Cholesterol: Down With the Bad, Up With the Good

You’ll never look at a cave painting and see an ad for cholesterol lowering drugs. There are also no ads for the yummy, yet less-than-healthy foods that dominate the modern diet. Advances in the technology of food have yielded countless alternatives to the grasses, roots, nuts, berries and meat gathered by hand, prepared simply and eaten whole. Today, consumers do not face the daily challenge of avoiding predators. Instead, we strive to escape the danger of our own dietary habits that, while far less scary than a brontowhatsit, are just as lethal, particularly in terms of cholesterol.

Hitching a ride

Cholesterol itself is not bad. It is a vital element for cell membranes, hormones, vitamin D and bodily processes such as digestion. Our liver manufactures roughly three-fourths of the cholesterol in our blood. The remaining fourth comes from dietary sources such as meat, poultry, fish and dairy products. When we eat, the liver pulls cholesterol from the bloodstream. Between meals, the liver secretes cholesterol back into the blood as needed.

But cholesterol is a lipid—a fat-like substance that is not soluble in aqueous systems like our blood. Unable to travel on its own, cholesterol is carried by lipoproteins, small bundles with fat on the inside and protein on the outside. These carriers are distinguished by their density, a function of the ratio of protein to lipid.

Low density lipoproteins, LDL, carry cholesterol from the liver out to the body. Commonly referred to as “bad cholesterol,” LDL in the blood can build up as plaque on the inside of arteries, hindering blood flow and eventually causing a heart attack or stroke. High density lipoproteins, HDL, carry cholesterol from the various parts of the body back to the liver for reuse or excretion. Referred to as “good cholesterol,” HDL is believed to reduce LDL build-up. Blood cholesterol levels to shoot for are less than 200mg/dl (milligrams per deciliter of blood) for total cholesterol, less than 100mg/dl for LDL, and more than 60mg/dl for HDL.

Do or diet

Dietary effects on cholesterol levels are vast, although not as clear as you might think. The American Heart Association (AHA), Dallas, recommends a daily intake below 300 mg cholesterol per day; 200 mg for those with heart disease. According to AHA, though, understanding which fats increase LDL is the first step toward reducing the risk of heart disease. Research has shown that elevated cholesterol, especially LDL, is more dependent upon the type of fat in food rather than the presence of cholesterol. Studies have shown that high levels of saturated fatty acids are linked with high LDL levels. Consider fat from coconuts vs. pork. Pork fat has roughly 95 mg cholesterol per 100 gram, and approximately 56% unsaturated fatty acids, according to USDA’s National Nutrient Database for Standard Reference. Coconut oil, being non-animal in origin, contains no cholesterol. With approximately 86% saturated fatty acids, however, coconut oil is on AHA’s list of fats to avoid, right along with pork fat. Pro-coconut groups like the Coconut Research Center, Colorado Springs, CO, disagree, arguing that coconut oil’s saturated fatty acids are predominantly medium-chain fatty acids that actually help increase HDL and reduce the risk of heart disease.

Similar increases in understanding have changed perspectives on another food once believed to be a cholesterol-elevating agent – eggs. Although high in cholesterol (423mg/100g), eggs are low in saturated fatty acids (3%) meaning they will have minimal effect on blood lipids

Turns out, saturated fatty acids are the primary culprit in LDL elevation. Fatty acids contain no double bonds. Their carbon atoms are “saturated” with hydrogen atoms, allowing for the chains to pack tightly together, typically resulting in a fat that takes a solid form at room temperature. AHA recommends a limit of 7% of total daily calories come from saturates.

All saturates are not created equal, though. Unlike common saturates lauric, myristic, and palmitic acids, stearic acid has been shown to have a neutral effect on LDL levels. Stable through storage and cooking, stearic acid can be used to create spreadable solids such as shortenings, margarines, and spreads, or as a cream base for baked items.

When one or more carbon pairs are joined with a double bond, the fatty acid is referred to as “unsaturated.” Fats with one double bond are referred to as “monounsaturated.” Fats with more than one double bond are called “polyunsaturated.” Replacing dietary saturates with unsaturates helps avoid LDL elevation. Oils contain varying amounts of mono- and polyunsaturated fatty acids. Canola and olive oils are high in monounsaturates, approximately 63% and 73%, respectively. Safflower and soybean oils deliver 77% and 61% polyunsaturates, respectively.

Linoleic sunflower oil is roughly 65% polyunsaturated, predominantly the essential omega-6 fatty acid, linoleic. Once the most common form of sunflower oil, it is now one of three types of sunflower oil. Mid-oleic sunflower oil was developed in the mid-1990s by the National Sunflower Association, Bismarck, ND. It contains higher levels of oleic acid, yielding roughly 65% monounsaturated fatty acids. High oleic sunflower oil contains over 80% of the monounsaturated fatty acid oleic acid.

Looking for ways to make unsaturated fats more user friendly, scientists found that hydrogenating unsaturated fats yielded products that were solid at room temperature, exhibited improved resistance to oxidative rancidity and possessed higher melt temperatures. Hydrogen atoms could be positioned around the carbon chains in either of two configurations: cis or trans. The former is more common in nature. The latter is the most often seen result of hydrogenation, although, there are some naturally occurring forms of trans fatty acids, such as conjugated linoleic acid (CLA).

Prior to the 1990s, trans fats were touted as a healthy alternative to saturated fats. Research has, however, revealed that trans fats actually increase LDL and decrease HDL. These revelations have resulted in mandatory labeling of any measurable level of trans fats (greater than 0.5g/serving), and AHA’s recommendation to limit trans fats to less than 1% of daily calorie intake. Contrary to the usual behavior of trans fats, CLA demonstrated potent anti-artheroslerotic properties in a study published in the Aug. 2007 edition of the British Journal of Nutrition (98(2):264-275).

Fatty fish such as salmon, trout, herring and mackerel, as well as some types of algae such as Crypthecodinium cohnii or Schizochytrium, deliver a special group of polyunsaturates, long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are available in ingredient form. Another omega 3, alpha-linolenic acid (ALA) can be obtained from flaxseeds and walnuts. Once consumed, ALA is converted to EPA and DHA.

While all three of these fatty acids provide healthful benefits, the allowable claims are different. Products containing EPA and DHA are eligible for FDA-approved qualified heart-health claims: “Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease. One serving of [name of food] provides [x] grams of EPA and DHA omega-3 fatty acids. (See nutrition information for total fat, saturated fat and cholesterol content.)”

Phyt-ing the good fight

Plants possess specialized compounds called phytosterols. Similar in structure and function to mammalian cholesterol, plant phytosterols are separated into two groups based on the presence or absence of a double bond. Stanols are saturated (no double bonds) sterols. Despite the structural difference, both compounds are effective cholesterol-reducing agents.

Dietary cholesterol is absorbed through the intestinal walls as part of a combination of bile salts, fats and sterols called mixed micelles. Phytosterols displace cholesterol in the mixed micelles, reducing the amount of cholesterol that is absorbed. Consumption of 1.5 to 1.8 grams per day has been shown to reduce cholesterol absorption by 30% to 40%. Increasing levels to 2.2 grams per day resulted in a 60% reduction. Reduced absorption triggers increased clearance of LDL from the blood stream. And, while reduced absorption can increase the body’s own cholesterol production, net blood cholesterol levels are reduced. Studies show that daily intakes of 0.8 to 2.0 grams per day can provide serum cholesterol reductions ranging from 8% to 15%.

Phytosterols are lipids. Free sterols have a high melting point, around 140 C, and a waxy nature that hinders dispersion and solubility. Grinding to very small particle size can help, but dusting and lumping can still occur, especially in aqueous systems. Esterification, joining the phytosterols with fatty acids, provides processors with product forms that can be incorporated into high-fat products like spreads and dressings, as well as low-fat items like breads, cereals and yogurts.

Beverages have been a difficult application to address. Laura Troha, marketing manager for plant sterols and sterol esters, Cognis Nutrition and Health, LaGrange, IL, points out that while adding free sterols to beverages often results in high amounts of sediment, specialized new processing can combine free sterols with sodium caseinate or gum acacia to yield a free flowing powder. “These products have excellent water-dispersibility, making it perfect for beverage applications,” she says. “With 90% free sterols, you’re getting the highest amount of free sterol possible in a water-dispersible form.”

Products enriched with stanols or sterols may be eligible for health claims relating to coronary heart disease (CHD), provided they meet the criteria stated in 21 CFR 101.83. Sample statements include: “Foods containing at least 0.65 gram per serving of vegetable oil sterol esters, eaten twice a day with meals for a daily total intake of least 1.3 grams, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [name of food] supplies __ grams of vegetable oil sterol esters;” or “Diets low in saturated fat and cholesterol that include two servings of foods that provide a daily total of at least 3.4 grams of plant stanol esters in two meals may reduce the risk of heart disease. A serving of [name of food] supplies __ grams of plant stanol esters.” Studies conducted since these statements were developed have indicated that frequency of consumption may have no effect.

Tomatoes provide other nutritionally beneficial phytochemicals: carotenes and lycopene. While each compound offers benefits to consumers, research now indicates that they work together to provide synergistic benefits. A Finnish study indicates that daily consumption of tomato products such as ketchup and juice can lower total cholesterol by almost 6% and LDL by almost 13%. Increased blood levels of lycopene, beta- and gamma-carotene were also observed, further supporting the synergy theory. No heart-health claims are currently available for these compounds.

Mother Nature is not the only manufacturer of synergistic combination products. Chet Rao, sales & marketing manager, functional & nutritional products, Hormel Specialty Foods, Austin, MN, describes “a patented formulation that combines plant sterols and omega-3s in a way that provides synergistic effects in lowering cholesterol, particularly LDL cholesterol.” Phytosterols stabilize the omega-3s, protecting them from rancidity, while EPA and DHA improve the phytosterols’ cholesterol-reducing effect by lowering triglycerides. “Typical reductions will be 10% to 20%,” he says.

Lower cholesterol? Yes glu-can!

Another important contribution plants make to our diet comes in the form of carbohydrates we cannot digest. Collectively known as fiber, these materials are either insoluble or soluble. Soluble fibers are dispersible in water. Insoluble fibers are not. This dispersability difference was once thought to be the basis for health effects. While this notion has been disproven, the terms remain in use by nutritionists and FDA for labeling indications.

Insoluble fiber affects digestion by increasing bulk and decreasing intestinal transit time, but has little to no effect on cholesterol. Soluble fibers, on the other hand, specifically beta-glucans, serve to improve cardiac health by lowering LDL. Also referred to as a viscous fiber, beta-glucan forms a thick gel that reduces intestinal absorption of cholesterol, fatty acids, biliary cholesterol and bile acids.

Found in yeast, mushrooms, bacteria and algae, beta-glucan is especially prominent in oats and barley (5% and 7%, respectively). It is these latter sources, along with Oatrim (defined by 21 CFR Part 101 as “the soluble fraction of alpha-amylase hydrolysed oat bran or whole oat flour with a beta-glucan soluble fiber content of up to 10% (dwb) and not less than that of the starting material (dwb)”) and psyllium husk, that were initially named in 21 CFR, 101.81, “Soluble fiber from certain foods and risk of coronary heart disease (CHD),” which requires 0.75 grams soluble fiber per reference amount of whole oat, barley, or Oatrim, or 1.7g per reference amount of soluble fiber from psyllium husk.

“Recently the FDA expanded the soluble fiber health claim to include barley betafiber,” says Pam Stauffer, global marketing programs & communications manager, Cargill Foods, Minneapolis, MN. Defined by FDA as the ethanol-precipitated soluble fraction of cellulase-hydrolyzed and alpha-amylase-hydrolyzed whole grain barley flour, betafiber contains 70% or more beta-glucan. “High purity reduced-molecula-weight beta-glucan soluble fiber has some very exciting product formulation attributes,” she notes, “including the ability to formulate into clear beverages.”

“That’s soy folks!”

Research through the years has since confirmed soy’s reductive effect on LDL. Traditionally held theories about inhibition of cholesterol synthesis and absorption have, however, given way to new information. A study published in the Journal of Agricultural and Food Chemistry (2007; 55(26): 10599-10604) described how using soy protein hydrolysates indicates that soy’s bioactivity stems from peptides stimulating LDL-receptor transcription, thus reducing blood cholesterol level.

Regardless of the mechanism, 21 CFR 101.82 reads: “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [name of food] supplies __ grams of soy protein,” or “Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease. One serving of [name of food] provides __ grams of soy protein.” In addition to being low in cholesterol and fat, foods bearing this claim must deliver at least 6.25 grams of soy protein per serving.

R.J. Foster is a wordsmith with a B.S. in food science from the University of Wisconsin-Madison and over 15 years of experience in the food industry. He can be reached through his website,wordsmithingbyfoster.com.