I need to start by reiterating that I am not a doctor. Just a human being, living and learning and reading and experiencing. And, of course, sharing some of those experiences here, on a publicly accessed page. (Wow, what am I thinking?)
Stress. From a dictionary perspective, stress is related to strain or pressure. This pressure can be physical (Like lifting a heavy sofa will strain various muscles) or it could be emotional. From a medical perspective, stress seems to be a trigger and/or a scapegoat. Any number of ailments can be related to stress; health issues can also cause stress. Relieving stress through meditation, or yoga, or simply by taking better care of your body can improve many symptoms that don't seem to have any other cause.
However, stress can be a complicated answer.
The symptoms of stress, according to Mayo Clinic, include fatigue, headache and stomach upset. All of these, in varying degrees, are also symptoms related to food allergies and other issues.
Ironically, if you dig deeper, food allergies and Celiac Disease can be triggered by stress. But once the mechanism is turned on in your body, no amount of meditation or yoga will turn it off again. Same goes with food allergies. Once that switch is flipped, the medical condition is yours for life. You can manage it, and stress management techniques will help. But, you will have lifelong dietary restrictions.
There are people who are able to expand their diets once they get their symptoms under control. To my understanding, there are a couple of reasons for this. The most important is that they do not have true allergies (or Celiac). I've discussed allergies before. They're caused by the body identifying normal proteins as threats, and sending out the firing squad. Your symptoms are your body being caught in the crossfire.
Foods can cause symptoms without there being a clinical reason like allergies or Celiac Disease. Some foods are innately hard on the digestive tract. Some people eat when they're stressed, or focus on specific foods when they feel stressed out. Since stress dampens the digestive process, and can cause digestive distress, stress-foods might become associated with discomfort when it's the stress that's to blame.
How do you know the difference? Honestly...it's hard. But, as long as you can keep a varied diet there is no reason you shouldn't avoid a suspect food. Even if it's a big food group like milk. (There are other sources of calcium.) The key is to keep your diet balanced. That means plenty of vegetables and multiple protein sources, as well as fruit and a couple of grains. Sometimes I wonder if people get better when they start avoiding certain foods just because they are now looking more closely at their diets and making better choices. It's certainly a possibility.
Likewise, no matter how much adjusting you do to your diet, it never hurts to do some stress reduction. Yoga. Meditation. Long walks in the woods. None of those include any potential trigger foods, and they'll all help you look at the bigger picture and live a more full life.
With or without specific food groups.