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?
Answer: No.
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 our daily requirement of these.
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 then the AI to cover for limited conversion issues)
Let's compare this to the amount of flax seeds, chia seeds or walnuts needed to reach the AI 1.6 for men using 300 mg/100 gm purslane. We can see that flax and chia seeds are very close in the amount they have and both are the better sources.
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
Walnuts - 2 tbsp - 18 gm - 118 calories
On a nutrient density scale, (nutrient/100 cal), we also see that flax and chia are very close again and they both are the better sources again.
Purslane - 1.87 gm
Chia - 3.66 gm
Flax - 4.28 gm
Walnuts - 1.4 gm
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.
In Health
Jeff
PS you can see another comparison of Walnuts, Flax and Chia here
viewtopic.php?f=22&t=42399&p=436326#p436326
If you have seen my full nuts talk, I walk you through this process and the 3 that come up scoring the highest are walnuts, flax seed and chia seed. So, let's compare them on several key issues so you can choose the best one. This comparison is based on equaling them all out to 1.6 grams of Omega 3's, which is the upper level of the recommended AI.
(excuse the formatting)
Nutrient - - - Flax Seed - - Chia Seed - - Walnuts
Weight - - - - 7 grams - - - 9 grams - - - - 18 grams
Calories - - - 37 calories - -44 calories- - -118 calories
Fat - - - - - - -3 grams - - - -2.8 grams - - 11.7 grams
Sat Fat - - - - .3 grams - - - .3 grams - - -- 1.1 grams
Omega 6 - - - .4 grams - - - .5 grams - - - 6.9 grams
Omega 3 - - - 1.6 grams - - - 1.6 grams - -1.6 grams
6/3 ratio - - - .25 - - - - - - - .32 - - - - - - 4.15
Fiber - - - - - - 1.9 grams - --3.1 grams - - 1.2 grams
*ND - - - - - - - -- 3.8 - - -- - - 3.4 - - - - - - 2.4 - - -
*ND - Nutrient Density based on NutritionData.com scale of 1-5
While this may definitely fall under the category of "minutia, but since you did ask, from my perspective & based on the above analysis, the flax and the chia clearly win.
Common purslane: a source of omega-3 fatty acids and antioxidants.
J Am Coll Nutr. 1992 Aug;11(4):374-82.
http://www.ncbi.nlm.nih.gov/pubmed/?ter ... tioxidants.
Abstract
omega-3 fatty acids, alpha-tocopherol, ascorbic acid, beta-carotene and glutathione determined in leaves of purslane (Portulaca oleracea), grown in both a controlled growth chamber and in the wild, were compared in composition to spinach. Leaves from both samples of purslane contained higher amounts of alpha-linolenic acid (18:3w3) than did leaves of spinach. Chamber-grown purslane contained the highest amount of 18:3w3. Samples from the two kinds of purslane contained higher leaves of alpha-tocopherol, ascorbic acid and glutathione than did spinach. Chamber-grown purslane was richer in all three and the amount of alpha-tocopherol was seven times higher than that found in spinach, whereas spinach was slightly higher in beta-carotene. One hundred grams of fresh purslane leaves (one serving) contain about 300-400 mg of 18:3w3; 12.2 mg of alpha-tocopherol; 26.6 mg of ascorbic acid; 1.9 mg of beta-carotene; and 14.8 mg of glutathione. We confirm that purslane is a nutritious food rich in omega-3 fatty acids and antioxidants.
PMID: 1354675
Fatty acids and beta-carotene in australian purslane (Portulaca oleracea) varieties.
J Chromatogr A. 2000 Sep 29;893(1):207-13.
http://www.ncbi.nlm.nih.gov/pubmed/11043602
Abstract
The fatty acid profile and beta-carotene content of a number of Australian varieties of purslane (Portulaca oleracea) were determined by GC and HPLC. The total fatty acid content ranged from 1.5 to 2.5 mg/g of fresh mass in leaves, 0.6 to 0.9 mg/g in stems and 80 to 170 mg/g in seeds. alpha-Linolenic acid (C18:3omega3) accounted for around 60% and 40% of the total fatty acid content in leaves and seeds, respectively. Longer-chain omega-3 fatty acids were not detected. The beta-carotene content ranged from 22 to 30 mg/g fresh mass in leaves. These results indicate that Australian purslane varieties are a rich source of alpha-linolenic acid and beta-carotene.
PMID: 11043602
Review Article
Purslane Weed (Portulaca oleracea): A Prospective Plant Source of Nutrition, Omega-3 Fatty Acid, and Antioxidant Attributes
The Scientific World Journal
Volume 2014 (2014), Article ID 951019, 6 pages
http://dx.doi.org/10.1155/2014/951019
http://www.hindawi.com/journals/tswj/2014/951019/
Purslane has the highest level of alpha-linolenic which is an omega 3 fatty acid essential for human nutrition compared to any leafy green vegetable. A 100 g sample of purslane contains 300–400 mg of alpha-linolenic acid (ALA). It also has 0.01 mg per gram of eicopentanoic acid (EPA), which is not present at all in flax oil. This would provide 1 mg of EPA for a 100 g portion of purslane or 10 mg for a kg (2.2 pounds), or 1 g for 100 kg (220 pounds) of sample.
