Researchers from Northwestern University in Illinois also said that breastfeeding babies for less than three months raised their chance of getting chronic inflammation in adulthood.
Chronic inflammation is associated with heart disease, strokes, type 2 diabetes, late-life disability and a greater risk of dying.
The CRP levels came down by 26.7 per cent if the child is breastfed for three to six months, in case of six to 12 months, it decreased by 29.6 per cent and if the duration is more than 12 months, the level decreased by 29.8 per cent.
According to the scientists, it had at least the same effect as that produced by treatment with cholesterol-lowering statin drugs. Statins reduce CRP by around 15 per cent.
Lead author Thomas McDade, professor of anthropology at Northwestern University, said, "This is a major public health issue. If we can raise breastfeeding rates it will pay dividends in healthcare savings in the future."
The researchers said that low birth weight was also not good as they found that for each pound of extra birth weight, CRP levels fell 5 per cent.
Dr Alan Guttmacher, director of the National Institute of Child Health and Human Development in Maryland, US, said, "This research helps us understand and appreciate the importance of breastfeeding, especially for low-weight infants."
Researchers said breastfeeding helps in making immune system stronger and affects metabolic processes that influence obesity.