This review summarizes three controversial areas of clinical practice that were discussed in many articles that appeared in the American Journal of Clinical Nutrition during the author's tenure as editor in chief. Controversy 1-obesity and high-fructose corn syrup. The increased frequency of obesity in the US is paralleled by increasing annual consumption of high-fructose corn syrup, an extracted sweetener that is routinely added to soft drinks and to many processed foods in the US diet. Metabolic studies implicate increased fructose consumption in increased body fat and obesity and with increased circulating triglyceride levels and hypercholesterolaemia in children. Controversy 2-folic acid fortification and supplements. Together with widespread use of supplemental multivitamins, fortification of the US diet with folic acid has resulted in high serum folate levels in much of the population, which may be associated with increased risk of cognitive decline in ageing people with low vitamin B12 status, decreased natural killer T-cell immune function and increased risk of recurrent advanced precancerous colorectal adenomas and breast cancer. Controversy 3-recommended intakes of vitamin D. Levels of serum 25(OH)D sufficient for fracture prevention are at least 75 nmol/l (30 ng/ml) but cannot be achieved by the current recommended dietary intakes in the US. A recent fracture risk prevention trial showed that the 4-year incidence of all cancers was reduced in US women who received high supplemental doses of both calcium and vitamin D.