I am running a simple regression repeated for ~1,000 variables in a loop. I would like to capture the beta coefficients, se, and p values for my exposure and 3 adjustment variables and output them to a csv file. I have used the following code for mixed models and cannot figure out how to alter it to use with this simple model. I get the following error code: equation xylose not found
post: above message corresponds to expression 2, variable ratio

I am using v16.1. Below are my sample data and code.

Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input int subjectid byte(timepoint sex age) float(aibwkg ratio xylose xylitol valine)
20001 3 1 39 74.58166 .09547353   -.7932054 -1.0131693   4.88012
20001 2 1 39 74.58166 .09547353   .57306993  -.8202816 4.3152866
20001 1 1 39 74.58166 .09547353  -.50978696 -1.1714463  4.004311
20002 3 1 35 74.30232 .06258648    1.187921 -1.0057454 4.0414968
20002 2 1 35 74.30232 .06258648  -.57098293  -.9478416   3.50136
20002 1 1 35 74.30232 .06258648  -.54130113  -.7070154  4.680255
20003 3 0 42 71.09388   .028846     -.87649  .57306993   5.20874
20003 2 0 42 71.09388   .028846      .29774     .27476   4.66839
20003 1 0 42 71.09388   .028846     -.39757    -.36489  4.004348
20004 3 0 36  59.1862 .04826844   -.4515804 -.06558012  5.631982
20004 2 0 36  59.1862 .04826844  -.50320864  -.7149013  4.967944
20004 1 0 36  59.1862 .04826844    -.588939   -.788257  5.110322
20005 3 1 51 58.46099 .04752519   -.9756348 -1.1163021  5.163349
20005 2 1 51 58.46099 .04752519   -.6698709  -.8362016  4.571539
20005 1 1 51 58.46099 .04752519   -.8011949 -1.2734073  5.349926
20006 3 1 19 76.56038 .05422749   -.1484685 -1.1551343  3.649079
20006 2 1 19 76.56038 .05422749   -.7596757  -1.080953  5.256241
20006 1 1 19 76.56038 .05422749 -.002501656 -1.0889778  3.596983
end
Code:
capture postutil clear
tempfile metabolitebresults
postfile handle str32 Metabolite float ratio se_ratio ///
    age se_age sex se_sex aibwkg se_aibwkg using `metabolitebresults'

foreach var of varlist xylose - valine {

    reg `var' ratio age sex aibwkg if timepoint==1
    
    local topost ("`var'")
    foreach x in ratio age sex aibwkg  {
        local topost `topost' (_b[`var':`x']) (_se[`var':`x'])
    }
    
    // POST IT
    post handle `topost'
}

postclose handle

use `metaboliteresults', clear

foreach v of varlist ratio age sex aibwkg {
   gen t_`v' = `v'/se_`v'
   gen p_`v' = 2*normal(-abs(t_`v'))
   order t_`v' p_`v', after(se_`v')
}
export delimited using my_metaboliteresults, replace