Comments on: Omega 6: good or bad for health? Part 2

By: Bill Shrapnel

Bill Shrapnel — Thu, 31 Jul 2014 08:19:20 +0000

Hello Emma. That’s the typical level of trans fat in modern margarines. It’s very low – butter has about 5-6 times as much trans fat.
It’s almost impossible to totally avoid eating trans fats. To do so you would have to avoid beef, lamb, cheese and all whole milk dairy products as well as butter and margarine.
Better to look at limiting the total intake of trans fats. The World Health Organisation recommends that trans fat intake be less than 1% of calorie intake. Current intake in Australia averages about 0.5-0.6% of calories intake, which is quite low. These days most of our trans fat intake comes from dairy fat and meat fat. If you limit saturated fat intake you will be limiting the intake of these animal fats anyway and your total trans fat intake will be low. Regards, Bill

By: Emma

Emma — Thu, 31 Jul 2014 06:11:20 +0000

Hi Bill,

Even though margarine trans fat contents are well below what they were, do you not think the small amounts they do still contain (e.g. Olivani, with the Heart Tick, contains 0.06g/10g serving) would add up over a life time of consuming that product? That, along with the taste, means I don’t touch the stuff ( I also ensure I consume butter sparingly)

Kind regards,

Emma

By: Bill Shrapnel

Bill Shrapnel — Wed, 30 Jul 2014 00:38:30 +0000

Hello Gordon. The margarine used in the Sydney Heart Study was Miracle, produced by Unilever. I consulted to this company for 14 years and I can assure you that the Miracle margarine used in the Sydney Heart Study contained about 15% of its fatty acids as trans fats, similar to all margarines available at the time. The first trans-free margarine produced by Unilever (and the first in Australia) was Becel, but that came over a decade after the Sydney study.
So the intervention in this study was not the replacement of saturated fat with omega 6 as Ramsden asserts; it was the replacement of saturated fat with omega 6 + trans fatty acids. Ramsden argues that the adverse effects observed in this study were due to omega 6 whereas most other observers say that they were due to the trans fatty acids.
I put this directly to Ramsden when he presented this work at a conference in Sydney but he had no answers. Regards, Bill

By: Gordon Rouse

Gordon Rouse — Wed, 30 Jul 2014 00:06:39 +0000

It is a complete fabrication to say the Sydney Diet Heart study was confounded by trans-fats. Dr C Ramsden looked into this and concluded that the margarine they were given was most likely low in trans fats, as it was chosen to be high in PUFA.
It was more likely that the control group were consuming more trans fats. Do you know something about this study that Dr Ramsden was unable to find?

see http://www.bmj.com/content/346/bmj.e8707

Nevertheless, the question of how trans fats affected this clinical study is an unknown – however it was a far bigger problem in other clinical studies which your preferred meta-analysis relied up. Your Havard meta-analysis assumes all these studies can be summed up as replacements of saturated fat with polyunsaturated fats, yet they were almost all multi-intervention studies, with the Oslo diet study notably advising the intervention group to avoid stick-margarines, and being provided with Cod Liver Oil (high in Vitamin D and O3 DHA/EPA).
The Sydney Diet Heart Study is the stand out study of the crowd, with the most simple of substitutions applied, it should be the study you trust the most!

Using your interpretation of the SDHS, you imply that benefits associated with replacing SFA with Linoleic Acid were more than negated by increases in trans-fat consumption (unproven), and negated to near statistically significant amounts. Yet, you do not consider the implications that this would have for the Oslo diet heart study or others where we know trans-fat consumption was significantly decreased in the intervention group. To uphold the veracity of the Havard meta-analysis is to apply a shocking double standard here.

The SDHS is not an outlier either, it’s findings were similar to the Rose et al corn oil study, although this study was not as well designed.

Your other evidence is of course population studies, which we know are very confounded. For every population study that purports to find a correlation, there is another that contradicts it. In some ways the macro population figures can be a better guide, as they are not reliant on food questionnaires. If replacing saturated fat with Linoleic acid was beneficial, you would not expect French paradoxes or the Isreali paradoxes (http://www.ncbi.nlm.nih.gov/pubmed/8960090), yet the existence of these paradoxes show that our assumptions are very likely wrong!

Finally, relying on surrogate end-points to suggest Omega 6 is beneficial is putting your faith in the theory and nothing else. The theory can only be trusted as far as its ability to make predictions go, and this theory failed to meet expectations in the only study that really tested it.

By: Shane

Shane — Tue, 29 Jul 2014 23:27:36 +0000

Of course. I didn’t mean to give the impression that I actually support these claims, but I do think it’s important to be aware of what the blogs are saying. And it looks like omega-6 is the next nutrient to be obsessed over and vilified.

By: Bill Shrapnel

Bill Shrapnel — Tue, 29 Jul 2014 23:19:41 +0000

Hi Shane. A couple of points here. The omega 6 content of the Australian diet has been steadily falling since about 1985. The last time I looked it was about 4-5% of daily calories, which is right at the lower end of recommended intakes, so we are not drowning in omega 6 as is frequently suggested.
There have been randomised controlled trials in humans lasting years in which omega 6 intakes of 14-15% were consumed – three times current intakes. The only consequence was a fall in coronary events. There is also consistent evidence from epidemiology, mechanistic studies and long-term feeding studies in primates which all indicates that omega 6 or polyunsaturated fats more generally are protective against heart disease. This is the evidence that the WHO, American Heart Association, NHMRC and the Heart Foundation take into consideration when they produce their dietary recommendations. A ‘consensus of internet nutritionists’ rates as the lowest form of scientific evidence available. Expert organisations wouldn’t even look at it.
In relation to cancer, the amount and type of fat that people eat has no effect on cancer risk. Regards, Bill

By: Shane

Shane — Tue, 29 Jul 2014 23:04:16 +0000

Bill,

Recently, the consensus of Internet nutritionists is that omega-6 is unhealthy in the amounts in which it is currently consumed. The claim that it’s inflammatory pops up, which you covered in part 1, but there’s also the claim that PUFAs are particularly unstable, and are readily oxidised in the body. Apparently this can lead to atherosclerosis or cancer, but most of the time the argument simply ends with the word “oxidised”. I’ve seen this claim appear an awful lot lately. In particular, the Internet consensus is that vegetable oils are undesirable, and should be replaced with butter or coconut oil.