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Life As We (Don't) Know It

Hybrid Biomolecules, Edible And Not

While writing up that eight-toxic-foods rebuttal the other day, I started reading up on Olestra, the “fake fat” that made the list. While it has to be considered a failure for its developers, I found the chemistry behind it interesting, and it got me to thinking.
First off, for those outside the chemical/biochemical field, a brief introduction to fat. We (and most other organisms) all store it in pretty much the same way: a backbone of glycerol (three carbons in a row, each with an alcohol), and each alcohol turned into an ester with a fatty acid. Those fatty acids are long carbon-chain compounds with a carboxylic acid group on the end, and when you’ve combined three of them onto a glycerol (fully loaded, as it were), you have a triglyceride. When the body wants to break that down for use as energy, it cleaves off the fatty acids one at a time (leading to diglycerides and monoglycerides), and the fatty acids are then chewed up two carbons at a time. (They’re made two carbons at a time, too, so the ones found in living creatures are very heavily biased towards even-numbered carbon counts).
That intro is enough to make sense of some of the things you’ll see in a blood test, like the tryglyceride levels and the free fatty acids. But there are a lot of details hidden in there. For one thing, there’s a whole suite of different enzymes that do the work of assembling and breaking down the glycerides, and they’re under all sorts of control mechanisms. And while glycerol is glycerol, the fatty acids themselves come in a huge variety – different lengths, presence of single or multiple double bonds up and down the chain (and keep in mind that double bonds in the middle of such a chain come in both cis and trans varieties), etc. So with this long list, glycerides get produced in all kinds of combinations, depending on diet, the tissue involved, and other factors. And beyond that, most all these components, up and down the list, are involved as signaling molecules on various proteins, substrates for other enzymes, starting materials for whole other chemical sequences, etc. Lipidology gets very complicated very quickly, and you may have noticed (via the changing dietary advice over the years) that we don’t quite have it figured out yet. Nowhere near.
So what’s Olestra? It’s nothing more than table sugar (sucrose) with its alcohol groups given the fatty-acid-ester treatment. What you end up with is a molecule that acts very much like normal fats – both of them are polyhydroxy compounds decorated with fatty acids, after all. But the enzymes that cleave the various fatty ester groups don’t recognize an esterified sucrose as anything they’ve seen before, and thus Olestra goes on its way uncleaved and unmetabolized. That, actually, is one of the things that seems to have sunk it in the market. A good-sized dose of Olestra has to go somewhere, namely, right through your digestive tract. The reports of the side effects this could bring on were not a good selling point, although there’s a debate about how often they were observed in the real world.
Otherwise, though, it seems to have been a reasonably convincing substitute for actual fats. I’ve never had any Olestra myself – it would be interesting to see if I could distinguish potato chips made with it from the conventional ones. Procter and Gamble were of the opinion that there was no discernable difference in taste or texture, but I’ve heard from people who say that they can tell under blinded conditions
Another side effect is that the stuff would tend to dissolve greasier substances and carry them along. Thus the problems with fat-soluble vitamin absorption with Olestra, which was compensated for by adding more of these vitamins (such as A, D, and K) the to potato chips made with it. It should be remembered that potato chips are not a major source of vitamins – well, not for most consumers – but the concern was that a steady diet of Olestra-containing foods could interfere with nutrient absorption from the other foods eaten at the same time. This is purely a greasiness/water solubility issue (logP being the medicinal chemist’s measuring scale), and Olestra has also shown an ability to sequester and remove things like ingested PCBs, for the same reasons. It doesn’t know a vitamin from anything else; it just knows what it can dissolve.
Olestra spent a lot of time in human testing. Since lipid molecules (as mentioned above) are involved in a lot of different processes, these studies were done to see if there were any signs of Olestra participating in other pathways. Nothing was ever found; the stuff was too odd-looking to the body’s enzymes to be digested, and too odd-looking to work its way into these other mechanisms as well. It just sort of made its way through.
But such cross-bred biomolecule hybrids are an interesting class. Just as you don’t see fully-esterified sugar molecules in cells, there are many other things like this that don’t show up – at least, as far as I know. The carboxylic acids at the C-terminals of amino acids, oligopeptides, and proteins don’t get handled in living systems as esters much (or if they do, I’ve missed it). Imagine glycerol with peptides esterified off the OH groups, for example, in sort of a protein-fat hybrid. Now try it with glucose – I’ve never seen that, either. In the same way, the OH groups on amino acids like serine are available to be esterified, but that’s another class of compounds I don’t know much about. Phosphorylation, yes, but not plain esters. It’s not like esters are somehow alien to biochemistry – you have the glycerides, for one, and esters of cholesterol are a well-known class of compound. Biochemistry as we know has just never gotten around to using these things.
It’s easy to imagine a slightly alien life form using fatty acid esters of the higher sugars as its energy storage class rather than stopping at glycerol. These creatures would have enzymes that would take Olestra apart like a wooden puzzle, and might be baffled at our own molecules. Somewhere, some unusual-looking alien is perhaps proposing glycerol esters as an indigestible substitute for the diet – worried, perhaps, about the way everyone’s tentacles are getting so swollen these days, what with the overabundance of cheap food and all, and sensing a market opportunity. Perhaps Zarkon & Yipslarg will succeed where Procter and Gamble failed.

43 comments on “Hybrid Biomolecules, Edible And Not”

  1. PPedroso says:

    Nice last paragraph!

  2. conspiracy theorist says:

    Zarkon and Yipslarg are a paid industry shills for Xfl9cztglorp Inc.

  3. luysii says:

    I told my late uncle about Olestra when it came out, noting the side effects of flatulence and bulky greasy stools.
    His comment:
    “I don’t need a pill to help me do that”

  4. In vivo Veritas says:

    I tried the chips vs. standard chips, blinded, when they first came out (at a P&G sponsored event). I couldn’t tell them apart, but I’m no chip connoisseur.
    You alluded to what might be the most interesting use for this stuff – lipid detoxification. Ron Jandacek was a P&G chemist on the Olestra patents, but now he’s an academic. He’s got a cool NIH funded project going on right now related to this:
    R21 ES019206 National Institute of Environmental Health Sciences. Intervention to Reduce Body Burden of PCBs in Residents of Anniston Alabama.

  5. Industry Guy says:

    Zargon and Yipslarg…..
    had the clean the coffee off my monitor after that one

  6. If Zarkon and Yipslarg hadn’t cut off their R&D tentacles in the Great Purge of Stellar Year 7634, they wouldn’t be behind Krokzarp Tentacle Tech!

  7. schinderhannes says:

    Esters build by random chance coupled with modern trace analytic can get you in trouble nowadays.
    To find out about your drinking habbits, trace amounts of fatty acid ethyl esters are analyzed in you hair, so one can find out about your dinking month ago….

  8. SP says:

    “The carboxylic acids at the C-terminals of amino acids, oligopeptides, and proteins don’t get handled in living systems as esters much”
    Aspartame, anyone?

  9. petros says:

    The side effects sound similar to those produced by Roche’s lipase inhibitor Xenical. These are described as rectal leakage!

  10. Tuck says:

    I got a complementary box of Nabisco olestra-containing products when it was first introduced.
    I assure you that one can tell the difference in taste; it may have merely been the lack of fats that your taste buds recognized, but they were notably disgusting. Other than the few things I tried initially, the rest went in the garbage.
    Olestra does pass through your digestive system unmolested, and its departure is unannounced and unscheduled.

  11. Puff the Mutant Dragon says:

    Worthy of note (perhaps) — MSN Health Living published an updated version of the Buzzfeed article after Derek had already critiqued it:
    you just can’t win with this kind of stuff — it’s like a weed, it keeps on growing

  12. Hap says:

    1) You can burn weeds for fuel or harvest them for energy. No, this is more like fungal infestations, or coal waste, with the toxicity well-known to originate in stupidity and generated in amounts that make it hard and expensive to get rid of.
    2) I can’t understand why Olestra didn’t do well, or Xenical. Why wouldn’t I want to buy products that give me the effects of losing my gall bladder? Perhaps there are other foods which could be used to give people the effects of diabetes, or hepatitis – that sounds like a lucrative potential food market, right?

  13. samadamsthedog says:

    Just wondering if those who consume significant quantities of mineral oil as a laxative have the same issues with vitamin scavenging. Or is mineral oil (a hydrocarbon) too non-polar to dissolve even greasy vitamins?

  14. Toad says:

    Aren’t Zarkon & Yipslarg on the SAB at Warp Drive Bio, or is that their IP firm?

  15. anon says:

    people drink mineral oil as a laxative? Wow. Do they also go for elemental mercury, perhaps to detoxify themselves of heavy metals? They thought that was a good idea a few centuries ago…
    And no, the polarity difference between mineral oil and olestra must be quite small, so that same concerns apply to the mineral oil vis-a-vis oil soluble vitamins.

  16. TX raven says:

    Two chemistry questions:
    1. Do any of the esters in olestra hydrolysis in the stomach in a significant extent?
    2. Being so greasy, I expect part of it will be absorb into the blood stream. Even get into the brain. Does it not disrupt cell membranes big time?
    Thanks for your thoughts…

  17. Mad Daog says:

    @11 Thanks for the link.
    Maybe Derek can write one with the catchy headline of “Why Reading MSN Healthy Living Could Kill You”

  18. hopefully not TMI says:

    Great post, Derek! Informative and hilarious. Your last paragraph made me think of the late great Far Side cartoon strip.
    As a former consumer of Olestra, my experience was like that of #4 In vivo Veritas — I couldn’t tell the difference, but I’m not a potato chip aficionado. I’m a witness that the most-known side effect is real, although in my case the exit was controllable, if you know what I mean.
    I think one of the reasons it did not succeed was chemophobia among the public. Despite the public’s general willingness to eat something with dozens of ingredients of various pronouncability, the fact that the makers were announcing “NOW WITH A NEW CHEMICAL!” may have turned people off. Also, I bet most people did not find themselves losing weight. Ever hear anyone say “I lost weight with Olestra”?

  19. Anonymous says:

    Olestra was great. I had an uncle who worked for Frito Lay, and tried lots of different olestra products. All tasted great.
    P&G is using their sucrose polyester in a lot of other areas now. Among other things, you can epoxidize the double bonds and cross-link the molecule into thermoset coatings. Biomacromolecules, 2011, 12 (6), pp 2416–2428

  20. Anonymous says:

    It appears that Olestra is an irritant of the large intestine, or at least “expedites” bowel movements. Thought less than savory, there is (I am being serious) an unmet need for effective laxatives. Phenolphthalein was removed from a number of commercially available laxatives in the late ’90’s. I can testify that there are many individuals, especially senior citizens (mostly ladies) who suffer severely from constipation and nothing worked as well as the aforesaid. I supply my aged mother and mother in law with said laxative that I brew, uhh, cook up with my wife’s help the generic equivalent of Exlax. The ladies are forever grateful. If you can’t take a dump except weekly or so, one could not appreciate the relief that they experienced once we supplied them with the officially proscribed laxative.
    If you’ve got lemons… make some lemonade.

  21. Vaudaux says:

    ” It’s not like esters are somehow alien to biochemistry – you have the glycerides, for one, and esters of cholesterol are a well-known class of compound. Biochemistry as we know has just never gotten around to using these things. ”
    Maybe human biochemistry has not gotten around to it, but gram-negative bacteria have. Fatty acids are directly linked to sugars by ester and amide bonds in the glycolipid called lipid A, the toxic moiety of lipopolysaccharides (endotoxin).

  22. Anonymous says:

    #17: unlikely they would hydrolyse to any great extent in the stomach since the esters are buried under a layer if grease and unlikely to come into contact with the (hydrolysing) water.

  23. Anonymous says:

    Hello All,
    Sorry for being off topic here. I am a long time reader, and a medchem rookie and I feel it is a highly enjoyable learning environment here.
    Recently, I have been trying to find ‘chemical tools’ for my enzyme of interest via target based HTS to be able to use later on in whole cells to help decipher the function of the enzyme in vivo. However, the whole effort seems to be failing mostly because of false positive hits (mostly redox compounds) which inadvertently fail during later work up. Lately, I realized that the assay validation focused on whether the assay was able to identify the known inhibitors as a hit, but did not focus on testing if the assay chemistry is prone to pick up false positives. While brushing up on Bayes theorem, I realized that this could be a potential reason.
    Ideally secondary assays are supposed to pick apart the false positives, however the chemistry in my secondary assay is similar and thus it seems useless. I was wondering if you could advise me whether a panel of frequent false positives exist, against which I could test my assay and atleast get an estimate of %false positives.

  24. Nick Semenkovich says:

    @petros Xenical / Orlistat is an interesting success. It’s a pancreatic lipase inhibitor (derived from a bacterial toxin) which (clearly) also causes fat malabsorption.
    Supposedly the side effect profile led to weak sales as a prescription medication, but incredible sales when it went OTC in ~2007.

  25. HTSguy says:

    @24 The NCI used to supply a plate of “challenge compounds”, but I don’t think those are still available. For redox cycler positive controls, see the hits for PubChem AID 828

  26. Algirdas says:

    “Biochemistry as we know has just never gotten around to using these things”
    Carboxylic esters seem to hydrolyze just a touch too easily, so I guess they must have lost out in the pre-biotic soup to polyamides and phosphodiesters. But consider – when the compounds are greasy and thus are exposed to lower water activity, carboxylate esters are abundant, as in phospholipids, triglycerides, waxes (2 genes for wax synthesis in humans, awat1 and awat2).
    As to esterification of C-terminus of a protein, I know of one example only – hedgehog protein, which in its active form is C-terminal cholesteryl ester. A review (PMID 15189162) mentions that there may be a few more proteins like that.
    For a protein-fat hybrid, GPI-anchor comes close, but of course it is amide linkage, not ester.

  27. gcc says:

    I’ve had Olestra-containing potato chips and they tasted good to me and I didn’t have any digestive issues with them at all. And actually, a friend of mine that has a very sensitive stomach had some too (before we found out they were made with Olestra) and they didn’t cause her any problems either.
    Still, I certainly wouldn’t seek them out. I just kind of get that this-stuff-really-can’t-be-good-for-you feeling when I think about Olestra and how it works. Perhaps not very scientific of me, but given how rarely I eat potato chips, I doubt it would be worth any marginal benefit.

  28. barry says:

    I’ve always found it bizarre that people would pay to ingest products that carry a “may cause anal leakage” warning rather than eat less. But for those who find humor in these things, just google

  29. gary says:

    Another example of a protein/lipid hybrid is prenylation of small G-proteins such as Ras. However, the link is a thioether bond via cysteine instead of an ester group.
    The WNT proteins are also palmitoylated by Porcupine via a ester linkage at a serine residue and a thioester residue at a cysteine residue.

  30. Hi Derek,
    I’ve been a fan of your writing ever since I was introduced to this blog a few months ago.
    Since you recently have been debunking myths about food, I was wondering if you could write something on organic food, if it really is beneficial or not. Today I came across this[1] post which explains why “organic is bad”. I’m not sure about correctness, but a lot of it it seems logical to me.
    Also, I’d love to see more “Things I won’t work with” posts — the form of humor you use there is exquisite!
    Thank you!

  31. Erik says:

    So the take away is that our future alien overlords may not be able to eat us after all, without serious digestive issues.

  32. UKPI says:

    Examples of protein esterification (and thioesterification) are found in post-translational lipidation. In addition, the C-terminal cysteines of isoprenylated proteins of the Ras superfamily are turned into their corresponding methyl esters. For members with a CaaX terminus such as Ras and Rho, the last three amino acids, aaX, are removed before ester formation.

  33. Ben Goldberg says:

    After learning of the initial problems with Olestra (namely, leaving the digestive system as greasily as it went in), P&G made a new version of the stuff, with the same name.
    The new version is hydrogenated, which raises it’s melting point sufficiently that it is solid at human body temperature. Food can still be fried in it, but when the stuff is eaten, it reaches the rectum it was a solid, not a liquid, and thus does not leak out.
    Sadly for P&G, the product name was sufficiently tainted by it’s early bad publicity (If you say Olestra, people think “anal leakage”) so that very few foods are made with it now, even though the problem’s been corrected.
    Why they don’t simply rename it, and market it as a fat substitute (instead of an oil substitute) I don’t understand.

  34. gippgig says:

    “The carboxylic acids at the C-terminals of amino acids, oligopeptides, and proteins don’t get handled in living systems as esters much”?
    Uh, every amino acid is esterified to ribose of tRNA before being incorporated into a protein by the ribosome as is the growing peptide chain.

  35. gippgig says:

    Has anyone screened for a bacterium that can use Olestra as a carbon source? (A good place to look would be downstream of an Olestra manufacturer.)

  36. milkshake says:

    the saturated version of Olestra found use as a edible grease-like substance applied on the skin of fruit, especially apples, so that they keep fresh longer on supermarket shelves
    Alien metabolism: You don’t have to go to another planet. There are species of fish called escolar and oilfish which are very tasty but unfortunately instead of fat have indigestible long-chain aliphatic monoster waxes. This fish lives few hundred meters deep in ocean but with industrial fishing they increasingly find their way into the food supply in Hawaii and Australia – they are tasty and cheap so they are used as a stand-in for more expensive species. If you consume a limited quantity of these olestra-fish in sushi rolls, not much happens but consuming a big serving of this fish is likely to send you to bathroom in hurry few hours after the meal

  37. Erebus says:

    Oddly enough, amino acid esters were popular as bodybuilding supplements circa 2006. ‘Leucine ethyl ester’, etc.

  38. crni says:

    I think Olestra was a great and bold idea. I wish P&G still had that kind of fortitude.

  39. Matthew K says:

    I’m a neuroscience guy, and although I don’t research feeding I have taught appetite and regulation a fair bit. My feeling about substitutes like Olestra and sweeteners, is that by fooling taste receptors they are essentially misrepresenting the nutritional content of food, and undermining the vast knowledge base the brain has about foodstuffs. Basically when we eat, we eat until sated, and satiety is determined by the brain not the gut. The reason is that digestion operates over the course of hours, and were we to eat until food-derived nutrients hit the bloodstream, every meal would last an hour or two. So instead we judge how much to eat, and base that judgement on a detailed understanding of the nutrient content of known foods plus the immediate analysis offered by tastebuds and mouth feel. People with short term memory damage will eat the same meal up to three times in a row if distracted in between servings.
    This calibration is so good that adults tend on average to gain 0.5kg a year in weight – the equivalent of one potato chip per day, excess to requirements. So we are very very good at deciding how much to eat.
    If you then begin to throw bad data into the system by mismatching the taste / feel of foods and the nutritional payload they carry, you undermine this knowledge. In the short term you will eat what seems to have enough energy content, but not actually receive that energy when you fail to digest the Olestra or aspartame, and that may help weight loss. But the new experiences will be noted by the brain, and over time things which taste like that will be judged as having lesser energy content if you give your system enough examples. Basically if Olestra tastes fatty, and fatty foods are normally high energy, repeated experiences of eating something which tastes fatty but doesn’t yield a lot of fatty acids and triglycerides in the blood after digestion, will persuade your brain that fatty taste doesn’t necessarily mean lots of energy content.
    So when you lose weight, and cautiously go back to eating foods with normal fats, you are likely to underestimate their energy content, and over consume.
    As I said, this is just my take, but imagine if you spent six months in an environment where gravity worked upside down – you could imagine catching a ball would be quite difficult on your return to normality. The nervous system uses experience to predict the world, and Olestra is essentially misinformation in the food choice domain.

  40. Anonymous says:

    “2. Being so greasy, I expect part of it will be absorb into the blood stream. Even get into the brain. Does it not disrupt cell membranes big time?”
    Ordinary triglicerides are not absorbed into the bloodstream, but are converted to micelles in the gut wall which enter the lymphatic system. The process is heavily enzyme mediated, and there’s neither any theoretical reason, nor evidence in the clinic, to believe the enzymes will work with Olestra.
    I think I may have tried Olestra products once. (I’m not a big chip eater.) My recollection is no particularly dramatic side effects, just a subjective sense that the chips didn’t feel quite right. Doubt that would hold up in a double-blind study.

  41. Guppy says:

    @Milkshake Jojoba oil is another example of a monoester lipid; the oil has excellent properties for cosmetic use, but is similarly indigestible.

  42. Morten G says:

    Triglycerides and their ilk is however a great example of how stomach acid catalysed ester hydrolysis isn’t actually a real thing. Sure, you get a great electrophile but the acidic water is a terrible, terrible nucleophile.
    Also: 39. Matt K has a point.

  43. Alan Christensen says:

    @luysii there are some products that our body can’t produce or that are not usually included in our diet. For example the quinoa, look for it. It is a really good Meal, and it is not expensive.

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