Prudent Diet and Preventive Nutrition From Pediatrics to Geriatrics: Current Knowledge and Practical Recommendations
(Part 4 of a Multipart Series)
Enas A Enas, A Senthilkumar, Hancy Chennikkara, Marc A Bjurlin
Coronary Artery Disease in Asian Indians (CADI) Research Foundation, and University of Illinois, Chicago, USA
Caffeine: Caffeine is found in coffee, tea, soft drinks, chocolate, and some nuts. Finland has one of the highest rates of per capita coffee drinking (13 kg/year).285 In a prospective study of 20 179 Finnish adults, coffee drinking was not associated with an increased risk of MI. However, consumption of large quantities of boiled unfiltered coffee raises cholesterol and homocysteine levels.285–287 In an experiment involving 10 volunteers, who consumed the equivalent lipid content of 6–7 cups of boiled unfiltered coffee daily for 6 weeks, the LDL levels increased by 33 mg/ dl.288–290 These data suggest that daily consumption of 1–2 cups of coffee is safe with no particular health benefits or risks.
Tea: Tea, the most widely consumed beverage in the world other than water, has been associated with lower cardiovascular risk.291–295 Unlike coffee, tea consumption is associated with a substantial reduction in LDL levels. Tea is rich in flavonoids. Green tea contains catechins, whereas black tea, formed from the polymerization of catechins, contains theaflavins.291 In one recent study, theaflavinenriched green tea extract reduced the LDL level by 16%.296 Tea is the major source of flavonoid intake in Japan (>80%); the Japanese consume an estimated 7 cups/day of tea compared to half a cup/day in the USA. Adding milk to tea, as is common in the UK and India, abolishes the beneficial effect of tea.297
Alcohol: Moderate intake of alcohol (one drink a day for women and 2 drinks a day for men) may decrease the risk of CAD.298 Recently, it has been shown that only one drink per week is enough to provide cardiac protection (45 ml of spirits or 350 ml of beer or 120 ml of wine); the cardioprotection is similar for beer, wine, whiskey, brandy, vodka, rum, and drinks in equivalent amounts.299,300 More than 2 drinks per day does not provide any additional protection and, in fact, the net effect may be harmful until the age of 45 years in men and 55 years in women.301 Like carbohydrates, consumption of large quantities of alcohol raises TG levels.6,302 Other dangers of excessive alcohol consumption includes alcohol dependence, liver disease, high blood pressure, obesity, stroke, traffic accidents, spousal abuse, suicide, and breast and other cancers. Given these risks, the American Heart Association cautions people against increasing their alcohol intake or starting to drink if they do not already do so.
Weight Gain and Weight Loss Diets
Excess calories and obesity: Diets of any type containing more energy than needed or expended will lead to obesity and dyslipidemia.303 A calorie is a calorie whether it comes from carbohydrates, fat, or protein. Excess calories of any kind will eventually be converted by insulin to body fat.304 A common misconception is that dietary fat of any kind is fattening, while low-fat and high-protein diets have slimming properties. It is absolutely vital that both physicians and the public understand that it is the excess calories and not diet composition that causes weight gain.304–309 There is no evidence of weight gain with a high MUFA diet, compared with a high carbohydrate diet, under isoenergetic conditions.310,311
Obesity is not only a reflection of overnutrition but also an important contributor to the mass dyslipidemia seen in India and western countries.6 Obesity in general is accompanied by the increased production of apo B and a decrease in the HDL levels.6,312 Humans have a limited capacity to store energy as carbohydrates. When carbohydrate intake exceeds storage and oxidation capacities, the excess is converted to fat by de novo lipogenesis that leads to high TG levels.313 This process is increased several-fold in people with the metabolic syndrome which, if left untreated, leads to overt diabetes (25-fold risk).312 Body fatness and not lean body mass is the principal determinant of diabetes and prediabetes.314 At a given BMI, Asian Indians have 7%–10% higher body fat; accordingly, BMI <23 is termed optimum; BMI 23–25 overweight, and >25 obese in Asian Indians. Likewise, the optimum waist circumference is lower in Asian Indians than Whites with a cut-off <90 cm in men and <80 cm in women.315 Although obesity and dyslipidemia are uncommon in less affluent societies, some individuals may be excessively sensitive to caloric excess.6
Fast foods rapidly produce plaques. The average American gained 9 lb in the past decade. A third of vegetable taken in the USA are either French fries or potato chips.305 In one study, overweight subjects who consumed fairly large amounts of sucrose (28% of energy), mostly as beverages, had increased energy intake, body weight, fat mass, and blood pressure after 10 weeks. These effects were not observed in a similar group of subjects who consumed artificial sweeteners.316 Restricting the dietary cholesterol can achieve a 3% reduction in TC level, whereas losing weight from trimming extra calories can reduce LDL by 5% to 20%.8
Weight loss: The recipe for effective weight loss is a combination of motivation, physical activity and caloric restriction; maintenance of weight loss is a balance between caloric intake, and physical activity, with life-long adherence. Each pound of body fat contains 3500 cal. Therefore, a person who consumes 500 cal less than he spends each day can lose 1 lb of fat a week. Any higher weight loss is due to a more severe caloric restriction or water loss rather than fat loss. The minimum caloric intake in a medically unsupervised weight loss diet is 1500 cal/day for men, and 1200 cal/day for women. Superior longterm participation and adherence is observed in a high-fat diet rather than a low-fat diet (35% v. 20%), especially in western cultures.309 The greater success rate is due to higher palatability of the high-fat diet provided by mixed nuts and lean meat.309 Furthermore, the long-term outcome of a reduced-fat diet consumed ad libitum for weight control is dismal. In one study, compared with the control group, weight decreased in the reduced-fat diet group significantly by 3 kg in 1 year but diminished to an insignificant 1 kg by 5 years.317 Until more information becomes available, "the prudent diet," which is a balanced diet, is the one to follow for young and old alike.318
Very low fat diet: Some experts have argued for a very low-fat diet (<10%).319 Since these diets are not highprotein diets (like the Atkins diet), they are in reality very high in carbohydrate. High-carbohydrate diets (the Macrobiotic diet) increase insulin resistance and induce the metabolic syndrome. In controlled trials, low-fat, highcarbohydrate diets decreased HDL levels. Replacing 10% of energy from SAFA with carbohydrate lowers the HDL levels by 5 mg/dl, even when the carbohydrate consumed is complex.62,173,320,321 There is also a marked increase in TG level, which makes LDL small, dense, and more dangerous.173,320–322 The effect is strongest when carbohydrates replace SAFA but is also seen when carbohydrates replace MUFA and PUFA. The effect is seen in both short- and long-term trials, and is therefore not a transient phenomenon. Therefore, replacement of SAFA must be achieved through increasing MUFA and not by carbohydrates. The adverse effects of high-carbohydrate diets (high glycemic load) in the metabolic syndrome and diabetes have not received due attention, especially in the Indian literature. The recommended carbohydrate intake is <50% of calories in people with the metabolic syndrome or diabetes (NCEP).
The allure and dangers of very low-carbohydrate, high-protein diets: High-protein diets that are extremely low in carbohydrates are touted as a new strategy for successful weight loss by many.323 Most such diets contain <10% carbohydrates, 25%–35% protein, and 55%–65% fat. Because the protein is provided mainly by animal sources, these diets are high in SAFA and cholesterol. Thus, these diets are truly high-fat diets masquerading as highprotein diets. Advocates of this diet often promote serious misconceptions about carbohydrates, insulin resistance, ketosis, and fat burning as the mechanisms of action for weight loss. To avoid excess load on the kidneys, the total protein intake should not exceed 100 g/day.324 More importantly, the body has an obligatory requirement for glucose of about 100 g/day, largely determined by the metabolic demands of the brain.324,325
In randomized studies, the extent of weight loss was small (4 kg), and adherence to the diet was low.326,327 In one study, although a low-carbohydrate diet produced a 4% greater weight loss at 6 months than did the conventional diet, the differences did not persist at 1 year. Furthermore, adherence was poor, and attrition was high in both the high- and low-carbohydrate groups. Longer and larger studies are required to determine the long-term safety and efficacy of low-carbohydrate, high-protein, high-fat diets.326 Two recent studies have provided insight into high-protein diets; the initial weight loss is due to fluid loss and ketosisinduced appetite suppression. The monotony of this diet also results in involuntary caloric restriction.326,327
The beneficial effects on blood lipids and insulin resistance are due to the weight loss, and not the change in caloric composition. Such diets increase LDL but decrease TG levels, in sharp contrast to high-carbohydrate diets, which increase TG, and decrease HDL levels. Although these diets may not be harmful for most healthy people over a short period of time, there are no long-term scientific studies to support their overall efficacy and safety. Markedly atherogenic profiles have also been reported in children with ketogenic diets. At 6 months, the high-fat ketogenic diet significantly increased plasma LDL levels by 50 mg/dl, triglycerides 58 mg/dl, apo B 49 mg/dl, and non-HDL cholesterol 63 mg/dl. The mean HDL-cholesterol levels decreased significantly.328 These lipid abnormalities in children are more than likely to translate into a high risk of heart disease as young adults.
High-protein diets also do not provide the variety of foods needed to continue the diet on a long-term basis. Highprotein diets are not recommended, and are perhaps dangerous because they restrict most healthful foods that provide essential nutrients, especially fruits and vegetables. Individuals who follow these diets are therefore at risk for compromised vitamin and mineral intake, as well as potential cardiac, renal, bone, and liver abnormalities overall.324 The consumption of a very low-carbohydrate diet for 6 weeks delivers a high acid load to the kidney, increases the risk of stone formation, decreases body calcium, and may increase the risk of bone loss and fractures.329 A highprotein diet is the ultimate antithesis of the prudent diet. It is important to realize that diets are not for 6 weeks, 6 months or 6 years, but for a lifetime. Although most quickfix diets have a short-term success rate >90%, the longterm failure rate is 100%.
Healthy and Contaminated Vegetarian Diets Omnivores or nonvegetarians outnumber vegetarians 10 to 1 in western cultures. Vegetarians include vegans who do not consume any animal products, ovo-vegetarians who consume egg, lacto-vegetarians who consume milk, ovolacto- vegetarians who consume egg and milk, and semilacto- vegetarians who eat small amounts of meat (<1 time/ week). Ironically, most self-defined vegetarians in western countries consume red meat and poultry, albeit infrequently, and in very small quantities. In a recent survey, only 1% of self-reported vegetarians did not eat meat in the USA, whereas about 6% of Americans who do not consume any meat did not identify themselves as vegetarians.330–332
Western vegetarians generally consume a healthier diet than omnivores; healthy foods such as soy, nuts, legumes and vegetables replace meat.333 They generally have twice the fish consumption of nonvegetarians.330 This is not the case with Indian vegetarians who shun fish. US vegetarians eat more whole-grain products, dark green and deep yellow vegetables, whole-wheat bread, brown rice, soy milk, tofu, meat substitutes, legumes, lentils, garbanzos, walnuts, and pecans.330 However, they eat the same amount of food as omnivores (1000 kg/year) but are usually thinner.334 A healthy vegetarian diet is characterized by more frequent consumption of fruits and vegetables, whole grains, legumes and nuts, resulting in higher intakes of dietary fiber, antioxidants and phytochemicals.335 Thus a vegetarian diet contains a portfolio of natural products that can improve both the carbohydrate and lipid abnormalities in diabetes.187
Vegetarians eat about two-thirds of SAFA, and one-half of cholesterol as omnivores; vegans consume one-half of SAFA and no cholesterol.9,336 Cholesterol levels among western vegetarians are 15–25 mg/dl lower than omnivores.337–340 Vegans have very low levels of LDL.341,342 Nuts, viscous fibers (from oats and barley), soy proteins, and plant sterols in vegetarian diets improve serum lipid levels.337 Furthermore, substituting soy or other vegetable proteins for animal proteins reduces the risk of developing nephropathy in type 2 diabetes.
With the exception of tropical oils, calories from plant sources are negatively correlated with CAD mortality, whereas calories from animal sources are positively correlated.16 Olive oil, fresh fruits, and vegetables are protective against heart disease, and seem to play a greater role in the French paradox than wine.16 Greater consumption of whole milk and other animal products were important contributors to Finland having the highest rates of CAD.16 In a prospective study of 4671 vegetarians and 6225 nonvegetarians, followed up for 10–12 years, BMI, TC, and CAD mortality was substantially lower among vegetarians than in the nonvegetarians. Other studies also suggest a protective effect of vegetarianism against many diseases. Vegetarians in western countries, but not in India, enjoy remarkably good health, exemplified by low rates of obesity,334,343 diabetes,344 CAD345–347 and cancer,337 and a 3–6 year increase in life expectancy.333,348 It is not clear whether this is due to abstinence from meat or to a greater consumption of heart-healthy food.349
Indian vegetarianism, a form of "contaminated vegetarianism": Most Asian Indians are lacto-ovovegetarians, unlike western vegetarians. About 50% of Asian Indians are vegetarians, but their lipoprotein levels, and rates of diabetes and CAD are no different from those of nonvegetarians.350,351 This phenomenon is due to contaminated vegetarianism, wherein vegetarians manage to consume excessive amounts of SAFA and TRAFA. In the CADI study, Asian Indian physicians in the USA followed a heart-healthy diet, with 32% energy from total fat, and 8% from SAFA, which is the recommendation by the NCEP.350 This appears to be an exception rather than the rule. In a Canadian study, Asian Indians consumed more fried foods and high-fat dairy products, such as full-fat milk than White Canadians.352 Although the intake of fat is 20%–25% energy in most Asian countries, many affluent Asian Indians consume >50% of their calories from fat.
Indian vegetarians consume liberal amounts of bakery products, butter, ghee, cheese, ice cream, curd, and other dairy products to overcompensate for not using meat. Contrary to popular belief, dairy products are the major source of SAFA, even in the western diet. It is worth highlighting that SAFA intake from high-fat dairy products increases LDL levels 3 times as much as it raises the HDL level.353 Meat is expensive, and consumed in very small quantities by Indian omnivores because of cultural and financial reasons. This is in sharp contrast to an annual per capita consumption of 124 kg meat and 23 kg fish by Americans.354 Prolonged cooking of vegetables, as is practised in India, virtually destroys every nutrient before it is consumed. A major problem overlooked in the Indian diet is the high glycemic load, resulting in high TG and low HDL levels.355 There appears to be a threshold for carbohydrate consumption with an intake >280 g/day often resulting in atherogenic dyslipidemia.350
Deep-frying and reuse of frying oil: Deep-frying, a common form of cooking among Asian Indians, is associated with spontaneous hydrogenation, and the formation of TRAFA. Reuse of oil used for deep-frying has been shown to produce endothelial dysfunction.356 Repeated reuse of such oil is exceedingly common among Asian Indians.357 HDL inhibits LDL oxidation primarily through its paraxonase activity; reuse of frying oil reduces paraxonase activity, and thus reduces the ability of HDL to prevent LDL oxidation.356–360 Fats that have been heated for prolonged periods in air contain many dangerous products from oxidation and breakdown of lipids. These compounds include hydroxy peroxides, aldehydes, polymers, hydroxy fatty acids, hydroperoxy epoxides, and hydroperoxy alkenals.361 In one study, fast-food restaurant cooking oil, just before the weekly change, was compared to unused oil. The repeatedly used oil had 4 times higher peroxide levels, 7 times higher carbonyl levels, and 17 times higher levels of acids.357
Ghee: Ghee is one of the most important sources of dietary fat and a common cooking medium.362,363 Use of ghee for deep-frying is considered gourmet among Asian Indians. Ghee or clarified butter is anhydrous milk fat, and is rich in MUFA (32%) and SAFA (62%), most of which are cholesterol-raising (myristic acid 17%, palmitic acid 26%). It is perhaps more harmful than butter due to the added presence of cholesterol oxides, which are generated during its preparation by prolonged heating of butter.362–364 Liberal dietary exposure to cholesterol oxides from ghee is a likely contributor to the high frequency of CAD among Asian Indians.364 There are conflicting data on the risk of heart disease with ghee.365,366 We are unaware of any biological explanation as to why Asian Indians can be immune to the unfavorable effects of butter and/or ghee. In addition to milk ghee, vegetable ghee (vanaspathi) is also immensely popular in Indian cooking, which exerts similar adverse effects through its high TRAFA content.
Tropical oils: The term tropical oils refers to coconut, palm kernel, and palm oils. These oils contain a very high percentage of SAFA, unlike other vegetable oils such as rapeseed oil (mustard oil), sesame oil, and rice bran oil, which are low in SAFA and high in MUFA (Table 3). Tropical oils are more atherogenic and thrombogenic than mutton and beef fat; the latter contains <5% myristic acid compared to 18% in coconut and palm kernel oils.104 In fact, these oils contain more TC-raising SAFA than animal fats—coconut oil 89%, palm kernel oil 71%, and palm oil 46% compared to <30% for butter fat, beef fat, pork fat, and chicken fat (Table 5).6,147 Tropical oils account for <2% of energy (<4 g/day) in the USA. but 25% or more in many other countries.147,367 Tropical oils are also found in commercially baked cakes, biscuits, cookies, and "snack foods". In Mauritius, a regulated change in the SAFA content by substituting soybean oil for palm oil resulted in a dramatic 32 mg/dl fall in TC level, and underscores the crucial role of cooking oils in population levels of TC.368
Coconut oil: Coconut oil contains mostly cholesterolraising SAFA (8% caprylic, 6% capric, 45% lauric, 17% myristic, and 8% palmitic acid).369 Rabbits fed a commercial chow diet containing 0.5% cholesterol and 14% coconut oil developed more severe dyslipidemia and atherosclerosis than rabbits fed the same diet containing olive oil instead of coconut oil. The average plasma TC level was 2-fold, and TG level 20-fold higher in the coconut oil-fed rabbits than in the olive oil-fed rabbits.28 Cox et al.369,370 have reported the cholesterol-raising effects of coconut oil to be similar to that of butter. In a comparative study of diets rich in beef fat versus coconut oil, the plasma TC, LDL, and HDL responses were lower with beef fat than coconut oil, commensurate with the lower proportion of cholesterolraising SAFA in beef (29%) than coconut oil (89%)371 (Table 5). A Malaysian study in which 22% of the energy intake was substituted with coconut oil found an increase of 40 mg/dl in TC, 29 mg/dl in LDL, 36 mg/dl in TG, and 4 mg/dl in HDL levels.372 The impact on LDL and HDL by using various fats as the sole source of fat in a Dutch population is shown in Fig. 1. Note the marked increase in LDL in contrast to HDL with the use of coconut oil.
Kerala, renowned for the universal and liberal consumption of coconut milk and oil, not only has the highest level of TC in India, but also the highest rate of CAD.373 The proportion of subjects with high TC (>239 mg/dl) in Kerala is almost double that of the USA. (32% v. 18%).374 This is in sharp contrast to the Japanese among whom only 6% have high TC.375 In Sri Lanka, which also has a very high rate of CAD, about 80% of the fat in the habitual diet comes from coconut.134,374,376
Consumers need to be educated about the atherogenic and antiatherogenic effects of various cooking oils, as well as animal and vegetable ghee. There is little awareness, and even controversy, about the atherogenic effects of certain foods and oils, especially in regions where the production, sale, and consumption of such oils have a profound impact on the regional economy.
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