An oil that consumed in excess, acts as a metabolic poison.

Many people think that sugar is the number one food ingredient that over time is the most hazardous to health. Here a nutritionist suggests there is something more detrimental: he suggests that if you consume more than 5 grams of it each day, you could be making your body susceptible to chronic diseases like obesity, heart disease and tumours.
.. .. ..

Diet is, as you might expect, a key strategy that can make or break your health (and your tolerance for stress). The Paleo diet, which has gained popularity over the years, essentially strives to mimic the diet our ancestors ate during the Paleolithic era. But we don’t actually have to go that far back.
Merely turning back the dial about 150 years will do. That’s when industrial food processing began. That’s also when industrial processed seed oils (aka, vegetable oils) were introduced as a replacement to healthy animal fats like lard and tallow, which had previously been the norm.

The first commercial food seed oil to be introduced was cottonseed oil — a waste product from cotton production. That was the primary ingredient of Crisco. Prior to the 1900s, only 1% to 2% of daily calories came from omega-6 fats, the primary one of which is linoleic acid (LA). Today, the average intake is 10 times that.

Like omega-3, LA is a polyunsaturated fat (PUFA), but unlike omega-3, LA, when consumed in excess, acts as a metabolic poison. Anything above 4% of your daily calories is likely to cause problems.

Importantly, LA is in virtually all foods, so it’s near-impossible to be deficient. This is why I disagree with claims that LA is an essential fat. You need very little of it, and you’re getting it from most whole foods. If you eat processed foods made with seed oils, you’re bound to get far too much and will suffer adverse health consequences. 

Most health-minded experts still believe the primary cause for these trends is sugar, but linoleic acid (LA) is far more dangerous than sugar, from a metabolic perspective. I’m convinced it’s really the massively excessive amounts of LA in our modern diet that drives these metabolic diseases.

Looking at statistics of seed oil consumption and chronic diseases such as obesity, cancer and heart disease, these trends all rise in tandem, even in areas where sugar consumption has remained extremely low well into the modern era. Another major difference between sugar and seed oils that demonstrate the superior risks of seed oils is this: sugar, when consumed in excess over time will result in insulin resistance and metabolic inflexibility. However, if you cut out sugar, you can rather rapidly restore both your insulin sensitivity and metabolic flexibility, because your body can only store about a day’s worth of glucose.
Not so with fat. Your body can store a lot of it, for long periods of time. LA is literally incorporated into and stored in your cell membranes, where it can remain for seven years. So, even if you go on a low-LA diet, it’ll take years to fully clear it out of your body. This also means you won’t notice improvements in your health as quickly as you do when cutting out sugar.

Damaging fats to avoid
So, which fats are high in LA and need to be avoided? Some of the most common ones to be avoided include:
Cottonseed oil
Canola oil
Corn oil
Soybean oil
Safflower oil
Sunflower oil

While avocado oil and olive oil are known for their health benefits, they too are high in LA and should be used in moderation — and ONLY if you can ensure their quality. I recommend limiting them to 1 tablespoon a day. A primary problem with both of these is food fraud.^[1]
Most of the avocado and olive oil on the market have been adulterated with one or more or the cheaper oils listed above. Another pesky quality problem is that of rancidity. A 2020 Food Control report^[2] found 82% of avocado oils went rancid before their expiration date.^[3]

Healthy fats
I recommend swapping all of the oils listed above with the following, all of which are great to cook with as they’re very stable and won’t oxidize when exposed to high heat:
Coconut oil
Tallow (fat from cows)
Organic grass-fed butter
Ghee
 
How to calculate and reduce your LA intake
The best way to ensure your LA intake is within a safe range is to use a nutritional calculator such as Cronometer. Ideally, it is best to enter your food for the day before you actually eat it. The reason for this is simple: It’s impossible to delete the food once you have already eaten it, but you can easily delete it from your menu if you find something pushes you over the ideal limit.

So, how do you cut seed oils out of your diet? Top culprits to minimize or eliminate include:
- Vegetable oils or seed oils used in cooking
- Processed foods, especially sauces, dressings and other condiments
- All restaurant foods (not just fast food), as most food is cooked in seed oil, not organic butter or lard
- Conventionally raised chicken and pork (both are high in LA due to being fed omega-6 grains^[4])
- Most seeds and nuts (most, with the exception of macadamia nuts are loaded with LA)
- Bread and other grain products
 
The potent benefits of Sun exposure
Beside cleaning up your diet, one of the most potent health strategies I know is to get sensible sun exposure. I have been fascinated with the effects of sun exposure on health for nearly three decades.
Over time, we’ve discovered more and more mechanisms by which sunlight influences health, and most recently, it was discovered that near-infrared radiation (NIR), which makes up 54.3% of sunlight,[5] triggers the production of melatonin in the mitochondria inside your cells.[6]
This is a phenomenal benefit, as melatonin is a master hormone,[7] a potent antioxidant[8] and antioxidant recycler,[9] and a master regulator of inflammation and cell death.[10] (These functions are part of what makes melatonin such an important anticancer molecule.[11])
Your mitochondria are where oxidative stress ends up doing the most damage. So, by producing melatonin in your mitochondria, your body is literally making it right where it’s needed the most — and it does this in response to sunlight!
Ideally, you’d want to get an hours’ worth of sunlight on large portions of your body, every day. For men, this means going out wearing only shorts, and for women, wearing shorts and a sports bra or tank top.
If you go out around solar noon, without sunscreen, you also get the benefit of vitamin D production. I have not swallowed a vitamin D supplement since I moved to Florida nearly 15 years ago, and my serum vitamin D is in the optimal range year-round. 
 
By Dr. Joseph Mercola, first published Jun 26, 2022 on Mercola.com
 
References
[1] Food Control October 2020; 116: 107328
[2] Food Control October 2020; 116: 107328
[3] The Counter June 17, 2020
[4] YouTube, Omega-6 Apocalypse 2, Chris Knobbe August 25, 2021, 15:01
[5] Journal of Photochemistry and Photobiology February 2016; 155: 78-85
[6] Physiology February 5, 2020 DOI: 10.1152/physiol.00034.2019 
[7] Indian J. Exp Biol. May 1996; 34(5): 391-402
[8] Frontiers in Pharmacology August 21, 2020 DOI: 10.3389/fphar.2020.01220
[9] Allergy Research Group, Melatonin, the Antioxidant Recycler
[10] Cell Death & Disease 2019; 10 article number 317
[11] Oncotarget June 13, 2017; 8(24): 39896–39921