Table 2.
Single Variable Linear Mixed Models of Calcium Absorption
| Fractional Calcium Absorption (FCA) |
Net Calcium Absorption (NCA) |
|||
|---|---|---|---|---|
| Variable | Slope | P value | Slope | P value |
| Demographic Characteristics | ||||
| Age, years | −0.00383 | 0.027 | −0.892 | 0.571 |
| Body Mass Index, kg/m2 | +0.00328 | 0.227 | −2.746 | 0.291 |
| Nutritional Characteristics | ||||
| Kilocalories, day | −0.00004 | 0.229 | +0.058 | 0.032 |
| Protein, g/day | −0.00115 | 0.065 | +0.879 | 0.144 |
| Fat, g/day | −0.00046 | 0.353 | +0.389 | 0.395 |
| Carbohydrates, g/day | −0.00005 | 0.791 | +0.368 | 0.025 |
| Fiber, g/day | −0.00220 | 0.083 | +2.108 | 0.101 |
| All Calcium intake, mg/day | −0.00008 | <0.001 | +0.079 | <0.001 |
| Iron, mg/day | −0.00497 | 0.062 | +1.722 | 0.538 |
| Magnesium, mg/day | −0.00028 | 0.019 | +0.312 | 0.004 |
| Oxalate, servings/day | −0.02648 | 0.061 | +15.113 | 0.275 |
| Phosphorus, mg/day | −0.00006 | 0.063 | +0.068 | 0.025 |
| Potassium, mg/day | −0.00003 | 0.084 | +0.045 | 0.001 |
| Vitamin D, IU/day | −0.00022 | 0.095 | +0.270 | 0.019 |
| Laboratory Characteristics | ||||
| Serum Calcium, mg/day | −0.01283 | 0.640 | −21.603 | 0.387 |
| Serum Creatinine, mg/dL | +0.01066 | 0.891 | −182.519 | 0.022 |
| GFR, mL/minute | +0.00032 | 0.571 | +1.375 | 0.018 |
| PTH, pg/dL | +0.00135 | 0.017 | −0.359 | 0.473 |
| 25(OH)D, ng/mL | −0.00033 | 0.608 | +0.291 | 0.440 |
| 1,25(OH)2D, pg/mL | +0.00035 | 0.382 | +0.995 | 0.009 |
FCA predictors were determined using all three inpatient fractional calcium absorption studies performed on twenty-one subjects taking part in the proton pump inhibitor study, and the baseline visit from the vitamin D insufficiency study, excluding two outliers, yielding 80 observations. NCA predictors were determined using all three calcium absorption studies minus 3 outliers, yielding 118 observations.