting of carbohydrates only . . however , the studies performed so far estimating the glycemic effect , mostly on postprandial glucose levels , of fat and protein ingestion had some serious limitations . for example , they evaluated either the effect of a meal containing both fat and protein [ 5 , 8 ] or the effect of just fat added to a mixed meal . to our knowledge , until now no study has examined the effect of sole protein ingestion . the aim of this study was to estimate the impact of ingestion of a pure protein load on glucose levels in t1 dm patients treated with personal insulin pumps . we examined 10 t1 dm patients ( 6 females , 4 males ) treated with insulin pumps ( medtronic paradigm 722 or veo ) equipped with a continuous glucose monitoring system ( cgms ) option . during the study , enlite sensors ( medtronic ) all of the patients were white caucasians under the medical care of the department of metabolic diseases , university hospital , krakow , poland . the selection of patients was based on good prestudy compliance as assessed by good glycemic control ( hba1c level less than 7.5% , 58  mmol / mol ) , the patient 's usage of the bolus wizard ( bolus calculator ) option for more than 90% of boluses , changing infusion sets according to manufacturer 's recommendation , and using at least one electrode for cgms per month during the preceding year . all patients gave informed consent , and the study was approved by the bioethical committee of the jagiellonian university . before study entry ( one to two weeks preceding day 1 ) , the patients ' baseline insulin infusion was optimized to minimize the differences in fasting glucose levels to less than 30  mg / dl between any two time points between 9 a.m. and 3 p.m. the procedure of optimization was based on a retrospective analysis of cgms records and involved increasing or decreasing the rate of basal insulin infusion two hours before the observed rise or fall in glucose level . subsequently , the new settings of the basal infusion rate were rechecked with cgms to meet the study criteria . in phase i ( day 1 ) , a fasting test ( between 9 a.m. and 3 p.m. ) was performed to confirm the stable glucose patterns ( as defined above ) on current basal insulin infusion settings . in phase ii ( day 2 ) , the patients were exposed to a single pure protein load by ingesting a commercially available preparation ( protifar , nutricia , milk derived proteins ) . in its 100  ml volume , the product contained 88.5 grams of pure protein , 1.6 grams of fat , and less than 1.5 grams of carbohydrates ( lactose ) , as well as minerals and micronutrients . all the patients were exposed to a dose of 0.3  g of pure protein ( 0.34  ml of protifar / kg dissolved in 200  ml of water ) for each kg of body weight ; the load was administered at 9 a.m. such a dose of protein is the equivalent of the usual protein portion in a medium - size meal , based on the dietary recommendations for patients with diabetes ( 1520% of total daily energy intake ) . both phases were performed in home settings ; the patients were given precise instructions concerning the procedure . the rate of basal insulin infusion during the protein load test was the same as that defined initially in phase i ; no modifications or extra insulin boluses were permitted . cgms record was performed in both phases , during which the patients avoided physical activity . glucose patterns were recorded during 6 hours of phase i ( fasting ) and 6 hours of phase ii ( protein load ) . there was no consistency in the age of cgm sensors during phase i and phase ii ; however , we strictly avoided performing tests during the first or last ( 6th ) day after sensor insertion . the difference between the two phases was assessed by using the dependent t - test or paired sample wilcoxon signed rank test , when applicable . the patients ' mean age was 32.3 years , mean t1 dm duration was 11.7 years , and mean hba1c was 6.85% ( 51  mmol / mol ) . mean baseline glucose levels were 119.8 and 117.6  mg / dl for phase i and phase ii , respectively ( p = 0.68 ) . mean maximal glucose levels were 146.4 and 145.2  mg / dl for phase i and phase ii , respectively ( p = 0.85 ) . mean maximal glucose level increment was similar for the entire 6-hour fasting and protein load test ( 26.6  mg / dl versus 27.6  mg / dl , resp . there was only a borderline difference between the change in baseline versus 6th hour glucose levels for the fasting state versus protein load test ( 12.5  mg / dl and 19.0  mg / dl , resp . , p = 0.04 ) . the glucose variability assessed by cgms - based standard deviation of mean glucose levels was 36.4 and 38.9  mg / dl for phase i and phase ii , respectively ( p = 0.01 ) . there were no episodes of infusion set malfunctions during phase i or phase ii of the study , and no hypoglycemia was recorded during fasting or after loading . here , for the first time , we evaluated the impact of the ingestion of a pure protein load on glucose levels in adult t1 dm subjects treated with insulin pumps . in this short - term clinical experiment , we found that protein consumption had very little effect on the glycemia of the examined cohort of patients . contradictory to our study results , there have been several earlier papers reporting a substantial rise in glucose levels in t1 dm patients as an effect of the consumption of noncarbohydrate food components [ 5 , 8 , 10 ] . however , these reports involved either fat only or fat and protein combined , because , in real - life settings , they are often consumed together in products chosen by diabetic individuals , such as meat , poultry , fish , and dairy products . thus , the discrepancy between earlier studies and our results may be explained by the variable short - term impact of fat and protein versus protein only consumption on glucose homeostasis through different mechanisms of hepatic gluconeogenesis , postmeal insulin resistance , release of glucagon and gut hormones , gastric emptying , and rate of absorption of other food components like carbohydrates and other factors [ 1113 ] . there are some earlier reports from different healthy and diabetic populations suggesting variable glycemic effects of high protein meals ; for example , they promote gluconeogenesis and slow gastric emptying [ 13 , 14 ] . in a recently published study in t1 dm , it was shown that a mixed meal consisting of 30  g of carbohydrate and 40  g of protein has a greater glycemic effect than a pure carbohydrate load . the study by smart was performed in a pediatric population , while ours involved adult individuals . the differences in outcomes of both studies may be associated with various physiological reactions to protein load in the examined age groups . furthermore , there may be discrepancies in the proportion of basal versus prandial insulin doses depending on the age of patients , which could affect study outcomes . moreover , the effect of protein when mixed with carbohydrates might be different compared to the effect of protein alone . finally , the impact of protein may be dose - dependent , because , in the earlier study , 40  g of protein per meal was used , while the protein dose in our study was much lower . it is also important to underline that factors other than meal size or composition may influence the rate of food absorption and postprandial glucose patterns . the list of such factors includes the method of preparation ( e.g. , cooking , frying , or grilling ) , rapidity of consumption , accompanying beverages , time elapsed since the previous meal ( second - meal phenomenon ) , and variability in individual rates of gut absorption , as well as some other factors . moreover , various types of protein consumed as a meal component or during the load test might have affected the postmeal / load glucose patterns . the outcomes of our study may have practical clinical consequences as there are some small protein - based snacks available , such as protein bars or shakes , which are small meal options for t1 dm patients . so , it is important to provide them with information about their impact on glucose level . this is particularly important as , through their satiating effect , they may be helpful in weight management . an important advantage of our study was the carefully optimized rate of basal insulin infusion based on the earlier fasting phase of the experiment . consequently , we were able to exclude the potential bias related to an excess or deficit of basal insulin on postload glucose patterns . additionally , our subjects were highly preselected ; they were adult t1 dm patients characterized by very good compliance prior to the study , frequent cgms use , and willingness to follow a challenging study protocol . the direct clinical implication of our study is the recommendation that small protein - based snacks may be consumed by adult t1 dm csii - treated patients without insulin bolusing . obviously , the general guidelines concerning daily protein consumption for patients with diabetes should be followed . the results of this study can not be generalized to other noncarbohydrate food components , especially fat . additionally , we examined glucose patterns for 6 hours ; thus , it is not possible to exclude the protein load effect on glycemia beyond this time , for example , during subsequent meal . finally one has to underline , that we have used cgm systems that are still characterized with limited accuracy and reliability . in conclusion , the ingestion of a pure protein load does not seem to have a clinically significant impact on glucose levels in adult t1 dm patients treated with insulin pumps .
we aimed to estimate the impact of ingestion of a pure protein load on the glucose levels in t1 dm patients treated with insulin pumps . 
 we examined 10 t1 dm patients ( 6 females , mean age32.3 years , mean hba1c6.8% ) treated with insulin pumps equipped with a continuous glucose monitoring system ( cgms ) . in phase 
 i , baseline insulin infusion was optimized to minimize the differences in fasting glucose levels to less than 30  mg / dl between any two time points between 9 a.m. and 3 p.m. in phase ii , the patients were exposed to single pure protein load . 
 cgms record was performed and the glucose pattern was defined for 6 hours of each phase . 
 the maximal glucose level increment was similar for the entire duration of the fasting and the protein load test ( 26.6 versus 27.6  mg / dl , resp . 
 , p < 0.78 ) 
 . there was only a borderline difference in change between baseline versus 6th hour glucose ( 12.5 and 19.0  mg / dl , p = 0.04 ) . 
 glucose variability , assessed by standard deviation of mean glucose levels , was 36.4 and 37.9  mg / dl , respectively ( p = 0.01 ) . 
 the administration of a pure protein load does not seem to have a clinically significant impact on glucose levels in t1 dm patients treated with insulin pumps .