Babies grow fast in that first year and developmentaly, 4 months versus 7 months is huge. What one is ready for at 4 months versus 7 cannot even be compaired. Each baby is different, of course, but as a general guidlines, you would want to wait till 6 months, except in certain induvidualized situations (severely underweight, GERD, reflux, etc)
The American Academy of Pediatrics (AAP) and the World Health Organization, the Dietary Guidelines for Americans, and numerous other orginizations and experts recommend waiting until a child is about 6 months old before introducing solid foods, including rice cereal, to them
Rice cereal contains arsenic, and babies can absorb up to three times more arsenic from rice cereal than adults. Arsenic is a known carcinogen that can affect a baby's development. The younger that they are the more they can absorb.
At one time werepast recomendations different? Yes but we also didnt realize the levels of arsenic rice cereals had , and the GI distress is causes to an infant. It's the same thing as people saying it was okay to give water to babies under six months. We now know thats a big no no as well.
Im done sperging since you seem to have made your mind up.