Are sterols the new trans fat?

By now, I'm sure you're well-acquainted with the hydrogenated, trans fat issue.

Hydrogenation of polyunsaturated oils was a popular practice (and still is) since the 1960s, as food manufacturers sought a substitute for saturated fat. Bubbling high-pressure hydrogen through oils like cottonseed, soybean, and corn generates trans fatty acids. These man-made fatty acids, while safe in initial safety testing, proved to be among the biggest nutritional mistakes of the 20th century.

Trans fatty acids have been associated with increased LDL cholesterol, reduction in HDL, oxidative reactions, abnormal rigidity when incorporated into cell membranes, and cancer. Trans fats still dominate many processed foods like chips, cookies, non-dairy creamers, food mixes, and thousands of others. They're also found prominently in fast foods.

Fast forward to today, and most Americans have become aware of the dangers of trans fats and many try to avoid them.

But I worry there is yet another substance that has worked its way into the American processed food cornucopia that has some potential for repeating the trans fat debacle: sterol esters.

Sterols are naturally-occurring oils found in vegetables, nuts, and numerous other foods in small quantities. Most of us take in 200-400 milligrams per day just by eating plant-sourced foods.

Curiously, the chemical structure of sterols are very similar to human cholesterol (differing at one carbon atom). Sterols, by not fully understood means, block the intestinal absorption of cholesterol. Thus, sterol esters, as well as the similar stanol esters, have been used to reduce blood levels of total and LDL cholesterol.

So far, so good.

The initial commercial products, released in the late 1990s, were Take Control (sterol) and Benecol (stanol), both of which were marketed to reduce cholesterol when 2-3 tbsp are used daily, providing 3400 – 5100 mg of sterol or stanol esters, about 10- to 20-fold more than we normally obtain from foods. Several clinical trials have conclusively confirmed that these products reduce cholesterol levels.

They do indeed perform as advertised. Add either product to your daily diet and LDL cholesterol is reduced by about 10-15%. In fact, in the original Track Your Plaque book, these products were advocated as a supplemental means of reducing LDL when other methods fell short.

In 2008, there are now hundreds of products that have additional quantities of sterol esters in them, such as orange juice, mayonnaise, yogurt, breakfast cereals, even nutritional supplements. Most of these products proudly bear claims like "heart healthy." Stanol esters have not enjoyed the same widespread application. (I believe there may be patent issues or other considerations. However, it's the sterols that are the principal topic here, not stanols.)

Now, here's where it gets a bit tricky. There is a rare (1 per million) disease called sitosterolemia, a genetic disorder that permits the afflicted to absorb more than the usual quantity of sterols from the intestine. While you and I obtain some amount of sterols from plant-based foods, absorption is poor, and we absorb <10% of sterols ingested. However, people with sitosterolemia absorb sterols far more efficiently, resulting in high blood levels of sterols that result in coronary disease and aortic valve disease, with heart attacks occurring as young as late teens or 20s. Treatment to block sterol absorption are used to treat these people.

There are also a larger number, though still uncommon (1/500) of people who have only one of the two genes that young people with sitosterolemia have. These people may have an intermediate capacity for sterol absorption.

Okay, so what does this have to do with you? Well, if you and I now take in 10-20 times greater amounts of sterol esters, do our blood levels of sterols increase?

Several studies now suggest that, yes, sterol blood levels increase with sterol ingestion. One study from Finland, the STRIP Study, showed that children who had double usual sterol intake increased blood levels by around 50%.

Similarly, a Johns Hopkins study in adults with only one of the genes ("heterozygotes") for sitosterolemia increased sterol blood levels by between 54-116% by ingesting 2200 mg of sterols added per day, despite reduction of LDL cholesterol levels.

Even people with neither gene for sitosterol hyperabsorption can increase their blood levels of sterols. But the crucial question: Do the blood levels of sterols that occur in unaffected people or in heterozygotes increase the risk of coronary heart disease? The answer is not known.

Despite the several clinical trials performed with sterol esters, all of them have examined LDL and total cholesterol reduction as endpoints, not cardiovascular events. It is conceivable that, while sterol esters reduce cholesterol, risk for heart disease is increased due to higher blood levels of sterols.

The question is not settled. For now, it is just a suspicion. But that's enough for me to steer clear of processed foods supplemented with these uncertain sterol esters. My previous recommendations for sterol ester products will be removed with the next edition of Track Your Plaque. Until we have solid evidence that there are no adverse cardiovascular effects of sterol esters, in my view they should not be part of anyone's heart-disease prevention program.

(The same argument does not seem to apply to stanol esters, such as that contained in butter-substitute Benecol, since stanol esters are not absorbed at all and remain confined to the intestine.)

Comments (16) -

  • lizzi

    9/13/2008 3:36:00 PM |

    My thoughts exactly.  I,too, used to use and recommend sterol ester containing margarine.  Stanols,as you pointed out, aren't absorbed, but who knows if they are worth the money. Obviously not everything that lowers our cholesterol is good for us. Still, lowering your cholesterol by 15% makes many of us feel like we just got an A+ on our report card, regardless of whether or not we have done something good for our health.
    I do believe that fish oil raises LDL cholesterol (probably large fluffy LDL) as it lowers triglycerides. But the evidence seems overwhelming that DHA and EPA are good for my health. But then I shudder about my report card.  Off smart balance, on Ghee, on 3,000 mg/day DHA/EPA.....

    Now they are esterifying fish oil. Lovasa, Big Pharma's new improved fish oil.  Now made more chemically stable. I wonder about it too. Is it the new trans fish oil?

  • Peter Silverman

    9/13/2008 8:28:00 PM |

    Since you wrote about how good almonds are for lowering LDL and how about half the calories don't get absorbed I have been eating close to half pound a day.  I wonder if that's a lot of sterol.

  • rabagley

    9/14/2008 1:54:00 AM |

    The next frankenfood.  Sigh.  When will we, as a culture, learn that it's extraordinarily difficult to synthesize something as nutritious and as wholesome as what nature provides?

    Give me butter, eggs, whole milk, chicken with skin on, and red meat with a healthy rind of fat any day of the week.  Twice on Sunday.

    On a diet dominated by those foods, my weight is steady as a rock and my lipid panel has never been better.

  • Anonymous

    9/14/2008 5:21:00 PM |

    The previous poster made an interesting comment abour esterified fish oil, which I am hoping Dr. Davis writes about one of these days.

    Fish oil's natural form is triglyceride, I believe, and there are only a couple of brands out there that sell this form. Everything else is ester.

    But is one form healthier than another? I know of 2 absorption studies that state omega-3 esters are the worst form regarding absorption. And are there any unknown health risks from taking altered Omega 3s long term?

    I'm personally sticking with the triglyceride form of fish oil for now, until this issue is studied properly.

  • lizzi

    9/16/2008 4:14:00 PM |

    A recent reference:  Vascular effects of plant sterols, Weingartner O, J Amer Clin Cardiol April 22, 2008.
       Mice with higher plant sterol levels had significantly more endothelial damage than those with low levels.

  • Anonymous

    9/17/2008 4:14:00 PM |

    Interesting discussion. I'm nurse practitioner (male). I've been fine tuning my diet and looking into fish oil's benefits for some time, as well as taking it.

    Would anyone know of non-esterified fish oil source(s) ?

    Also, with regards to the food content of esters, how do we know how to avoid them, since I can't seem to recall if labels display whether or not esters are part of the ingredients/manufacturing method.


  • Chipdouglas

    9/17/2008 4:20:00 PM |

    I'm a nurse practitioner (male) ever optimizing my diet, exercise and other modifiable risk factors for CVD.

    Regarding fish oil, would anyone know of company(ies0 manufacturing ester-free fish oil ? I recall one poster mentioning that most are esterified though.

    So far as foods, I don't think esters are shown on any food label--although I might be off. So, how would one avoid esters in foods, as it seems to be a growing issue.

    Many thanks.

  • Marilyn Mann

    9/18/2008 2:52:00 PM |

    Here's a post on this topic from another blog:

  • Anonymous

    9/18/2008 11:26:00 PM |

    "FACT: Researchers in Norway found that when 14 healthy male volunteers took equivalent amounts of omega-3 as ethyl esters or glycerol esters (triglyceride form), the absorption from both forms of omega-3 was just as good. As reported in the medical journal, “Thus, after administration twice daily for 14 days, the amounts of EPA and DHA in total serum lipids and in serum phospholipids were essentially identical for the two ester forms of the n-3 fatty acids.” [i]

    FACT: Another human study comparing the absorption of omega-3 fatty acids in the form of ethyl esters or triglycerides, showed that both were well absorbed and had produced results. According to the American Journal of Clinical Nutrition, “This study showed that n-3 fatty acids in fish oil given as ethyl esters or triglycerides were equally well absorbed.”[ii]"

    [i] The enteral bioavailability of eicosapentaenoic acid and docosahexaenoic acid is as good from ethyl esters as from glyceryl esters in spite of lower hydrolytic rates by pancreatic lipase in vitro. Biochim Biophys Acta 1993 May 20;1168(1):59-67

    [ii] Absorption of the n-3 eicosapentaenoic and docosahexaenoic acids as ethyl esters and triglycerides by humans. American Journal of Clinical Nutrition, 1991 Vol 53, 1185-1190

    "Res-Q 1250 offers an ethyl ester form of omega-3 which is appropriate for encapsulation (Res-Q 1250 Capsules), and a triglyceride form (Res-Q 1250 Liquid) which is appropriate for a liquid product."

  • susan

    10/6/2008 8:07:00 PM |

    I've noticed a huge increase in these and use them in both my cooking oil and margarine.  I wonder if I should switch?  It should just be common knowledge that there is a good and bad side to everything, I don't know why we are not more careful about this from the beginning.

  • Anonymous

    4/12/2009 7:24:00 AM |

    There is a review on plant sterol esters and hypercholesterolemia:

    It is open access !

  • Anonymous

    4/13/2009 7:50:00 AM |

    Interesting review on plant sterol esters! Seems to be a pretty hot discussion. Wounder why the stuff is still available !!!

  • patricia

    9/9/2009 4:31:11 PM |

    my 3 year old grandson has sitosterolemia and because of the way our food today is made with all the sterols to keep us healthy it is virtually impossible to buy him anything that it is ok for him to eat .   Plant sterols are in almost everything but not always advertised that they are there.   The long term outlook for our grandson is pretty bleak and i would be gratefull if anyone could give us some ideas on what it is actually possible for him to eat.

  • Anonymous

    9/10/2009 2:10:45 AM |

    To Patricia.  I am sorry that your grandson has sitosterolemia.  I am a 60-ish mother of three grown men and I raised them all on home cooking of whole foods: Fruits, vegetables, lean meats, lean dairy, cheese, yogurt, eggs, nuts, wild rice, small amounts of potatoes, olive oil and small amounts of butter. I was not a stay at home mom, either. It fascinates me that people have to ask the question, what to feed a child when you can't count on verity in packaging.  Please, feed them whole food, organic whenever possible.

  • buy viagra

    7/12/2010 1:37:38 PM |

    Sterol can be pretty dangerous as trans fat or sugar. So FDA must ban it too for the sake of our population. I wonder whatswhy FDA doesn't search healthy alternatives for us.

  • buy jeans

    11/3/2010 6:59:07 PM |

    They do indeed perform as advertised. Add either product to your daily diet and LDL cholesterol is reduced by about 10-15%. In fact, in the original Track Your Plaque book, these products were advocated as a supplemental means of reducing LDL when other methods fell short.