Despite extensive research into the environmental factors that affect cardiovascular health, the consensus regarding what constitutes a heart-healthy diet appears, once again, to have been thrown into a state of flux. This is especially true with regard to dietary fat.
The point of confusion centers on saturated fats, as recent studies have called into question long-standing recommendations to decrease dietary saturated fat and increase polyunsaturated fats in the diet.
This paradigm had been promoted for decades in order to lower the blood levels of low-density lipoproteins (LDL), referred to (somewhat over-dramatically) as “bad” cholesterol. Saturated fats were considered a major risk factor for cardiovascular disease.
Obesity, which has increased dramatically worldwide, is characterized by a chronic inflammatory state that lays the foundation for cardiovascular diseases, type 2 diabetes and even cancer.
Accumulation of excess body fat leads to hyperlipidemia, oxidative stress and other cardiovascular disease risk factors, including elevated circulating free fatty acid (FFA) and insulin resistance. The collective package is termed “lipotoxicity,” a status that can adversely affect liver, heart, skeletal muscle and pancreatic function. In experimental animals, this condition has been shown to be the direct effect of a high-fat diet.
A comprehensive—and overdue—assessment of the relationship between dietary fatty acids and coronary risk in humans was published last year in the Annals of Internal Medicine by researchers Ritam Choudhury, PhD, et al. The results, “Association of Dietary, Circulating, and Supplement Fatty
Acids with Coronary Risk: a systematic review and meta-analysis,” were based on the review of 32 observational studies on dietary fatty acids; 17 observational studies on fatty acid biomarkers in blood; and 27 randomized, controlled trials of fatty acid supplementation.
All fats are mixtures of different fatty acids. Fatty acids are the components that make up fats; they’re the chains of carbon atoms that determine their unique properties. Technically speaking, there actually is no such thing as a saturated fat or an unsaturated fat, but rather, fats that are rich in saturated fatty acids or unsaturated fatty acids.
Data from reviewed studies on dietary fatty acid intake have demonstrated that the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the dominant functional lipid components of fish oils, algae and other marine life, were associated with reduced coronary events. Total dietary trans fatty acids correlated to increased risk.
No other dietary fatty acids appeared to either increase or decrease cardiovascular risk.
Other reviewed studies considered the effects of circulating fatty acids as biomarkers of cardio events. All circulating, long-chain omega-3 fatty acids—with the exception of linolenic acid—correlated with reduced coronary events. Circulating omega-6 fatty acids presented a picture of coronary risk that was similar in its variability. Only arachidonic acid was associated with a substantial reduction in coronary risk.
Stats on Sats
The data on circulating saturated fatty acids were even more heterogeneous: Palmitic acid and stearic acids were associated with increased coronary events, yet odd-chain saturated fatty acids (generally markers of dairy fat intake) appeared to decrease coronary risk. However, it must be noted that circulating palmitic and stearic acids could also be a function of fatty acids synthesized from excess carbohydrates, amino acids or alcohol and are in a transitional state. These are the fatty acids the body makes from excess calories.
Odd-chain saturated fatty acids (most have an even number of carbons, 12, 14, 16, 18, etc.) were by far the least abundant fatty acids. The highest coronary risk was seen in circulating trans fatty acids (mostly from highly processed foods). When considering all the data, the authors concluded that their evidence did not support present recommendations for replacing saturated fatty acids with omega-6 unsaturated fatty acids as a method of reducing coronary risk.
The Choudhury paper received a firestorm of criticism from a number of prominent researchers who questioned the methods and expressed concern that spurious conclusions might be drawn from this study. In particular, the worry was that consumers would believe absolutely no harm would come from eating unlimited saturated fatty acids, or that saturated fatty acids even confer protection to the heart.
Most notable among the critics is Walter Willett, MD, PhD, chair of the Department of Nutrition of the Harvard School of Public Health.
Willett declared, “This paper is bound to cause confusion. A central issue is what replaces saturated fat if someone reduces the amount of saturated fat in their diet. If it is replaced with refined starch or sugar, which are the largest sources of calories in the US diet, then the risk of heart disease remains the same. However, if saturated fat is replaced with polyunsaturated fat or monounsaturated fat in the form of olive oil, nuts and probably other plant oils, we have much evidence that risk will be reduced.”
Willett further notes that “this meta-analysis contains multiple serious errors and omissions; the study conclusions are misleading and should be disregarded.”
Yet, as Choudhury’s paper implies, definitive statements in either direction cannot be legitimately made at this stage. Put another way, while statistics show that, at most, 50% of persons who suffer a cardiac event have high blood cholesterol (and its likely less than 20%), it should be recognized that this means the majority of sufferers do not.
Nuts for the Heart
The often-attacked advice to reduce saturated fatty acids is consistent with numerous studies that show consumption of nuts in moderation, including walnuts, pistachios, almonds, peanuts and others, reduces the risk of cardiovascular disease. Nut consumption is an integral part of the Mediterranean Diet, which is linked to low rates of cardiovascular disease.
This association is corroborated by two recent studies, one published recently in the European Journal of Preventative Cardiology. The study investigated cardiovascular mortality in diabetic patients following the Mediterranean pattern of eating, including increased use of nuts; high intake of (whole grain) cereals and vegetables; and reduced consumption of dairy and meat products.
A newly published study in the American Journal of Clinical Nutrition (AJCN), “Nut consumption and risk of mortality in the Physicians’ Health Study,” investigated the relationship between nut consumption and all-cause mortality in a large population. The population was a group (cohort) of US male physicians that have been studied for decades and is now known as “The Physicians Health Study.”
“The Physicians Health Study” is a large, long-term study initiated in 1982 to look at the effects of aspirin and beta-carotene on cancer and cardiovascular disease. Its initial finding was that daily low-dose aspirin decreased the risk of a first myocardial infarction by 44%. The study also showed no benefit or harm from beta-carotene. (Note: this refers to supplemental beta-carotene, not foods rich in beta-carotene or other carotenoids, which have been shown to be beneficial.)
The study began Phase II in 1997, testing the benefits and risks of three other widely used, but still unproven, supplements—vitamin E, vitamin C and a multivitamin—for their potential to prevent cardiovascular disease, cancer and age-related eye disease. The vitamin E and C portion ended in 2007 and found no protective effect when taking the supplements.
The multivitamin portion results were reported in 2012 in the Journal of the American Medical Association. It concluded that “among this population of US male physicians, taking a daily multivitamin did not reduce major cardiovascular events.”
As expected, in the AJCN study, participants with the highest nut consumption also had a greater intake of magnesium, fiber, and mono- and polyunsaturated fatty acids. These nutrients all are characteristic of nuts.
The study demonstrated a significant inverse relationship between nut consumption and mortality from cardiovascular disease (CVD). This apparent protection did not extend to mortality from cancer, stroke or coronary artery disease (CAD).
Surprisingly, in the AJCN study, the apparent benefit of nut consumption was not affected by body mass index (BMI) or diabetes. These results were consistent with previous observations of a 20% lower mortality rate among groups with moderate nut consumption compared to minimal or no nut consumption, as shown in the “Nurses’ Health Study” and the “Health Professionals Follow-Up Study.”
Smaller observational studies, including the Adventist Health, the Netherlands Cohort Study and a UK cohort study, also showed similar inverse associations between nut consumption and mortality among whites, African Americans and seniors.
The inclusion of pistachios in the diet of individuals at risk for CVD has been shown to improve their cardiometabolic profile. While plants do not have cholesterol, they have similar molecules called plant sterols. In fact, these compounds are similar enough to cholesterol that they can inhibit the absorption of dietary cholesterol.
Daily ingestion of plant sterols inhibit cholesterol absorption, and thus, when ingested at levels reaching 2g/day, are capable of lowering LDL cholesterol levels up to 10% with no adverse health effects. Plant sterols, such as sistosterol, specifically appear to play this important role in lowering LDL levels and increasing HDL levels.
The Mediterranean Diet has gained a reputation for being heart healthy. For many, the go-to ingredient that accounts for a significant share of the benefit is olive oil. However, the Mediterranean Diet also is highly varied and contains multiple components that are potentially cardioprotective. One emerging example is carob (Ceratonia siliqua). The simple carob pod has been a traditional food in countries that border the Mediterranean Sea.
Olive trees provide more than oil from the fruit to help prevent cardiac disease. Mediterranean folk medicine attached medicinal properties to the leaves; several years ago, olive leaf extract became the subject of closer scientific attention. The leaf of the common Olea europaea tree is a recognized source of components that appear to help lower blood pressure and cut risk of strokes.
The chewy pod of the carob tree is a rich source of insoluble fiber. Insoluble fiber generally benefits the large intestines, reducing the transit time and pressure against the relatively thin walls that are well-adapted to absorb water.
Soluble fiber has been shown to reduce blood cholesterol concentrations by trapping bile used to emulsify dietary fats. Since bile is made from cholesterol, the liver is forced to pull more cholesterol out of the blood in order to make up for the bile trapped by the soluble fiber and excreted.
The particular insoluble fiber characteristic of carob is believed to be cardio-protective by a very different mechanism, as outlined in a recent Journal of Nutrition article. In this study, conducted on rabbits, administration of carob insoluble fiber reduced the development of atherosclerosis induced by a diet containing 0.5% cholesterol, plus 14% coconut oil. Here anti-atherosclerotic effects of the carob pod fiber appeared to result from the reduction in endothelial inflammation and fibrosis.
Many other plants have shown cardio-protective ability—either through content of plant omega fatty acids, as is the case with chia and flax, or through antioxidant abilities—as with superfruits like berries.
Heart and Balance
Oats, barley, and many ancient and whole grains—such as millet and teff, as well as all legumes—are rich sources of soluble fiber. Whole grains also contain small amounts of oils in the germ and bran portions. Oils of grains tend to be rich sources of omega-6 fatty acids. Rice-bran oil lowers cholesterol up to 10%, and oat oil was found in animal studies to lower plasma and liver cholesterol levels by promoting the excretion of lipids.
Oats were one of the earliest ingredients to be marketed for heart health. In addition to their fiber benefits, they are a well-known source of beta-glucans. Beta-glucans are a bioactive polysaccharide shown in studies to lower blood cholesterol levels and help reduce liver LDLs. In this manner, they also help reduce risk of atherosclerosis and CVD.
Dietary guidelines always have stressed a balance of energy sources for a healthy heart, not extremes. The tendency to blame carbohydrates disproportionately for modern ills ignores USDA data on food consumption. Americans have never kept a low-fat diet. Such a notion is a fantasy that is too often repeated.
Since each macronutrient (protein, fat and carbohydrate) affects the other, very low-carb diets necessitate very high-fat diets, as protein cannot be the primary energy staple for long without resulting in physical impairment.
In spite of the current carbo-phobic climate, recent research confirms the association between decreased longevity and a chronic high-fat diet. It also is beginning to demonstrate possible molecular mechanisms behind high-fat diet-induced insulin resistance and the chronic inflammation that mediates cardiovascular disease. Though often not acknowledged, insulin resistance in animals is produced most often in cases of feeding a high-fat diet.
Diets rich in fat tend to be associated with the activation of the innate immune response, including cells called macrophages. Macrophages are called in to clean up fatty deposits found in blood vessel walls. When the macrophages take up the excess fat, they take on a foamy appearance. These “foam cells” are an important marker of atherosclerosis.
Activation of these macrophages also have been found to be responsible for a reduced lifespan in studies of lower-order life forms, such as drosophila flies.
The structure of Co-enzyme Q10 (CoQ10) was worked out by Karl Folkers, PhD, in the 1950s. Research on CoQ10 contributed to the discovery of how the electron transport chain works. This is the final stage of aerobic adenosine triphosphate (ATP) synthesis in the mitochondria. ATP is considered the “energy currency” of the cell.
The energy-demanding heart muscle is rich in mitochondria. The body manufactures CoQ10, but as it ages and deals with the many environmental factors that place oxidative stress on tissues, manufacture of CoQ10 becomes equally stressed.
The exact traits that make CoQ10 an essential part of the electron transport chain—its ability to shuttle electrons within the membranes of the mitochondria—make it a perfect fat-soluble antioxidant that can protect membranes from damage and reduce the oxidation of LDL cholesterol.
The other notable relationship between CoQ10 and the heart is by way of statin drugs used to lower cholesterol. This class of drugs functions by inhibiting HMG CoA reductase, an enzyme critical for cholesterol synthesis. The tail of CoQ10 consists of 10, 5-carbon units that arise from this synthesis pathway. Inhibition of cholesterol synthesis to dramatically lower cholesterol also inhibits the synthesis of CoQ10.
The body makes more CoQ10 than is necessary to run the electron transport chain due to its alternative role as an antioxidant. Still, deficiency—especially after about age 35—is a problem, and this is why CoQ10 often becomes a necessity when statin drugs are taken. However, CoQ10 does not experience the popularity it merits as a supplement.
CoQ10 and other ingredients for heart health have a huge place in the food and beverage formulations serving an aging population. Manufacturers have plenty of opportunities to provide consumers with products that perform cardioprotective function while also delivering flavor and satisfaction.
Botanical Boosts for the Heart
Herbs and spices are plants with a long record of known or perceived cardioprotective effects. Traditional herbs and spices characterize many ethnic cuisines as healthy, and for good reason: They often play a diversity of roles that include providing flavor, color, texture, natural preservation and protection against disease.
This includes cardiovascular damage and other conditions that lead to heart disease. Here are just some of the rising botanical stars noted for their cardioprotective qualities. (For more comprehensive information on these and other botanicals and health, check out “Botanical Benefits” in Prepared Foods’ April issue or online at www.NutraSolutions.com).
• Dietary cinnamon shows promise to affect with regard to affecting cholesterol levels. This has been demonstrated in rats, where administration of cinnamon has been shown to reduce triglycerides (blood fats) and total serum cholesterol and low-density lipoproteins (LDL).
• Curcumin, the naturally occurring phytochemical that gives turmeric is characteristic yellow color, has many purported biological properties that make it a prominent candidate for research in relation to natural disease prevention, as does its long and detailed history in ancient medicines, such as Ayurveda and traditional Chinese medicine (TCM).
In numerous studies, curcumin has been shown to function as an antioxidant, anti-inflammatory, anticancer, antimicrobial, antiviral and antifungal agent. In a study published earlier this year in the Journal of Molecular and Cellular Cardiology, researchers suggested a strong potential of curcumin as a cardioprotective agent.
This study used cell culture and mice fed a high-fat diet to explore the mechanistic basis of the anti-inflammatory and antioxidant properties of curcumin. In cell culture, administration of the free fatty acid palmitate, a 16-carbon fatty acid the body creates from excess calories, to cardiac-derived cells (called H9C2) triggered an increase in harmful reactive oxygen species, inflammation, apoptosis (cell death) and hypertrophy.
All of these changes were effectively suppressed by curcumin treatment. Oral administration of curcumin completely suppressed high-fat diet-induced oxidative stress, inflammation, apoptosis, fibrosis and hypertrophy that lay the foundation for atherosclerosis. A current explanation of the beneficial effect observed is that curcumin affects the expression of molecules that control inflammation.
• Garlic has been shown in many studies to reduce total cholesterol while increasing levels of HDL, the form of lipoprotein that transports cholesterol from tissues back to the liver, where it can be converted to bile, the pre-vitamin D compound (7-dehydro cholesterol) and various steroid hormones. Garlic also has been shown to inhibit platelet aggregation, lower blood pressure and increase serum antioxidant status. Allicin, the sulfur-containing compound responsible for the distinctive garlic aroma, has been shown to reduce fatty streaks characteristic of atherosclerosis of animals fed a cholesterol-rich diet.
• Ginger has been used as a medicinal herb for at least 2,000 years. Its active ingredient, gingerol, is believed to relax blood vessels, stimulate blood flow and relieve pain. Ginger contains phenolic compounds, including shogaols and gingerols. Coronary artery disease patients administered a single, 10g dose of ginger powder in a placebo-controlled clinical trial showed a significant reduction in platelet aggregation with no change in blood lipids and blood sugar. In animal studies, ginger extract reduced total cholesterol and serum LDL-cholesterol, and ginger extracts aided in the conversion of cholesterol to bile acids.
• Green tea is a major source of phytochemical compounds called flavonoids, especially the subclass known as catechins. Catechins have demonstrated multiple cardiovascular health benefits in years of studies. Not only do they possess powerful antioxidant capacity, catechins have the ability to inhibit an inflammatory response that induces the formation of adhesion molecules that make endothelial blood vessel walls sticky, thus contributing to the build-up of arterial plaque.