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Flax or Fish?

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Brown Flax Seeds.

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A groundbreaking study reports both good and bad news for flax fans, so if you rely on flax seed and/or flax oil supplements to provide your omega-3 fats, read on.

Supplements of flax oil, rich in alpha linolenic acid (ALA), an omega-3 plant form,  boosted the blood levels of one the two key omega-3’s found in fish oil – but not the other.

ALA is found in flax, walnuts, canola and soybean oils have health benefits alone.  But the heart healthy benefits of omega-3 fats is primarily due to the longer chain fatty acids called eicosapentaenoic (EPA) and docosahexaenoic acid (DHA).  For my science-minded friends, ALA has 18 carbons with 3 double bonds.  EPA has 20 carbons with 5 double bonds and DHA has 22 carbons with 6 double bonds. All are polyunsaturated fats.  The body can convert ALA to EPA and DHA, but this process isn’t always very efficient.

To test the benefits of doses of each type of oil, the researchers randomly assigned 62 firefighters to one of six groups for 12 weeks.

The doses are considered to be obtainable levels of ALA in the diet:

  • 1.2 grams of flax oil daily
  • 2.4 grams of flax oil daily
  • 3.6 grams of flax oil daily
  • 0.6 grams of fish oil daily
  • 1.2 grams of fish oil daily
  • a sunflower oil placebo (no omega-3 fats)

The results yielded both good and bad news.  The lowest dose of flax oil (about that found in a single pill) didn’t significantly raise levels of omega-3s other than ALA – this was expected.

Both the 2.4 gram and 3.6 gram flax oil doses raised the levels of EPA between 30-40 percent.  But the bad news is that there was no increase in DHA for any flax oil dose, which confirms the very low conversion of ALA to DHA as reported in previous studies. Most studies on heart health involve both EPA and DHA and EPA has not to my knowledge been studied alone.

Unfortunately, modern Western lifestyles and eating habits interfere with the human conversion of ALA into EPA and DHA.  Some of the major interfering factors are:

  • A high intake of omega-6 fatty acids (common in many vegetables oils, except olive oil)
  • A high intake of trans fatty acids common in shortenings, deep fat fried foods, and processed foods.
  • Excess insulin in the blood from sugar and refined starches.
  • Alcohol abuse
  • A deficiency of nutrients that suuport the function of the converting enzymes – vitamins B3 (niacin), B6, C and minerals zinc and magnesium.

Conversion rates also vary by gender, age, and genetic factors. Due to these physiologic and lifestyle factors, human conversion of ALA into EPA ranges from 8% to 20%.  Conversion of ALA into DHA ranges from 0.5% to 9%.

So the bottom line on flax oil as a major source of omega-3 fats is still up in the air.   If you want the most benefits you can get from omega-3s, it is still best to eat more oily fish (salmon, mackerel, tuna, trout and herring) or take fish oil supplements containing EPA and DHA.

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