Grains have been used as food for roughly 100 000 years, but until about 50 years ago they were prepared in a very specific way. The traditional preparation of grains before consumption was to allow for proper digestion by removing the myriad of anti-nutrients that grains contain as their self-protective mechanism. Unfortunately in our modern lives of instant gratification we have let this process slide and this may be the reason for the rise in digestive problems linked to grain consumption.
It is so important to soak grains before cooking them because they contain enzyme inhibitors and anti-nutrients like phytic acid, tannins and lectins. These bind with minerals, prevent digestion and absorption, contribute to anaemia and other nutrient deficiencies, lead to bone loss and tooth decay, irritate and damage the gastrointestinal tract and lead to allergies and chronic health issues. By soaking grains before we cook them helps to release and break down these anti-nutrients so that the grains and the nutrients within them can be digested and absorbed correctly.
There is no need to exclude grains from your diet if they have been properly prepared; in fact they are an important source of many nutrients such as the B vitamins - thiamin, riboflavin, niacin, and folate and minerals like iron, magnesium, and selenium. Grains are also packed with complex carbohydrates for energy and plenty of fibre.
How to properly soak grains:
Sources
http://thenourishinghome.com/2012/03/how-to-soak-grains-for-optimal-nutrition/
https://www.weedemandreap.com/guide-soaking-sprouting-grains/