Question: I was told that to make sure I get adequate Omega 3 fatty acids, I have to eat purslane daily because purslane is the highest plant source of Omega 3 and it contains EPA. Is this true?
This all goes back to a study on purslane that came out in 1992 which said it is a rich source of Omega 3. Since then, there have been a few other studies looking at the omega 3 content of purslane, and some have reported that it also may contain EPA & possibly DHA.
Like all plants, purslane contains all the essential nutrients (except B12) including Omega 3 and therefore, it can contribute to their daily requirement.
It is true that purslane is the richest source of Omega 3 out of all vegetables, including the green leafy vegetables, but it is not the richest plant source. Studies have estimated its omega 3 content to be about 300-400 mg per 100 grams. Considering this, it would take just over a pound of purslane to reach the Adequate Intake of 1.6 for men set by the NAS. (Some professional vegan advocates think vegans need even more that the AI to cover for limited conversion issues so)
Let's compare this to the amount of flax and chia seeds needed to reach the AI 1.6 for men, using 300 mg/100 gm purslane.
Purslane - 12 cups - 533 gm - 85.3 calories
Chia Seeds - ~1 tbsp - 9 gm - 43.7 calories
Flax Seeds - 1 tbsp - 7 gm - 37.4 calories
On a nutrient density scale, (nutrient/100 cal), we also see that flax and chia are better sources.
Purslane - 1.87 gm
Chia - 3.66 gm
Flax - 4.28
In regard to EPA & DHA, one study reported that they found some EPA in it, but it was 1 mg per 100 gm. Other studies found no EPA or DHA in it at all. There is no AI or DRI for EPA but there are some recommendations out there that recommend around 250-500 mg a day. So to get to just 250 mg, one would need to consume at least 55 lbs of it.
In regard to the original questions, you do not have to eat purslane every day (or at all), purslane is not the highest plant source of Omega 3's and if it does contain EPA, it is in a minuscule amounts that would not matter.
If you do enjoy purslane, and are able to grow it or buy it, feel free to include it in your diet.