<A<em>b</em>stractText>Com<em>b</em>ined pro<em>b</em>iotic and selenium supplementation may improve Alzheimer's disease (AD) <em>b</em>y correcting meta<em>b</em>olic a<em>b</em>normalities, and attenuating inflammation and oxidative stress. This study aimed to determine the effects of pro<em>b</em>iotic and selenium co-supplementation on cognitive function and meta<em>b</em>olic status among patients with AD.</A<em>b</em>stractText><p><div>(<em>b</em>)METHODS</<em>b</em>)</div>This randomized, dou<em>b</em>le-<em>b</em>lind, controlled clinical trial was conducted among 79 patients with AD. Patients were randomly assigned to receive either selenium (200 μg/day) plus pro<em>b</em>iotic containing Lacto<em>b</em>acillus acidophilus, Bifido<em>b</em>acterium <em>b</em>ifidum, and Bifido<em>b</em>acterium longum (2 × 10<sup>9</sup> CFU/day each) (n = 27), selenium (200 μg/day) (n = 26) or place<em>b</em>o (n = 26) for 12 weeks.</p><A<em>b</em>stractText>Selenium supplementation, compared with the place<em>b</em>o, significantly reduced serum high sensitivity C-reactive protein (hs-CRP) (P &<em>lt</em>; 0.001), insulin (P = 0.001), homeostasis model of assessment-insulin resistance (HOMA-IR) (P = 0.002), LDL-cholesterol (P = 0.04) and total-/HDL-cholesterol ratio (P = 0.004), and significantly increased total glutathione (GSH) (P = 0.001) and the quantitative insulin sensitivity check index (QUICKI) (P = 0.01). Compared with only selenium and place<em>b</em>o, pro<em>b</em>iotic and selenium co-supplementation resu<em>lt</em>ed in a significant increase in mini-mental state examination score (+1.5 ± 1.3 vs. +0.5 ± 1.2 and -0.2 ± 1.1, respectively, P &<em>lt</em>; 0.001). Pro<em>b</em>iotic plus selenium intake resu<em>lt</em>ed in a significant reduction in hs-CRP (-1.6 ± 1.4 vs. -0.8 ± 1.0 and +0.1 ± 0.5 mg/L, respectively, P &<em>lt</em>; 0.001), and a significant increase in total antioxidant capacity (+89.4 ± 129.6 vs. +20.0 ± 62.5 and -0.7 ± 27.2 mmol/L, respectively, P = 0.001) and GSH (+122.8 ± 136.5 vs. +102.2 ± 135.2 and +1.5 ± 53.2 μmol/L, respectively, P = 0.001) compared with only selenium and place<em>b</em>o. In addition, su<em>b</em>jects who received pro<em>b</em>iotic plus selenium supplements had significantly lower insulin levels (-2.1 ± 2.5 vs. -1.0 ± 1.3 and +0.7 ± 2.0 μIU/mL, respectively, P &<em>lt</em>; 0.001), HOMA-IR (-0.5 ± 0.6 vs. -0.2 ± 0.3 and +0.1 ± 0.4, respectively, P &<em>lt</em>; 0.001), and higher QUICKI (+0.01 ± 0.01 vs. +0.005 ± 0.007 and -0.002 ± 0.01, respectively, P &<em>lt</em>; 0.006) compared with only selenium and place<em>b</em>o. Additionally, pro<em>b</em>iotic and selenium co-supplementation resu<em>lt</em>ed in a significant reduction in serum triglycerides (-17.9 ± 26.1 vs. -3.5 ± 33.9 and +0.3 ± 9.3 mg/dL, respectively, P = 0.02), VLDL- (-3.6 ± 5.2 vs. -0.7 ± 6.8 and +0.05 ± 1.8 mg/dL, respectively, P = 0.02), LDL- (-8.8 ± 17.8 vs. -8.1 ± 19.2 and +2.7 ± 19.0 mg/dL, respectively, P = 0.04) and total-/HDL-cholesterol (-0.3 ± 0.7 vs. -0.4 ± 0.9 and +0.3 ± 0.6, respectively, P = 0.005) compared with only selenium and place<em>b</em>o.</A<em>b</em>stractText><A<em>b</em>stractText>Overall, we found that pro<em>b</em>iotic and selenium co-supplementation for 12 weeks to patients with AD improved cognitive function and some meta<em>b</em>olic profiles. This study was registered in the Iranian we<em>b</em>site (www.irct.ir) for registration of clinical trials (http://www.irct.ir: IRCT20170612034497N5).</A<em>b</em>stractText>