Written by
Louise W Lu, PhD, MPH, BMLS
Written/Reviewed by
Alexandra V Goldberg, Registered Dietitian
In our previous article, we discussed a surprising discovery:
👉 In high-fat diets, oleic acid from olive oil may help cancer cells “arm themselves” and spread faster.
This raised an important question:
Does this mean olive oil is unsafe?
And what kind of oil can truly be considered safe?
If you haven’t read that article yet, check it out here:
Is Olive Oil Really Tied to Cancer Spread? Here’s How to Pick the Right Oils Every Day
But the real issue isn’t about one single oil —
it’s the imbalance of Omega-3, Omega-6, and Omega-9 in modern diets.
What Are Omega-3, Omega-6, and Omega-9?
Omega-3, Omega-6, and Omega-9 are all unsaturated fatty acids, but they differ in sources, functions, and health impacts. Understanding their differences is the key to truly learning how to “eat oils smartly.”
Omega-3
Mainly found in deep-sea fish oil, flaxseed, chia seeds, etc.
It is an important “anti-inflammatory factor” in the body, helping reduce inflammation,
protect cardiovascular health, and support brain function and emotional stability.
Simple explanation: Omega-3 is like the braking system in a car,
helping the body “put the brakes” on inflammation so cells don’t overreact.
Omega-6
Commonly found in soybean oil, corn oil, sunflower oil, as well as in many processed
and fried foods.
In small amounts, it helps with immune response and wound healing,
but modern diets often lead to excessive intake, keeping the body in a state of
chronic low-grade inflammation.
Simple explanation: Omega-6 is like the accelerator—a little push
helps the body respond to injury, but pressing too hard makes inflammation speed out of control.
Omega-9
The most typical form is oleic acid found in olive oil.
It can improve blood lipids and support heart health,
which is why it’s often considered a “healthy oil.”
However, as mentioned in the previous article, under a high-fat diet,
oleic acid may contribute to cancer cell metastasis through special mechanisms.
Simple explanation: Omega-9 usually acts like a “stabilizer,”
beneficial for metabolism, but under extreme conditions,
it may also be exploited by harmful cells.
Therefore, Omega-3, -6, and -9 are not simply “good” or “bad.” The key lies in whether the ratio is balanced.
Why Is Imbalance the Real Problem?
Nutrition science has long recognized: a single fatty acid does not determine health — the key lies in the balance among Omega-3, Omega-6, and Omega-9.
Healthy Ratios and Normal States
- In traditional dietary patterns (such as the Mediterranean diet), the Omega-6 to Omega-3 ratio is about 4:1.
- This balance allows the immune system to respond to infections and injuries without tipping into chronic inflammation.
- In this context, Omega-9 (from olive oil, avocado oil) can better play its role in improving blood lipids and protecting cardiovascular health.
Imbalances in Modern Diets
In modern eating habits — especially diets high in eating out, takeout, and fast food — the Omega-6 : Omega-3 ratio often reaches 15:1 – 20:1, and in some cases even exceeds 30:1.
Main reasons for this imbalance include:
- Heavy use of Omega-6–rich vegetable oils (soybean oil, corn oil, sunflower oil);
- Frequent consumption of processed foods, fast foods, and fried foods;
- Insufficient intake of Omega-3–rich fish, flaxseed, and nuts.
Combined with overall fat intake being too high — when more than 40% of daily calories come from fat, it qualifies as a “high-fat diet.”
Under conditions of excess Omega-6, insufficient Omega-3, and high total fat intake, if Omega-9 (mainly oleic acid) is also disproportionately high, it worsens the imbalance:
inflammation becomes harder to control, metabolic stress rises, and specific mechanisms (such as FABP5–PKC/ALDH) may increase the risk of cancer metastasis.
👉 From a metabolic perspective, the problem with modern diets is not “lacking one type of oil,” but the severe imbalance in overall ratios:
- The accelerator (Omega-6) is pressed too hard;
- The brake (Omega-3) is severely lacking;
- The steering wheel (Omega-9) is “misused” in this unbalanced environment.
The result is chronic inflammation, elevated cardiovascular risk, and higher cancer progression.
How to Achieve the Right Balance of Omega-3/6/9 in Daily Diet?
After understanding the dangers of imbalance, the key question becomes: how to adjust Omega-3, Omega-6, and Omega-9 to a healthier ratio in everyday life.
1. Reduce Omega-6 Intake
- Cut down on high Omega-6 vegetable oils such as soybean oil, corn oil, and sunflower oil.
- Eat less fried, processed, and fast foods, which usually contain large amounts of Omega-6.
👉 In simple terms: don’t keep pressing the “accelerator” all the way down.
2. Increase Omega-3 Sources
- Eat deep-sea fish (such as salmon, sardines, mackerel) 2–3 times per week.
- Add flaxseed, chia seeds, walnuts to your daily meals, or consider fish oil/algae oil supplements.
👉 In simple terms: put the “brake system” back in place.
If balancing through diet alone is difficult, you can choose
high-purity Omega-3 supplements
.
The advantage is that they provide only Omega-3, without adding extra Omega-6 or unwanted fats,
making it a more precise way to restore balance.
3. Use Omega-9 Wisely
- Oils rich in monounsaturated fats (olive oil, avocado oil) are good for salad dressing or low-heat cooking.
- But only when Omega-3 intake is sufficient and Omega-6 is not excessive—otherwise even Omega-9 may be “misused”.
👉 In simple terms: the steering wheel only works when the accelerator and brake are balanced.
Recommended ratio: Omega-6 : Omega-3 around 4:1–5:1.
For most modern people, this means:
- Reduce Omega-6,
- Increase Omega-3,
- Moderate Omega-9.
