We don't want to give the impression that the only factor in healthy food is the potassium sodium ratio of the food you eat. Other factors play a role. One that is often discussed is the importance of omega-3 fats. DHA is an important omega-3 that improves heart health. But how does it make a difference?
What Good Are Fats?
Fats have multiple functions in our bodies. In the cell, fats have a structural function, becoming part of both the cell membrane and various intracellular membranes, such as the membrane of mitochondria. Two other functions of fats are 1) to be burned as fuel, and 2) to participate in cell signaling.
The functions are not exclusive however. One fat does not do one function and another fat another function. Each fat is involved in several aspects of cell function at the same time.
Structure and cell signaling are two functions that are often interrelated. When a fat enters the cell and becomes part of a cell membrane or a mitochondrial membrane, it is not just providing structure. It is also affecting cell signaling.
How Structure Affects Cell Signaling
One way a fat that is part of the structure of a membrane may affect cell signaling is by changing the shape of channels that go through the membrane. These channels allow various molecules to pass from one compartment of the cell to another. Different fats in a membrane will cause a channel to be open more or closed more.
DHA is a polyunsaturated omega-3 fat that has a strong effect on health. One of its effects is to make a cell channel known as a BK(Ca) channel open more easily. This channel is one that allows potassium to move from one compartment to another inside the cell to affect cell signaling.
In heart muscle cells the BK(Ca) channels let potassium flow from one area to another depending on the calcium concentration in parts of the cell (1). When the calcium concentration inside the mitochondria gets too high, another channel known as the mPTP channel lets fluid in and the cell dies (2). By letting potassium flow into the mitochondria, the BK(Ca) channel can stop the mPTP channel from killing the heart muscle cell, discussed here.
DHA And Potassium
An important way that DHA protects the heart is by opening the BK(Ca) channel, making it easier for potassium to pass through the channel. This results in less heart muscle cell death, less scarring in the heart, and less heart failure.
You can get more DHA into your cell membranes by getting more DHA in your diet. A recent article (3) showed that consuming more DHA will cause more of the DHA to be deposited in the mitochondrial membranes of heart cells. The more DHA that is deposited in the mitochondrial membranes, the more BK(Ca) channels will be able to stop the harm done by the mPTP channels.
Stopping the action of the mPTP channels means stopping the cell death, scarring and heart failure resulting from the channels' activity. So one way DHA improves health is to improve the action of potassium. It would be interesting to know if some of DHA's other favorable effects are associated with potassium.
Watch The Source Of DHA
However, you must be careful about your source of DHA. DHA in food may differ from DHA in supplements. The two major food sources of DHA are fish and algae. Wild fish are generally better than farmed fish because they are more likely to be eating algae. Algae is where the fish get their DHA.
The studies discussed above used pure DHA. The form sold in fish oil capsules, or as DHA capsules, may be the ethyl ester form. As pointed out in a previous post, the ethyl ester form of DHA will block the BK(Ca) channel. If the BK(Ca) channel is blocked, mPTP will not be hindered. The heart muscle cells then will be more easily damaged from a low potassium sodium ratio diet. This may account for the seeming failure of fish oil supplements to improve health.
Another aid to stop the cell death from mPTP activity is to have enough potassium inside the cell. By eating foods with more potassium, more potassium is available inside the cell. This means more potassium is available to pass into the mitochondria to stop the action of the mPTP channel and thus stop cell death.
To Find High Potassium Foods
If you are looking for tables with the amount of potassium and sodium in a particular food, go to the “Links to Food Potassium Tables” page by clicking on the tab at the top of this page.
1. Intracellular BK(Ca) (iBK(Ca)) channels. Singh H1, Stefani E, Toro L. J Physiol. 2012 Dec 1;590(Pt 23):5937-47. doi: 10.1113/jphysiol.2011.215533. Epub 2012 Aug 28.
2. Intracellular calcium overloading and oxidative stress in cardiomyocyte necrosis via a mitochondriocentric signal-transducer-effector pathway. Mazen Shaheen, MD, Yaser Cheema, MD, Atta U Shahbaz, MD, Syamal K Bhattacharya, PhD, and Karl T Weber, MD. Exp Clin Cardiol. 2011 Winter; 16(4): 109–115.
3. Improved mitochondrial function with diet-induced increase in either docosahexaenoic acid or arachidonic acid in membrane phospholipids. Khairallah RJ, Kim J, O'Shea KM, O'Connell KA, Brown BH, Galvao T, Daneault C, Des Rosiers C, Polster BM, Hoppel CL, Stanley WC. PLoS One. 2012;7(3):e34402. doi: 10.1371/journal.pone.0034402. Epub 2012 Mar 30.