Besides from the overall effects of stress on your body, one thing to consider is that stress causes your digestion to work less effectively. To me it seems likely that if you aren't digesting your food well it's more likely to be bad for your UC.
Hopefully you aren't stressed all day. You may want to try to make sure that you eat during the less stressful times of your day.
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The typical stress response involves the release of hormones like adrenaline and cortisol from the adrenal glands. The hormones trigger reactions like an accelerated pulse. They also cause changes in the digestive system, like sudden lack of appetite, heartburn, nausea and stomach pains. Stress also causes inflammation throughout the digestive system, which leads to aggravation of the digestive tract and affects the assimilation of nutrients. Over the long term, stress can actually cause chronic digestive problems like irritable bowel syndrome (IBS) and stomach ulcers.
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From:
www.naturalnews.com/028766_stress_digestion.html