Cardiovascular disease is the leading cause of death, and most of us know someone whom heart disease has affected in one way or another.
In honour of heart health month, I interviewed Dr Aimee Gould Shunney — medical advisor for Nordic Naturals and naturopathic physician. We talked about how fish oil supplementation can have a positive effect on the cardiovascular system, lowering risk of stroke, high blood pressure, heart attack and blood clots, and improving lipid profiles (triglycerides, LDL, HDL).
Why Omega-3s Are Essential
Omega-3 fats, found in fish oil, are long-chain fatty acids which the human body cannot produce — making them truly essential. Omega-6 is also an essential long-chain fatty acid; however, most people get plenty of this through their diet. Omega-3, found in certain nuts, fish and grass-fed beef, is commonly missing from the typical Western diet.
How Omega-3s Support Cardiovascular Health
Omega-3s Keep Cell Membranes Healthy
Omega-3 fats play many roles in the health of our bodies, one of which is to keep cell membranes fluid and flexible. When the cell membrane becomes rigid from poor dietary fats, receptors cannot function well, movement of fluid and nutrients in and out of the cell is hampered, and the cell is unable to do its job optimally. This is critically important in cardiovascular health. The blood vessels, like cell walls, need to be flexible — rigidity of the blood vessel indicates plaque formation and can lead to hypertension and other cardiovascular problems.
Omega-3s Improve Lipid Profiles
Think of LDL as the Litter bug of the bloodstream — depositing cholesterol throughout the cardiovascular system — while HDL acts as the Highway patrol, picking up that littered cholesterol and triglycerides and returning them to the liver where they are excreted or re-utilised. Omega-3 fats in fish oil increase HDL (the highway patrol) while reducing LDL and triglycerides (the litter bugs), thereby reducing the risk of heart disease, myocardial infarction, atherosclerosis and stroke.
As for LDL, omega-3 fatty acids do not simply reduce the number of circulating LDL particles. However, they do change the subtypes of LDL cholesterol for the better. LDL type A — the lighter, fluffier type — is increased by omega-3 fats, while LDL type B — the denser, stickier, atherogenic subtype — is decreased. In combination with the increase in HDL and reduction in triglycerides, the total LDL number becomes less of a risk factor overall.
Omega-3s Reduce C-Reactive Protein
C-reactive protein (CRP) is elevated in the blood as a result of inflammation in the body, and has been implicated as a risk factor for cardiovascular disease. Omega-3 fatty acids have been shown to decrease CRP — and therefore reduce the risk of cardiovascular disease — in individuals with elevated levels not caused by a genetic variation.
Chronic inflammation is also closely linked to cortisol dysregulation and adrenal stress. If you experience persistent fatigue, poor sleep or high stress alongside cardiovascular concerns, our Stress & Adrenal Imbalance testing page explains how a cortisol diurnal profile can reveal whether your stress hormones are contributing to systemic inflammation.
How to Get More Omega-3s
The Case for Fish Oil Supplements
According to Dr Shunney, you can get enough omega-3 fats from your diet if you eat a serving of omega-3-rich fish each day (such as sardines). However, the problems of wild fish toxicity — mercury, PCBs — and farmed fish toxicity — fewer omega-3 fats, pesticides, antibiotics, food dye and PCBs — make that difficult to achieve consistently.
For those who cannot or will not eat a daily serving of healthy, non-toxic, omega-3-rich fish, there are excellent fish oil supplements available. Dr Schroeder recommends Nordic Naturals Arctic D Cod Liver Oil in liquid form for cost-effectiveness and tolerability. Nordic Naturals also offers a policy that if any of their products produce a fishy burp, you can return the bottle — a fishy aftertaste being a tell-tale sign of rancid fish oil.
Watch Out for Mercury and Toxin Exposure
If you do eat fish regularly — or are considering increasing your intake — it is worth knowing your baseline heavy metal levels. Mercury and arsenic accumulate in the body over time and can undermine the very cardiovascular and hormonal benefits you are trying to achieve. Our Comprehensive Elements Profile (Dried Blood & Urine Spot) tests for mercury, arsenic, lead and other toxic elements alongside key nutrients like zinc and selenium — giving you a complete picture of your toxic load.
The Hormone Connection
Cardiovascular risk does not exist in isolation. Thyroid hormones play a significant role in regulating cholesterol metabolism, heart rate and blood pressure — and an underactive thyroid is a well-recognised but frequently missed contributor to poor lipid profiles. If your cholesterol levels are not responding as expected to diet and supplementation, it may be worth investigating your thyroid function. Our Weight Management Profile Plus Thyroid Test measures TSH, free T3, free T4 and key metabolic hormones in a single at-home test kit.
Originally by Dr Elise Schroeder, ZRT Laboratory. Reproduced with permission. Last reviewed: May 2026.