Srila Baladeva Vidyabhushana, a great commentator on the Bhagavad-gita, writes as follows: ye indrady-angatayavasthitam yajnam sarvesvaram vishnum abhyarcya tac-chesham asnanti tena tad deha-yatram sampadayanti, te santah sarvesvarasya yajna-purushasya bhaktah sarva-kilbishair anadi-kala-vivriddhair atmanubhava-prati bandhakair nikhilaih papair vimucyante. The Supreme Lord, who is known as the yajna-purusha, or the personal beneficiary of all sacrifices, is the master of all the demigods, who serve Him as the different limbs of the body serve the whole. Demigods like Indra, Candra and Varuna are appointed officers who manage material affairs, and the Vedas direct sacrifices to satisfy these demigods so that they may be pleased to supply air, light and water sufficiently to produce food grains. When Lord Krishna is worshiped, the demigods, who are different limbs of the Lord, are also automatically worshiped; therefore there is no separate need to worship the demigods. For this reason, the devotees of the Lord, who are in Krishna consciousness, offer food to Krishna and then eat — a process which nourishes the body spiritually. By such action not only are past sinful reactions in the body vanquished, but the body becomes immunized to all contamination of material nature. When there is an epidemic disease, an antiseptic vaccine protects a person from the attack of such an epidemic. Similarly, food offered to Lord Vishnu and then taken by us makes us sufficiently resistant to material affection, and one who is accustomed to this practice is called a devotee of the Lord. Therefore, a person in Krishna consciousness, who eats only food offered to Krishna, can counteract all reactions of past material infections, which are impediments to the progress of self-realization. On the other hand, one who does not do so continues to increase the volume of sinful action, and this prepares the next body to resemble hogs and dogs, to suffer the resultant reactions of all sins. The material world is full of contaminations, and one who is immunized by accepting prasadam of the Lord (food offered to Vishnu) is saved from the attack, whereas one who does not do so becomes subjected to contamination.