Landmark UK study heightens importance of maternal omega-3 intake; related analysis ties Britain’s mental health crisis to a 50-year decline in fish consumption
by Craig Weatherby
Two esteemed scientists who we heard speak at last December’s Seafood & Health Conference in Washington, D.C.—Cmdr Joseph Hibbeln, M.D. and Professor Michael Crawford, PhD.—played central roles in news that’s making waves around the world.
Last week, Dr. Hibbeln released new findings that confirm and significantly expand on prior evidence that mothers’ intake of long-chain marine omega-3s exert a major influence on children's brain development and emotional well-being.
The news came out of a conference mounted by Dr. Crawford’s Institute of Brain Chemistry and Human Nutrition, titled “Generating Healthy Brains: Nutrients and Hormones in Development”.
Dr. Crawford is the renowned researcher whose compelling keynote lecture at last year’s Seafood & Health conference presented convincing evidence of two propositions:
- aquatic plants and animals rich in marine omega-3s dominated the diets of our immediate evolutionary predecessors.
- marine omega-3s played a critical, defining role in the evolution of the uniquely large, powerful human brain.
Dr. Hibbeln's new results—which flow from his analysis of data from Britain’s famed Avon Longitudinal Study of Parents and Children—show a close relationship between mother’s intake of omega-3s and their toddlers’ performance on tests designed to measure intelligence, fine motor coordination, and tendencies toward anti-social behavior.
The Avon data bank is a uniquely valuable research resource, as it contains detailed diet, environmental, and developmental information on some 14,000 expectant mothers and their offspring.
Dr. Hibbeln presented the joint US/UK team’s findings at last week’s "Generating Healthy Brains" conference, which focused on ways to ameliorate the staggering social and financial impact of mental health problems on modern industrial societies.
According to the conference organizers, the societal costs of mental illness and brain disorders in the European Union (EU) totaled €386 billion (about $380 billion) as of 2004: an enormous amount that far exceeds the EU countries’ outlays for other diseases.
“Healthy Brains” forum highlights landmark findings
Dr. Hibbeln—a practicing psychiatrist and leading researcher at the National Institutes of Health—took the opportunity of Dr. Crawford’s “Generating Healthy Brains" conference to present the as yet unpublished new Avon study findings.
The alarm-raising results indicate that maternal omega-3 intake is even more important to their children than prior research proved, and that exaggerated fears of maternal mercury intake from fish can be quite counterproductive.
There were four main findings:
- Higher maternal omega-3 intake enhances verbal IQ: Children's scores on this key developmental variable rose with increasing maternal omega-3 intake. And, the children of the women who had consumed the smallest amounts of omega-3 fatty acids during their pregnancies had verbal IQs six points lower than average. This is a substantial difference for any individual, but it has even more serious implications for a country's collective brainpower.
- Higher omega-3 intake yields better fine-motor skills at age 3½: The mothers of the children with the highest scores on fine-motor performance tests were the ones who reported the highest intake of omega-3s.
- Low pre-natal intake of omega-3s impairs social development: The children of mothers who consumed the least omega-3s during pregnancy had a harder time making friends at age seven. As Dr Hibbeln said, this “frightening data” shows that the seven-year-olds whose mothers had the lowest intake of omega-3s during pregnancy had twice the risk of socialization problems (14 percent versus eight percent), compared with children of the highest-intake mothers. And, as the authors noted, socialization problems in childhood are the best predictor of anti-social behavior in adolescence and adulthood.
- Excessive fish/mercury avoidance may yield negative consequences: The results suggest that in this large group of mothers and children, the developmental benefits from high maternal fish consumption during pregnancy substantially outweighed any developmental risks posed by the relatively higher resulting levels of mercury intake. The Avon study children exposed to the lowest levels of methyl mercury were at greatest risk of having a low verbal IQ score. In the U.S., pregnant women are advised to eat no more than 12 ounces a week of fish low in mercury, including wild salmon. (Fish oil supplements offer an equally safe alternative). And they're told to avoid shark, swordfish, tilefish, and king mackerel entirely. Given the dismal results of surveys testing public understanding of this well-intentioned health warning, it could result in an inadequate intake of omega-3s during pregnancy and nursing.
Results align with prior findings
Epidemiological nutrition-disease studies like this one draw conclusions based on statistical correlations between variables such as maternal omega-3 intake and outcomes such as their offspring’s intelligence.
However, as scientists say, “correlation is not causation.” Simply because variable A bears a significant statistical relationship to outcome B does not mean that A causes B.
But the Avon children’s test scores show a “dose response” to maternal omega-3 intake. That is, increasingly higher levels of omega-3s produced increasingly better cognitive/behavioral outcomes, and vice versa: increasingly lower levels of omega-3s related with increasingly worse developmental scores.
These findings also come in the context of ample evidence for the cognitive impacts of omega-3s, and credible explanations for omega-3s’ brain/behavior benefits; for example:
- One of Dr. Hibbeln's prior investigations showed that, among a group of 3,581 urban white and black young adults, regular consumption of fish rich in omega-3 fatty acids correlated with lower rates of hostility.
- Research at Japan’s Toyama University indicates that omega-3 supplements can alleviate stress and hostility substantially in college students experiencing exam pressures. The student subjects took 1.5 grams of DHA—the marine omega-3 that constitutes about 12 percent of the human brain’s dry weight—during the study. (This dose is roughly double the average Japanese person’s daily DHA intake—about 800 mg, from dietary fish—and it’s about 20 times the average American’s daily DHA intake of 50-90 mg.)
- When Canadian researchers gave omega-3 supplements to piglets, it doubled the levels of serotonin and dopamine in their brains’ frontal cortexes. Serotonin helps growing nerve cells connect from the “rational” frontal cortex to the “emotional” limbic system, and dopamine is key to motor control.
- Omega-3 intake affects the amount of omega-6 in the membranes of nerve cells, which affects its permeability to key messenger molecules. The average American’s diet is low in omega-3-rich fish and high in omega-6-rich vegetable oils. (Currently, Americans derive five to ten percent of their daily calories from the omega-6 fat in corn and soy oils.) This dietary imbalance results in a badly skewed omeg-3/omega-6 consumption ratio of about 1 to 10 or worse, versus the widely recommended 1 to 3 consumption ratio. Consequently, the average American’s cell membranes contain omega-3s and omega-6s in a ratio of about 1 to 5. (Membrane ratios are strongly influenced by the dietary ratio, but because other factors come into play, it will not mirror the dietary ratio exactly.) But, in fish-loving Japan—which enjoys very high student achievement scores and very low violent crime rates—the average person’s cell membranes contain omega-3s and omega-6s in the far healthier ratio of 2 to 3.
Fish-consumption fall-off tied to UK’s mental health crisis
The findings of the new Avon study bolster those of a report issued by two British charities last week.
The authors of a study sponsored by The Mental Health Foundation and Sustain found that people in the UK eat 59 per cent less fish—the main source of omega-3 fatty acids—than they did 60 years ago.
They concluded that the precipitous drop in Britons’ consumption of omega-3 fats—and the steep rise in their consumption of omega-6 fats—over the past 60 years accounts for much of the UK’s alarming rise in mental illness rates and costs over the same period. Britain now spends a staggering £100 billion ($200 billion) a year dealing with the consequences of mental illness.
- Diet and the unborn child: The omega point. The Economist, Jan 19th 2006. Accessed online January 18, 2006 at http://www.economist.com/science/displaystory.cfm?story_id=5407595
- de la Presa Owens S, Innis SM. Diverse, region-specific effects of addition of arachidonic and docosahexaenoic acids to formula with low or adequate linoleic and alpha-linolenic acids on piglet brain monoaminergic neurotransmitters. Pediatr Res. 2000 Jul;48(1):125-30.
- de la Presa Owens S, Innis SM. Docosahexaenoic and arachidonic acid prevent a decrease in dopaminergic and serotoninergic neurotransmitters in frontal cortex caused by a linoleic and alpha-linolenic acid deficient diet in formula-fed piglets. J Nutr. 1999 Nov;129(11):2088-93.
- Mental Health Foundation. New reports link mental ill-health to changing diets. Accessed online January 18, 2006 at http://www.mentalhealth.org.uk/page.cfm?pageurl=press_2006_01_16.cfm
- Umhau JC, Dauphinais KM, Patel SH, Nahrwold DA, Hibbeln JR, Rawlings RR, George DT. The relationship between folate and docosahexaenoic acid in men. Eur J Clin Nutr. 2005 Nov 9; [Epub ahead of print]
- Iribarren C, Markovitz JH, Jacobs DR Jr, Schreiner PJ, Daviglus M, Hibbeln JR. Dietary intake of n-3, n-6 fatty acids and fish: relationship with hostility in young adults--the CARDIA study. Eur J Clin Nutr. 2004 Jan;58(1):24-31.
- Noaghiul S, Hibbeln JR. Cross-national comparisons of seafood consumption and rates of bipolar disorders. Am J Psychiatry. 2003 Dec;160(12):2222-7.
- Hibbeln JR, Nieminen LR, Lands WE. Increasing homicide rates and linoleic acid consumption among five Western countries, 1961-2000. Lipids. 2004 Dec;39(12):1207-13.
- Hibbeln JR, Linnoila M, Umhau JC, Rawlings R, George DT, Salem N Jr. Essential fatty acids predict metabolites of serotonin and dopamine in cerebrospinal fluid among healthy control subjects, and early- and late-onset alcoholics. Biol Psychiatry. 1998 Aug 15;44(4):235-42.
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, D. C.: National Academies Press; 2002. National Academies Press.