24 September 2007

The Medical Officer and associates for Toronto Public Health have just released a major Technical Report entitled 'Fish Consumption: Benefits and Risks for Women in Childbearing Years and Young Children'. The report recognizes the particular importance of DHA omega-3 fatty acid (docosahexaenoic acid omega-3) for physiological functioning and development of the brain and retina for optimal neuronal and visual functioning, respectively. Furthermore, the importance of adequate DHA intakes in pregnant women, women in child-bearing years, nursing women, and young children is acknowledged. These target groups are advised to completely avoid eating fish with high levels of mercury and listed fish with high levels of mercury to include shark, swordfish and fresh or frozen tuna. The report also says that pregnant women and children should not eat more than two servings (170 grams each = 340 grams total) per week of fish containing low levels of mercury (0.5 ppm of mercury and below) - including wild and canned salmon, herring, mackerel (except king mackerel), sardines, trout, catfish, pollock, and tilapia. The complete report can be read via the following link: http://www.toronto.ca/health/hphe/fish_mercury.htm

Comment from Professor Holub:

The amount of DHA which would be provided in mg/day based on the average of a maximum of 2 fish servings per week (340 grams/week) is given below in Table 1 for various types of fish (low in mercury) as advised for pregnant women. It is noteworthy that the target intakes as recommended by the ISSFAL workshop (1) held in 1999 in Bethesda , Maryland for pregnant women (300 mg DHA per day) can be attained, in some cases, by fish consumption at the level of 2 servings per week. For other fish, their provision of DHA can be complemented by the selection of non-fish sources of DHA. It is noteworthy that a large number of encapsulated fish oil products (containing significant amounts of DHA (reaching 120-500 mg per capsule) are available in the marketplace as alternatives to fish consumption. Furthermore, most (but not all) of these products are essentially free of any risk levels of methylmercury and other environmental contaminants. Finally, functional foods such as omega-3 shell eggs (containing up to 125 mg DHA/egg), liquid eggs enriched in DHA plus EPA, and other DHA-containing functional foods such as bakery products, yogurts, etc. containing microencapsulated DHA preparations are now appearing in the marketplace as additional options to those who, for various reasons, choose not to consume sufficient quantities of DHA via fish.

Table 1 : Amount of DHA provided in the maximum of two servings (170 grams each = 340 grams total) per week of fish containing low levels of mercury as recommended for pregnant women

Fish	DHA in mg per 340 grams*	Averaged DHA intake in mg/day (from 340 gms fish/wk)
Salmon (Coho, wild)	1458	208
Salmon ( Atlantic , farmed)	2102	300
Salmon (Sockeye)	1764	252
Sardines (Pacific)	1808	258
Herring ( Atlantic )	2410	344
Mackerel ( Atlantic )	3054	436
Trout (farmed)	884	126
Pollock ( Atlantic )	242	34
Catfish (Channel, wild)	442	64
Tilapia	18	3

*Based on compositional data from the USDA

(1) Simopoulos, A.P., et al. Essentiality of recommended dietary intakes for omega-6 and omega-3 fatty acids. Ann. Nutr. Metab. 43: 127-30, 1999.