Purslane vs. Fish for Heart Health

A recent article in The Baltimore Sun is headlined “Purslane: A weed with nutritional punch.” The major nutritional component in the punch of this “superfood” is supposedly its content of omega-3 fatty acid, which is said to exceed that of any other plant. But how does it compare to eating fish?

The AHA recommends getting Omega-3 fatty acids in your diet

Many studies have shown that fatty fish contain two specific, heart-healthy omega-3 fatty acids: EPA and DHA (20-carbon eicosapentaenoic acid (EPA) and 22-carbon docosahexaenoic acid (DHA)). The American Heart Association (AHA) recommends that everyone get these heart-healthy omega-3s by eating at least two 3.5 ounce servings of fatty fish each week. People diagnosed with coronary heart disease (CHD) should obtain an even higher amount--one gram of EPA/DHA daily--by eating fish on most days or by taking a fish oil supplement each day.

Since the DHA/EPA content of over-the-counter fish oil supplements varies from 30 to 60 percent, it would be necessary to take two or three of these capsules daily to get one gram of the desired omega-3s. The purified, and more expensive, prescription product Lovaza contains about 90 percent DHA/EPA, so that a single one gram capsule per day would meet the AHA recommendation for people with CHD. (However, the cost of Lovaza is at least 3 times greater than that of over-the counter fish oil capsules.)

Another benefit, fish oil capsules containing about 4 grams of DHA/EPA daily can lower high triglyceride levels substantially.

Fish oil vs. Plant oil

Unlike fish oil, the omega-3 in purslane starts as a different fat; it's almost exclusively the 18-carbon fat alpha-linoleic acid (ALA). Unlike DHA/EPA in fish oil, ALA likely confers most of its heart benefits only after it is converted in the body to DHA or EPA. But this conversion is very inefficient; our bodies convert only 5 percent or less of ALA to the EPA and DHA found in fish. As a result, the 350 milligrams of ALA in one cup of purslane would at best be converted to only about 0.02 grams of EPA/DHA--a very small amount. Compare that with the 1.2 grams of EPA/DHA found in one serving (3.5 ounces) of sockeye salmon. This means that you would have to eat about 60 cups of purslane to obtain the equivalent amount of the EPA and DHA found in one serving of salmon! 

Flax seed oil is also touted as a heart-healthy food because of its high content of ALA, but similarly small amounts of the ALA in flax seed oil would be converted to the omega-3s present in fish. Although the ALA in flax seed oil, as well as in purslane, may have some heart benefits independent of its conversion to EPA and DHA, neither of these plant sources can substitute for eating fish or taking fish oil supplements.               

Purslane has apparently become one of the recently favored components of salads. My suggestion is that you eat purslane because you like the taste, not in order to live a longer life.

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