food allergies: avoidance or soil building?

So we’re seeing an increase in food allergies and sensitivities. The seemingly-obvious diagnosis is don’t eat these things. Foods, menus, and even dinner parties are now covered with whathaveyou-free labels catering to people with growing lists of foods they feel are toxic to their bodies.

I’m not in any way qualified to give medical or nutritional advice, so this is just a question.

Organic farmers say that healthy plants are less vulnerable to pests, blights, diseases, drought, alkalinity, cold, etc. And what makes a healthy plant? Healthy soil. While there are some “natural” pesticides that are acceptable for use on certified organic crops, serious farmers say that the best defense is to build the soil. Building the soil doesn’t mean inserting specific nutrients as did the NPK petrochemical fertilizer paradigm, but adding masses of diverse organic material and humus which provide nutrients, acids, aeration, microorganisms, moisture retention, minerals, hormones…

Could this recognition be relevant to robust nutrition? Instead of banning foods from clients’ diets, should nutritionists instead be seeking to build a richer, more complex nutritive arena so that the body will be more robust to all kinds of interactions?

Could the practices of avoidance be depriving people of the rich nutritional input that would build systemic health so they would be more resilient?