Vegan

People should be eating high fiber foods everyday, in significant quantities. You body does adapt. If even small quantities of these foods causes issues, then you can try increasing slowly and consistently, over say a month or two. Or you can try changing your diet quickly if you have time to deal with any potential side effects short term.

So, just make sure to cook the grains and legumes properly, don't worry about how cooking degrades nutrients, and eat lots consistently. If one methods of cooking digests or tastes better for you, stick to that.

It's like people who ask why exercise hurts after being sedentary for a long time. Just exercise more, and it won't hurt.

As you introduce more fiber into your diet you will probably want to increase water throughout the day. If you drink alot normally there may not be much of an impact to your bowels by increasing the amount you drink, but it is something to think of as your diet changes.

I've been primarily vegan for decades, and I've found that #4 is mostly true, but some amount of gas emission is normal for everyone.

#1 is similar to a known method of prepping crispy fries (using ice water baths), because it removes starch in potatoes. Not sure how well that would work for other veggies, tho. I'd certainly think they'd need to be sliced up for that to work best.

#3 is definitely a known method of changing the chemistry of a thing, so yes, AFAIK both chemistry and nutritional science suggest that nutrients can and will be lost that way.

You also might experiment with digestive enzymes (like "Bean-O" and others) to see if that helps out eating high-fibre meals. You might also start with a prelude of daily psyllium husk fibres to get your gut used to more fibre. As I understand it, it also has the side benefit of lowering 'bad' cholesterol, as fibre has a 'scrubbing action' onthe gut.

One small tweak you can make: Cook beans in a pressure cooker instead of buying the canned stuff. It’s low effort, tastes better, and leads to less gas.

Add kombu (seaweed) strips to further aid digestion.

Beano works. It's an enzyme thatll break down the gassy bits. Eat one pill before eating your hi-fiber deal and youre good for the all you can eat night at the bean factory.

Your gut fauna will adapt over time too

I turned 30 and the doctor told me my cholesterol and triglycerides were too high. I had a 0 fiber diet but overnight adopted a diet consisting of 30-40 grams a day. The first few weeks were gaseous. I didn't eat too many beans instead supplemented and ate as many vegetables with a lean protein as I could.

Its been a year, I still dont eat too many beans and I get atleast half my fiber from supplements. I also eat tofu, oatmeal and veggies. I am only gassy when I eat large amounts of protein for the gains.

There's ingredients that counter farts. For example cylantro. Just add a luxurious amount next time and see if that fixes it for you. There are also others, and it has a special name.

Rinsing beans before cooking them helps a lot.

I dont think fiber has anything to do with gas? But that may depend on it being digestable fiber or nondigestable. Both are important for a healthy gut.

It is said that you get used to Lentils and Beans, not sure if that fits everyone, but it is fine.

Stop caring what others think, let er rip

Content warning: a little graphic re: farting and pooping

I've only been vegetarian or vegan, and I generally don't have issues with farting (or any GI issues). What I eat doesn't affect farting, but there is another variable that is highly influential: time since last (full) bowel movement. On a healthy vegan diet, I tend to have daily BMs like clockwork (the body has metabolized everything and wants to empty once a day). If I eat a lot of (saturated) fat (which slows down transit time; ie, how long between eating and pooping), that is how I can miss a BM and be susceptible to excess flatulence for a while.

With more exposure, I think your body will adapt to eating high-fibre foods with less flatulence. My recommendations would be to monitor which foods are easier or more difficult for you to handle right now (eg, maybe fewer farts on oats than beans), and to 'work your way up the ladder'. My other suggestion is to consider the role of 'time since last BM' to the flatulence attributed to high-fibre foods. My guess would be you're getting gassy several hours after eating high-fibre food but you may also have low-fibre food from yesterday or the day before still sticking around - and I think it's probably the combination of the two that results in excess flatulence.

I think the analogy to exercise that someone else gave is very apt.