I want to offer a common-sense approach to the colon question from the toilet viewpoint. Don't laugh.
I suspect the busy lifestyle of Singaporeans has resulted in little to no time for proper toilet visits, as well as higher levels of stress, leading to more cases of constipation. These may be the contributing factors to the high incidence of colon cancer in Singapore.
We commonly eat three meals a day. Our first meal, processed by the digestive system, would arrive in our colon roughly 16 hours later. If we defecate only once a day, that first meal stays in the colon, and possibly gets added to by the processed remains from the other two meals about 12 hours later. This means the excreta from the meals stay in our colon and may contaminate it as it tries to re-absorb the toxic material in our waste.
My tai-chi teacher taught me that even if we defecate twice a day, we are still mildly constipated, because logically, we need to release the processed remains of earlier meals.
I advise all readers to do the "big one" three times a day and stay healthy. Even if you do not think this is a scientific approach, there is common sense to it and there is no harm to your body when you do so.
After it becomes a habit, I assure you that you'll enjoy the routine and become a happier person.
In return for my free advice, may I also request you demand for clean toilets because that is another reason you could be holding back your urge and that is so unfair to your colon.
Founder, Restroom Association of Singapore, World Toilet Organisation, World Toilet College