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Misinformation exposed about Linoleic acid, Ulcerative Colitis and Irritable Bowel Syndrome
Introduction
In July 2009, a UK newspaper, The Guardian, published an article headlined Sunflower oil and red meat linked to bowel disease. It was reporting the e-pub ahead of print of a study from the University of East Anglia (the same university whose climate scientists have been accused of 'massaging' the data to show that climate change is man-made, but that's another story), which showed that linoleic acid inflamed the gut and increased the risk of conditions such as ulcerative colitis and irritable bowel disease.
Well, they got it half right, I suppose: sunflower oil is certainly high in linoleic acid, but red meat has hardly any.
Now the study has been published officially in the December 2009 edition of the medical journal, Gut. Its abstract is below.
Linoleic acid
To save you having to shoot off to wikipedia to look it up, here are a couple of facts about linoleic acid and the foods that contain it:
- Firstly, linoleic acid is a polyunsaturated fatty acid — the omega-6 (n-6), essential fatty acid. So we have to eat some.
- The thing is, we don't need to eat much — about a teaspoonful a day
- Another fact is that all fats and oils in nature, whether they are from plants or animals, are a mixture of different fatty acids, and all of the natural ones contain some linoleic acid; the only difference is the various amounts. So whether you are a carnivore or a vegan, you're unlikely to be deficient.
This means that we are going to ingest linoleic acid whether we want to or not and, as I have already said, we do have to eat some. So, obviously, what we should do is avoid the foods that contain a lot of linoleic acid, and eat only the foods that contain the small amount we need.
And that's where it has all gone wrong!
Misinformation about linoleic acid and red meat
You see, The Guardian, and pretty much all the other websites that reported this story, gave the impression that red meat was a major source of linoleic acid. Yet beef fat (and that's what we are thinking of when we talk about red meat) has the lowest percentage of linoleic acid of all the fats and oils found in nature, except for palm oil. Beef fat is a mere 2% linoleic acid, and lamb fat, at 2.5%, isn't much higher. Beef and lamb, the red meats, are the sort of food we should eat!
The Guardian was right in indicting sunflower oil, which can be more than 70% linoleic acid. Other seed oils: safflower oil, corn oil, soy oil, — the cheap-to-produce, but great profit-maker products — are all over 50% linoleic acid. Margarines and cooking oils made from these oils are also very high in linoleic acid. This is why these processed vegetables have proved to be so harmful. The plant source with the lowest linoleic acid is palm oil at 1%, while coconut oil is 2.5%. Incidentally, olive oil is 9% linoleic acid.
So, to sum up, if you want to avoid eating harmful amounts of linoleic acid and the risk of serious bowel disease:
- Eat animal fats, particularly from cattle and sheep, tropical oils (coconut and palm oils), and olive oil
- Don't eat vegetable margarines and cooking oils.
I would have thought that this should be easy, reasonable and straightforward, and the advice that health websites would be warning against, just as I have. But not so, it seems. These websites below warn against red meat!!
The misinformers are:
Newsmax Health
USNews and Health Report
Reuters Health
http://stanford.wellsphere.com/weight-loss-article/fried-and-fatty-food-may-cause-ulcerative-colitis/754125, Be Well @ Stanford
MedscapeCME (Registration required).
High Beam Research
DoctorNDTV
HealingWell.com
Irish Health
EmaxHealth
WebMD isn't carrying the story, but then WebMD classifies linoleic acid as a 'good' fat
http://www.rxlist.com/script/main/art.asp?articlekey=104039. RxList accessed 2008
Dr Pressman
And probably many more.
Some of these are newspaper items, and one can't expect news journalists to be particularly knowledgeable about the subject. What is really worrying is the number of 'health' websites who are also disseminating this misinformation without comment. It's worrying because they don't seem to understand the very basics of nutrition — and the harm that they could do as a result.
The study
Tjonneland A, et al, IBD in EPIC Study Investigators. Linoleic acid, a dietary n-6 polyunsaturated fatty acid, and the aetiology of ulcerative colitis: a nested case-control study within a European prospective cohort study. Gut 2009 Dec;58(12):1606-11. Epub 2009 Jul 23.
University of East Anglia, Norwich, NR4 7TJ, UK. a.hart@uea.ac.uk
ABSTRACT
OBJECTIVE: Dietary linoleic acid, an n-6 polyunsaturated fatty acid, is metabolised to arachidonic acid, a component of colonocyte membranes. Metabolites of arachidonic acid have pro-inflammatory properties and are increased in the mucosa of patients with ulcerative colitis. The aim of this investigation was to conduct the first prospective cohort study investigating if a high dietary intake of linoleic acid increases the risk of developing incident ulcerative colitis.
DESIGN AND SETTING: Dietary data from food frequency questionnaires were available for 203 193 men and women aged 30-74 years, resident in the UK, Sweden, Denmark, Germany or Italy and participating in a prospective cohort study, the European Prospective Investigation into Cancer and Nutrition (EPIC). These participants were followed up for the diagnosis of ulcerative colitis. Each case was matched with four controls and the risk of disease calculated by quartile of intake of linoleic acid adjusted for gender, age, smoking, total energy intake and centre.
RESULTS: A total of 126 participants developed ulcerative colitis (47% women) after a median follow-up of 4.0 years (range, 1.7-11.3 years). The highest quartile of intake of linoleic acid was associated with an increased risk of ulcerative colitis (odds ratio (OR) = 2.49, 95% confidence interval (CI) = 1.23 to 5.07, p = 0.01) with a significant trend across quartiles (OR = 1.32 per quartile increase, 95% CI = 1.04 to 1.66, p = 0.02 for trend).
CONCLUSIONS: The data support a role for dietary linoleic acid in the aetiology of ulcerative colitis. An estimated 30% of cases could be attributed to having dietary intakes higher than the lowest quartile of linoleic acid intake.
Latest update 6 December 2009>
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