DHA
Possible Deficiencies
Premature infants who are not breast-fed are often DHA-deficient.1 A link has appeared between DHA deficiency and Alzheimer’s disease; however, no evidence at this time indicates that supplementation with DHA will help Alzheimer’s patients.2 Similarly, preliminary evidence shows that children with attention deficit disorder (ADD) have low DHA levels. However, no evidence demonstrates that DHA supplementation improves ADD.3 Preliminary evidence suggests that people with a variety of rare but related congenital diseases (Zellweger’s syndrome, neonatal adrenoleukodystrophy, and infantile Refsum’s disease) may be DHA-deficient, and may even benefit from DHA supplementation.4 Many doctors believe the diets of most people eating a Western diet do not provide optimal amounts of omega-3 fatty acids.
At least four studies have reported a reduced blood level of omega-3 fatty acids in people with depression.5,6,7,8
Side Effects
While those with heart disease and diabetes often benefit from fish oil (the primary source of DHA in the diet),9,10 such people should check with their doctor before taking more than 3 or 4 grams of fish oil per day for several months. Elevations in blood sugar have sometimes been reported,11 though this may simply be due to small increases in weight resulting from high dietary fish oil.12 While DHA combined with EPA from fish oil consistently lowers triglycerides, it occasionally increases LDL cholesterol.13
According to a report in a Japanese medical journal, three people at high risk for colon cancer developed a variety of cancers after one to two years of supplementation with DHA.14 To date, this report has not been confirmed by other researchers. To the contrary, test tube studies report that DHA is toxic to cancer cells15 and may someday be considered as an adjunct to conventional treatment for cancer.16 Similarly, animal studies suggest that DHA may inhibit cancer.17