What is the scientific evidence that DHA is important?

There are literally thousands of studies on the role of and need for DHA during pregnancy and after birth. Like virtually all areas of human nutrition, there is some controversy about DHA as well. Some believe that even the low levels of DHA in the breast milk of American women is good enough for babies. Others contend that higher levels (like those in Japan, where DHA levels are eight times higher than in the United States) give babies an intellectual “head start.”