Is feeding an infant solid food at 4 1/2 months too soon?

My daughter is 4 months and 2 weeks old. I started feeding her some of the gerber first foods and she seems to be liking it very well. I feet her maybe 1/2 a jar a day mixed with rice cereal. My husband took her to the doctor today to ger shots and the doctor told him if we feed her food before 6 months it will cause stomach damage. I don't beleive that 100%, any advice?