Omega-3s and Blood Pressure

Elevated blood pressure often has no symptoms

What comes to mind when you hear “high blood pressure”? A stressed-out, red-faced businessman with a blood vessel throbbing in his forehead? The truth is, even when blood pressure becomes elevated, it typically doesn’t have any recognisable symptoms.

In fact, fewer than 50% of people with elevated blood pressure are even aware that they have it (1).

Plus, blood pressure usually increases naturally with age regardless of stress levels, an inconvenient fact for those who’ve spent their lives never having to think about it (1).

Blood pressure can offer an early indication of bigger health issues

But why should you care about your blood pressure anyway? Why does the doctor always measure it, even if you’re there to see them about something totally unrelated? It’s because doctors know (and soon you will too) that blood pressure provides an early indication of issues involving your heart, arteries, and organs due to cardiovascular disease. Elevated blood pressure is not only a preventable risk factor for cardiovascular disease (heart attack, stroke, peripheral artery disease, and others), but also for chronic kidney disease and cognitive impairment (1).

Understanding what blood pressure is and how it becomes elevated are important, but you also need to know what you can do to keep it healthy.

As you will learn, omega-3 fatty acids from marine sources have been shown, in no less than 78 clinical trials over the last 35 years, to help support healthy blood pressure (2-9).

Arteries affect blood pressure through vasodilation and vasoconstriction

Arteries, such as the aorta, are composed of three basic layers. The tunica adventitia is the outermost layer (and isn’t involved in blood pressure). The tunica media is the middle layer, and is composed of alternating layers of muscle and structural fibers. There are two types of structural fibres: elastin and collagen (10). Elastin provides the distensible, or flexible, properties of arteries, while collagen provides stiffness (10). The tunica intima includes the endothelium, a single layer of cells that makes direct contact with the blood.

One of the main functions of the endothelium is to promote widening, or dilation, of blood vessels (vasodilation). For example, in response to increased blood flow (such as when your heart beats faster), the cells of the endothelium cause the blood vessel to dilate (11). Vasodilation happens because faster blood flow across the endothelial cells causes them to produce a tiny gas molecule called nitric oxide. Nitric oxide then travels into the middle (tunica media) of the blood vessel and causes the muscle layer to relax (11).

Once the blood flow decreases again, the blood vessel constricts (vasoconstriction). Importantly, the ability of blood vessels, especially arteries, to dilate and constrict in response to blood flow allows your blood pressure to remain within a healthy range.

Let’s take a second to think about the implications of what we’ve learned so far by asking two questions:

1. What would happen if your artery was so stiff that it was unable to dilate when blood flow increases?

It would act like a garden hose—since the hose doesn’t expand, the more water going through increases the pressure of that water. Thus, your blood pressure would increase.

2. What would happen if the endothelial cells lining the artery couldn’t produce nitric oxide in response to increased blood flow?

Your artery would have a hard time expanding to accommodate more blood, and your blood pressure would increase.

As you will learn next, stiff arteries and decreased production of nitric oxide are two of the primary ways by which chronically elevated blood pressure occurs.

What causes elevated blood pressure?

While the causes of elevated blood pressure are complex and not completely understood, there are two processes known to be involved: endothelial dysfunction and arteriosclerosis. Both of these processes are strongly associated with the classic cardiovascular risk factors, such as smoking and obesity. In fact, both endothelial dysfunction and arteriosclerosis significantly predict the development of cardiovascular disease, independently of other risk factors (12-15).

1. Endothelial dysfunction

Endothelial dysfunction basically means that the endothelial cells of the artery (described earlier) don’t function normally. Specifically, the cells don’t produce enough nitric oxide to dilate blood vessels (14). Without sufficient production of nitric oxide, the balance between vasodilation and vasoconstriction is disrupted, resulting in a greater tendency toward vasoconstriction (i.e., increased blood pressure) (11).

One of the proposed causes of endothelial dysfunction is oxidative stress, which occurs when the abundance of pro-oxidative molecules is greater than the abundance of antioxidant molecules. Pro-oxidative molecules include reactive oxygen species (ROS), which damage important molecules like DNA and enzymes. ROS are normally produced throughout the body, and have important functions within blood vessels themselves (11). However, excessive ROS decreases the availability of nitric oxide, and may use nitric oxide to form molecules that are potentially toxic to cells (16).  In addition to decreasing the production of nitric oxide oxidative stress can actually cause the endothelial cells to produce ROS instead! (11, 16).

2. Arteriosclerosis

With age, our arteries lose their elastic properties and become stiff. This ‘hardening’ of the arteries is called arteriosclerosis. During this process, the layers of elastin in the tunica media degrade and are replaced by collagen (14). The replacement of elastin with collagen in arteries is a problem because collagen cannot bear physical loads like elastin does. As load-bearing components are lost, blood pressure increases (17). This elevation in blood pressure sets in motion a vicious cycle of further breakdown of elastin, deterioration of the vessel wall, and higher blood pressure (14).

EPA and DHA support blood pressure through multiple mechanisms

Unsurprisingly, given their involvement in cellular structure and cell signalling, there seem to be multiple mechanisms by which EPA and DHA support healthy blood pressure. These fatty acids are incorporated into the phospholipid membranes of every cell in the body, where they influence how the cell responds to its environment. Specifically, the extensive double-bonded structure of EPA and DHA imparts much needed fluidity to the membrane. Membrane fluidity is critical for the formation of appropriate molecular complexes that facilitate communication between the cell’s external and internal environments.

EPA and DHA affect the production of nitric oxide

Importantly, EPA and DHA can also directly affect the production of nitric oxide when incorporated into endothelial cell membranes (14, 21-24). There are many cell culture and animal studies which indicate that omega-3 fatty acids can increase production of nitric oxide from the endothelium, by affecting molecular complexes and gene expression (22, 24-26).

EPA and DHA help reduce oxidative stress

In addition to their effects on cell membranes, EPA and DHA also help address inflammation (27). Oxidative stress and the production of ROS are normal aspects of the inflammatory process; however, these reactions become damaging when inflammation is ongoing. Fortunately, EPA and DHA can help address inflammation by producing special molecules (low-affinity eicosanoids) that interfere with inflammatory processes. These omega-3s also decrease gene expression of inflammatory molecules, which has the effect of reducing production of ROS (14, 28, 29). As EPA and DHA diminish oxidative stress, production of nitric oxide is restored (30, 31).