The Top 5 Nutritional Benefits of Omega-3 Fatty Acids and Other Essential Vitamins and Minerals Found in Fish and Seafood

1. Heart Health
2. Stroke Risk Reduction and Prevention
3. Brain Function
4. Visual Acuity
5. Cancer Risk Reduction and Prevention
   

Compiled by Bruce Holub, PhD, University Professor Emeritus, Dept. of Human Health & Nutritional Sciences, University of Guelph; Founder DHA/EPA Omega-3 Institute

1. Heart Health

A review of numerous population research studies (on over 222,000 people followed for 12 years) has indicated an overall 23% and 38% reduction in coronary heart disease mortality for those consuming two to four, or at least five fish servings/week, respectively.¹ Two fish servings/week would be expected to provide approximately 250 mg/day on average of the long-chain omega-3 fatty acids (as DHA plus EPA) while five to seven servings/week would yield 650-900 mg/day. Unfortunately, the average fish serving in Canada is close to only one serving per week with a daily average intake of DHA plus EPA of approximately 125 mg/day. Canada’s Food Guide (Health Canada) has advised that regular fish consumption should be at least two servings per week (total of 150 grams)², while the Dietitians of Canada have recommended a daily intake of 500 mg of DHA plus EPA daily.³ The American Heart Association’s Dietary Guidelines advise seven servings of fish/week or 900 mg/day of DHA plus EPA for those with pre-existing coronary heart disease.⁴

There is general scientific agreement that much of the cardioprotective effects of increased fish intake arises from the DHA/EPA omega-3 fatty acids residing therein. These have been found to offer favourable effects on various risk factors for heart disease⁵ including anti-thrombotic, anti-arrhythmic, anti-inflammatory effects including blood lipid-lowering (as triglyceride). Amongst the elderly from the U.S., higher fish and omega-3 intakes were associated with significantly lower rates of heart failure.⁶

In addition to their enrichment in the cardioprotective omega-3 fatty acids, fish are very low in saturated fats and devoid of trans fatty acids which are also associated with a decreased risk for coronary heart disease.⁷ While high quality protein as found in fish supports muscle development, fish protein itself has been found to favourably influence circulating blood lipids, a risk factor for heart disease.⁸

Selected References:

¹ He, K. et al., Accumulated evidence on fish consumption and coronary heart disease mortality. Circulation, 109: 2705-2711, 2004.
² Health Canada, Canada’s Food Guide: http://www.hc-sc.gc.ca/fn-an/food-guide-aliment/index-eng.php.
³ Kris-Etherton, P. et al., Position of the American Dietetic Association and Dietitians of Canada: dietary fatty acids. J. Am. Dietetic Assoc., 107: 1599-1611, 2007.
⁴ Krauss, R. et al., AHA Dietary Guidelines. Circulation, 102: 2284 -2299, 2000.
⁵ Holub, B. J., Clinical Nutrition: Omega-3 fatty acids in cardiovascular care. Can. Medical Assoc. J., 166: 608-615, 2002.
⁶ Mozaffarian, D. et al., Fish intake and omega-3 fatty acid consumption and risk of incident heart failure. J. Am. College Cardiol., 45: 2015-2021, 2005.
⁷ Woodside, J.V. et al., Saturated and trans fatty acids and coronary heart disease. Curr. Atheroscler. Rep., 10: 460-466, 2008.
⁸ Jacques, J. et al., Role of fish protein in the regulation of plasma lipids. Can. J. Cardiol., 11: 63G-71G, 1995.

2. Stroke Risk Reduction and Prevention

The early study (in 1994) from The Netherlands found that the regular consumption of at least one serving per week of fish by men aged 50-69 years was associated with a significant reduction in the risk of a stroke.¹ Men who consumed more than 140 grams of fish per week (just under two servings per week – one serving of fish is 75 grams according to Canada’s Food Guide) had an approximately 50% lower risk of a stroke.

Since then, there have been many population studies of this type in both genders which have been reviewed by He et al.² In this review, based on over 200,000 subjects followed for 13 years, the research scientists reported that five or more fish servings per week was associated with a 31% lower risk of stroke mortality as compared to those who ate little or no fish.

Dr. Mozaffarian and his colleagues from the Harvard Medical School followed elderly subjects (ages 65-98 years at the beginning) for 12 years.³ They found that elderly subjects who ate tuna or other baked or broiled fish at the frequency of one to four times/week had a 27% lower risk of ischemic stroke while eating such fish five or more times/week gave a 30% reduction in ischemic stroke frequency as compared to those who ate fish less than once/month.

The apparent protective effects of increased fish consumption against the risk of stroke have been attributed mostly to fish being the predominant dietary source of the long-chain omega-3 fatty acids as DHA (docosahexaenoic acid) plus EPA (eicosapentaenoic acid). Current intakes of fish and DHA/EPA in the Canadian population are generally low with average consumption being only one serving every 10 days.

Selected references:
¹ Keli et al., Fish Consumption and Risk of Stroke: The Zutphen Study. Stroke, 25: 328-332 (1994).
² He at al., Fish Consumption and Incidence of Stroke: A Meta-Analysis of Cohort Studies. Stroke, 35: 1538-1542 (2004).
³ Mozaffarian et al., Fish Consumption and Stroke Risk in Elderly Individuals. Arch. Internal Medicine, 165: 200-206 (2005).

3. Brain Function

DHA (docosahexaenoic acid), as consumed in the diet predominantly from fish, is recognized as a physiologically essential omega-3 fatty acid in the brain where it is found at relatively high concentrations.¹ The special structural and physical properties of DHA underlies its critical role in mediating optimal brain functioning and cognitive performance including memory and learning ability. Dietary consumption of appropriate fish on a regular basis during pregnancy is recommended to mothers for ensuring the delivery of pre-formed DHA to the brain of the infant during gestation. Furthermore, the omega-3 fatty acid from selected plant sources known as ALA (alpha-linolenic acid) can only form very small amounts of DHA via its limited conversion to DHA in humans.

The ALSPAC study from the U.K.² found a significantly higher risk of sub-optimal mental and developmental outcomes (verbal IQ, behaviours) up to eight years later in those children from mothers who consumed no fish/seafood as compared to those consuming three or more servings of fish containing omega-3 fatty acids during pregnancy. The PERLIP project (via the European Commission) has recommended³ that pregnant women should consume at least 200 mg DHA/day on average – which contrasts with average intakes of only 82 mg DHA/day in pregnant Canadian women. The paucity of fish consumed by Canadian children during a period of ongoing brain development has resulted in them having extremely low intakes of DHA (averaging only 54 mg/day) as determined directly⁴ in contrast with markedly higher intakes in Japanese children. Swedish schoolchildren who ate fish more frequently (once or more per week) were found to produce higher academic grades as compared to those eating fish less often.⁵

Fish also contains an abundance of essential vitamins and minerals (key ones being vitamin D, calcium, iodine, among others). For example, it is well known that a substantial number of pregnant women worldwide don’t consume enough iodine – a very important mineral needed for the development of the baby’s brain and nervous system thereby reducing the risk of cognitive impairment.⁶ Ocean fish are generally considered as the richest source of this essential mineral.

For middle-aged adults, a higher DHA status was associated with better cognitive functioning based on a battery of neuropsychological tests.⁷ There is substantial population evidence to indicate that increased fish consumption over several years in the elderly can reduce age-related cognitive decline and protect brain function.8

Selected References:
¹ Uauy, R. and Dangour, A.D., Nutrition in brain development and aging: role of essential fatty acids. Nutrition Rev., 64: S24-33, 2006.
² Hibbeln, J. R. et al., Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): an observational cohort study. The Lancet, 369: 575-585, 2007.
³ Koletzko, B. et al., Dietary fat intakes for pregnant and lactating women. Br. J. Nutr., 98: 873-877, 2007.
⁴ Madden, S.M. et al., Direct diet quantification indicates low intakes of (n-3) fatty acids in children 4 to 8 years old. J. Nutr., 139: 528-532, 2009.
⁵ Kim, J. L. et al., Fish consumption and school grades in Swedish adolescents: a study of the large general population. Acta Paediat., 99: 72-77, 2010.
⁶ Melse-Boonstra, A. and Jaiswal, N., Iodine deficiency in pregnancy, infancy and childhood and its consequences for brain development. Best Pract. Res. Clin. Endocrinol. Metab., 24: 29-38, 2010.
⁷ Muldoon, M. F. et al., Serum phospholipid docosahexaenoic acid is associated with cognitive functioning during middle adulthood. J. Nutr., 140: 848-853, 2010.
⁸ Cunnane, S. C. et al., Fish, docosahexaenoic acid and Alzheimer’s disease. Prog. Lipid Res., 48: 239-256, 2009.

4. Visual Acuity

DHA (docosahexaenoic acid) is a long-chain omega-3 fatty acid which is needed at substantial levels in the retina of the eye to support optimal visual development and acuity.¹ Fish is the predominant source of DHA in the Canadian diet despite the very low intakes. The consumption of fish provides for the direct availability of DHA for assimilation into the retina and visual cortex in contrast to the very limited conversion of the plant-based omega-3 ALA (alpha-linolenic acid) to DHA in the human body.

Increasing DHA intakes during pregnancy from 80 mg/day (typical of Canadian mothers) to 300 mg/day was found to significantly improve visual acuity scores of their infants at four months of age.² Population studies have clearly indicated that higher intakes of DHA via fish/seafood during pregnancy has long-term benefits for childhood visual processing.³ Higher levels of DHA in breast milk as produced by greater DHA intakes in lactating mothers has been associated with significantly better performances in hand-eye coordination by their children at 30 months.⁴ It is not surprising that the breast milk fat of Japanese mothers is much richer in DHA than found in Canadian mothers since the former consume more fish than meat in contrast to the latter. In Europe, mothers have been advised to consume at least 200 mg DHA/day during lactation to increase DHA levels in breast milk. For the elderly, population studies have shown a marked protective effect of eating more fish and shellfish containing DHA/EPA against advanced macular degeneration – a leading cause of blindness.⁵

In addition to having an abundance of omega-3 fatty acids, fish are rich in high quality protein plus important vitamins and minerals (vitamin D, calcium, selenium, others) which support overall growth and health including visual development throughout life.

Selected References:

¹ Eilander, A. et al., Effects of n-3 long chain polyunsaturated fatty acid supplementation on visual and cognitive development throughout childhood: A review of human studies. Prostagl. Leuk. And Essential Fatty Acids, 76: 189-203, 2007.
² Judge,M. et al., A docosahexaenoic acid- functional food during pregnancy benefits infant visual acuity at four but not six months of age. Lipids, 42: 117-122, 2007.
³ Jacques, C. et al., Long-term effects of prenatal omega-3 intake on visual function in school-age children. J. Pediatrics, in press, 2010.
⁴ Jensen, C. et al., Effects of maternal docosahexaenoic acid intake on visual function and neurodevelopment in breastfed term infants. Am. J. Clinical Nutr., 82: 125-132, 2005.
⁵ Swenor et al., The impact of fish and shellfish consumption on age-related macular degeneration. Ophthamology, in press, 2010.

5. Cancer Risk Reduction and Prevention

There have been several population studies which have supported an apparent protective effect of increased intakes of fish on the risk of certain cancers in both genders. The Physicians’ Health Study from the U.S. assessed the relationship between fish and omega-3 fatty acid intakes in men and the risk of colorectal cancer over a 22-year period.¹ An inverse relationship was found such that the highest intakes of fish were associated with the lowest incidence of both colon and rectal cancers. Independent of omega-3 intakes, this population study found that higher intakes of fish resulted in a 37% reduction in colorectal cancer risk. Further, independent of fish intakes, the higher omega-3 intakes were associated with a 26% lower risk of colorectal cancer. The similar apparent protective trends suggest that much (likely not all) of the fish benefits are due to the omega-3 fatty acids in fish. Most of the DHA/EPA omega-3 as consumed come most predominantly from fish.

In a very recent review² of population studies specifically on fish consumption and prostate cancer, the authors found no strong evidence for an association with disease incidence. However, fish consumption was associated with a significant 63% reduction in mortality from prostate cancer.

High intakes of fatty fish were found to be associated with a substantial decrease in the risk of breast cancer in both pre-menopausal and post-menopausal women in a major study from South Korea.³ This protective relationship was also found with higher intakes of the omega-3 fatty acids as DHA (more than 213 mg/day) plus EPA (more than 101 mg/day) from fish in the case of post-menopausal women. It is noted that these latter intakes are considerably higher than current intakes of DHA/EPA from fish amongst Canadian women.

The proposed mechanisms for the beneficial effects of DHA/EPA from fish on carcinogenesis include suppression of pro-inflammatory molecules known as ‘eicosanoids’ and the alteration of hormone-stimulated cell growth. Fish/seafood are amongst the most dependable sources of important vitamins and minerals. For example, the mineral selenium functions as a cellular antioxidant which underlies supportive evidence for its purported role in reducing the risk of certain cancers.⁴

Selected References:

¹ Hall, M. N. et al., A 22-year prospective study of fish, n-3 fatty acid intake, and colorectal cancer risk in men. Cancer Epidemiol. Biomarkers Prev., 17: 1136-1143, 2008.
² Szymanski, K. M. et al., Fish consumption and prostate cancer risk: a review and meta-analysis. Am. J. Clinical Nutr., in press, 2010.
³ Kim, J. et al., Fatty fish and fish omega-3 fatty acid intake decrease the breast cancer risk: a case-control study. BMC Cancer, 9:216, 2009.
⁴ Boosalis, M. G., The role of selenium in chronic disease. Nutr. Clin. Pract., 23: 152 , 2008.

Dr. Bruce Holub: Video 1

Dr. Bruce Holub discusses the Top 5 benefits of consuming fish and seafood.

Dr. Bruce Holub: Video 2

Fish and Seafood offer a wealth of health benefits and are a rich source of omega-3 fatty acids, calcium, protein and provide other essential nutrients in the diet.