Cardiovascular Effects of Omega-3 and Omega-6 Fatty Acids

Essential fatty acids (EFAs) are fatty acids necessary for life in humans and other mammals. Because they cannot be synthesized by the body, they must be taken in through diet. Omega, the last letter of the Greek alphabet, means “the end.”

Omega-3 (alpha-linolenic acid) and omega-6 (linoleic acid) fatty acids play important roles in brain development, strengthening the immune system, and preventing coronary heart disease.

The significance of omega-3 fatty acids was first recognized in studies on Greenland Eskimos. Despite consuming a diet high in fat, Eskimos were observed to have low rates of heart disease, rheumatic conditions, asthma, and many illnesses commonly seen in industrialized nations. This protective effect was attributed to their high intake of fish and marine mammal fats rich in polyunsaturated fatty acids.

Some fatty acids, including linolenic acid, are in omega-3 form and can easily be converted into eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Linoleic acid is abundant in vegetable seed oils, while linolenic acid is abundant in fish oil.

Omega-3 fatty acids have anti-inflammatory, analgesic, antithrombotic, and antimitogenic (anti-cancer) effects. They are essential in the prevention and treatment of various diseases—from coronary artery disease to inflammatory conditions. Studies also indicate that dietary omega-3 intake may help prevent hypertension, diabetes, immune disorders, allergies, and neurological disturbances.

Regarding cardiovascular effects, omega-3 fatty acids exhibit antiarrhythmic, antithrombotic, antiatherosclerotic, anti-inflammatory actions, improve endothelial function, have mild antihypertensive effects, and reduce triglyceride levels.

Physiological Role and Risks of Omega-6 Fatty Acids

Linoleic acid (LA) is the primary component and source of dietary omega-6 fatty acids. Omega-6s support skin health, regulate body temperature, and reduce water loss. However, excessive omega-6 levels may contribute to arteriosclerosis, thrombosis, rheumatoid arthritis, and visual problems.

Dietary fat intake influences cancer development and progression. A high omega-6/omega-3 ratio is associated with increased cancer risk and progression (omega-6 promotes, omega-3 suppresses). Fish oils are more widely recognized for their protective and analgesic effects than for direct cancer treatment.

Omega-3 and omega-6 fatty acids compete in the bloodstream. Excess omega-6 enhances omega-6 metabolism and may contribute to arteriosclerosis, thrombosis, rheumatoid arthritis, and visual problems. Thus, the ratio of omega-6 to omega-3 in the body is crucial.

The ideal omega-6/omega-3 ratio is 5:1 to 10:1, according to WHO. However, the truly optimal ratio is considered 1:1 to 4:1.
In Western diets, this ratio ranges from 10:1 to 30:1.

Lyon Diet Heart Study:
In patients who had experienced myocardial infarction, a 4-year follow-up demonstrated that maintaining a 4:1 omega-6/omega-3 ratio had protective and preventive cardiovascular effects.

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Mediterranean Diet Heart Study:
High dietary ALA intake showed cardiovascular benefits.

GISSI-Prevenzione Trial:
Supplementing MI patients with 850 mg/day omega-3 fatty acids significantly reduced cardiovascular mortality

Dietary Sources

Omega-3-rich foods

• Fish oil
  
• Flaxseed
  
• Soy
  
• Green leafy vegetables
  
• Rapeseed (canola)
  
• Blackcurrant seed oil
  

Omega-6-rich foods

• Vegetable oils (corn, peanut, cottonseed, soybean oil)
  
• Peanut oil
  
• Cottonseed oil
  
• Safflower oil
  
• Walnuts
  
• Pumpkin seeds
  

Recommended Intake

• Healthy individuals:
  Two servings of fish per week, or 1.5–3 g/day ALA from oils and foods.
  
• Patients with coronary artery disease:
  1 g/day EPA + DHA from fatty fish or supplements.
  
• Hypertriglyceridemia or hypertension:
  2–4 g/day EPA + DHA from capsules or marine sources.
  

Exceeding 15 g/day of fish oil increases bleeding risk. Therefore, supplemental EFAs should not exceed 3 g/day without medical supervision.

Drug–nutrient interactions are important:

• Combined use with digoxin may increase digoxin sensitivity.
  
• Combined use with warfarin may prolong bleeding time.
  Omega-3s may also cause hypotension and, rarely, allergic reactions.