A healthy body uses ALA to make the secondary Omega-3’s – EPA and DHA, which it needs for healthy brain/eye/nerve function. EPA is a key building block your body uses to make prostaglandins – key hormone like substances which control many bodily functions like the “flight or fight” reactions – think stress. So you do need both types of Omega-3.
However all the Omega-3s – ALA, EPA and DHA are alike, in that they all block the actions of some compounds that cause inflammation in your body. Most chronic diseases, like heart disease, stroke, diabetes, cancer and arthritis are marked by inflammation. By blocking inflammation, ALL omega-3 fats help to reduce the risk of chronic disease.
How does your body do this conversion?
The first step in this process uses an enzyme called the Delta-6-desaturase (D6D) – this is widely recognized as being the step that restricts the rate of this process. This rate can be impacted by a number of factors – more on this later.
You can get also get EPA and DHA direct from fish oil, but there are some serious limitations for your body if you just take a few fish oil capsules:
1. You only get the effects of better oxygenation and membrane integrity from the ALA in flax-seed oil – see “Oil on the mem-brane”
2. Your body needs to have roughly equal amounts of Omega-3 and Omega-6 – see “The balancing act- Omega 3:Omega 6”, so taking a gram or two of fish oil in capsules is going to do little to change this.
A very common argument used by the proponents of fish oil, is that humans can only convert limited amounts of ALA to the long chain Omega-3 EPA and even less to DHA.
Yes – some of the initial studies did indicate quite low conversion rates, but as the measurement techniques have become more sophisticated, the estimates of conversion rates have increased substantially. A recently published review on the subject suggests that the conversion of ALA to EPA, as measured in the blood, is in the order of 8 – 20% and the conversion to DHA is 0.5 – 9%5.
But this is only part of the story:
• The conversion rate is influenced by oestrogen levels, so that young women can convert up to 20 times more ALA to DHA than young men (so that they can grow their baby with a healthy brain perhaps?).
• Preterm infants on formula were converting about 15% of the ALA to DHA.
• When a group of healthy individuals were supplemented with flax oil, the levels of DHA in the brain and retina increased, even though there was no change in the amount of DHA circulating in the blood. This explains why all the early studies measuring the rates of conversion of ALA to DHA in either the blood serum or blood platelets did not tell the full story.
So, in a nut shell, the latest research is suggesting that the body is capable of making the amount of secondary Omega-3s it needs from the primary EFAs, delivered to the site where the body needs it.
Considering that humans are thought to have evolved in Eastern Africa, well away from oily cold water fish, rich in EPA and DHA, this is not really a surprising result – aren’t our bodies clever?