In my eyes diets like the Fodmap diet are complete BS, those are things that are trying to tackle symptoms, ignoring the underlying problem.
It is not uncommon in this day of age for people (especially woman) to have problems with their intestines, there are many things that can cause this, yet there are a couple of things that are often times ignored, especially when it comes to holistic practices. Below i will give a couple of tips, that could be of use.
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1. Apple cider vinegar, i know this stuff can be nasty, but it is a very potent ''intestine & liver cleaner'', it will help healing, cleaning and digesting.
When using apple cider vinegar know that this is extremely acidic, it is great for your intestine but not for your teeth, also if used improperly it can ''burn a hole' in your stomach.
How to use it: Pour a swig of apple cider in a glass, fill up the rest of the glass with warm water (About body temp.), drink this with a straw!- Do this once or twice a day.
2. I have come to understand that it is very important, contrary to popular believes, that eating fatty foods are a necessity for a healthy liver, gallbladder & intestines. Preferably natural healthy fats like beef tallow or butter.
Beef tallow is delicious when used to prepare meats, not so much when used with anything else in my opinion.
3. Eat plenty of meat! meat and other animal produce are often times ''demonized'' in modern diets, this is done under a false assumption that cows etc. are bad for the environment and thus for human consumption. this is of-course not true, in contrary it is very healthy!
4. Avoid ultra processed foods, for obvious reasons.
5. Sun light, especially if you are living in the northern hemisphere it is very important to catch some sunlight when you are able to, as the sun is very healing to the body.
6. Earthening, skin to earth contact will help in reducing inflammation among other things, we humans are essentially walking electricity generators that just like anything else electric needs to be earthed to be regulated.
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On a last note i am curious about the bloating part, as this could be a sign of malnutrition. If your wife is worried about eating to much, it would be healthier to choose for a intermittent fasting route, where you do eat more than enough to support the body, yet leave enough time in between meals for your body to heal and strengthen itself (as the body has trouble doing this when you eat constantly throughout the day). Only eating small portions of food every day will cause your body to shutdown, this will cause the body to start eating its own flesh, organs etc., thats what happens when the body is malnourished, bloating will be a result of this.
It could be other things besides malnourishment, for example a poor working intestine or liver. To help fix issue's with this i highly recommend apple cider vinegar to clean the liver and intestine out, and eating more fats like discribed above to ensure a healthier intestine. Fats are also essential for a healthy gallblatter, not enough fat in your diet will cause gallstones!