Restricting calories from fats has not been shown to prolong life. In fact, as discussed last week, increasing the right kinds of fats in your diet can improve your health. Getting large amounts of some polyunsaturated and monounsaturated fats, such as the right kind of omega 3 fatty acids, has been shown to improve the markers of cardiovascular disease. These fats reduce adverse markers when taken as a food. But when taken in capsule form, some studies have not seen any benefit to health. Omega 3 foods have advantages over supplements.
Omega 3 Foods Versus Omega 3 Supplements
A recent article (1) about DHA gives some clues about why there is an advantage to omega 3 foods over some omega 3 supplements. It studied why DHA in food gives a favorable effect, but in capsule form does not. In fact, from this particular research study, the capsule even may be harmful.
It has been poorly understood how DHA improves cardiovascular health. However these researchers have found that the molecule dilates vascular smooth muscle to reduce blood pressure. It does its magic by attaching to a pore in the cell membrane that allows potassium to pass. The molecule in food is docosahexaenoic acid (DHA), but in a capsule it is usually the ethyl ester version of the molecule (DHA-ethyl ester).
How DHA Helps
DHA acts at a pore in the cell membrane of the smooth muscle cells of the blood vessels, letting potassium pass. This dilates the blood vessel by relaxing the smooth muscle cells. The dilated blood vessels lower blood pressure.
There are several different pores in the cell that allow potassium to pass. The pore DHA acts on is the BK1 pore. Potassium is crucial to smooth muscle relaxation. When enough DHA is present, the DHA attaches and changes the electrical charge 20-fold at the pore. This opens the pore allowing potassium to pass.
How DHA Capsules Differ
When in a capsule, DHA often is an ethyl ester. The ethyl ester form is able to attach to the same receptor site on the BK1 pore where DHA attaches. But the ethyl ester form does not change the charge and does not open the pore. And it blocks DHA from attaching. So DHA attaches to fewer pores. Fewer pores open and less potassium can pass.
This means the smooth muscle cells do not relax as much and the blood pressure stays up.
So if you are eating fish you are getting DHA in its effective form. If you are using fish oil supplements, you may be getting DHA ethyl ester. This is the form that blocks the pore and blocks the passage of potassium. This may explain why some studies that studied fish oil supplements showed no improvement in blood pressure or cardiovascular disease, whereas studies of populations eating fish showed improved blood pressure.
Table Of Potassium In Fish
For a table with the potassium content of different fish click here.
1. Omega-3 fatty acids lower blood pressure by directly activating large-conductance Ca2+-dependent K+ channels Toshinori Hoshi, Bianka Wissuwa, Yutao Tian, Nobuyoshi Tajima, Rong Xu, Michael Bauer, Stefan H. Heinemann, and Shangwei Hou. Published online before print March 4, 2013, doi: 10.1073/pnas.1221997110 PNAS March 4, 2013 201221997