Conjugated linoleic acid (CLA) and breast milk


Researchers in the Netherlands conducted and published the kind of study I would love to see more of. The scientific literature is crawling with papers showing the benefits of low-carb diets, the advantages of having this or that vitamin, taking this or that mineral, and flossing regularly, but seldom is a study published showing the health difference the quality of the food makes. In April the British Journal of Nutrition published a study showing that the conjugated linoleic acid (CLA) in human breast milk increased as the mothers ate more organic dairy and meat products.

CLA is collectively a group of isomers of the 18-carbon linoleic acid. (Isomers are different configurations of the same molecule.) CLA, as a group, have a trans configuration in their structure, making them trans fats, but healthful trans fats. Yes, there are such things. (We humans even make our own trans fats.) There is some controversy swirling around CLA because studies have shown both health advantages and disadvantages to taking them in supplement form. As research progresses more information is being gleaned as to which of the many isomers are the ones that are good for us. So far, it seems, (as might be expected) the natural forms of CLA, i.e., those found in the meat and dairy products of ruminant animals are the good ones.

As the paper puts it:

The various CLA are produced in the rumen of ruminant animals mainly by the bacteria Butyrivibrio fibrisolvens through reactions of isomerization and biohydrogenation. These reactions lead as well to the formation of a wide variety of trans- and cis-monoenic fatty acids (especially C18 : 1 trans isomers). In addition, trans-vaccenic acid (trans11-C18 : 1, TVA) which originates from linoleic and linolenic acid plays an important role as precursor of rumenic acid. Very recent work has shown that the conversion of TVA in rumenic acid does occur as well in man. CLA are currently receiving much attention in nutritional research, since there is experimental evidence suggesting that these fatty acids might have anti-carcinogenic, anti-atherosclerotic, anti-diabetic and immune-modulating effects, as well as a favourable influence on body fat composition, i.e. on the proportion of fat tissue to muscle mass. Most of this experimental evidence derives from in vitro experiments or animal tests, which justifies the recent interest in clinical trials concerning the relevance of CLA for human health. The newly published reports concerning the effect of CLA supplementation on health-related outcomes have contradicting messages and in some cases an isomer-specific effect on the lipid profile could be shown. A double-blind study revealed that the consumption of dairy products naturally enriched in cis9, trans11-C18 : 2 increases the level of this fatty acid in plasma and cellular lipids.

The authors had done a pilot study in Switzerland showing that women who consumed at least 50 percent of their energy from organically produced foods had 30 percent higher CLA levels in their breast milk at 4 and 40 days post partum. They decided to refine their study by looking at the CLA concentrations in the breast milk of women who ate varying amounts of meat and dairy products from animals raised on organic feed.

It is known that the lipid composition of cow’s milk is strongly influenced by the stable conditions and feeding management, with milk from cows held in organic farms (Germany, Italy) containing significantly more CLA than that from their conventionally held counterparts. Note that farms certified as ‘organic’ are those in which the use of synthetic inputs, such as synthetic fertilizers and pesticides, preventive veterinary drugs, genetically modified seeds and breeds, most preservatives, additives and irradiation are excluded (htpp:// Since the major source of CLA in man is the diet, we have hypothesized that the amount of CLA in the milk of breastfeeding women could be augmented by increasing the amount of organic dairy nutrients within their diet. The sources of CLA for man comprise not only dairy products but also ruminant meat; therefore, emphasis was put on these two groups of nutrients.

Subjects were grouped as a function of what percentage of the meat and dairy products they consumed were produced by ‘organic’ methods. The groups were stratified as follows: those consuming >90% of their meat and dairy products as organic; those who ate organic meat and dairy anywhere from 50-90% of the time; and those who consumed less than 50% of their meat and dairy as organic.

The 312 lactating mothers in the study provided breast milk for determination of CLA content.

After analysis it was found that those mothers consuming the greatest percentage of their meat and dairy from organically produced sources had the highest levels of CLA in their breast milk with a decrease in levels as the consumption of organic meat and dairy fell.

I believe this is an important study because it shows (along with the pilot study done by this group earlier) that pregnant and lactating women eating high quality, organically produced meat and dairy have higher CLA levels in their milk as compared to those eating the same quantity of meat and dairy but of the conventionally produced variety. As I mentioned at the start of the post, it’s one of the few studies I’ve seen even looking at the difference consuming a higher quality of food might make. And it turns out that the higher the quality of the food the greater the health benefit.

The meat and dairy products used in this study came from animals raised without the use of

synthetic fertilizers and pesticides, preventive veterinary drugs, genetically modified seeds and breeds, most preservatives, additives and irradiation…

The meat and dairy is considered ‘organic’ even if it is from grain-fed animals as long as the grain isn’t genetically modified, and has been grown without pesticides, synthetic fertilizers, etc. The levels of CLA in grass-fed animals are the highest of all, so it would be interesting to see this study repeated comparing the breast milk CLA levels in mothers who got their meat and dairy from grass-fed animals verses those who got theirs from the standard ‘organic’ sources.

I know which side my money would be on.

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11 thoughts on “Conjugated linoleic acid (CLA) and breast milk

  1. What, precisely, makes organically produced meat “higher quality”? I mean other than cooties and technophobia?

    Of course there can be parallel selection reasons for “organic” things to be higher quality…like organic tomatoes are usually a better-quality cultivar (from the standpoint of the person eating it) than mass-produced tomatoes. And the organic ones are probably cared for in a nicer way, aside from organic/synthetic treatment. But I’m unaware of any solid evidence that, using exactly the same cultivar and agricultural techniques (aside from the organic/inorganic pest control and fertilizers), you get any different quality at all.

    Aside from organic techniques being more capable of transmitting biological pathogens to humans, of course. Cow poop CAN have organisms that were not successfully killed in processing, whereas some chemical from DuPont almost certainly cannot.

    This whole thing does remind me of how women were once discouraged from nursing their children, regardless of their diets. That kind of dimwitted “consensus” among the scientific establishment is why I generally say we should all make our own decisions, never trusting the advice of the “experts” uncritically.

    Hi Kaz–

    I think you’re right that ‘parallel selection reasons,’ as you call them, for ‘organic’ products to be superior.  They do probably receive better care than those mass produced.  (This is certainly the case for animals.)  But I part ways with you on the idea that cow manure and other allowed ‘organic’ fertilizers and pest control methods are no different that high tech-based chemical ones.  I agree that with all things held constant – cultivar, care, water, etc. – and the only thing different being the type of fertilizer and pest control, you would get a product that looks the same.  And I agree that the one fertilized with cow crap might have a remote possibility of having a bad E coli bacterial contamination, which the high-tech one wouldn’t.  But, the one treated with chemical pesticides may contain small amounts of potentially toxic compounds that are consumed when the plant is eaten.  You can make the case that these are all safe nowadays, but the same case was made for the organochlorines that still pollute and haven’t really degraded much since the 70s when they were banned.  The problem with chemicals is that one just doesn’t know, sometimes until the damage is already done.  I would rather take my chances eating a little cow crap than I would eating a little of a ‘perfectly safe’ chemical.

    Whenever plants grown with chemical pesticides are fed to animals, most of these compounds accumulate in the fats of the animals.  So, when we eat these animals, we are eating the pesticides from a huge amount of plant food that the animal has eaten.  These pesticides also accumulate in the milk these animals produce, so we get a real multiplier effect when we eat dairy products.

    This study (and the pilot study) shows that there is a difference at least in terms of CLA depending upon whether the meat and dairy came from ‘organic’ or conventional sources.  Whether these differences came because of the ‘parallel selection reasons’ you stated or not, I don’t know.  But since I don’t know when I look at a conventionally grown fruit or vegetable or conventionally produced meat or dairy in the grocery store whether or not these plants and/or animals have had the same care as the ‘organic’ ones, I usually opt for ‘organic.’  And I’m willing to pay a little more to get a product that I can safely (I hope) assume doesn’t have a concentration of organophosphate pesticides.



  2. Welcome Back.

    Interesting story. As an avid consumer of factory tours, I am always wondering at the differences between making something in a factory and making something in nature’s factory. It would seem, for something like CLA (and other vitamins, minerals and supplements) the useful way to manufacture them would be to replicate inorganically nature’s factory. So, if CLA comes from rumens with bacteria X, can we make an artificial one, and use it to crank CLA that is just right, and takeable in supplement form? I dunno.

    Recently read “What’s Your Dangerous Idea?” which presents a number (108 I think) leading thinkers from various sciences, arts, and other realms (they should get you in on the next Edge Question, if you ask me). At least one of the 108 respondents dangerous idea was that we are approaching a time in the next 5-20 years, where we will be at the end of knowledge. We will know everything there is to know about everything on the planet. It’s been a month or so since I read it, but it turns out this might be a dangerous idea from the “what happens when we don’t have to ask questions anymore” frame of things. On the flip side, if the secret to everything were open, imagine the commercial possibilities for putting pieces together. Like artificial robot cows to produce CLA and whatever else we get out of natural cow meat. Me, I don’t think curiosity would die. But considering how every question we answer raises two new questions (in addition to the million questions about our methodology in answering the question), I don’t think we will ever know EVERYTHING. There’s always a deeper mystery, no? Like why faith over reason.

    I ramble. Thanks for the post. Hope you are able to post more frequently. I blame the mac (which is probably not a popular pov around here and is a religious war waiting to open equal to at least Yankees-Red Sox or Ohio State – Michigan).

    Hi Max–

    Many of these ‘products’ can be made in regular factories.  Factory-produced vitamin C, for example, is no different than naturally produced vitamin C: they are identical.  The problem isn’t so much in the making of them as it is in the identifying whether or not the specific chemical in question is actually healthful.  Green leafy and colorful vegetables contain a lot of flavenoids and carotenoids.  If we isolate a few of them, make them in a factory, and take them, do we get the same benefit as eating the same amount in vegetable form?  The answer is pretty much a big NO.  So, either we’re not isolating and synthesizing all of them, or we haven’t discovered all of them, or there is some synergy with other components of the actual plants that we don’t get in the factory versions.

    Right around the turn of the century one of the Gods of physics (Rutherford, I think) made the pronouncement that the study of physics had been taken as far as it was likely to go.  There was nothing new to learn.  Then in 1905 Einstein published his five papers turning the world of physics upside down.  I always remember this lesson when I hear that we are nearing the limits of knowledge.

    I haven’t taken a break from posting due to the Mac.  In fact, I’m answering this comment on a PC, which I still use as my desktop computer.  I’ve been involved in a business project that right after I wrote the ‘Back in the saddle’ post suddenly and without warning had occasion to occupy almost all of my time.  I wasn’t shed of it until last night.



  3. One must bear in mind that “we don’t know” doesn’t default to “is bad for us”. For every thing that turned out to be bad for us, there were probably dozens of ones that did not. Even when they decide something is bad for us, it’s often because of junk science leaping to conclusions, as with DDT and the millions of human deaths banning that least harmful of all insecticides caused.

    Essentially, you’re weighing a “we don’t know” versus a known risk. That spinach outbreak last year was from an organic farm, and against that we only have a “what if someday this changes your odds of getting cancer”.

    Note, too, that Fear Equals Funding bureaucrats like the NiH and CDC assume, irrationally, that if N exposure causes 100% death, then a N*.01 exposure causes one percent of all people exposed to die. This is utterly crazy…water is toxic, in sufficient amounts, as is oxygen, but obviously a smaller percentage is actually healthful.

    Why, in fact, would we worry more about synthetic chemicals than anything else? Perhaps the latest cultivar of tomatoes causes cancer. Or the purple carrots I’m growing this year.

    Take genetic engineering, for example. When you genetically splice a gene into corn, you are actually doing precisely the same thing that would happen if you hybrid the corn, except more efficiently. Every new corn hybrid has a chance of somehow being harmful, whether gene-spliced or made by some little old granny with a fondness for horticulture. But people focus on the geneered corn as an unknown risk, as if it were somehow more dangerous.

    Similarly, I wonder if anyone’s ever bothered to thoroughly test worm casting tea for carcinogenic qualites.

    When tending my own garden, I use companion plants as an alternative to pesticides, as I’ve mentioned before. I actually believe that I get superior results because of it, as well as not having to risk all the funky chemicals.

    But it’s worth noting that, on an industrial scale, you get less than half the yield using “organic” techniquest than conventional ones, with the conventional yields also increasing every year as technology advances.

    YOU may be willing to pay extra for organic foods, but it would be a disaster if all American agriculture went that way, or even a sizable percentage. We’d have to double the amount of land used for farming, plus massively increase the amount of workers involved, which would be an economic disaster. The fewer workers required to produce a given thing, the more prosperous the society.

    I do, by the way, use artificial fertilizer. I’m far less concerned with that than actual pesticides…but more importantly, if my plants start suffering a nutrient deficiency, and I treat half of them with Miracle Gro, the other half with fish emulsion and worm tea, the half getting the miracle gro will recover faster, be healthier, and produce larger, better-tasting fruit. This is because organic techniques are very slow to amend soil and meet needs. You have to anticipate and build up, constantly.

    So there is, in fact, some chance even in home gardening that conventional techniques will produce healthier food. Similarly, imagine a pest outbreak that brutalizes some crop…you still get some produce, but it’s less healthy, perhaps therefore less nutritious. What if the pesticides they could have used WOULD have washed off? Isn’t one better off, then, with the healthier fruit?

    If a real crisis occurs, where my companion plants don’t do the trick, I will fall back on pesticides, albeit with great care to use what I think is least risky to myself.

    Hi Kaz–

    A couple of things…

    First, I didn’t go back and look it up, but I don’t believe the spinach outbreak came from an organic farm.  I think it was conventionally grown spinach.  The thinking was that the O157:H7 E. coli was tracked into the spinach by wild pigs that roam in the area.

    Second, I agree with you about chemical fertilizers in one’s own food.  I wouldn’t mind using them myself and eating the results because I would know precisely what I was eating.  What I’m not so sure is eating something that I’m not sure about.



  4. I’ve always thought it was more important to “buy high quality” with animal foods, as opposed to produce. I tell people if they can only afford one organic/free range food, make it eggs. Second is dairy (esp. full fat dairy products) and then meat/poultry/seafood.

    Hi Paul–

    Probably a good progression.



  5. Just like new year’s resolutions, which are meant to be broken, you are still responding to comments Dr. Eades. Just don’t fight it and do what feels right.

    Hi Hellistile–

    I guess I just can’t resist.



  6. Oh this so just hit my Philosophy Button. There have always been people who claim all the physical questions of the universe have been answered. These people just aren’t asking the right questions!! These people need to back off their own arrogance and ignorance, develop a different Philosophical Outlook, and get on with the business of discovery.

    Uh, am I missing something here?  I can’t see how this post would inspire a philosophical debate.  Did you post this comment to the wrong post?



  7. The two companies implicated in the e. coli hysteria of 2005 were Natural Selection Foods and River Ranch Fresh Foods, both organic growers. In the former case, at least, the cause is suspected to be a field of organically raised cattle uphill, whose runoff drained into the field.

    I was talking about the more recent spinach problem from California just a few months ago. 

  8. LCForevah:

    The person I was talking about was talking, if I recall, about sciences, not philosophy. So, if every currently unanswered question has an answer developed for it, and the only unanswered questions are things like String Theory and the Landscape, or multiple dimensions and alternate universes with differing physics. Things that are pretty much unknowable and inherently unobservable.

    I suspect that there is a limit to the sum total of knowable things. But, I don’t think we’re really near it. Of course, if you look at the exponential rate of growth in knowledge, century by century, what we know in 2107 will make us look less informed than people in 1907 look to us. Maybe even less informed than the people of 1807.

    Last thought: philosophy is to open the mind to broader possibilities, including the end of new discoveries. Relax a little, be open to ideas, and you’ll probably live long enough to see some pretty strange days indeed.

  9. In the discussion of chemical vs. organic fertilizers what KAZ described is puzzling to me. Yes, miracle grow will get plants healthy again quicker but wouldn’t organic growing methods keep the problem from reoccuring? That’s been my limited experience. Organic growing methods take better care of the land and in the long run will result in healthier produce year after year. I have friends who maintain an organic garden and they start their tomato plants indoors and by the end of our short, New England growing season they have 10-12 ft tall plants every year. And those are some tastey tomatos!

  10. To add a different observation, the article you cited said CLA may have anti-diabetic and anti-atherosclerotic properties as well. However, since it’s a fatty acid, you won’t find it in skim milk and will probably find little of it in low fat dairy and beef.

    Yet, the standard dietary advice for diabetics (and to prevent atherosclerosis) is to limit saturated (animal) fat and consume only low fat or fat free dairy. That dietary advice is depriving diabetics of a nutrient that may help them. Oh well, the pharmaceutical industry can manufacture it’s own CLA apart from animal fat and make $$$$$ off a product that may not be as effective as the natural version.

    Hi Dan–

    You’re right.  Grass-fed and/or organically-raised animals have the most CLA, but you don’t get it if you only eat the low-fat or fat-free dairy products from them.

    Not only is manufactured CLA not as good as natural, some of the factory-made stuff is in an isomeric form that has been shown to be detrimental to health.  The many isomers of CLA is what has prevented CLA as a supplement from gaining traction.  For every study showing a benefit of one or a group of isomers there was one showing negative effects using other isomers or groups of isomers.   Since CLA is the all-encompassing term for a bunch of isomers, no one knew where it was all leading.



  11. Hi doctor

    I’m a spanish lowcarb girl and i’m following your book and method since two months ago (so happy with the results!). Now that you’re writting about cla, i’d like to know what you think about the pills of cla. May the pills help with the weight loss? Thanks a lot for all your help and for telling us the truth about nutrition :-)

    Hi Pilar–

    Thanks for the kind words, and I’m glad you’ve been so successful on the program.

    You must be careful with the CLA because CLA isn’t one single substance, but a mixture of many.  I don’t take it myself because all the data isn’t sorted out to my satisfaction yet.  The best way to get CLA is from the meat and dairy products of grass-fed animals.

    I hope this helps.