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A double-blind placebo-controlled study was performed to determine the triglyceride-lowering effect of DHA compared with EPA. In this seven-week study, 234 healthy men were randomly given: DHA in the ethyl ester form at a dose of 3.6 grams daily, the ethyl ester of EPA at 3.l8 grams daily or corn oil at 4 grams daily. Triglycerides decreased by 26% in the DHA group and 21% in the EPA group compared with placebo. Some retroconversion of DHA to EPA was noted, but no significant conversion of EPA to DHA was observed. A slight, but significant, increase in HDL-cholesterol was seen in the DHA group.
In another study on the effect of DHA on serum triglycerides, 27 hypertriglyceridemic subjects were randomized to receive either 1.25 grams of DHA daily, 2.5 grams of DHA daily or a vegetable oil placebo. The DHA was in the natural form derived from triglycerol microalgae, and the study lasted six weeks. Serum triglycerides decreased 17 to 21% and were of similar magnitude in both DHA groups. HDL-cholesterol increased by 6% and again were of similar magnitude in both DHA groups. LDL-cholesterol increased by 9.3% in the 1.25 gram DHA group. This was not significant. An increase of LDL-cholesterol of 13.6% was noted in the 2.5-gram DHA group, which was statistically significant.
DHA is essential for the growth and functional development of the fetal and infant brain and visual system. Human breast milk contains DHA but, unless supplemented with DHA, infant formulas in the U.S. do not contain any significant amounts. (The DHA level in the breast milk of the average American woman is among the lowest in he world.) In Europe and Japan, by contrast, infant formulas are routinely supplemented with DHA.
Whether to supplement these formulas in the U.S. continues to be a matter of considerable controversy. A recent double-blind, randomized, controlled efficacy and safety trial of infant formulas with and without DHA failed to resolve the controversy. No beneficial effects were noted, but more long-term studies are needed to settle the issue. No adverse safety outcomes, measured by growth, infection, atopy and gastrointestinal tolerance, were noted.
The data for supplementation of DHA in infant-formula milk for pre-term infants are more compelling. One study compared pre-term infants on formula without supplemental DHA with infants getting breast milk. The breast-fed infants had an IQ 8.3 points higher at 71/2 to 8 years of age.
Another study comparing pre-term infants receiving formula supplemented with DHA with those receiving formula unsupplemented with DHA demonstrated a significantly higher Bayley Mental Development Index at 12 months in the infants receiving the DHA-supplemented formula. Large scale retrospective studies have shown that pre-term breast-fed infants have an average 5- to 12-point higher IQ later in life than babies fed formula milk without supplemental DHA. The difference in term infants is 2 to 5 IQ points.
Preliminary research suggests that some other therapeutic roles might emerge for DHA. There is some indication that, in both humans suffering from cystic fibrosis and in the cystic fibrosis mouse model, in cell membranes of the lung, pancreas and intestine (the organs most affected by this disease) there are abnormally elevated levels of arachidonic acid and abnormally diminished levels of DHA. In a pilot animal study, daily supplementation of the mouse diet with DHA corrected the lipid imbalance and reversed the progression of the disease after one week. These results have prompted a human clinical trial, the results of which are not yet available.
DHA is similarly deficient, this time in the brain, as well as in the blood and all body tissues, in those suffering from congenital peroxisomal disorders. This includes those with Zellweger cerebro-hepato-renal syndrome, neonatal adrenoleukodystrophy (made famous by the film Lorenzo's Oil) and infantile Refsum disease, characterized by severe psychomotor retardation, retinopathy, liver disease and early death.
In one very encouraging early study of Zellweger Syndrome patients, the ethyl ester of DHA in daily doses of 100 to 500 milligrams was given to 13 patients. Blood DHA levels became normal within a few weeks, liver enzymes returned nearly to normal, and most of the patients showed improvement in vision, liver function, muscle tone and social skill. Normalization of brain myelin was confirmed by MRI in three patients.
DHA deficiencies have been established in the plasma phospholipids of those with attention deficit disorder, and it has been suggested that such deficiencies may be a risk factor in those with Alzheimer's disease. Nutritional intervention trials are indicated.
A small study suggests that DHA might prove beneficial in the treament of dyslexia. Dark adaptation was found to be impaired in 10 dyslexic subjects?compared with a non-dyslexic control group. A fish oil high in DHA improved dark adaptation in five subjects after one month of supplementation.
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