Direct and indirect effects of low carbohydrate diet on markers of CVD risks with BMI, WC and HbA1c as mediators among UK adults aged 45–80 years in NDNS (2008/2009–2016/2017)
| Mediator and outcomes | Direct effect | Indirect effect | ||
| Estimate | 95% CI | Estimate | 95% CI | |
| BMI as mediator (model 1) | ||||
| HbA1c | 0.07 | −0.03 to 1.13** | 0.02 | −0.1 to 0.12 |
| TRIG | −0.67 | −3.45 to 2.9 | 1.04 | −4.65 to 4.63 |
| TC | 0.67 | −2.15 to 5.56 | 1.07 | −5.95 to 6.09 |
| HDL | 0.97 | 0.39 to 3.57 | −0.66 | −2.73 to 2.67 |
| LDL | −1.53 | −4.34 to 3.74 | 1.48 | −6.02 to 5.48 |
| SBP | 0.46 | −0.38 to 2.76 | −0.9 | −2.37 to 2.4 |
| DBP | 0.66 | −0.1 to 1.71 | −0.03 | −1.51 to 1.37 |
| CRP | −0.25 | −0.85 to 0.2 | 0.08 | −0.79 to 0.78 |
| BMI and WC as mediators (model 2) | ||||
| HbA1c | 0.06 | −0.02 to 0.13 | −0.02 | −0.1 to 0.11 |
| TRIG | −1.95 | −3.3 to 2.99 | 2.27 | −4.55 to 4.75 |
| Total Chol | 3.07 | −1.49 to 6.8 | 0.03 | −5.97 to 6.53 |
| HDL | 2.12 | 0.43 to 3.58*** | −0.29 | −2.46 to 2.97 |
| LDL | −0.04 | −3.89 to 3.78 | 0.85 | −5.64 to 5.26 |
| SBP | 1.1 | −0.27 to 2.63 | −1.06 | −1.99 to 2.69 |
| DBP | 0.74 | −0.23 to 1.58 | −0.2 | −1.46 to 1.54 |
| CRP | −0.19 | −0.72 to 0.29 | 0.0 | −0.69 to 0.83 |
| BMI, WC, HbA1c as mediators (model 3) | ||||
| TRIG | 1.75 | −3.49 to 3.12 | 3.68 | −4.72 to 4.75*** |
| Total chol | 1.24 | −2.17 to 6.95 | −0.51 | −5.92 to 6.5 |
| HDL | 2.63 | 0.32 to 3.54*** | −0.01 | −2.31 to 2.52 |
| LDL | −0.74 | −3.59 to 3.85 | −0.37 | −5.5 to 5.03 |
| SBP | 1.67 | 0.83 to 4.07** | −1.12 | −2.17 to 2.46 |
| DBP | 0.91 | 0.14 to 2.11 | −0.06 | −1.54 to 1.44 |
| CRP | −0.31 | −0.57 to 0.45 | −0.22 | −0.67 to 0.83 |
The confounders for the analysis are age, sex, ethnicity, economic status, smoking status, total calories intake, alcohol intake and whether taking general medicines.
Indirect effect: the effect of diet on the outcome that is explained by the mediator.
Direct effect: the effect of diet on the outcome that is not explained by the mediator.
**p≤0.05, ***p<0.01.
BMI, body mass index; CRP, C reactive protein; CVD, cardiovascular disease; DBP, diastolic blood pressure; HbA1c, glycated haemoglobin; HDL, high-density lipoprotein; LDL, low-density lipoprotein ; NDNS, National Diet and Nutrition Survey; SBP, systolic blood pressure; TC, total cholesterol; TRIG, triglycerides; WC, waist circumference.