Cholesterol

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Cholesterol is not fat, but a waxy substance (lipid) produced by all humans and animals, and is essential for bodily function. Cholesterol is found in all cells and is an important component of the central nervous system. Cholesterol is used to produce bile acids which are required for the body to absorb fats and fat soluble vitamins from the digestive tract. The body also uses cholesterol to make steroid hormones, and as the starting material for the synthesis of vitamin D.

 

Dietary cholesterol is the cholesterol consumed in foods while blood cholesterol is the cholesterol that circulates in the bloodstream. Dietary cholesterol does not automatically raise blood cholesterol when a high cholesterol food is eaten. Cholesterol does not have to be supplied by the diet like vitamins since the body produces all the cholesterol it needs. The amount of cholesterol the body makes is determined by weight. People who are obese produce more cholesterol than lean people and weight loss can decrease the amount of cholesterol the body makes. In most people the body balances the amount of dietary cholesterol by changing cholesterol synthesis in body tissues. Eating excess saturated fat causes the liver to put more cholesterol into the blood circulation and slows down the removal of blood cholesterol. This is why too much saturated fat in the diet is considered to be the most important dietary factor in causing high blood cholesterol levels and increased heart disease risk. Elevated levels of cholesterol in the bloodstream carried by low density lipoproteins (LDL) are associated with an increased risk of heart disease. The LDL cholesterol (“bad cholesterol”) is responsible for cholesterol entering artery walls resulting in blocked arteries. The high-density lipoprotein cholesterol, (HDL), helps move cholesterol from tissues to the liver for removal from the bloodstream. High values of HDL cholesterol (“good cholesterol”) are desirable. Currently, the new perspective on heart disease risk now identifi es the LDL: HDL ratio and the Total: HDL ratio (the sum of all cholesterol components to the “good cholesterol”) as the best indicator of heart disease risk. A review of over 30 studies published in the Journal of the American College of Nutrition in 2008 1 presents evidence that the LDL:HDL ratio is a better indicator of heart disease risk than either indicator alone because, according to the authors, the ratio refl ects the “two-way traffi c” of cholesterol entering and leaving the blood system.

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1. Fernandez ML, Webb D., The LDL to HDL Cholesterol ratio as a valuable tool to evaluate coronary heart disease risk. J Am Coll Nutr, 27(1);1-5,2008.

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Protein

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Eggs are a highly nutritious food making valuable contributions to one’s diet. A large egg provides six grams of high biological value protein, 10% of the daily value based on a 2,000 calorie diet. In fact, egg protein is the standard against which other food proteins are measured. Amino acids are the building blocks of proteins which the body requires for cells and tissues, regulation of body processes, and source of energy. When proteins are broken down and used for energy they cannot be used to build and repair body tissue since there is little reserve supply of protein in the body. Everyone needs a constant supply of protein to repair body cells as they wear out and to make new body tissues especially during times of growth. The National Academy of Sciences’ Institute of Medicine 2006 recommendation is to include 10-35% of daily calorie intake as protein. Recent research has indicated that muscle mass in older adults is better preserved when protein intake approaches the upper range of this recommendation.

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Proteins are composed of different combinations of 20 amino acids. The human body needs all 20 amino acids for the synthesis of its wide range of proteins. The body can synthesize 11 of these amino acids, but is unable to make 9 essential amino acids, which must be obtained from the diet. The egg contains all the essential amino acids in a proper proportion to fulfil the needs for human growth and tissue maintenance. The only food that contains a more ideal mix of essential amino acids than an egg is mother’s milk.

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Two eggs can be used to equal two ounces of lean meat, which is considered a serving in the Meat, Poultry, Fish, Dry Beans, Eggs, and Nuts Group of the USDA MyPyramid nutrition guidance meal plan. Eggs are lower in cost and in calories than many other animal-protein foods grouped in the same food group.

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Duyff, R. The American Dietetic Association’s Complete Food and Nutrition Guide. Chronimed Publishing, Minneapolis, MN. 1998. Dietary Reference Intakes, Institute of Medicine, The National Academies Press, 2006. www.MyPyramid.gov

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Choline

 

Choline is an essential nutrient needed for normal function of all cells. It is a critical component of the cell membrane and the neurotransmitter acetylcholine. The human body is dependant upon choline for normal muscle function, lipid transport, fetal development and memory center development. Eggs are an excellent source of the nutrient choline which, like folate, is essential for proper neural tube closure and nervous system function in the developing fetus. In fact, it has been found that dietary choline intakes vary enough in healthy women in the United States (from <300mg to >500mg/day) to significantly influence the risk of birth defects.1 Choline is also needed to control the buildup of homocysteine in the blood by contributing to the production of methionine, an amino acid needed for protein synthesis. Elevated levels of homocysteine in the blood have been associated with increase risk of heart disease. A choline defi cient diet has been shown to signifi cantly increase DNA damage in humans and is the only nutrient defi ciency shown to induce spontaneous carcinoma.2

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Two eggs contain about half the recommended daily amount of choline considered an adequate intake. During pregnancy and lactation, recommendations for choline intake are increased. In fact, the placenta delivers choline to the fetus by pumping it against a concentration gradient through the umbilical blood stream, indicating how important choline is for fetal development. Sadly, a review of USDA consumption study data shows that only about 10% of the population is consuming an adequate intake of choline from their diet. Among adults; younger and older women including pregnant women, had the lowest estimated mean intakes of choline.3 Egg intake can help close this unfortunate gap.

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1. Shaw GM et al. Periconceptional dietary intake of choline and betaine and neural tube defects in offspring. Am J Epidemiol, 160, 102-9, 2004.

2. Sanders LM and Zeisel SH, Choline: Dietary Requirements and Role in Brain Development, Nutr Today, 42(4), 181-6, 2007.

3. Jensen H et al, Choline in the Diets of US Population: NHANES, 2003-2004 presented at Experimental Biology 2007.

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Satiety

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One of many reasons we enjoy eating is that food can quell the feeling of hunger and provide us with energy to perform our chosen activities. A food that satisfies the pangs of hunger and gives us sustained energy is one that provides satiety. A major benefit of eating eggs is not only that it satisfies hunger but, it keeps you from needing snacks before the next meal which has been demonstrated to be a valuable asset in any weight reduction and weight maintenance strategy. Researchers at Wayne State University compared the reported feeling of satiety and weight loss of overweight and obese men and women who consumed either an isocaloric egg or bagel based breakfast while following a weight loss diet. They found that compared to an isocaloric, equal weight bagel-based breakfast, the egg-breakfast induced greater satiety and enhanced weight loss by 65% and a 34% greater reduction in waist circumference without a significant difference in blood lipid levels between groups.1

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1. Vander Wal JS et al. Egg breakfast enhances weight loss. Int J Obes advance online pub, 5 August 2008; dol:10.1038/ijo.2008.130

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Eye Health

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Age related macular degeneration (ARMD) occurs when the macula of the retina deteriorates and central vision becomes affected. ARMD occurs mostly in people over 50 years of age, and is the leading cause of irreversible blindness in the elderly. There presently is no cure for ARMD but laser therapy can be an effective treatment.

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New research suggests that ARMD may result from lack of certain nutrients in the diet. Vitamins and minerals, mainly antioxidants found abundantly in fruits and vegetables may reduce the risk of ARMD. One group of vegetable chemicals, carotenoids seem to have a protective effect against ARMD. Carotenoids exist in high concentrations in eye tissues and function as antioxidants to neutralize damage to cells caused by free radicals from sunlight. Carotenoids act as fi lters and form a pigment that protects the eye tissue from blue wavelength light, a potentially destructive band of radiation present in ordinary sunlight.

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Lutein and zeaxanthin are two xanthophyll antioxidants making up the macular pigment of the eye and recent research has shown they reduce a person’s risk and slow the progression of ARMD. The chicken egg yolk contains lutein and zeaxanthin within its fat-soluble matrix dispersed with other fat-soluble micronutrients such as vitamin A, vitamin D, and vitamin E. The yolk of the chicken egg provides a readily bioavailable source of lutein and zeaxanthin which has been shown to have greater bioavailablity than lutein from supplements and spinach. Researchers at the University of Massachusetts reported that the addition of one egg to the diet of subjects with an average age of 79 years signifi cantly increases both their serum lutein and zeaxanthin concentrations without elevating serum total cholesterol or the serum concentration of the LDL fraction.1 Similarly, women between the ages of 24 and 59 years were found to have increased serum zeaxanthin and macular pigment optical density after 12 weeks of eating an egg daily with no increase in their serum cholesterol concentrations.2

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1. Goodrow EF et al. Consumption of One Egg Per Day Increases Serum Lutein and Zeaxanthin Concentrations in Older Adults without Altering Serum Lipid and Lipoprotein Cholesterol Concentrations, J Nutr, 136: 2519–2524, 2006.

2. Wenzel AJ et al. A 12-Wk Egg Intervention Increases Serum Zeaxanthin and Macular Pigment Optical Density in Women, J Nutr, 136(10):2568-73,2006.

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Nutrient Density

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Eggs were designed by nature to be a complete nutrient reserve for the developing chick. Eggs are an important food for humans because of their high nutrition value at a comparably affordable price. A major concern however is that many Americans are sedentary and need to watch their caloric intake to maintain a healthy weight. Yet within their allowable caloric intake they must obtain all of the essential nutrients needed for health. In order to achieve this goal they need to consume foods that are nutrient dense and keep them from feeling hungry. Nutrient density refers to the quantity of one or more nutrients supplied by a food in relation to its caloric content. Nutrient-dense foods provide a high proportion of a person’s daily diet needs of essential nutrients while supplying a small proportion of the daily need for calories. Eggs are a nutrient dense food because they are an excellent source of high quality protein, provide a wide range of vitamins and minerals, and are relatively low in calories.

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One large egg has 72 calories with 13 vitamins and minerals. The amounts of various nutrients supplied in two large eggs are shown in the chart (right). As the nutrient daily values show, eggs provide a wide variety of nutrients for relatively few calories. One large egg offers only 7% of the total daily calorie intake of a person on a 2,000 calorie diet and provides 12.5% DV for protein, and 14% for riboflavin, and 8% or more of the daily value for several other nutrients including vitamins A, D, E, B-6, B-12, folate, iron, phosphorus, and zinc. And, it is important to realize that the egg is one of the few natural sources of vitamin D in the diet. With all of these nutritional benefi ts it is not diffi cult to see why eggs are considered a nutrient dense food.

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Conclusion

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Limiting egg intake would be a missed opportunity to benefit from the many naturally occurring nutritional benefits found in an egg such as:

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• High quality protein • Excellent source of choline

• Balanced assortment of essential vitamins and minerals

• Highly bioavailable antioxidants lutein and zeaxanthin

• Individual portion sized packaging, only 72 calories per egg offering satiety

• A moderate fat content

• A healthy ratio of mono-unsaturated and polyunsaturated fats to saturated fats

• Easily chewed food

• Easily prepared

• Abundantly available

• Culturally familiar

• Affordable low cost protein

• Extensive storage capacity: 4-5 week shelf life when refrigerated

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