Tuesday, 29 May 2012

Fish - the Ultimate Brain Food

Growing up I decided I didn't like fish. A shame really considering I lived beside the Pacific Ocean where the salmon and fishing opportunities were plentiful. Fortunately I've had a change of taste and have come to appreciate the beauty and simplicity of seafood. I also developed an appreciation for sashimi until a meal of vegetarian sashimi sent my gestational diabetes sugars through the roof. Did you know they put sugar in sushi rice? I digress.

Fish is good for us. Populations that eat more fish live longer. Of course these types of studies (epidemiological) only find possible associations and you can't assume their findings to be cause and effect (it could be that they also have less cars and walk more, or have stronger community support etc.). However their findings were so strong they have spurred a great deal of research into fish and the components of fish (omega 3 fatty acids) that may contribute to good health. In brief our North American lifestyles promote inflammation in our bodies (high omega-6 fat intake, stress, lack of sleep etc.), whereas omega-3 fatty acids are precursors to anti-inflammatory agents in our bodies. Ultimately re-tipping the scales towards a balance. They also play an important role in the development and function of the central nervous system. Hence the expression that fish is brain food.

What are the three main Omega-3 fatty acids? 
ALA- alpha-linolenic acid, the smaller (less carbon and double bonds) omega-3 fatty acid that is found in vegetable sources (flax seed, chia seed, hemp seed, walnuts, canola oil, soybean).

EPA - eicosapentaenoic acid, the fatty acid that is converted into anti-inflammatory messengers in the body. It's good for your heart.

DHA- docosahexaenoic acid, the fatty acid that is incorporated into the cell membranes of nervous tissue and retina. Because of it's structure it makes these membranes very fluid/flexible. It's good for your eyes and brain.

How much should I be eating per day?
The dietary reference intakes recommend consuming 1.1g/day (females) and 1.6g/day (males) of ALA. For children ages 1-3 years old, it is 0.7g/day and 0.9g/day for 4-8 years old. This recommendation was based on the average intake of North Americans. The DRI is to prevent deficiency, and it is difficult to determine optimal intake for health.

Unfortunately our bodies ability to convert ALA to EPA and DHA is limited, therefore in addition to ALA we need a dietary source of EPA and DHA. We don't have an official recommendation for DHA and EPA intake. An expert panel of researchers concluded in 2008 that there was sufficient evidence to recommend 250-500mg of DHA+EPA per day for cardiovascular health. (Harris et al. 2009 J.Nutr.)

A consensus statement in the British Journal of Nutrition in 2007 recommended that pregnant women consume 200mg/day of DHA.

So my next goal is to evaluate my family's intake and try to get the adults up to a minimum of 1.5 grams of omega-3 fatty acids per day with 300-500mg being DHA+EPA (averaged over the week). I am not a big fan of supplements as omega-3 fatty acids may not be the only part of fish that is beneficial for our health, therefore I will look to food sources primarily. However I will be open to them if we fall short of the mark.

Food Sources of DHA/EPA: (this is not an exhaustive list just some of the foods we eat on a regular basis)
Salmon (75 grams): 1900 mg
Rainbow Trout (75 grams): 900mg
Omega-3 eggs (chickens can convert the ALA to EPA/DHA so they feed them flax seed): 75mg DHA
Light Tuna canned in water (75 g or 1/2 cup): 200mg
(I usually buy canned light, not albacore/white because it is from smaller fish and contains less mercury, although it also has less DHA/EPA)
Anchovy (1 fillet 4g): 84mg
Sardines and Mackerel are good sources too.

Food Sources ALA:
Flax Seeds (1 Tbsp): 1.6 grams
Chia Seeds (1 Tbsp): 1.9 grams
Hemp Seeds (1 Tbsp): 0.84 grams
Walnuts (30g or 1/4 cup): 2.6 grams
Canola oil (1 Tbsp): 1.3 grams
My source is the Canadian Nutrient File. An excellent database if ever you want to look up the detailed nutrition information of your foods. The American one did not contain omega-3s.

So general plan will be two meals of fatty fish a week with a serving of a food source rich in ALA daily (ground flax on yogurt, or snack of walnuts). Do you like fish? If not, what are your food and/or supplement sources of DHA/EPA?

As we don't live and eat in a vacuum. Those of you interested in reading more about the best seafood choices for sustainability, there is a great table at National Geographic. http://ocean.nationalgeographic.com/ocean/take-action/impact-of-seafood/#/seafood-decision-guide/

4 comments:

  1. Very interesting post.

    In what way does the cooking process affect the omega-3 fatty acids? I'm assuming some get destroyed, but is there a big difference between various cooking modalities (ie. steaming vs baking vs grilling...)?

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    Replies
    1. Thank you for your comment! I believe the omega-3 fatty acids in foods are minimally altered by the cooking method. They aren't like water-soluble vitamins. A group studied the effect of deep-frying mackerel on EPA and found no alteration to it's structure or quantity. The alteration is to the fatty acids in the isolated oil used in the cooking process (i.e. the canola oil used to fry it in). That being said using a method that minimizes the exposure to the development of trans fats (deep frying - alters the oil it is cooked in) and carcinogens (charred fish on the grill - better to wrap in foil) is always preferable. Happy fish eating!

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  2. I should have warned you of the sushi rice. I also learned the hard way some years ago!

    What do you do if your kid literally vomits his obligatory taste of salmon?

    ReplyDelete
  3. Will someone help me to find more details about how to find a way to having an outstanding Flaxseed oil vegetable with omega nutrition dishes ?

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    ReplyDelete