fructose is poison and lactose is tough for the digestive system
as Caucasians we're lucky cos we have developed lactase persistence meaning we continue to produce the lactase enzyme that cuts up lactose into absorbable monosaccharides after puberty at up to 95% pre-pubescent levels (depending on the person of course).
African and Asian genetic background people produce much less lactase than we do into adulthood and have more gut probs when taking in lactose. It's interesting that Native American Indians are 100% lactose intolerant. They can't take their booze like the Japs either.