The present invention relates to a method for reducing an amount of dissolved impurities in an oxygen containing renewable feedstock, the dissolved impurities being selected from impurities comprising phosphorus and impurities comprising at least one metal. The method comprises obtaining a net elementary charge of a first feedstock; mixing the first feedstock with an elementary charge balancing component to obtain the feedstock to be treated, whereby the feedstock to be treated has a net elementary charge which is closer to zero net elementary charge than the net elementary charge of the first feedstock; and subjecting the feedstock to be treated to a heat treatment at a temperature of 180-400° C. in order to precipitate compounds containing said phosphorus and said at least one metal.