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Fats to Feel Good AboutFats to Feel Good About

August 1, 2006

27 Min Read
Fats to Feel Good About

Pity the poor lipid. Its been battered about in the press, browbeaten by labeling mavens, and embraced by fickle fad dieters, only to get dropped like a hot, greasy French fry the minute the nutrition revisionists hop to the next it nutrient. Few nutrients have seen their reputations subject to such crushing contempt and heady praise in equal measure. But the relationship between lipids and health is more complexand more basicthan the simple good fat/bad fat story suggests.

That puts the onus on product developers to approach fat selection with eyes wide open. Ideally, every fats nutritional resume would look as impressive as its functional one. However, choosing the best fat for the job usually means finding the right compromise.

Fear not the fat 

Communicating the fat and fatty acid message is challenging, says Mary Van Elswyk, Ph.D., principal scientist, scientific affairs, Martek Biosciences Corporation, Boulder, CO. Some fats are desirable. Some are less desirable. Some should be avoided. Some should be embraced. Yet in a world that craves heroes and villains, fats often wear the black hat.

Thats no way to treat critical nutrients, according to Mark Matlock, senior vice president, food research, ADM, Decatur, IL. Certain fatty acids, he points out, are essential parts of the diet; we have to eat them because our bodies cant make them from scratch.

Why would the body want to make them in the first place? So it can produce phospholipids, for example, essential to functioning cell membranes. Lipids protect the neuronal axons that conduct nerve impulses. Fatty acids serve as precursors to hormone-like eicosanoids and are the vehicles for, and sometimes the sources of, fat-soluble antioxidants and vitamins, like lycopene and vitamins E and K.

They contain things such as plant sterols, which are potentially important bioactive nutrients and tocopherols, which are essential nutrients, adds Brent Flickinger, Ph.D., senior research manager of nutrition science, ADM. So valuable are fats that the USDA 2005 Dietary Guidelines for Americans states, A low intake of fats and oils (less than 20% of calories) increases the risk of inadequate intakes of vitamin E and of essential fatty acids and may contribute to unfavorable changes in high-density lipoprotein (HDL) blood cholesterol and triglycerides.

Triacylglycerols 101 

Diacylglycerol oilsperhaps blended with a distinctive, flavorful oil like almond makes sense in healthy salad dressings, particularly when reformulating to remove trans fats and cut saturated fats.
Photo: Almond Board of California

If fats are so remarkable, then why do they polarize us so? To answer that, we first have to revisit some basics of lipid chemistry, starting with nomenclature. What we call fat, lipid chemists name triglyceride, or, even more accurately, triacylglycerol, referring to the configuration of the lipidthree fatty acids, or acyl units, esterified to the three carbons of a glycerol molecule. Each of the esterification points has a positional, or stereoscopic, number1 and 3 for the outer spots, and 2 for the spot at the center. Thus, a triacylglycerol that loses both of its outer fatty acids becomes a 2-monoacylglycerol; snip off the central residue, and its a 1,3-diacylglycerol.

The most obvious distinction among fatty acids is the number of carbons in the acyl chain, which normally ranges in even intervals from 4 to 26. The bond linking the carbons is another distinguishing feature; when hydrogen atoms occupyor saturateall of a carbons bonding sites, the fatty acid is called saturated. Fatty acids whose carbons are free to form double bonds are called unsaturated fatty acids, or monounsaturated fatty acids (MUFAs) when they contain one double bond, and polyunsaturated fatty acids (PUFAs) when the double bonds number two or more.

A fatty acids relative saturation influences its physical properties, especially melting point. In general, more saturation confers greater solidity, and vice versa. Therefore, because fats and oils are the sum of their fatty acid parts, a lipid made predominantly of saturated fatty acids will remain solid at higher temperatures, whereas one with primarily unsaturated fatty acids tends to be liquid, even at low temperatures.

However, even highly unsaturated oils stiffen up in the refrigerator. Thus, classifying a lipid as uniformly saturated or unsaturated may misrepresent its composition and short-change the acyl diversity that makes cocoa butter so different from coconut oil. Even an unsaturated fatlets say soybean oil or corn oilhas some saturated fatty acids, says Pramod Khosla, assistant professor, department of nutrition and food science, Wayne State University, Detroit. And even a saturated fat like cocoa butter or palm oil has unsaturated fatty acids.

Achieving energy security 

Fatty acids are also collections of highly reduced, anhydrous carbon-carbon bonds, the sum of which nets a jackpot of stored caloric energy once oxidized9 kcal/gram vs. 4 kcal/gram for proteins and carbohydrates. Back in the feast-or-famine era, an ability to store fats caloric densityand to cultivate a taste for itproved evolutionarily proadaptive. Transformed into adipose tissue, dietary fat kept us warm on long winter nights.

Our postindustrial leisure society doesnt require as much fat. Yet our bodies innate suspicion that starvation lurks around the corner keeps fat cells running at a surplus, promoting everything from high blood pressure and heart disease rates to the prevalence of diabetes and obesity.

One thing that I think consumers often lose sight of is the substantial energy density represented by fat versus other macronutrients, says Robert Wainwright, technical director, refined oils, Cargill North America, Charlotte, NC. Consumers in general just dont understand that when it comes to caloric intake, fat is a very dense source. The American Dietetic Association (ADA), Chicago posits that a mere 10% reduction in dietary fat could trim 238 kcal from daily energy totals.

Transforming the marketplace 

While interesterified fats retain their healthful polyunsaturates and lack trans fats, they pose challenges when it comes to the fryer. Interesterified frying oils typically require frequent replacement.

With respect to illnesses such as heart disease, not all fats are created equal. Studies show that a high serum level of low-density lipoprotein cholesterol (LDL, or bad cholesterol) is the most important biomarker, far and away, when it comes to cardiovascular disease risk, Flickenger says. What appears to increase the bodys amount of circulating LDL is saturated fat.

Since the 1980s and 90s, this prompted consumers to scan products for the lard, tallow, butter and tropical oils that they learned were code for saturated fat. They got the message when the American Heart Association (AHA), Dallas, advised them to limit saturated fat to 7% to 10% of total calories, while keeping total fat calories to 30%. They noticed again last year when the USDA Dietary Guidelines for Americans set its sat-fat ceiling at 10% of total calories.

Our saturated fat intake now hovers around 12% to 13%, but we havent gotten here alone. Once the food industry saw the writing on the wall, it realized that it was in everybodys best interest to reduce products saturate content. However, doing so involved more than just putting formulas on a diet.

Thats because many foods depend on fats unique functional qualities. Food processors would be hard-pressed to find another ingredient that holds and transfers heat better. Were it not for fats ability to carry flavor, many foods would hardly be worth eating. Fats participate in vital browning reactions, delay staling in baked goods, and prevent ice-crystal formation in frozen foods. And as for the textures that make mealtime a pleasurable experience, many wouldnt be possible without fat.

Some applications rely specifically on saturated fats properties. You need saturated fats to get a solid fat, Khosla explains, and you need a solid fat in your cookies, your shortenings, your baked goods, etc. And with their stable single bonds, saturated fatty acids are less vulnerable than unsaturates to oxidation and the rancidity, off flavors and potentially harmful byproducts, such as hydroxyl-trans-2-nonenal (HNE). When manufacturers cut back on saturates, they needed a replacement that looked, tasted and performed the same. The answer lay in hydrogenation, a technology that bubbles hydrogen gas through unsaturated liquid oils at high temperatures and in the presence of a nickel catalyst to break the unsaturated double bonds and allow them to reform as single bonds.

If taken to full extent, hydrogenation completely transforms a liquid oil into a solid fat. At the chemical level, Khosla says, 18-carbon fatty acids like oleic and linoleic, which have double bonds, get fully saturated to stearic acid. But we didnt always run the process to completion. If you control the temperature, the catalyst, etc., you can stop at different stages and get a partially hydrogenated fat, he says. This left some of the fatty acids unsaturated, producing a partially hydrogenated oil whose texture split the difference between a saturates solidity and oils fluidity.

And, as Wainwright says, From a nutritional and functional perspective, that made all the sense in the world.

Whats the matter with trans ?

Then came the unintended consequences. Partial hydrogenation, while sparing some double bonds from saturation, switches their isomeric conformation from the cis isomerwhere the double bond creates a kink in the fatty acidto trans, a much straighter form. The straighter trans chains lay flatter, much like a saturated fatty acid, and thus pack more rigidly than their cis cousins. This is important, Khosla notes, because the reason that saturated fats are solid is because theyre straight-chain molecules and you can basically stack them on each other.

So a trans fat is an unsaturated fat that behaves much like a saturated onea dream come true for formulators. But not for those concerned with health. As David Dzisiak, global business leader for oils, Dow AgroSciences, Indianapolis, says of trans fats, Theres no other macronutrient that has that kind of health impact they do. Different fats have different shapes, and trans fat has a shape that really confuses our bodies. Our bodies arent really used to seeing it and so they have a pretty negative reaction to that shape.

Trans fat not only raises total blood cholesterol, it raises LDL while lowering HDL at the same time, both of which up heart disease risk. Studies also implicate trans fat in promoting inflammation and the development of non-insulin- dependent diabetes. Khosla says data suggests that trans fatty acids raise levels of lipoprotein a, or Lp-a, a molecule structurally similar to LDL thats another independent predictor of heart disease. A new study from Wake Forest University School of Medicine, Winston-Salem, NC, presented at the 66th annual Scientific Sessions of the American Diabetes Association, Washington, D.C., even found that trans-fat consumption may not only increase overall body weight but may also trigger a redistribution of adipose tissue to the abdomen where it, too, increases heart disease risk.

Granted, you have to assume that part of the problem is going to be dose-related, as Dzisiak points out. And its true that trans fats comprise only about 2% to 4% of total calories, according to the American Society for Clinical Nutrition (ASCN) and the American Institute of Nutrition (AIN), Bethesda, MD.

But even at low levels, Khosla says, they pose a threat. On a gram-for-gram basis, he claims, trans are twice as potent as saturated fat. In other words, if you take one gram of saturated fat and you replace it with one gram of trans, you get double the effect on cholesterol levels.

In June 2006, the AHA suggested specific limits for dietary trans fat: 1% of total calories. The first real studies started coming out in the 1990s showing that trans fats were bad, says Khosla, and then things just accelerated from there. If somebody had asked me 15 years ago what difference it would make if I had just flipped the hydrogen around the double bond on an unsaturated fat, I probably wouldve said, Nothing.

But, as Gerald McNeill, Ph.D., R&D director, Loders Croklaan, Channahon, IL, notes, if we had known 20 or 30 years ago what we know about trans fat today, One questions whether the FDA would ever have approved it.

Out, damned trans!

If anyone were to ban trans fatty acids, however, which ones would they ban? While trans fats from hydrogenation account for about 80% to 90% of whats in our diets, a small number arise naturally in meat and dairyand some may actually pose health benefits. (See sidebar, CLA:The Trans Fat You Can Love.) 

We focus on trans in general, Khosla says, but theres really no single trans isomer. Take vaccenic acid, common in milk fat and possessing a trans double bond on the eleventh carbon. In contrast, elaidic acidprominent in partially hydrogenated fats and perhaps responsible for their ill effects has its trans double bond on the ninth carbon. We dont know if each trans isomer is equally problematic, but prudence has dictated that we keep lumping them all together and saying that this is something we should do something about, he says.

The only rule binding industry, which FDA put into effect on Jan. 1, 2006, mandates a trans fat grams-perserving line item on all nutritional labels. However, the words trans and hydrogenated no longer get a free pass from label-readers. Even so, to completely eliminate trans fat I think is a bit extreme, Wainwright cautions. He cites reports from the Institute of Medicine (IOM) of the National Academy of Sciences, Washington, D.C., that stop short of recommending total trans elimination, in part because doing so, may, in fact, introduce additional noise into the diet and, as a result of such extreme dietary practices, we might in fact also start to take in inadequate amounts of other macronutrients and micronutrients.

In any case, the central issue for formulators has been aligning functional and nutritional concerns. From a nutrition standpoint, Wainwright asks, What do they want the label to look like? What kinds of words can appear on it, in terms of hydrogenation or partial hydrogenation? What kinds of source oils would they like or like not to have? Are there particular polyunsaturated contents they would like to deliver? They need to think through what they would like to deliver at the end of the day.

A replacement fats crystallization behaviorrate, extent and crystalline formcomes into play, particularly in quality parameters such as mouthfeel. In situations where structure and body are required from the fat, Wainwright says, we have to be considerate of those structural attributes. We neednt match a partial hydrogenates melt point exactly, he says, but we cant replace something that had a semisolid structure at room temperature with something that is liquid at room temperature and expect to have the same sort of outcome.

Matching partially hydrogenated fats oxidative stability with trans-free oils has been a challenge. Typically, what is happening is that people are generally having to step down to things that are not as oxidatively robust, Wainwright says. As these start to undergo oxidation, they develop some notes that are different from the notes that the consumer is accustomed to in the traditional product.

Saturates second chance 

So wheres a formulator to turn? Perhaps turn back the clockto saturated fats. When trans fat was introduced, McNeill points out, it was a one-to-one substitution for saturated fats. The real answer is just to do a one-to-one substitution for trans fat with saturated fat.

Nutritionally, that may at first seem daft. However, with trans fats displaying twice the cholesterol-raising potency of saturates, Khosla reminds us that any replacement of trans with saturates, on a gram-per-gram basis, is going to be beneficial.

While no ones suggesting that we start popping butter balls, were learning that some saturates dont raise cholesterol levels as much as others. Research on 18-carbon stearic acid in particular hints at what might be its neutral effect on serum cholesterol. According to Flickinger, A recent meta-analysis done by a leading group of researchers in Europe, published in the American Journal of Clinical Nutrition in 2003, actually showed that stearic is slightly on the negative side when it comes to LDLmeaning that it brings bad cholesterol down. Clearly, this supports that concept of neutrality.

Another saturate to reconsider is palm oil. Only about half of palms fatty acids are saturated (45% palmitic acid and 5% stearic), whichif youre the glass-half-full typemeans that the other half are unsaturated. In baked goods that require solid shortenings, palm oil mimics traditional baking fatsbutter and beef tallowthat dominated because they yielded the best sensory results. They, like palm, are high in palmitic acid, McNeill says, which forms very small, stable crystals that give you a very creamy texture in the final product, and are very effective in entrapping air bubbles.

Palm oils physical solidity is wellsuited to frying applications that demand a solid fat. Palm oil came into its own as a donut frying oil, McNeill says. It was a necessarily solid alternative to liquid frying fat, which drips out, soaks into the cardboard boxes, and looks awful. If you coat the donut with anythingsugar or a chocolate coatingit migrates into the sugar and turns it yellow, or into the chocolate coating and melts it. Finally, a donut fried in liquid oil is just plain floppier.

Interest in interesterification 

But not all manufacturers feel comfortable returning to saturated shortenings. When they dont, interesterification can deliver the functionality of a traditional saturate or a partial hydrogenate, but with less saturated fat, and without trans.

If we take soybean oil and fully hydrogenate it,Matlock says, we end up with a completely hydrogenated oil thats about 90% stearic acid in the solid fat portion. Then we mix, maybe, 20% of that materialdifferent proportions will yield different resultswith 80% totally non-hydrogenated soybean oil, whose fatty acid complement is primarily unsaturated, with about 55% linoleic acid (16 carbons, two double bonds) and 8% linolenic (16 carbons, three double bonds). Neither the liquid oil nor the solid fat has a measurable amount of trans fatty acids.

Processors then treat this physical blend with enzymes or chemicals that selectively cleave individual fatty acids from their glycerol backbones. These fatty acids then rearrange to create triglycerides with mixtures of saturated and unsaturated fatty acids. What that does from a functionality standpoint, Matlock explains, is it gives us a population of triglycerides with different fatty acid structures that all melt at different points. So now Ive got a solid at room temperature that, at mouth temperature, completely melts. When I look at the fatty acid profile, its even higher in PUFAs than a traditionally partially hydrogenated oil, because when youre partially hydrogenating to create solids, you completely wipe out the PUFAs.

But the fats health implications are unknown. A trans-fat replacement roundtable composed of research, industry and medical figures, and moderated by Dr. Dennis Bier, professor of pediatrics, Baylor College of Medicine, concludes that interesterification does not necessarily alter the cholesterolraising properties of the fat.

However, the jury has yet to weigh in on what effect widespread increases in dietary interesterified fat will have. Wainwright, for his part, maintains cautious optimism about interesterification. Its a good tool, a good solution, he says. But he also believes that industry needs to be very deliberate as we develop this, not to overburden the food supply.

As Khosla says: When we started on this whole trans journey many years ago, nobody wouldve predicted whats happened. And the same thing is true with interesterification because were basically generating triglyceride species with fatty acids in different positions than occur naturally. And if we suddenly have a vast amount in the food supply, what will that do?

When good oils go bad 

Its to interesterifications credit that it preserves many of the constituent oils healthful polyunsaturates. But when processing and storage situations cant guarantee tight temperature or oxygen controls, Wainwright says, we start to get concerned about the oxidative stability.

Theres no tougher neighborhood for a fat than a deep-fryer, and while oxidation of unsaturated fatty acids usually just raises concerns about rancid off-flavors and deleterious viscosity changes, the same process can spawn problems that include generation of deleterious compounds. A. Saari Csallany, Ph.D., and colleagues, department of food science and nutrition, the University of Minnesota, St. Paul, found that the oxidation of linoleic acid in vegetable oils that are heated above 185°C, even for as briefly as 30 minutes, produced HNE (a highly reactive and potentially toxic compound that disrupts proteins), DNA and other biomolecules. The levels rise in proportion to the length of heat exposure and accumulate over time. Reuse of frying oil is an extremely worrisome area, McNeill says. There are going to be all kinds of unforeseen consequences if polyunsaturated oils are used in, for example, fast food restaurants where the oil is reused for, perhaps, days. The best-practices, albeit costly, solution would prescribe changing out frying oil early and often, he adds.

Healthful fats, encapsulated 

No matter the application, any fat heavy in unsaturates will need protection from oxidation. Notes Prescott H. Bergh, sales and marketing, Ciranda Inc., Hudson, WI: We get a lot of calls from people trying to make a shelf-stable food bar, but they want to use what I would consider a highly reactive oil, like canola or safflower. And while those are great oils, they need to be kept in the dark, refrigerated, and used fairly quickly because theyre so oxidative. So if you want a shelf-stable bar with a six- to nine-month shelf life, thats probably not the best oil choice.

Unless the oil were spray-dried and encapsulated. Juan Menjivar, Ph.D., R&D director, Kerry Specialty Ingredients, Beloit, WIalong with some colleagueshave created emulsions of high-oleic canola, extra-virgin olive, and trans-free sunflower, spray-dried them, and offered them as encapsulated creamer powders. The beauty of this technology is that the fat is pre-emulsified and in powdered form, he says. The process grants the oils shelf lives on the order of a full year. The challenging part for us is to find oils that will be stable for that length of time, he says. If the oil can go through the drying process, then its relatively protected from oxidation by the encapsulation process.

While you cant deep-fry with the creamer powders, they work in applications amenable to a stable, healthful, pre-emulsified and spray-dried fat, including powdered and reconstituted beverage bases, soup and sauce mixes, bakery mixes, hot cereals, bars and alcoholic liqueur bases.

Another product to enhance nutritional appeal is encapsulated medium-chain triglyceride powders. While most fatty acids number 16 to 24 carbons and require both bile salts and multiple metabolic steps for conversion to energy, medium chain triglycerides, or MCTs (examples include six-carbon caproic, eight-carbon caprylic, and 10-carbons capric acids), are shorter and more water-soluble and bypass storage in fat cells for direct metabolism in the liver, where they yield about 6.8 kcal/gram.

MCTs occur naturally in milkfat, palm oil and coconut oil, the last of which, in interesterified and fractionated form, is their main commercial source. Primarily saturated, they display inherent stability that spray-drying and encapsulation only increase. And because manufacturers now interesterify MCTs onto canola oil, Menjivar says, You get some of the benefits of canola, some of the benefits of the mid-chain fatty acids, and then you get lower sats than you would with coconut. The MCT powder could replace fats in a sports bar, where its less likely to oil out than a liquid oil.

MCTs may also increase metabolism in general, thus promoting weight loss. However, dieters would need to reap about 50% of their calories from MCTs to experience benefits. Nevertheless, says Menjivar, they have found use in applications for people with special dietary needs, like infants or older people, because the MCTs are very easily digested.

Omega optimization 

In an age when malnutrition is less a result of starvation than of mismanaged food choices, how do we set consumption levels for healthful fats that will go beyond providing enough to achieving optimization? Its difficult research to do, says Van Elswyk. But its the animating question in the debate over omega-6s, omega-3s, and how much we should be eating.

Omega-6 and omega-3 fatty acids are polyunsaturates of varying length, the first of whose double bonds appear on the sixth and third carbon, respectively, from the fatty acids methyl, or omega, end. Theyre also perhaps the most researched and talked-about lipids on the scene, thanks to their potential health benefits.

Linoleic acid (LA) is the factory model omega-6; using a complicated series of reactions, the body transforms it into longer and more highly unsaturated omega-6s, such as the 20-carbon, four-double-bond arachidonic acid (AA). Similarly, alpha-linolenic acid, or ALA, is the basic unit of the omega- 3s. Of the long-chain omega-3s to which its a precursor, the two with the highest profile are docosahexaenoic acid, or DHA (22 carbons, 6 double bonds), and eicosapentaenoic acid, or EPA (20 carbons, 5 double bonds).

The human body cant make AA, DHA or EPA without LA or ALA, and it cant make LA or ALA, periodthese essential fatty acids are obtainable only through the diet. The IOM sets adequate intakes (AIs) of 14 grams/day of linoleic and 1.6 grams/day of ALA for men, and 11 grams/day of linoleic and 1.1 grams/day of ALA for women. At these recommended levels, the ratio of omega-6 linoleic to omega-3 ALA in the diet works out to about 10:1, which is approximately where American consumption now stands.

Van Elswyk points out, That doesnt necessarily mean that those AIs are going to help reduce risk of chronic disease or promote any particular health benefit. However, mounting evidence suggests that DHA and EPA figure in everything from heart disease prevention and infant health to inflammation and the immune response. FDA took note and, in 2004, issued a qualified health claim for foods containing DHA and EPA, stating, Supportive but not conclusive research shows that consumption of EPA and DHA omega- 3 fatty acids may reduce the risk of coronary heart disease.

Dietary sources of DHA and EPA include organ meats and, most notably, cold-water fatty fish, like wild Coho and Atlantic salmon, rainbow trout, sardines, mackerel, bluefin tuna and herring. We can form both from the ALA consumed in oils such as flaxseed, soybean and canola; walnuts and sesame seeds; green, leafy vegetables; and grass-fed beef. Omega-3 suppliers are also happy to help us increase consumption, with products for use in everything from energy bars to salad dressings to milk.

But, how much is enough? Anywhere from 32 mg up to 200 mg per serving would be consistent with an excellent-source claim for DHA, Van Elswyk says. Achieving cardiovascular results warrants higher levelson the order of 200 mg or above. If you were looking at an actual lipid-reduction effect a very specific lowering of triglyceridesdaily doses tend to be more toward a gram per day of DHA. But when you look at the qualified health claim for heart disease and long-chain PUFAs from DHA and EPA, FDA didnt set a minimum level because they felt that when you look at the cumulative data out there, its hard to say what the minimum would be.

Were seeing more and more of these nutritionally oriented oils occupy grocery shelf space, Wainwright says. The opportunity to incorporate positive fats such as omega-3s and trans-free options into mainstream products, he says is the most exciting opportunity as we move forward.Kimberly J. Decker, a California-based technical writer, has a B.S. in Consumer Food Science with a minor in English from the University of California, Davis. She lives in the San Francisco Bay area, where she enjoys eating and writing about food. You can reach her at [email protected]

CLA: The Trans Fat You Can Love

Its tempting to interpret the mere presence of a trans double bond as grounds for a fats banishment from the diet. But a trans fatty acid called conjugated linoleic acid, or CLA, proves that some trans fats arent so bad. In fact, CLA may actually do us some good.

An 18-carbon fatty acid with two double bonds, CLA is the product of a naturally occurring microbial hydrogenation of linoleic acid that takes place in ruminant animals stomachs. This changes factory-model linoleic acid into several CLA isomers by switching one of its cis double bonds to trans, and shifting that bonds position on the fatty acid chain.

The two most common CLA isomers are the cis-9,trans-11 and trans-10,cis-12 forms, and unlike trans fatty acids produced through industrial hydrogenation, they come bearing benefits. The former, also known as rumenic acid, appears to reduce the risk of such cancers as prostate, colorectal, stomach, lung and skin by slowing precancerous-cell growth; it may also reduce breast-cancer rates by affecting a gene that up-regulates programmed cell death, thus shrinking tumors. Studies hint at the ability of the trans-10,cis-12 isomer to help burn fat, enhance muscle tone, increase nutrient absorption, and improve the bodys efficiency at extracting energy from food.

Given these potential benefits, it makes sense that FDA excludes CLA from the censure of its trans-fat labeling rule. But the reasons have less to do with CLAs healthful properties than with FDAs definition of a trans fat, which, for labeling purposes, is any unsaturated fatty acid with one or more isolated double bonds. CLAs two double bonds are conjugatedseparated by a single bondand not isolated. Talk about your lucky breaks.

Milk and muscle of ruminants have traditionally been our main CLA sources. But many people are consuming less meat and dairy fat, and missing out on some of the aforementioned health gains. Then again, so may the ruminants themselves, as modern livestock feeding emphasizes grains over grass, reducing their linoleic acid intake and giving rumen microbes less raw material to work with. While CLA has yet to merit an established benchmark for daily intake, supplement manufacturers suggest its inclusion in formulas at around 1.5 grams per serving. (For more on CLA ingredients and formulation tips, see Fatty Acid Basics in the November 2001 issue of Food Product Design.)

The Power of Two: Diacylglycerols & a New Way to Metabolize Fat

What happens when you knock one of the fatty acids off a triacylglycerol molecule? It depends on which one. If you clip off the fatty acid in the central, or 2, position, you get a diacylglyceride (DAG) that the body is more likely to use as energy than store as fat.

In the intestine, the body secretes lipases. These lipases remove the fatty acids from the 1 and the 3 positions of a triglyceride, so you have a 2- monoglyceride remaining, explains Mark Matlock, senior vice president, food research, ADM, Decatur, IL. This passes into the intestines epithelial cells. Once its inside,the body, with its 1,3-specific lipases, puts those fatty acids back onto the outer positions of the glycerol, and the triglyceride gets packaged into chylomicrons and passes, ultimately, into the bloodstream, he says.

When a 1,3-diacylglycerol without a central fatty acid tries to pull off the same process, things work out a bit differently. First, before passing into the epithelial cell, it loses one of its fatty acids to become a 1-monoglyceride.

Inside the cell, the 1,3-specific lipases stick a fatty acid back onto the empty 3 position, but that lipase isnt specific to the 2 position, Matlock says,so it does a less effective job of putting a middle fatty acid on. What youre left with is a 1,3-diaclyglycerol that the body cant package into a chylomicron and instead shunts into the portal vein to the liver for beta-oxidation.

What does this mean for lipid nutrition? The end point is that it looks to promote more fat being used as energy rather than being stored, says Brent Flickinger, senior research manager of nutrition science, ADM. While DAGs are calorically the same as triglycerides, how they get metabolized after absorption is different, especially 1,3-DAGs.DAGs and triglycerides will have different effects on circulating triglycerides. As Matlock points out, after a meal whose lipids come primarily from DAGs, You will find that the postprandial triglycerides are lower, just like a lower glycemic index food would produce lower glucose levels.

ADM, in a joint venture with Kao Corporation, Tokyo, offers Enova, an 80%- DAG oil self-affirmed as GRAS for use in home cooking oils, home-use spreads, baked goods, salad dressings and mayonnaise, pizza, snack bars, soups, gravies, frozen entrées, and meal replacements. Made from soybean and canola fatty acids esterified to the 1 and 3 positions of glycerol, its not only a boon to circulating triglycerides and fat metabolism, but, with zero trans fat and the lowest saturated fat content of any conventional oil, its a boon to those looking for a fat whose nutritionals they can feel good about.

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