Special Diets

• By Maureen Williams, ND

Adults May Think Better with DHA

Omega-3 fatty acid from fish has been associated with beneficial effects on vision, mood, and heart health. Now a study published in the American Journal of Clinical Nutrition has found that adults performed better on memory and reaction time tests after taking 1,160 mg of DHA (docosahexaenoic acid) per day for six months.

The study included 228 healthy adults between 18 and 45 years old whose regular diets were relatively low in DHA. They were assigned to take a supplement with 1,160 mg of DHA and 170 mg of EPA (eicosapentaenoic acid) or a placebo with a similar amount of sunflower oil daily for six months. Mental performance tests and blood tests were done at the beginning and end of the study.

As sources of DHA, all types of salmon are considered good, but for the safest fish, stick to wild salmon

DHA makes a meaningful difference

Women performed better than men on some mental performance tests at the beginning of the study. The women and men taking DHA did better than their placebo counterparts at the end of the study in the following ways:

• Episodic memory scores improved more in women taking DHA than placebo. This means they performed better on tests that asked them to remember or recognize words and pictures.
• Reaction times on the episodic memory tests improved more in both men and women taking DHA. This means they responded more quickly to the words and images they remembered or recognized.
• Reaction times on working memory tests (more quickly recalling lists of words or numbers) were also more improved in men taking DHA.

Fish fat for a healthy brain

DHA has been found to play an important role in infants’ and children’s nervous system–development and to protect against loss of mental functioning in the elderly. This study shows that it might also have a role to play in normal cognitive functioning in adults, defined as "young adults" within this study, to differentiate them from people older than 45.

“This study showed, for the first time to our knowledge, that DHA supplementation improved memory and reaction times of memory in healthy young adults whose habitual diet was low in DHA,” the study’s authors said, noting that men and women were affected differently.

Eat smart

It’s not hard to get enough DHA from food—in fact, you can get the amount used in the study by eating a serving of oily fish two to three times per week. But there are some other things to keep in mind:

• Small fish for a big benefit. Herring, sardines, and anchovies are good choices: they are high in DHA and low in contaminants that accumulate in fish, like PCBs (polychlorinated biphenyls), mercury, and pesticides.
• Choose tuna with care. Albacore (“white”) tuna has a lot more DHA than canned “light” tuna, but it also has higher levels of contaminants. In general, canned tuna should be eaten in moderation (once or twice per week for non-pregnant adults), and tuna steaks should be eaten infrequently (no more than once per month).
• Salmon is always rich. As sources of DHA, all types of salmon are considered good, but for the safest fish, stick to wild salmon like chum, coho, and pink. Canned salmon is easy, nutritious, and safe to enjoy several times per week.
• Think outside the box. Less commonly eaten fish that have high levels of DHA and are relatively nontoxic include Alaskan sablefish (also called black cod), North Atlantic mackerel, Arctic char, and Pacific oysters.
• Specialty eggs fill in a gap. Some people just don’t like fish. In that case, omega-3-rich eggs from chickens fed flax meal can provide a bit of the DHA missing from the diet—about 100 mg per egg.

(Am J Clin Nutr 2013;97:1134–43)