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Food, Health, and Eco-news
Dietary Fat May Affect Kids' Memories

Fish and plant foods seen superior to meat and dairy for children's memory

by Craig Weatherby

Childhood obesity is a rising concern, and many parents are prompted to cut their children's fat intake in an attempt to limit daily calories.

The results of a new study suggest another reason why parents should be concerned about their kids' fat consumption.   But, rather than decrying fat intake as a key source of excess calories—which it can be—the issue raised by this study is the type of fat children consume.

In fact, the results suggest parents should exercise some caution about extreme fat-avoidance in their children's diets. We know that kids need moderate amounts of the essential polyunsaturated fatty acids (PUFAs) otherwise known as omega-6s and omega-3s.

New analysis puts “PUFAs” first

In a study published earlier this month, researchers at the University of South Carolina reported the results of their analysis of data from the U.S. government's Third National Health and Nutrition Survey (NHANES III), conducted from 1988 to 1994, which collected information about families' diets, children's performance on intelligence and achievement tests, and parents' perceptions of their kids' psycho-social functioning.

To perform the just-published analysis, the University of South Carolina team correlated diet information with test scores and parent's perceptions. They concluded that, compared with children who got more of their calories from cholesterol (a fatty substance found primarily in meats and dairy foods), children who got more of their calories from nutritionally essential polyunsaturated fatty acids (PUFAs) did better on a commonly used measure of short-term memory called the digit span test.

Specifically, children whose families participated in the NHANES III study enjoyed an increased chance of good performance on the memory test with each five per cent increase in energy intake from PUFAs, while the risk of poor performance increased by 25 per cent with every extra 100 mg of cholesterol consumed.

The correlations found between PUFA intake and performance were independent of socioeconomic status, maternal education level, marital status, and children's overall nutrition status.

Results verify value of omega-3 PUFAs

This study supports the findings of decades of research showing that people depend on PUFAs for optimal physiological performance and primary disease prevention. But they tend to obscure the important differences between omega-6 PUFAs and omega-3 PUFAs.

The results of dozens of studies show that long-chain marine omega-3s help enhance mental acuity and reduce the risk or severity of depression and other mental disorders.

But, as explained in our last issue (see “Beware the Omega-3 Bait-and-Switch”), most Americans consume far too many omega-6 fats relative to omega-3 fats.

The primary food sources of omega-6 PUFAs are nuts, seeds, and vegetable oils (omega-6s), while fish are the best sources of usable, long-chain omega-3 PUFAs.

This is why every credible nutrition research institute and U.S. health agency recommends that we eat less vegetable oil and packaged food (often high in vegetable oil), and either enjoy more fish or take fish oil supplements containing long-chain omega-3s (EPA and DHA).

What's a parent to do?

Based on the results of this new analysis, and those of hundreds of prior studies, which categories of foods should be downplayed in children's diets, and which are desirable? The answer is simple:

  • Minimize cholesterol-contributors:Only animal foods contain cholesterol: a fat-like steroid alcohol that the body moves around within protein-fat compounds called lipoproteins.  The richest dietary sources are meats, poultry, and full-fat dairy foods (e.g., common cheeses).  Fish contain only small amounts.
  • Favor PUFA foods:The primary food sources of essential PUFAs are nuts, seeds, and vegetable oils (omega-6 PUFAs) and fish (omega-3 PUFAs).
  • Favor omega-3s over omega-6s:The fats in fish are 90 percent or more omega-3s, while the fats in vegetable oils are 80 to 100 percent omega-6s.  The only common vegetable oils with substantial amounts of omega-3s are flaxseed oil (80 percent omega-3), canola (50 percent omega-3), soy oil (12 percent omega-3) and walnut oil (20 percent omega-3).

We should note that the relatively high percentages of omega-3 in select nuts, seeds, and vegetable oils may be misleading. The body can only use the long-chain omega-3s found in fish (EPA and DHA) for key cellular functions, and converts only about 10 percent of the short-chain omega-3s in nuts, seeds, and vegetable oils to EPA and DHA.

Consequently, a small amount of fish oil delivers the same brain benefits as a much larger amount of omega-3-rich plant oil, at a much lower calorie level.


  • Zhang J, Hebert JR, Muldoon MF. Dietary fat intake is associated with psychosocial and cognitive functioning of school-aged children in the United States. J Nutr. 2005 Aug;135(8):1967-73.