Dangers of Conjugated Linoleic Acid

[F Trooper]

Ok, so based on the idea that an individual is healthy, lean and athletic with a good dietary intake, an efficient metabolism and a balanced hormonal system (ie-None of the test subjects in the studies), what is the likelihood of that individual developing anything which could lead to diabetes or reduced function of the glucoregulatory system of any form?

[NU_nutrition_TS]

I don't think anyone, not even experts in the field, could answer that definitively.

Diabetes, and its aetiology, is still being investigated and hypotheses are being formed and tested. There is a lot we know but a lot that remains to be discovered and elucidated.

We can draw some tentative conclusions from a number of lines of evidence - both provided by clinical interventions and real life experiences and observations - but they can never be set in stone or considered a final or definitive answer as there may always be more to it than is presently known or fully understood.

My personal feeling is that obtaining these nutrients from whole foods is always going to be more beneficial (and less harmful) than by taking them as isolated supplements. Just as vitamin C is thought to be more effective when taken along with the bioflavinoids usually found alongside it in whole food sources and vitamin E (as tocopherol) is more beneficial when taken with the tocotrienols found with it in natural sources, so CLA (in all its various forms) will be better from foods than any one isolated form.

When it comes to insulin resistance, one has to ask "which tissue or cells is/are resistant and why"? Is it the liver? Is it the muscle tissue? Is it adipose tissue? To what degree are they resistant and are they all resistant to the same degree?*

It may be that one of the mechanisms by which CLA works to our benefit is to increase insulin resistance in certain tissues (and maybe selectively only in those with pre-existing health problems). Is this resistance peripheral or systemic? Is it transitory or permanent?

The problem is people want quick, easy solutions to all problems. They want a 'magic bullet'. They want to see things in monochrome instead of full spectrum - they seek a reductionist view of everything instead of accepting the holistic, synergistic and complex nature of the real world.

*While insulin appears to act on tissues to make them more receptive to glucose uptake and clearance - it is by no means certain that that is its most important function. There is even a hypothesis that insulin's chief role is to prevent the release of glucose from the liver (either via glycogenolysis or gluconeogenesis) when the system is already flooded by exogenous glucose and that most cells will take up this glucose without much input from insulin. In this instance, it is insulin resistance in the liver (usually the first organ to become resistant in systemic insulin resistance) that is most likely the cause of hyperglycaemia.

[Elvis]

I pulled out a chunk of recent research in this thread:

CLA Research

one looks relevant to the question asked:

Quote

The effect of 6 months supplementation with conjugated linoleic acid on insulin resistance in overweight and obese

C Syvertsen1, J Halse2, H O Høivik3, J-M Gaullier1, M Nurminiemi1, K Kristiansen1, A Einerhand4, M O'Shea4 and O Gudmundsen1

International Journal of Obesity - Abstract of article: The effect of 6 months supplementation with conjugated linoleic acid on insulin resistance in overweight and obese

Quote

Conclusions:

CLA does not affect glucose metabolism or insulin sensitivity in a population of overweight or obese volunteers.

If it were me, I'd want to go to the resource Wotan points to looking for research relevant to insulin sensitivity, since a single study is not normally considered enough to hang your hat on. You also said healthy weight and this is talking of overweight volunteers. In any case I'd be surprised if you found a conclusion that it does have a negative effect, considering most studies show improving body composition (but at pretty small rate).

[NU_nutrition_TS]

You have basically confirmed what I have been saying about the isomers used in supplemental forms of CLA. In the study you have just quoted above they say:

Quote

Objective:To evaluate if CLA as a mixture of the main isomers trans-10 cis-12 and cis-9 trans-11 affects the insulin resistance in healthy overweight and obese male and female adults.

Notice that they used a blend of the two main isomers of CLA...and found no effect. Whereas the study I mentioned previously used only the single isomer trans-10 cis-12...and found there was an effect (in obese subjects)!

[F Trooper]

I see what you guys are saying, and I'm sure that many conflicting studies can be found for even what are considered to be the safest of supplements...For example, some people think that creatine supplementation may reduce or even stop the body's natural ability to process creatine. And one that worries me especially is the thought that the vast quantities of protein recommended by almost any body builder could lead to kidney stones. One study even suggested that even as little as twice your RDA of protein, which is significantly lower than the consumption of many gym users, could cause the above problem.

As we all have said, side-effects greatly depend upon the given situation, and I guess that each person has to read the available information and decide for themselves... It really is amazing that despite what we think we know about the human body, we have barely scratched the surface as to how it functions.

[hailtotheking]

For me personally the way i see it CLA this is one of those substances where a small amount, in the right configuration (which alot of CLA supplements dont have) is probably a good thing, but too much probably isnt (insulin resistance and pancreatic enlargement have been seen in some studies using high doses).

Its one of those things thats best gotten in food such as whole dairy and good quality meat, which inevitably means you will not be getting large dodgy doses of it.