We’ve been bombarded for years with the evils of trans fat…
…and for once, the mainstream advice appears to be mostly correct. Trans fats cause coronary heart disease, they’re strongly associated with obesity, depression, infertility in women, and breast cancer, and they interfere with critical liver enzymes. (More.)
I’ve written about trans fats before: if you want to learn their basic chemistry—and more importantly, how to avoid them when shopping for food—read my article Eat More “Heart-Healthy” Trans Fats! (We hid them in plain sight).
“Help! There’s Trans Fat In My Grass-Fed Beef!”
However, an alert commenter (Steven) pointed out that beef contains a significant amount of trans fat. And while his estimate was a bit high, it is absolutely true that one ounce of beef fat (28.3g) usually contains 0.5g-1.4g of trans fat.
In fact, the meat and milk of ruminants contains a significant amount of trans fat—roughly 2-5% of the total. Even worse, grass-fed milk and meat contains even more trans fat than grain-fed milk and meat!
Journal of Dairy Science
Volume 82, Issue 10 , Pages 2146-2156, October 1999
Conjugated Linoleic Acid Content of Milk from Cows Fed Different Diets
T.R. Dhiman, G.R. Anand, L.D. Satter, M.W. Pariza
“Cows grazing pasture and receiving no supplemental feed had 500% more conjugated linoleic acid in milk fat than cows fed typical dairy diets.”
What’s going on here?
Trans-Vaccenic Acid and the Conjugated Linoleic Acids
No, I haven’t just named an obscure prog rock band from the 1970s. I’ve named the culprits: vaccenic acid and rumenic acid (a conjugated linoleic acid). Though vaccenic acid comprises most of the total, our bodies convert vaccenic acid directly to rumenic acid (just as they convert stearic acid directly to oleic acid), so nutritionally, we only need to investigate the effects of rumenic acid.
(This conversion is not reflected in American nutritional labeling—which requires stearic acid to be counted as saturated fat and vaccenic acid to be counted as trans fat, despite the fact that our bodies immediately convert them to different forms.)
A Short Biochemistry Excursion
Rumenic acid is known formally as (9Z,11E)-octadeca-9,11-dienoic acid, and informally as cis-9, trans-11 18:2. Vaccenic acid is known formally as (E)-Octadec-11-enoic acid, and informally as 18:1 trans-11.
Interestingly, the enzyme that converts vaccenic acid to rumenic acid—delta-9-desaturase—is the same enzyme that converts stearic acid (a saturated fat, 18:0) to oleic acid (a monounsaturated fat, 18:1 cis-9). That’s because delta-9-desaturase creates a cis-handed double bond at the 9th position. If you look at their informal names (or their chemical structure), you’ll see that the difference between vaccenic and rumenic acid is a cis-9 double bond, just the same as the difference between stearic and oleic acid is a cis-9 double bond.
Rumenic acid is part of a family of fats known as conjugated linoleic acids. “Conjugated” means that it contains both cis- and trans- bonds, just as its name (cis-9, trans-11 18:2) says.
Where Do The Trans Fats In Beef and Milk Come From?
Multicellular animals create only cis-handed fats with their enzymes…so where do trans-rumenic and trans-vaccenic acid come from?
Answer: they come from bacteria.
Cows, and other ruminants, can’t digest grass any more than we can. However, they have extra “stomachs” that are basically big microbial fermentation vats, in which bacteria digest the grass for them. (Whereupon they burp it up again, “chew the cud”, and finally swallow it into the regular digestive system once the rumen bacteria are done working.) Trans-rumenic and trans-vaccenic acid are created by these rumen bacteria via biohydrogenation of polyunsaturated fats (link).
To learn more about the ruminant digestive system, click the picture.
When Trans Fats Are Good For You: Our Friend Rumenic Acid
As with most rules of thumb, “trans fats are bad” is an oversimplification. “Molecules found nowhere in real food are bad” is the correct statement. People have been eating ruminants for millions of years, so one might expect that our bodies might have a nutritional use for rumenic acid.
This is, in fact, the case. The health benefits of rumenic acid are well-established—to the point where conjugated linoleic acid supplements (usually labeled “CLA” in big letters) are found in every vitamin store!
Conjugated linoleic acids (CLA) are a group of positional and geometric isomers of linoleic acid with proven beneficial influence on health. They show e.g. anticarcinogenic, antiobesity, and antiatherogenic effect. Milk, dairy products and meat of poligastric animals are their most valuable dietary sources, with cis-9, trans-11 CLA (RA – rumenic acid) being the predominant isomer.
This group of fatty acids has been extensively studied for recent years, in both in vivo and in vitro models, because of their beneficial biological effects: protection against cancer [7-10], prevention of atherosclerosis [11-14], reduction of obesity [15-17] and hypertension .
Since vaccenic acid (which becomes rumenic acid) and rumenic acid comprise 2-5% of beef and milk fat, this gives us yet another excellent reason to consume fatty meat and butter. Sign me up!
CLA Supplements: Not The Same As Real Food
It’s easy to get trapped in “nutritionism”: the idea that we can eat whatever junk we want, and take supplements to replace the nutrients we’re not getting from our food. This rarely works…and in the case of CLA supplements, we know why.
Recall that “conjugated linoleic acid” can mean a whole host of different fats, depending on the positions of the double bonds. Most CLA supplements are derived from safflower oil—
—and they contain equal parts rumenic acid (cis-9, trans-11 18:2) and an unnamed trans-10, cis-12 18:2 isomer. In other words, half of a CLA supplement is an entirely different chemical than what you’re getting from meat and butter.
Unfortunately, trans-10, cis-12 doesn’t have all the same beneficial effects. While it still seems to have anti-cancer properties in mice, it doesn’t have the same effects on human metabolism as rumenic acid:
Circulation. 2002; 106: 1925-1929
Supplementation With Conjugated Linoleic Acid Causes Isomer-Dependent Oxidative Stress and Elevated C-Reactive Protein: A Potential Link to Fatty Acid-Induced Insulin Resistance
Ulf Risérus, MMed; Samar Basu, PhD; Stefan Jovinge, MD, PhD; Gunilla Nordin Fredrikson, PhD; Johan Ärnlöv, MD; Bengt Vessby, MD, PhD
“The significant increase from baseline in 8-iso-PGF2α, 15-K-DH-PGF2α and CRP after t10c12 CLA was 1.04±0.7 (578%), 0.30±0.31 (77%), and 2.89±3.66 (110%), respectively.
This randomized, double-blind, placebo-controlled trial demonstrates that dietary supplementation with t10c12CLA causes isomer-specific oxidative stress that is related to induced insulin resistance.”
Diabetes Care September 2002 vol. 25 no. 9 1516-1521
Treatment With Dietary trans10cis12 Conjugated Linoleic Acid Causes Isomer-Specific Insulin Resistance in Obese Men With the Metabolic Syndrome
Ulf Risérus, MMED1, Peter Arner, MD, PHD2, Kerstin Brismar, MD, PHD3 and Bengt Vessby, MD, PHD1
“This randomized placebo-controlled trial has revealed unexpected metabolic actions by conjugated fatty acids in humans—actions that seem isomer-specific. The t10c12 CLA isomer, but not a CLA mixture, significantly increased insulin resistance, fasting glucose, and dyslipdemia in abdominally obese men.”
[I can’t resist an editorial comment at this point: why did neither study test rumenic acid alone, the way it occurs in real food? Might it have actually reduced oxidative stress and decreased insulin resistance, when not forced to fight equal amounts of the imposter t10c12?]
It’s important to note that many of the studies that claim benefits for t10c12 are on mice or rats. As Risérus et.al. note:
“Conjugated linoleic acid (CLA) is a group of dietary fatty acids with antiobesity and antidiabetic effects in some animals. The trans10cis12 (t10c12) CLA isomer seems to cause these effects, including improved insulin sensitivity.”
Unfortunately, as their experiment proved, the safflower-derived t10c12 doesn’t have the same benefits for humans as it does for rodents. And perhaps we shouldn’t be surprised that ingesting a chemically extracted fraction of a seed oil doesn’t produce the same benefit as eating real food.
Conclusion: Keep Eating Like a Predator, Keep Eating Real Food
Our conclusions should be obvious, but I’ll restate them:
- If we’ve eaten something for millions of years, the odds are very good that we’re adapted to eating it.
- Be skeptical of studies that feed fat to mice—herbivores that naturally subsist on plants and seeds.
- Whenever possible, eat real food, not supplements. You might not be getting the same benefits…or even the same nutrients.
- Most importantly: keep eating delicious fatty red meat and butter!
Spend money on vitamins...
...or prime rib?
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Anyone who makes a serious effort to understand the science behind nutrition will understand immediately that news items—most of which simply reprint the press release—are usually pure baloney. In order to learn anything interesting, we require access to the papers themselves.
Unfortunately, that’s not the end of the shenanigans. Abstracts and conclusions often misrepresent the data. Data is selectively reported to omit negatives (for example, statin trials trumpet a decrease in heart disease while intentionally failing to report all-cause mortality). And experiments are often designed in such a way as to guarantee the desired result.
Is there any way to deal rationally with the unending onslaught?
This approach, though satisfying, is discouraged by our legal system.
How To Get The Results You Want
First, I’ll walk through a few examples of studies carefully designed to produce a result opposite to what happens to all of us in the real world. Please note that I am not accusing anyone of scientific fraud! What I’m showing is that you can ‘prove’ anything you want if you set up your conditions and tests correctly, and choose the right data from your results.
Example 1: Quit While You’re Ahead
Public Health Nutrition: 7(1A), 123–146
Diet, nutrition and the prevention of excess weight gain and obesity
BA Swinburn, I Caterson, JC Seidell and WPT James
This paper, which purports to be an objective review of the evidence, claims with a straight face that “Foods high in fat are less satiating than foods high in carbohydrates.”
The authors cite two sources. One is a book I don’t have access to. The other is:
Eur J Clin Nutr. 1995 Sep;49(9):675-90.
A satiety index of common foods.
Holt SH, Miller JC, Petocz P, Farmakalidis E.
“Isoenergetic 1000 kJ (240 kcal) servings of 38 foods separated into six food categories (fruits, bakery products, snack foods, carbohydrate-rich foods, protein-rich foods, breakfast cereals) were fed to groups of 11-13 subjects. Satiety ratings were obtained every 15 min over 120 min after which subjects were free to eat ad libitum from a standard range of foods and drinks. A satiety index (SI) score was calculated by dividing the area under the satiety response curve (AUC)…”
Only the abstract is available online, but here’s the list of foods they tested, each with its measured ‘satiety index’—from which we find the surprising ‘facts’ that oranges and apples are more satiating than beef, oatmeal is more satiating than eggs, and boiled potatoes are 50% more satiating than any other food in the world!
This is obviously nonsense…but what’s going on here?
Upon reading the abstract, we can see the problem right away: they only measured satiety for two hours! Last I checked, it was more than two hours between breakfast and lunch, or between lunch and dinner. In fact, if you have any sort of commute, two hours doesn’t even get you to your morning coffee break! And given that a mixed meal of protein, carbohydrate, and fat hasn’t even left your stomach in two hours, we can see that this data does not support the breathtakingly bizarre conclusion drawn by Swinburn et. al.
In fact, it’s hard to see what conclusion this study supports beyond “when you don’t let people drink any water with their food, foods that are mostly water take up much more room in their stomach.” This is why oatmeal makes you feel so full…
…for about two hours, until the glucose is all absorbed and your sugar high wears off.
To see what happens when you track oatmeal vs. eggs for more than two hours, you can read the exhaustively-instrumented study in How “Heart-Healthy Whole Grains” Make Us Fat.
Example 2: Construct an Artificial Scenario
American Journal of Clinical Nutrition, Vol 61, 960S-967S
Carbohydrates, fats, and satiety.
“Fat, not carbohydrate, is the macronutrient associated with overeating and obesity…Although more data are required, currently the best dietary advice for weight maintenance and for controlling hunger is to consume a low-fat, high-carbohydrate diet with a high fiber content.”
Really? And what evidence are we supporting this with?
“The most direct way to assess how these differences in post-ingestive processing affect hunger, satiety, and food intake is to deliver the nutrients either intravenously on intragastrically. Such infusions ensure that taste and learned responses to foods will not influence the results. Thus, to examine in rnore detail the mechanisms involved in the effects of carbohydrate and fat on food intake, we infused pure nutrients either through intravenous or intragastric routes.”
And the author goes on to cite her own study to that effect, found here:
American Journal of Clinical Nutrition, Vol 61, 754-764
Accurate energy compensation for intragastric and oral nutrients in lean males.
DJ Shide, B Caballero, R Reidelberger and BJ Rolls
There’s only one problem with this theory: I don’t eat via intravenous or intragastric infusion, and neither do you.
Physiol Behav. 1999 Aug;67(2):299-306.
Comparison of the effects of a high-fat and high-carbohydrate soup delivered orally and intragastrically on gastric emptying, appetite, and eating behaviour.
Cecil JE, Francis J, Read NW.
“When soup was administered intragastrically (Experiment 1) both the high-fat and high-carbohydrate soup preloads suppressed appetite ratings from baseline, but there were no differences in ratings of hunger and fullness, food intake from the test meal, or rate of gastric emptying between the two soup preloads.”
That’s what the Rolls study above also found. Yet…
“When the same soups were ingested (Experiment 2), the high-fat soup suppressed hunger, induced fullness, and slowed gastric emptying more than the high-carbohydrate soup and also tended to be more effective at reducing energy intake from the test meal.”
Oops! Apparently when you eat fat (as opposed to injecting it into your veins or stomach), it is indeed more satiating than carbohydrate. Raise your hand if you’re surprised.
Example 3: Confound Your Variables
Am J Clin Nutr December 1987 vol. 46 no. 6 886-892
Dietary fat and the regulation of energy intake in human subjects.
Lauren Lissner, PhD; David A Levitsky, PhD; Barbara J Strupp, PhD;
“Twenty-four women each consumed a sequence of three 2-wk dietary treatments in which 15-20%, 30-35%, or 45-50% of the energy was derived from fat. These diets consisted of foods that were similar in appearance and palatability but differed in the amount of high-fat ingredients used. Relative to their energy consumption on the medium- fat diet, the subjects spontaneously consumed an 11.3% deficit on the low-fat diet and a 15.4% surfeit on the high-fat diet (p less than 0.0001), resulting in significant changes in body weight (p less than 0.001). A small amount of caloric compensation did occur (p less than 0.02), which was greatest in the leanest subjects (p less than 0.03). These results suggest that habitual, unrestricted consumption of low- fat diets may be an effective approach to weight control.”
This study looks much more solid at first glance: test subjects were given prepared foods which theoretically differed only in fat content, and which were theoretically tested to have equal palatability. Let’s take that at face value for the moment, and ask ourselves: why were they eating more on the high-fat diet?
First, let’s look at what made the diet “high-fat”. They helpfully list the ingredients added to each meal to make it higher in fat in Table 1.
Notice what’s been added in the right column? I see a lot of n-6 laden “vegetable oil” (store-bought mayonnaise is made with soybean oil) and margarine. Since this study was done back in 1987, the margarine would be absolutely loaded with trans fats, which we now know are strongly associated with obesity, heart disease, inflammation, and…disrupted insulin sensitivity. (Research review.)
So they’re testing what happens when carbohydrates are replaced primarily with seed oil and trans fats—which makes this study irrelevant to anyone considering a healthy diet.
Second, we have the problem that both breakfast and lunch were served in unitary portions.
“All foods, including those served as units (eg, muffins, sandwiches), could be consumed entirely or in part. … Sandwiches were available in whole or half units.”
Though the study doesn’t say explicitly, it’s probably a good assumption that the higher-fat versions contained far more calories, since the researchers tried to make them as similar as possible in appearance. It’s well-known that offering people larger portions causes them to eat more…especially since unlike breakfast and dinner (which were eaten in the laboratory), lunch was taken out. (If you take a sandwich with you, what are the odds you won’t finish it that afternoon, regardless of size?)
That’s not the worst part, though. The worst part is that their data is completely worthless because of interaction between the different diets!
Normally, controlled trials are done on separate, statistically matched groups of subjects, in order to make sure that effects from one treatment don’t bleed over into another.
However, in some cases, “crossover trials” are conducted, where each group is given each treatment in sequence—separated by a “washout period” that is supposed to let any effects of the previous treatment dissipate. This is less desirable (how do you know all the effects have ‘washed out’?), and is usually done because it allows the experimenters to screen and follow a smaller group.
However, Lissner et. al. didn’t even follow a crossover protocol. Instead, they employed a complicated “latin square” design, in which each test subject consumed a different meal type each day! A typical subject would consume a low-fat meal one day, a high-fat meal the next, a medium-fat meal the third day, and the sequence would repeat.
Can you imagine a drug trial where patients took one drug on odd days, and another drug on even days? How could you possibly disentangle the effects?
All of us have eaten a huge dinner and not been hungry the next morning…or gone to bed hungry and been ravenous when we awakened. In this insane design, each high-fat meal was guaranteed to be surrounded by two days of lower-fat meals. Yet in Figure 2, they graph energy intake for each day as if it were the same people eating each diet for two weeks!
In conclusion, this study is triply useless: first, due to using known industrial toxins for the “high-fat” diet, second, due to unequal portion size, and third, due to an intentionally broken design that commingles the effects of the three diets.
Holding Back The Ocean
The purpose of this article—and of gnolls.org—isn’t to debunk silly press releases, misleading websites, or even misleading scientific papers. I’ve given you some useful debunking weapons for your arsenal, but they’re not enough—because trying to dodge every slice of baloney thrown at us on a daily basis is like trying to hold back the ocean with a blue tarp and some rebar.
The usual strategy is to find a belief we like and stick with it, regardless of the evidence—but that way lies zealotry. What we need is a higher level of understanding. We need knowledge that lets us rationally dismiss the baloney and junk science, while conserving our time and attention for the few nuggets of real, new, important information.
We need to understand how human bodies work.
In other words, we need to understand ourselves.
We need to understand the basics of human biology and chemistry, how it was shaped from ape and mammal biology and chemistry, and how much it shares with all Earth life. We need to understand our multi-million year evolutionary history as hunters and foragers, how we were selected for survival on the African savanna, and how that selection pressure turned little 80-pound apes into modern humans.
And once we’ve used this understanding to answer basic questions like "How is food digested?" and "How are nutrients converted into energy?", we can use those answers to dismiss the baloney and junk science, allowing us to spend our valuable time and attention on real information. Because while it’s blindingly obvious to anyone who’s tried both that eating eggs for breakfast is more satiating than eating a bagel, it’s important to know why.
Conclusion: There Is No Easy Way, But There Is A Better Way
“Here’s a study that says so” isn’t a reason: it’s just a set of observations. We need to know how our bodies work. Only then can we rationally judge the meaning of these observations.
There is no shortcut to this knowledge. If there were one, and I knew it, I would already have told you. The best I can do is to continue to hone my own understanding—and I’ll continue to share what I know (or think I know) with you.
Live in freedom, live in beauty.
As this upcoming weekend is a holiday, I may not have time to write an article for next week.
In the meantime, you can occupy yourself with my “Elegantly terse”, “Utterly amazing, mind opening, and fantastically beautiful”, “Funny, provocative, entertaining, fun, insightful” novel, The Gnoll Credo. (More effusive praise here, and here.) It’s a trifling $10.95 US, it’s available worldwide, and you can read the first 20 pages here.
The world is a different place after you’ve read The Gnoll Credo. It will change your life. This is not hyperbole. Read the reviews.
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Tireless media coverage, and government-mandated nutritional labeling, has convinced everyone that trans fats are bad for us.
Fortunately, unlike most dietary scares of the past 50 years, the government and the ADA appear to have got this one mostly right: trans fats are indeed toxic. According to this data (yes, it’s a prospective study and therefore contaminated by associational confounders), consuming just 2% of your calories from trans fat doubles your risk of heart disease! They’re also associated with obesity, Alzheimer’s, and infertility in women, and they may interfere with liver function.
What’s a Trans Fat? (You can skip this if you’re not interested in chemistry)
Oleic acid, a cis-fatty acid (Source: Wikipedia)
“Hydrogenation” means that a hydrogen atom is forced into the space where a double bond once was, making it into a single bond. For instance, hydrogenating a monounsaturated fat makes a saturated fat.
Dietary fats are either saturated, monounsaturated, or polyunsaturated. “Saturated” means that there are no double bonds in the molecular structure, and no hydrogens can be added. “Monounsaturated” means one double bond, and “polyunsaturated” means…well, more than one.
The interesting part is that double bonds can be cis- or trans-…basically the chemical equivalent of right- or left-handed. It turns out that fats created (or hydrogenated) by enzymes, in mammal bodies, are all cis-handed. But chemical hydrogenation creates a mixture of cis- and trans- fats that actually favors the unnatural trans- configuration 2:1. And the resulting trans- molecules have a dramatically different shape!
Eliadic acid, the same fat in trans- form
This is why trans fats wreak havoc in your body: they’re the wrong shape, and your body simply doesn’t know what to do with them. It’s like putting brake fluid in your engine oil, or antifreeze in your gasoline.
(The alert observer will note that it is impossible to create a saturated trans fat.)
Hidden Trans Fats: They’re Everywhere
So you think “I’ll only buy products with 0g of trans fat on the nutrition label. Then I’ll be safe.” Right?
Does it contain trans fat? This won't tell you.
Trans fat hides in plain sight.
Trans Fat: Hiding on the Nutrition Label
Here’s the first place it hides: on the nutrition label. If a ‘serving’ of food has 0.5 grams or less of trans fat, the label can say “0 grams”. But how many ‘servings’ are you eating? If a ‘serving’ is 50 calories, you can easily eat eight servings at a sitting—or four grams of trans fat!
How can you tell? Look on the ingredient list. If you see the words “hydrogenated” or “vegetable shortening”, you can guarantee the presence of trans fats—no matter what the nutrition label says.
Trans Fat: Hiding in ‘Heart-Healthy’ Seed Oils
Of course, we should be eating those ‘heart-healthy’ polyunsaturated seed oils instead, right? Like ‘canola’ (rapeseed) oil?
Well, aside from the fact that seed oils contain mostly pro-inflammatory n-6 (“omega-6″) polyunsaturated fats, both n-6 and n-3 polyunsaturated fats are less chemically stable than saturated fats. It turns out that the process of extracting and deodorizing them (which requires both hexane, a poisonous industrial solvent, and high heat) turns some quantity of them into…trans fats!
SEAN. O’KEEFE, SARA. GASKINS-WRIGHT, VIRGINIA. WILEY, I-CHEN. CHEN. LEVELS OF TRANS GEOMETRICAL ISOMERS OF ESSENTIAL FATTY ACIDS IN SOME UNHYDROGENATED U. S. VEGETABLE OILS. J Food Lipids Vol 1 #3 pp.165-176 Sept. 1994
Concentrations of trans isomers of 18:2w6 and 18:3w3 were measured in soybean and canola oils purchased in the U. S. […] The degree of isomerizations of 18:2w6 and 18:3w3 ranged from 0.3% to 3.3% and 6.6% to 37.1%, respectively. The trans contents were between 0.56% and 4.2% of the total fatty acids.
Vegetable oil solvent extraction plant, China.
Yes, that’s the ‘heart-healthy’ canola oil that they put in everything nowadays because it has ALA in it (the least useful omega-3). Yet the average canola oil contains over 2% trans fat! (Remember: 2% of calories = doubling of heart disease risk.) And if extraction under carefully-controlled conditions creates that much trans fat, how much more does the uncontrolled heat of cooking and frying create?
(We don’t know—but we do know that n-3 fats are less chemically stable than n-6 fats, and generally get hydrogenated first. So all those “Omega-3 Enriched!” oils become “Trans-Fat Enriched!” when you cook with them. For evidence of this, we move to the next section…)
Trans Fats: Hiding In The Deep Fryer
The third place trans fats hide is in the deep-fryer. Canola oil is the most common frying oil, because everyone knows canola is ‘heart-healthy’…right?
If you can run a city bus on it, it's not food.
Unfortunately, since polyunsaturated oils are unstable under the continuous heat of the deep fryer, canola oil is hydrogenated so it’ll last longer. (This is why we fried everything in saturated fats, like beef tallow, before the now-discredited “Lipid Hypothesis” took over American nutrition theory: saturated fats can’t hydrogenate by definition, and they don’t degrade nearly as much or as quickly under heat.)
Industrial canola oil for deep-fat frying contains 27% trans fat. (Source.)
Still want that order of French fries?
Live in freedom, live in beauty.
(Did you enjoy this article? Share it with your friends! For more articles about fat, try “Why Humans Crave Fat” or “Fat and Glycemic Index: The Myth of ‘Complex Carbohydrates’“.)
Postscript: What Should I Use Instead?
Use saturated fats, which don’t hydrogenate—and monounsaturated fats, which hydrogenate to saturated fats, not trans fats. Butter, beef tallow, and coconut oil each contain only a tiny fraction of polyunsaturated fats…and if you buy grass-fed beef or butter, that fraction contains more healthy n-3 fats and less unhealthy n-6 fats.
And since a surprising number of people still believe that saturated fat is bad for you: no, it isn’t.
Patty W Siri-Tarino, Qi Sun, Frank B Hu, and Ronald M Krauss. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr Jan 2010
“A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.”
And here’s the layman’s version, from Scientific American: “Carbs Against Cardio: More Evidence that Refined Carbohydrates, not Fats, Threaten the Heart“, Scientific American, May 2010
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