Can you construct for us an effective prayer for blessing food before mealtime and discuss the benefits so this can be a part of the intention of those using the prayer?

Yes, a good prayer for food would be to simply say: Source Creator, bless this food and everything within, to remove all negativity. Leave what is highest and best for my health and well-being and the health and well-being of all who partake. This would be enhanced by being aware of the various sources of potential negativity that can be ingested with foodstuffs. This includes all unnatural, man-made, adulterations—everything pertaining to agricultural as well as processing and food preparation. So you have the array of chemicals used for fertilizer, used for insect control, for weeding out competing plants with herbicides, the consciousness of the plants themselves or animals if dealing with meat, as these can have a deleterious effect and be imparted to the constituents that are harvested and consumed. If the animals are mistreated, that energy will persist within the physical body and will remain within the meat that is eventually ingested by the people as part of the food chain. The same is true of plant material. If plants are mistreated or neglected in some way, being subjected to fear or hatred or the harshness of conditions to drive the growth artificially, to alter the plant in some way through manipulation, chemically or genetically, this can impinge on the consciousness as well. The thoughts and feelings of those who handle the plants can be transferred. If the agricultural workers are unhappy and resentful, this can cause psychic attacks that persist in the energy of the material harvested and then consumed by other humans. The adulteration of food with preservatives and colorants is a major source of negativity because there can be chemical toxicity, as well as such materials often attracting great negativity energetically because of what they are designed to do. If they are designed to kill the life of microorganisms, they will attract the energy of destruction and this will be an inevitable additional transference into the food chain. The energy of all humans in the production, handling, and processing of the food can impart further psychic energies of negativity into the finished product. The processing of food can produce many changes in altering the chemical composition through excess heat or microwaves, as this will produce carcinogens and will degrade nutritional quality in many cases. All of these negative influences can be overridden or compensated for by the simple blessing of the constituents of a meal prior to ingestion. Done as a routine, given the many, many, meals consumed over a lifetime, can help protect people from an accumulation of negativity that can undermine them significantly, and this can forestall initiation of illness as well as the consequences of aging, and be a positive factor in conferring longevity to some degree.