Don’t believe all you read.
Whether you use iTunes, Audacity or any other application for encoding your MP3s, it is essential that you select appropriate settings for the MP3 encoding to suit your needs.
The default MP3 encoding options in the current version of Audacity are 170 - 210 kbps VBR (preset “Standard”). While this is a good choice for stereo music, it is not generally recommended for Podcasts.
For podcasts, “CBR” (constant bit-rate) is recommended, and not “VBR” (variable bit-rate).
The choice of mono/stereo depends on the type of podcast. For voice only podcasts, mono is usually preferred as you can achieve better sound quality with less data. If the podcast contains a lot of music you may prefer to use stereo, but higher bit-rates will probably be required (bigger file size).
64 kbps CBR mono can give reasonable quality for voice if you are wanting to minimise the file size.
96 kbps CBR mono can give excellent quality for voice.
128 kbps CBR stereo can give reasonable quality where stereo is required.
192 kbps CBR stereo can give very good quality where stereo is required.
256 kbps VBR stereo can give excellent quality stereo music, though not recommended for streaming.
See here for how to set the MP3 export options: Export Audio - Audacity Manual
Audacity uses LAME for encoding MP3s, which is generally considered to be the best MP3 encoding library, and is the only MP3 encoding library that is still being actively developed (http://lame.sourceforge.net/)