Hi,
This recomendation was for this specific condition.
The reason for it is because a white potatoe is starch and if eaten without Alkaline minerals, it will cause your body to become very Acidic, which in this case they were having problems sleeping at nite and the cause for this is because their body was becoming Way Too Acidic at Nite.
By taking onions with the potatoe, the onions are highly Alkalizing and will help buffer the acids produced by the White potatoe!!