Prudent Diet and Preventive Nutrition From Pediatrics to Geriatrics: Current Knowledge and Practical Recommendations 

(Part 3 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

Whole Grains: The Foundation of Healthy Food

Whole grains have been the staple food worldwide for centuries, especially among vegetarians.^187,188 Whole grain and legume consumption not only decreases blood sugar and insulin resistance but also prevents the development of diabetes, particularly in people with the metabolic syndrome.^185,186 Whole-grain products are a good source of fiber, minerals, as well as several vitamins, including vitamins B and E. In a 12-year follow-up of 42 898 men, the risk of developing diabetes was 42% lower in those with the highest intake of whole grains. The risk was reduced by 52% in those who also engaged in physical activity, and 87% in those who also had a low BMI.¹⁸⁹ The risk reduction was attributed to higher intakes of cereal fiber and magnesium. Intake of whole-grain cereal is inversely associated with hypertension, CAD, stroke, and CVD mortality^190,191 (Table 7).^192–206 In another study, 25% –30% reduction in stroke was observed with the intake of whole grains—similar in magnitude to that of statins.^206–208 In sharp contrast, intake of refined grains increases the risk of diabetes, stroke and CVD.^{191,205–212} These prospective data highlight the importance of distinguishing whole-grain from refined-grain cereals in the prevention of CVD and diabetes.²⁰⁹ Efforts should be made to replace refined-grain with whole-grain foods.¹⁸⁹

A whole-grain food includes all the edible parts of the grain: the bran, the germ, and the endosperm.²¹³ Grinding or milling, using modern technology, leads to the loss of many beneficial micronutrients, antioxidants, minerals, phytochemicals, fiber, and much of the germ.²¹⁴ As a result, refined grain products are devoid of most vitamins and essential fatty acids, and contain more starch.²¹⁵ Because of the loss of bran and pulverization of the endosperm, refined grains are digested and absorbed rapidly, resulting in a large increase in the levels of blood sugar and insulin.²¹⁵ The common grains consumed in the West include wheat, oats, rye, rice, barley, and corn.²¹³ In the USA, rye bread is an important source of whole grain consumption, and results in a lower glucose response than white bread.^152,212 Whole-grain, ready-to-eat cereal contains >25% whole grain content by weight.¹⁸⁹ The recommended intake is at least 6 servings of grain (but not more than 11) with at least 3 being whole grains. The current intake of whole grains is less than half a serving/day or 15% of the grain intake. Only 2% of the 150 lb of wheat flour consumed per capita in the USA is whole-grain flour.216 Commonly consumed refined grain foods include white rice (idli, dosa), refined wheat and flour (white bread), pancakes, cakes, sweet rolls, English muffins, muffins, waffles, rolls, biscuits, pizza, and refined-grain ready-to-eat breakfast cereal, and their use should be minimized.

Nuts: A Wholesome Food and Powerhouse of Healthy Fats and Nutrients

Extensive studies during the past decade have transformed the image of nuts from fattening snacks to a wholesome and heart-healthy food to be consumed daily.^{198–202,215} Nuts are rich sources of protein, antioxidants, fiber, vitamins and minerals (especially potassium and magnesium). Nuts yield 5%–10% fiber, and 12%–25% protein. The consumption of nuts is also associated with a reduced risk of CAD in several studies.^{198–202,217,218} Yet, nuts are not generally recommended as snacks because of their high fat content.  Although nuts contain 45%–80% fat, most of the fats are the highly beneficial MUFA and PUFA (Table 8).⁶⁵

Nuts, particularly almonds, significantly improve lipid profiles because of the high fiber and MUFA component. The dose–response effects of almonds were compared with low-SAFA (<5% energy), whole-wheat muffins used as the control diet in a randomized crossover study involving 27 dyslipidemic men and women. Three isoenergetic supplements each (mean 423 kcal/day; 22% of energy) were consumed for 1 month. The supplement consisted of full-dose almonds (73 g/day), half-dose almonds plus halfdose muffins, and full-dose muffins. Full-dose almonds produced a highly significant decrease in the Lp(a) level (8%), LDL:HDL ratio (8%), and oxidized LDL (14%) compared to the control diet.²¹⁹ A 9% decrease in the LDL level occurred with 73 g/day of almonds, and 4% decrease with 37 g/day (handful) of almonds. This result translates to a 1% reduction in LDL for every 7 g/day of almonds, and is consistent with other studies.^220,221 More importantly, there was no difference in body weight between the almond and muffin diet.²²² Nuts are energy-dense, and contain 160–200 cal/oz. It cannot be overemphasized that energy from nuts should replace the unhealthy calories from SAFA and refined grains to prevent weight gain.

Consumption of other nuts (except coconuts) is equally beneficial. For example, a 10% reduction in the LDL level can be achieved by the daily consumption of 40 g of walnuts, peanuts or pistachios, 70 g almonds, 100 g macadamia nuts, and 110 g of pecans.^223–230 Nuts are as effective as increasing physical activity and trimming calories to increase HDL levels. Adding 2 oz or 60 g of nuts to a diet is a delicious way to decrease the TC/HDL ratio and CAD risk.^{8,14,23,231,232} Nuts also improve insulin sensitivity and prevent diabetes.²³³ In a prospective study of 83 818 women, 3206 new cases of type 2 diabetes were observed during a follow-up of 16 years.²⁰³ Consumption of nuts was inversely associated with the risk of type 2 diabetes after adjustment for age, body mass index (BMI), physical activity, smoking, alcohol use, and dietary factors (total calories, fat calories, and fiber). The risk of diabetes was reduced by 27% in those who consumed >5 oz/week of nuts or peanut butter compared to those who almost never ate these products.²⁰³ The proscription of nuts can no longer be justified. In fact, regular nut consumption as replacement for refined grains and high-fat meats is strongly recommended.^161,234

Fruits and Vegetables, the Natural Way to Consume Antioxidants and Flavonoids

Fruits and vegetables are rich in a myriad of nutrients and phytochemicals, including fiber, vitamins B and C, antioxidants, potassium, and flavonoids.^190,215 Phytochemicals are bioactive nonnutrient plant compounds linked to a reduced risk of chronic diseases. Fruits and vegetables decrease blood pressure, homocysteine, and cancer, especially that of the GI tract.^211,235,236 Since fruits and vegetables are rich in potassium, their liberal intake is recommended for the prevention and treatment of hypertension.²³⁷ Good sources of potassium include bananas, oranges, beans, fish, and dairy products. While you can get an overdose of potassium from pills, you cannot get an overdose of potassium from food. Moreover, dietary supplements do not have the health benefits associated with a diet rich in fruits and vegetables. For example, the antioxidant value of 100 g of apple is equivalent to 1500 mg of vitamin C.³

Several large studies, including one comprising 84 000 women and 42 000 men, have shown a significant inverse association between the consumption of fruits and vegetables and CVD mortality^190,194,195 (Table 8). The relationship is particularly strong with vitamin C-rich fruits, green leafy vegetables, and carotenoid vegetables (carrots, broccoli, spinach, lettuce, tomatoes, and yellow squash).^{192–196,238,239} Consuming fruits and vegetables (3 times/day compared with <1 time/day was associated with a 27% lower incidence of stroke, a 42% lower stroke mortality, a 24% lower CAD mortality, a 27% lower CVD mortality, and a 15% lower all-cause mortality after adjustment for standard CVD risk factors.¹⁹² In sharp contrast, consumption of potatoes and French fries increase the risk of CAD and stroke.^152,215

The landmark study of the Dietary Approaches to Stop Hypertension (DASH)240 has yielded tremendous insights into the benefits of increased intakes of various types of fruits and vegetables. The DASH diet is rich in vegetables, fruits, and low-fat dairy products (9 servings of fruits and vegetable combined per day).²⁴⁰ As compared with the control diet with a high sodium, the DASH diet with a low sodium intake led to a decrease in systolic blood pressure of 7 mmHg in normotensive individuals, and 11.5 mmHg in hypertensive individuals. The benefits of the DASH diet on lipoprotein levels were equally spectacular, with an 11 mg/dl decrease in LDL and a 4 mg/dl increase in HDL levels without significant effects on TG levels. Men had a greater reduction in LDL level than women, with no difference between Whites and Blacks. These results suggest that the DASH diet is likely to reduce the risk of CAD and can be recommended as an overall eating plan.²⁴¹ The current intake of fruits and vegetables is 3 servings/day each in the USA; only 23% consume the recommended 5 servings/day each.²⁴² The DASH diet is feasible in the real world, unlike the array of drastic diets which are impossible to continue for more than a few months.²⁴⁰

Flavonoids: Flavonoids are secondary metabolites that plants use to attract pollinators, repel predators, and to color flowers, leaves, and fruits.²⁴³ Important biological effects of flavonoids include the scavenging of oxygenderived free radicals, inhibition of LDL oxidation, increase in HDL levels, and protection against CVD and several chronic diseases.^244–248 The beneficial effects of these natural products on health were known long before the discovery of flavonoids. The major sources of flavonoids are vegetables (onions, kale, broccoli), fruits (apples, grapes, berries), olive oil, and beverages such as tea and wine.^244,248,249 Other sources include grains, bark, roots, stems, and flowers. Flavonoids present in red wine could be partly responsible for the low CAD mortality seen in red wine drinkers ("French Paradox"). Red wine is the major source of flavonoid in France and Italy (40%), onions and apples in Finland, and olive oil in Greece.²⁵⁰ The strong taste of extra-virgin olive oil is partly caused by the abundance of flavonoids.

Antioxidants: Oxidative modification of LDL accelerates atherosclerosis whereas dietary antioxidants prevent LDL oxidation. These antioxidants include vitamin C, vitamin E, beta-carotene, selenium, flavonoids, magnesium, and MUFA.²⁵¹ It is worth emphasizing that vitamin pills are no substitute for a healthy diet. Although an earlier study suggested some benefits from antioxidant vitamin supplementation, several subsequent studies involving more than 100000 patients have consistently failed to demonstrate any benefit. More recent studies suggest that possible harm may outweigh the benefit of these vitamins.^252–254 In a recent study, the use of vitamins E and C reduced the lipid-lowering efficacy of statins and niacin by 50%. More importantly, the clinical event reduction was lowered from 90% to 60%.²⁵⁵ The current scientific evidence does not support any protective role of vitamins E, C, and beta-carotene supplements; their use only creates a diversion away from proven therapies.²⁵⁶ The US Preventive Service Task Force (USPSTF) recommends against the use of beta-carotene supplements.²⁵⁷ It is worth noting that the oxidative modification of LDL continues to be relevant, and people should obtain their antioxidant vitamins from food sources. (However, folic acid fortification is recommended in women who are pregnant or might become pregnant.)

Non-nutritive Food Adjuncts

Fiber: The term dietary fiber was coined to describe the plant cell wall removed during the refining process.²⁵⁸ Dietary fiber improves coagulation, fibrinolysis, insulin sensitivity, LDL, and blood pressure levels.^259–265 Fiber is particularly concentrated in bran. Insoluble fiber shortens the intestinal transit, resulting in less time for carbohydrate absorption.²⁶⁶ Soluble (viscous) fiber, such as beta-glucan, which is found in oat bran, delays gastric emptying, and slows the absorption and digestion of carbohydrates. These processes lead to a slower release of glucose into the circulation, resulting in a reduced demand for insulin.^187,189,267 An intake of 16 g of total fiber is associated with a 12% decrease in CAD risk.²⁶⁸ FDA has permitted cardiovascular health claims to be made by the industry for 2 viscous fibers, beta-glucan and psyllium.²⁶⁹ Psyllium supplementation significantly lowers TC and LDL levels; it is safe and well tolerated.²⁷⁰

The benefit of whole grains appears to be mediated primarily through the greater intake of fiber, and is greater with cereal fiber than vegetable or fruit fiber.^{212,263,264,271,272} Approximately one-fourth of the fiber provided by cereal sources is water soluble.²⁶⁸ Cereal fiber consumption is associated with a 21% lower risk of incident CVD, and 30% lower risk of diabetes.^{164,188,259,273} (Fig. 2). Cereal fiber consumption may reduce the risk of CVD via the substitution effect, replacing the intake of other foods having potentially detrimental effects. In addition to cereal grains, legumes are also excellent sources of water-soluble dietary fiber. Half a cup of cooked beans contains, on an average, 6 g of total fiber and 2 g of soluble fiber.²⁷⁴

The current ADA recommendation for a healthy diet is to consume 25 g/day of fiber with about one-third from soluble fiber. In one study, type 2 diabetics consuming 50 g/day of fiber (25 g soluble, 25 g insoluble) lowered the blood sugar by 13 mg/dl, plasma TC by 7%, and TG levels by 10%.²⁷⁵ Thus, a high intake of dietary fiber, above the level recommended by the ADA, particularly of the soluble type, improves glycemic control, insulin levels, and plasma lipid concentrations in patients with type 2 diabetes.²⁷⁵

Plant sterols and stanols: Plant sterols and stanols are structural analogues of cholesterol. Low-fat plant stanolcontaining margarines lower plasma LDL levels (by as much as 12%) in those with hypercholesterolemia by suppressing cholesterol absorption.^276–279 In one randomized controlled study, the reduction in LDL with such supplements was similar to 20 mg of lovastatin (30% with statin v. 28.6% with diet).²⁸⁰ Various plant supplements have been shown to reduce LDL by 40% (Table 9).^{146,219,265,280–283}

Spices: Plants have the capacity to synthesize a diverse array of chemicals. Spices are aromatic vegetable substances, the significant function of which is food seasoning rather than nutrition. Typically, spices are the dried aromatic parts of plants, generally the seeds, berries, roots, pods, and sometimes leaves, that mainly grow in tropical countries. Common spices include turmeric, paprika, saffron, cinnamon, nutmeg, red and black pepper. In contrast, herbs used in cooking are typically composed of leaves and stems.²⁸⁴

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