Serum vitamin D levels decreased significantly from baseline to 24 weeks among those randomized to efavirenz/lamivudine/zidovudine ( mean change : -7.94 [ 95 % Confidence Interval ( CI ) -10.42 , -5.54 ] ng/ml ) and efavirenz/emtricitabine/tenofovir-DF ( mean change : -6.66 [ 95 % CI -9.40 , -3.92 ] ng/ml ) when compared to those randomized to atazanavir/emtricitabine/didanosine-EC ( mean change : -2.29 [ 95 % CI -4.83 , 0.25 ] ng/ml ) .