Here's what you need to know...
- Linoleic acid is unavoidable and fine in small amounts. But excess accumulates and causes metabolic damage and fat gain.
- Linoleic acid is in polyunsaturated fats found in things like cooking oils, nuts, and even animal fat.
- Though beef and dairy fat is relatively low in linoleic acid, you may be consuming larger amounts of it in poultry and pork fats.
- Most vegetable oils contain excess amounts of linoleic acid. American consumption of these oils is through the roof.
- Health experts who encourage you to lower your cholesterol claim that a low saturated fat and high linoleic acid intake is healthy. It's not.
Increased Intake = Increased Disease
For years, scientists, doctors, and nutritionists have been telling us to replace saturated fats with polyunsaturated fats, or PUFAs.
While the practice did bring down cholesterol, the incidence of heart disease, obesity, and metabolic disorders skyrocketed. Why?
Americans are consuming an unnaturally high intake of the polyunsaturated fat linoleic acid (LA) and that intake is a prime cause of disease.
Diet History in the South Pacific
The Polynesians on Tokelau Island had a very high saturated fat intake, most of it from coconuts, but also fish. Over 50% of their calories came from this high-saturated-fat diet, while the percentage of linoleic acid (LA) in the body fat of these healthy natives was only 3.8%.
Their saturated-to-polyunsaturated fat ratio was over 22:1, which would cause fainting spells in just about every American nutritionist. Almost uniformly, nutritionists want the saturated fat ratio to be less than polyunsaturated, not 22 times higher.
Since high saturated fat intake tends to increase blood cholesterol values, unsurprisingly the Polynesians' blood cholesterol values were high, averaging about 212 mg/dL. The American Heart Association says that anything over 200 is bad.
If the mainstream medical theories on diet, cholesterol, and heart health were right, these natives should have been a wreck... but their health was excellent.
There's no sign of them having cardiovascular problems until they moved to New Zealand and adopted a Western-influenced diet. (For that matter, cardiovascular problems were rare in America until well into the 20th century.)
Other Incriminating Studies on Linoleic Acid
In another study, researchers looked at an older population that followed the same dietary practices they always had. At the start of the study, the subjects averaged about 10% linoleic acid in their body fat.
Half the subjects switched to a diet that included added corn oil to match what was becoming typical in the American diet.
Their adipose LA content gradually rose. By the time it reached 20%, their rates of diabetes and obesity rose significantly too. The higher LA, the more their health declined and waistlines expanded.
Members of the control group, in contrast, remained healthy.
Other reports have analyzed human adipose tissue from the 1960s and prior, and while there's no one study providing a final conclusion on the subject, multiple "natural diet" studies find a range of about 4% to about 10% LA in human fat.
This will occur naturally over time where the percent of LA in the dietary fat is in that same range.
When dietary LA is high, studies show that the LA content of human adipose tissue slowly rises to approximately match the LA content of the diet, up to at least about 35% LA. The process can take a couple of years.
Scientists have also studied the linoleic acid loss-rate in body fat. LA has a half-life in adipose tissue of about 1-2 years from exchanging with other fats. In other words, if you greatly reduce your LA intake, it will take one or two years for the percentage in your body fat to be halved.
The message is this: If you've allowed this problem to develop – a mucked up metabolism and weight gain due to excessive LA intake – it's fixable, but it won't happen fast.
The Poison Is In The Dose
All substances, even water, become harmful to ingest at some point. With linoleic acid and today's food environment, that harmful point can come pretty early.
Here are five foods we can analyze based on their LA content.
1 – Beef
This is a benign, or relatively benign, source. Even today, with cattle being fed exceedingly cheaply, you could eat all of the greasiest cuts of beef you could stand, and if that were your sole source of LA, your intake wouldn't be excessive.
Even with grain-fed livestock, which doubles the LA content of beef, no more than about 4% of that fat would be LA. If you ingested 3,000 calories per day and 50% of that came from beef fat, it would only come to 7 grams of LA, which is a reasonable amount.
Likewise, milk fat from even non grass-fed cows, whether within milk, butter, cheese, yogurt, or kefir, has only about 2% LA and poses no problem. You'd also have no trouble with fish, or with coconut, macadamia, or high-oleic sunflower oil.
2 – Pork and Chicken
The level of LA found in animals like pigs and chickens depends largely on what you feed them.
For example, the pigs and chickens of the Tokelau Islanders had only about 2.0 – 2.5% LA. Contrast that with the extremely high values in US pork and chicken of 20 to over 30% as a result of the diets we stupidly choose to feed our livestock.
This diet saves money for the farming industry, but our added health expenditures dwarf the savings on animal feed.
Free range, pastured, forest-raised, organic, and GMO-free pork and chicken may all have elevated LA, too, as soy is often still fed to these animals. This isn't necessarily dishonesty, though. Even a quality-oriented farmer may honestly think that organic soy is premium feed.
Consider that the US produced and used over 100 million tons of soybeans in 2014. Most went to feed our livestock. That's one hell of a lot of soy in our food chain. It's likely part of your food chain too.
3 – Nuts
The only nut – though it isn't technically a nut – that's a major offender is the peanut.
It's about 32% LA, and peanuts are often consumed in far greater quantity than other nuts. If you're a peanut addict, swap out for moderate quantities of almonds, cashews, hazelnuts, or macadamias.
Almonds and cashews contain about 17% LA, whereas hazelnuts are at about 10% and macadamia nuts are at under 2%. All other nuts are above 20%, sometimes far above.
What's important, however, is the amount of LA relative to the entire fat intake of the day. A small amount of a high-LA food can be okay if the rest of the day's fats are low in LA.
4 – Dietary Oils
Extra virgin olive oil (EVOO) isn't bad. It has somewhat more LA at about 9%, but not enough to be a problem. For example, if you consumed 2 tablespoons per day of EVOO, this comes to only about 2.4 g of LA.
It's an entirely different story with most vegetable oils. Corn, sunflower, cottonseed, and soybean oil are all over 50% LA, and safflower is over 75%.
If a person took in 500 calories per day from these oils, he'd have sopped up 30 or more grams of LA! Many individuals consume much more than this via prepackaged foods.
Some vegetable oils, however, are less problematic. For instance, high-oleic sunflower is only 15% LA and can be fine in moderation, as can palm oil. Others, not mentioned, contain between 25-50% LA.
What Makes Linoleic Acid a Menace?
A high percentage of LA in the body is strongly associated with impaired metabolic health.
LA makes up a relatively high percentage of LDL cholesterol and oxidizes easily within it. Very briefly, it's likely that the higher the body's LA content, the higher the oxidized LA content within LDL, and the higher the rate of resulting damage.
Increasing amounts of LA impairs insulin sensitivity and plays a role in metabolic disorder, diabetes, and obesity. The exact mechanism isn't known, but it likely has something to do with adversely changing gene expression.
Also, there's some evidence showing that oxidized LA can interfere with PPAR-alpha receptor function, which would impair fat metabolism.
Whether gene expression changes with large increases in the body's percentage of LA, rather than the immediate diet's percentage of LA, is as yet unstudied.
What About Cholesterol Levels?
What about all that data showing that a high polyunsaturated fat diet including LA can improve cholesterol?
It's true, high LA intake can improve blood cholesterol numbers. However, being dead, hospitalized, or overweight with better cholesterol numbers really doesn't count for much.
High LA intake will improve your cholesterol numbers, but with increased death and disease risk.
A Campaign Against My Own Stupidity
From about 1994 to 2010, my diet was suitably low in linoleic acid.
After shedding the 30 pounds of fat I'd been carrying in 1994, I had no problems getting and staying pretty lean. I was never one of those guys who could eat piles of food without adding fat, but really I had no metabolic troubles, either as judged by experience or by blood testing.
Then in 2010, I got married and my diet changed.
My wife is a great cook, and the only oils she adds are coconut or olive, but a fair proportion of the meats have been chicken (including the fat) and pork. Further, we've eaten out a lot, probably twice as often as eating in, and have bought a lot of foods that have added oils.
My linoleic acid intake over this time was probably nearly the same as for the general American population. My ability to stay lean decreased gradually and eventually became pretty poor. I also suffered an injury and had to refrain from training for 14 weeks.
So now I'm just another fat American on a fat intake that, like the typical American diet, had way too much linoleic acid. I'm probably carrying around 10 pounds of the stuff!
Undoing The Damage
I have to get this off. To do this, I've eliminated all fats other than coconut, beef, dairy, Flameout®, fish, and occasionally a little olive oil.
I'll lose it through this low LA diet plus a lot of physical work, with methods no different than taught here at T Nation.
As for the too-high LA percentage of the body fat that will remain, research shows that it will take a year or two for the percentage to drop by half. It can't be selectively burned off, but only slowly interchanged with different fats, depending on LA content of the current diet.
I'll be paying the price for a while. But the problem is fixable for me, as it is for everyone.
Tips For Purging Your Body of LA
If you've had high LA in your diet for years, levels in your body have built up.
Reducing LA intake to moderate or preferably low levels will allow your body to return slowly to healthful body fat composition. The following dietary practices will get you there:
- Relative to what's common today, limit your LA intake.
- Avoid chicken fat and pork fat. Beef fat is acceptable.
- Avoid safflower oil, especially as it's over 75% LA.
- Soybean, corn, sunflower, and cottonseed oils all contain over 50% LA, but small amounts are acceptable.
- Use oils such as coconut, macadamia, olive, or high-oleic sunflower.
- Moderate intake of nuts is okay. Macadamias and hazelnuts are lowest in LA, followed by almonds and cashews. Skip peanuts or keep intake minimal.