Taking supplements doesn't always work and I believe wherever possible you should try and get your nutrients from your food and drinks, so it seems logical to remove as much phytic acid as possible.
Cooking doesn't help that much - kidney beans still retain 92% after cooking.
Sprouting does help but you might not always want to eat sprouted grains, nuts and seeds. Chickpeas retain around 60% once sprouted.
Soaking gets the best results providing you soak your beans for around 18 hours. Remember that kidney beans when cooked still had 92% but soaking decreases it down to 48%.
There is a better way! Soaking your beans at 60 degrees centigrade has the best reduction of all. Three hours gives the same results as soaking for 18 hours in room temperature water. Combine the heat, soaking and cooking and you are going to end up with very little phytic acid left in your food and so gain far more minerals from the food you are eating.
How to get the best results
Boil your kettle with one litre of filtered water and add to one litre of cold water, add your beans and about one tablespoon of apple cider vinegar for every 100g of beans and put in a warm place. After a few hours add some more boiling water and keep topping up as the beans absorb more water. A real bonus is that the beans will cook much more quickly.
Another benefit is no leaching from the chemicals found in the tins of most beans, plus the cost is amazing - so much cheaper to cook your own. Are you going to give it a try?