Journal of Nutrition and Health (J Nutr Health) 2014; 47(6): 385 ~ 393 http://dx.doi.org/10.4163/jnh.2014.47.6.385 pissn 2288-3886 / eissn 2288-3959 Review 계란의영양적특성및건강에미치는영향 * 양은주 1 이영은 2 문현경 3 호남대학교식품영양학과, 1 원광대학교식품영양학과, 2 단국대학교식품영양학과 3 Nutritional roles and health effects of eggs* Yang, Eun Ju 1 Lee, Young Eun 2 Moon, Hyun-Kyung 3 1 Department of Food and Nutrition, Honam University, Gwangju 506-714, Korea 2 Department of Food and Nutrition, Wonkwang University, Iksan 570-749, Korea 3 Department of Food and Nutrition, Dankook University, Yongin 448-701, Korea ABSTRACT Purpose: The aim of this study is to examine the effects of egg consumption and suggest proper guidelines for consumption of eggs by determining the relationship between eggs and cholesterol. Methods: Literature review was conducted on the relationship between nutritional, functional properties of eggs and serum cholesterol, as well as cardiovascular disease. Results: Eggs, which are a good protein food with complete amino acid composition, contain vitamin A, riboflavin, vitamin B1 2, folic acid, vitamin D, vitamin E, vitamin K, calcium, iron, choline, selenium, β-carotene, lutein, zeaxanthin, etc. However the egg yolk has a high cholesterol content, which is associated with chronic diseases, including heart disease and hypertension. As a result, its intake is subject to regulation. Outbreak of heart disease by yolk intake can show different results depending on the characteristics of the subjects, amount of egg intake, and the implications of other foods eaten. It is difficult to determine whether eggs are beneficial, as they are the main supplying source for other major nutritive elements as well. Several research studies insist that when cholesterol intake increases by 100 mg, the level of serum cholesterol increases by 2.2~4.5 mg/dl and when serum cholesterol increases by 1%, the risk of heart disease increases by 2%. This indicates that a large intake of eggs can increase the risk of heart disease. Although the cholesterol of egg yolk and serum cholesterol are correlated, it is insufficient to conclude that only cholesterol and not other components are related to heart disease. In fact, other components in egg such as various unsaturated fatty acids and phospholipids could be related as well. Rather than concluding egg as a good or bad food according to its cholesterol content, it is important to define egg as a part of dietary patterns. Conclusion: Generalizing an indiscriminate and uniform amount of egg intake for all seems inadequate. However, patients with diabetes or heart disease should pay particular attention to the amount of egg intake. As for the norm, eating egg with vegetables as a substitute for other animal products seems beneficial. KEY WORDS: eggs, serum cholesterol, cardiovascular diseases, guidelines 서론 계란은아미노산조성이우수한완전단백질식품으로서비타민 A, 리보플라빈, 비타민 B 12, 엽산, 비타민 D, 비타민 E, 비타민 K, 칼슘, 철, 콜린, 셀레늄, β-카로틴, 루테인, 제아잔틴등을함유하고있어단일식품으로서인체에필수적인중요영양소를골고루함유한식품이다. 그러나계란노른자 1개의콜레스테롤함량이 185~240 mg으로일반인의하루콜레스테롤섭취목표량인 300 mg/dl에쉽게도달할수 있는수준으로심장병, 고혈압등과같은성인병을야기할수있으며, 특히심장병환자나심장병발생의위험이높은사람에게는섭취가제한되고있다. 1 계란섭취에대한건강상의장단점에대해논란이되는이유는식품으로섭취한콜레스테롤의체내흡수및대사, 배설등의작용이복잡하고, 섭취대상의유전적인특징, 건강상태및콜레스테롤섭취수준, 함께섭취한식품등에따라콜레스테롤이인체에미치는영향이다른것으로보고되고 2-4 있기때문이며, 계란의콜레스테롤에대한상반된연구결과가제시되고있다. Received: October 29, 2014 / Accepted: December 5, 2014 *This work was supported by grants from National Agricultural Cooperative Federation. To whom correspondence should be addressed. tel: +82-62-940-5414, e-mail: ejyang@honam.ac.kr 2014 The Korean Nutrition Society This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
386 / 계란의영양적특성 콜레스테롤섭취량이증가하면혈액중 LDL-콜레스테롤양이 10% 까지증가될수있으며, 혈액중 LDL-콜레스테롤수준을 12% 감소시키면관상동맥질환의발생위험도를 19% 까지감소시킬수있는것으로보고되어실제식사중의콜레스테롤양을감소시키는것이중요하다고주장되고있다. 4 그러나일부연구에서는계란노른자의콜레스테롤이심장병의발생과직접적인관련성이적다는주장이제기되었으며, 5,6 여러연구에서계란과심장병, 사망률과의관계에관련하여일관성있는연구결과가보고되기보다는상반되는연구결과들이보고되기도하였다. 7-11 International Egg Commission의보고서에의하면, 2011 년도국민 1인당계란소비량 ( 가공식품포함 ) 은일본 329 개, 중국 295개, 미국 247개, 프랑스 222개등이었으며, 우리나라의 1인당연간계란소비량은 218개로보고되었다. 12 국민건강영양조사에의하면 (2007), 13 우리나라국민의 1인당계란섭취량은하루평균 19.9 g ( 콜레스테롤 87 mg) 으로전체콜레스테롤섭취량의 37% 에해당되었으며, 특히 65세이상노인의경우에하루계란섭취량은 7.6 g으로섭취량이매우적은것으로보고되었다. 우리나라 65세이상노인의영양상태는전반적으로불량한편으로각영양소별로영양섭취기준을충족하지못하는노인의비율이매우높기때문에 13 계란이노인의영양상태개선에긍정적인효과를나타낼수있으며, 저소득층노인의중요영양급원이될수있다. 계란노른자섭취에따른심장병발생은조사대상자의특성, 계란섭취수준, 함께식사하는다른식품의특성등에따라다른결과를나타낼수있으며, 계란은콜레스테롤이외에도다른영양소의주요공급원이될수있기때문에식품으로서계란의섭취에대한유해성이나유익성을결정하는것이어려우며학자마다다른견해를제시하고있다. 따라서본연구에서는문헌고찰을통하여계란과콜레스테롤의관계를조사 정리하여, 우리나라식생활에서계란섭취의장단점을살펴보고, 바람직한계란의소비방향을제시하고자한다. 계란의영양적 기능적특성 계란의영양적특성계란 ( 전란기준 ) 은쇠고기, 돼지고기, 닭고기등다른육류에비해에너지및지방함량이낮으면서비타민 A, β-카로틴, 비타민 D, 비타민 E, 리보플라빈, 비타민 B 12, 엽산, 칼슘의함량이높다. 또한난황의경우, 지방및콜레스테롤뿐만아니라철, 아연, 셀레늄의급원식품이될수있으며, 특히영양소급원이일부식품에제한되어있는비타민 D 와비타민 K의주요급원식품이될수있다 (Table 1). 1,14 계란의영양소기여도를살펴보면 (Table 2), 19~29세성인여자가하루에계란 1개를섭취하면, 하루필요에너지의 3.3% 를계란으로부터공급받지만, 단백질의 11.8%, 비 Table 1. Nutrition composition of representative animal foods (per 100g edible portion) 1) Nutrient Whole eggs Egg whites Egg yolks Beef (sirloin) Pork (sirloin) Poultry Whole milk Energy (kcal) 138.0 49.0 353.0 192.0 262.0 180.0 60.0 Carbohydrate (g) 2.8 1.8 1.8 0.2 0.2 0.1 4.7 Protein (g) 11.8 9.8 15.3 20.1 17.4 19 3.2 Total fat (g) 8.2 0 29.8 11.3 19.9 10.6 3.2 Cholesterol (mg) 475.0 1.0 1,281.0 64.0 55.0 75.0 11.0 Vitamin A (μgre) 153.0 0 454.0 7.0 5.0 50.0 28.0 β-carotene (μg) 18.0 0 54.0 0 0 0 12.0 Vitamin D (μg) 3.0 0 6.0 - - - 1.0 Vitamin E (mg) 0.7 0 3.6 0.3 0.1 0.3 0.1 Vitamin K (mg) - - 0.7-0 1.5 0.2 Thiamine (mg) 0.05 0.02 0.22 0.09 0.61 0.20 0.04 Riboflavin (mg) 0.28 0.44 0.44 0.20 0.15 0.21 0.14 Vitamin B 6 (mg) 0.07 0 0.26 0.29 0.23 0.30 0.02 Vitamin B 12 (μg) 1.29 0.09 2.0 1.04 0.53 0.31 0.4 Folic acid (μgdfe) 124.5 4.0 146.0 8.3 4.0 16.7 9.7 Calcium (mg) 43.0 3.0 139.0 22.0 6.0 10.0 105.0 Magnesium (mg) 1.2 11.0 5.0-21.0 - - Iron (mg) 1.4 0.3 5.4 4.6 0.8 0.9 0.1 Zinc (mg) 1.3-4.2 2.8 1.8 2.2 0.4 Selenium (μg) 31.7-56.0 28.5 33.2 14.4-1) Data from reference 14 [The Korean Nutrition Society, 2009 Food Values]
Journal of Nutrition and Health (J Nutr Health) 2014; 47(6): 385 ~ 393 / 387 Table 2. Contribution of eggs to the Korean diet (per one egg) 1) Nutrient KDRI (19-29y female) one egg % KDRI Energy (kcal) 2,100 69 3.3 Protein (g) 50 5.9 11.8 Vitamin A (μgre) 650 76.5 11.8 Vitamin D (μg) 8 1.5 18.8 Riboflavin (mg) 1.2 0.14 11.7 Folic acid (μgdfe) 400 62.3 15.6 Vitamin B 12 (μg) 2.4 0.65 26.9 Calcium (mg) 650 21.5 3.3 Iron (mg) 14 0.8 5.4 Selenium (μg) 55 15.9 28.8 1) Data from reference 15 [The Korean Nutrition Society, Dietary Reference Intakes of Koreans, 1st revision, 2010] 타민 A 의 11.8%, 비타민 D 의 18.8%, 리보플라빈의 11.7%, 엽산의 15.6%, 비타민 B 12 의 26.9%, 셀레늄의 28.8% 를계란으로부터섭취할수있어계란의영양소기여도가높음을알수있다. 15 미국인의경우에도계란 1개를섭취하면단백질의 10%, 리보플라빈의 15%, 비타민 B 12 의 8%, 비타민 K의 31%, 셀레늄의 17% 를계란으로부터공급받는것으로조사되어식생활에서계란의영양소기여도가높은것을알수있다. 2 국민건강영양조사결과 (2007) 에의하면, 계란은한국인에게단백질공급의 5번째주요급원식품이며, 리보플라빈은 3번째, 철은 7번째, 칼슘과비타민 A는 9 번째급원식품으로보고되어, 한국인에게가장많이부족한영양소인칼슘과리보플라빈을동시에보충할수있는식품이기도하다. 13 식품의단백질질을비교하면, 계란, 육류, 우유순이며, 계란의단백질함량은인체에필요한필수아미노산조성과가장비슷하여세계보건기구는계란단백질을완전단백질로분류하였으며, 다른식품의단백질질을평가할때기준으로이용되기도한다. 16 계란의단백질은식품중에서생물가 (BV, biological value) 가가장높기때문에성장기어린이뿐만아니라간질환환자, 신장질환환자의식사요법에이용되며, 단백질효율도식품중에서가장높아계란이성장기어린이에게중요한식품이될수있다 (Table 3). 또한계란단백질의소화흡수율은 97% 로서다른단백질에비해소화흡수율이높음을알수있다. 16 (Table 4) 그이외에도계란단백질은항균, 항암, 항산화작용에관여하는성분을함유하고있는것으로보고되고있는데, 난백단백질의주요성분인오브알부민 ( 난백단백질의 54%), 오보트랜스페린 (12%), 오보뮤코이드 (11%), 오보뮤신 (3.5%), 라이소자임 (3.5%), 난황단백질인면역글로불린Y (IgY) 등이항균작용및면역작용에관여하는것으로보고되고 Table 3. Comparison of protein quality of foods 1) Foods Eggs Meat Milk Soybean Amino acid score 100 66-70 60 47 Biological value 94 74-76 85 71 Protein efficiency ratio 3.92 2.30-3.55 3.09 2.32 1) Data from reference 16 Table 4. Protein digestibility of foods 1) Foods Eggs Meat Milk Soybean digestibility (%) 97 85-99 81 90 1) Data from reference 16 있다. 17,18 계란의지방은난백에거의존재하지않고난황에 31% 정도함유되어있으며, 난황의지방은중성지방 (62.3%), 인지질 (32.8%), 스테롤 (4.9%) 등으로구성되어있고, 전체지방산중 60% 이상이불포화지방산으로구성되어있다. 17 계란의인지질은주로레시틴 (phosphatidylcholine) 과세팔린 (phosphatidylserine) 으로혈액중에서지단백의구성성분으로존재하며, 스테롤은주로콜레스테롤로이루어져있다. 계란은쇠고기나돼지고기에비해포화지방산의함량이낮은편이며, 올레산, 리놀레산, 리놀렌산등과같은불포화지방산의함량이높기때문에 14 난황의콜레스테롤함량이높음에도불구하고다른동물성지방에비해혈액의콜레스테롤수준이섭취한만큼증가되지않는것으로보고되고있으며, 19 계란의불포화지방산은포화지방산에비해콜레스테롤보다는케톤체로더많이전환되고, 불포화지방산이간의 LDL 수용체의활성을증가시키는것으로주장되고있다 (Table 5). 2 계란의건강기능성특징계란인지질의주요성분인레시틴은세포막의구성성분이며, 항산화작용및노화예방에효과가있는것으로알려져기능성식품으로활용되고있다. 또한, 레시틴은혈액중의콜레스테롤농도를낮추어심장병예방에관계되는것으로보고되고있다. 20 레시틴은소장에서콜레스테롤의흡수를저하시키고, 콜레스테롤합성효소인 HMG CoA reductase의활성을감소시켜콜레스테롤합성감소에관여하고, 간의 LDL 수용체의활성을증가시켜혈액중의콜레스테롤을감소시키고, 변으로지방의배설촉진및담즙으로콜레스테롤배설등을통하여혈액중의콜레스테롤농도를낮추는것으로보고되고있다. 21 흰쥐에게고지방식이 (41% 지방 ), 고지방저레시틴식이 ( 지방 41%, 레시틴 1%), 고지방고레시틴식이 ( 지방 41%, 레시틴 5%) 를공급한후, 혈액중의콜레스테롤량을비교한실험 19 에서고지
388 / 계란의영양적특성 Table 5. Fat amount of representative animal foods (per 100g edible portion) 1) Nutrient Whole eggs Egg whites Egg yolks Beef (chuck) Pork Chicken Whole milk Total fat (g) 11.8-31.2 12.3 16.1 14.6 3.2 Cholesterol (g) 0.47-1.3 0.07 0.06 0.09 0.01 Fatty acid (g) 9.11-25.4-23.3 12.6 3.2 SFA 2 (g) 3.1-8.7 4.7 9.9 3.9 2.2 MUFA 3 (g) 4.4-12.2 6.0 10.8 6.5 0.9 PUFA 4 (g) 1.6-4.5 0.3 2.5 2.3 0.1 PUFA:MUPA:SFA 1:3:2-1:3:2 1:20:16 1:4:4 1:3:2 1:9:2 Palmitic acid (C 16:0 ) 5 25.5 29.6 24.0 27.9 26.6 23.4 30.4 Stearic acid (C 18:0 ) 5 8.6 15.9 8.1 9.8 12.3 5.7 14.9 Oleic acid (C 18:1 ) 5 45.3 30.4 45.3 43.3 44.7 43.5 28.6 Linoleic acid (C 18:2 ) 5 12.6 8.8 13.1 2.7 10.1 15.2 3.4 Linolenic acid (C 18:3 ) 5 0.5 0.8 0.4 0.1 0.4 1.2 0.3 1) Data from reference 14 [The Korean Nutrition Society, 2009 Food Values] 2) Saturated fatty acid 3) Monounsaturated fatty acid 4) Polyunsaturated fatty acid 5) per 100 g fatty acid 방식이군에비해고지방고레시틴식이군의혈액중총콜레스테롤이낮았으며지방흡수율도낮았으며, HDL: 총콜레스테롤, 총콜레스테롤배설량이많았다. 레시틴의구성성분인콜린은뇌세포막뿐만아니라신경전달물질인아세틸콜린의구성성분으로서신경세포발달과지적능력개선에관여하여태아의뇌발달및노인의치매예방에도움이되는것으로보고되어임신기및영아기, 노인기에그중요성이대두되고있다. 콜린이풍부한식이는염증관련물질인호모시스테인농도감소에관여하여심혈관질환및치매예방에관계되는것으로보고되고있다. 22 ATTICA study에서 18~89세사이의정상성인을대상으로콜린의섭취량을 4분위수 (250 mg 이하, 250~310 mg, 310 mg 이상 ) 로구분한후, 콜린섭취량과염증반응물질농도와의관련성을조사한결과를살펴보면, 혈액중의호모시스테인은콜린섭취량과유의적인상관성이없었으나, 250 mg 이하로콜린을섭취한사람에비해 310 mg 이상으로콜린을섭취한사람의혈액중에는염증반응물질인 C-reactive protein, interleukin-6, tumor necrosis factorα 수준이유의적으로낮은것으로보고되었다. 22 한국인상용식품중콜린함량이높은상위 10종류의식품이모두동물성식품으로서, 콜린의함량이높은계란은우리식생활에서콜린의주요급원식품이될수있을것이다. 23 난황 1개에는 200~300 µg의카로티노이드를함유하고있으며, 계란에함유되어있는주요카로티노이드는 β-카로틴, 루테인, 제아잔틴등으로, 이러한카로티노이드들은체내에서항산화작용을통하여유해산소를제거하고혈액중의 LDL 산화감소를통해플라그형성방해및혈관경화를늦추는역할을하여심장병발생위험도를감소시 키고, 항암작용등을하는것으로보고되고있다. 24 또한, 루테인과제아잔틴은자외선을흡수하여산화적손상으로부터망막을보호하고망막의황반주위에축적되어황반변성을억제하는작용을하여, 노인기주요질병인황반변성예방에도움을주는기능성물질로알려져있다. 24-26 루테인과제아잔틴이풍부한식품을섭취할수록노인기황반변성의위험도가낮았으며, 실제로황반변성이일어난노인의황반에루테인과제아잔틴의농도가낮은것으로보고되었다. 27 루테인과제아잔틴은난황이나녹황색채소에풍부하나, 난황에존재하는루테인과제아잔틴은비타민 A, 비타민 D, 비타민 E 등과같은지용성비타민과함께존재하기때문에채소나식이보충제보다체내에서효과적흡수되어이용되며, 24 지속적으로계란을섭취하는경우에황반에루테인과제아잔틴이증가하는것으로보고되었다. 27 노인을대상으로하여하루에계란한개씩 5주간지속적으로섭취하게했을때 ( 계란 1개에함유된평균루테인 143 µg, 제아잔틴 94 µg, 콜레스테롤 210 mg), 혈액중의콜레스테롤수준은증가하지않았으나, 혈액중루테인수준은 26%, 제아잔틴은 38% 증가하였고, 24 성인여성이 12주동안일주일에 6개의계란을섭취하였을때혈액중의콜레스테롤농도는증가없이제아진틴의농도가증가하였으며, 황반색소도증가하여 27 노인기시력보호를위해하루 1개정도의계란을섭취할필요성이있다고주장되었다. 그러나고콜레스테롤환자에게하루 1.3개의난황을 4.5주동안공급했을때, 루테인과제아잔틴의농도는증가하였으나혈액의 LDL-콜레스테롤농도도 8~11% 증가하여적절한수준의난황섭취가중요하다고주장되었다. 26
Journal of Nutrition and Health (J Nutr Health) 2014; 47(6): 385 ~ 393 / 389 계란과체내콜레스테롤대사 콜레스테롤의기능및생성콜레스테롤은동물조직에존재하는필수성분이나혈액중에과도하게존재할때심혈관질환의주요위험인자로작용하게된다. 28 콜레스테롤은세포막과뇌와신경조직의중요구성성분이고, 에스트로겐, 프로게스테론, 코르티코스테로이드등과같은스테로이드계호르몬의전구물질로작용하고, 지방의소화흡수를돕는담즙산의전구물질이며, 콜레스테롤에서유도된 7-디히디로콜레스테롤은자외선에의해피부에서비타민 D로전환되는등체내에서중요한작용을수행한다. 16 섭취한콜레스테롤은일부가흡수되고일부는배설되는데, 체내의콜레스테롤양은콜레스테롤흡수정도와담즙산배설및재흡수정도에따라조절되어체내에서일정수준을유지하게된다. 16,29 체내총콜레스테롤생성량은식이콜레스테롤섭취량과체내합성량으로이루어지며, 정상성인의경우하루총콜레스테롤생성량은 1,000 mg 정도이다. 일반적으로식이콜레스테롤의 40~60% 정도가체내에서흡수되며, 흡수된콜레스테롤은체내총콜레스테롤의 20~25% 를차지하게되고, 75~80% 정도는간에서합성되기때문에혈액중의콜레스테롤농도는체내합성량에의해더큰영향을받게된다. 16,29,30 식이콜레스테롤과혈액콜레스테롤과의관련성과거 50년간콜레스테롤대사와관련된 167개의연구내용을분석한 Hopkins 3 의연구결과를살펴보면, 콜레스테롤섭취량이 100 mg 증가할때혈청총콜레스테롤은 2.2 mg/dl 증가하였다고보고하였으며, 역으로하루콜레스테롤섭취량이 100 mg 감소하면혈청총콜레스테롤이 2.5 mg/dl (LDL-콜레스테롤 1.9 mg/dl 감소, HDL-콜레스테롤 0.4 mg/dl 감소 ) 감소하는것으로보고하였다. 여러연구결과를살펴보면콜레스테롤섭취량이 100 mg/dl 증가하면혈청콜레스테롤수준이 2.2~4.5 mg/dl 증가하는것으로보고하였다. 30-32 McNamara는콜레스테롤섭취량이증가하면 LDL-콜레스테롤뿐만아니라 HDL-콜레스테롤수준도증가하므로 LDL:HDL 비율이크게변하지않아건강상문제가되지않는다고주장하였다. 30 즉, 혈청콜레스테롤수준이정상인사람에게매일계란 1개를추가로섭취하도록하였을때, LDL-콜레스테롤은 4.1 mg/dl 증가하였으며 HDL-콜레스테롤은 0.9 mg/dl 증가하여 LDL:HDL 비율이크게변화하지않았다고보고하였다. 30 그러나 Liebman과 Bazzarre 는콜레스테롤섭취량이증가할수록혈액중의 LDL:HDL 비율이증가하였으며, 특히불포화지방산 : 포화지방산의비율이 0.7 이하인경우에는식이콜레스테롤섭취량에비례해혈청콜레스테롤이더많이증가하는것으로주장하였다. 33 이는적절한수준으로콜레스테롤을섭취하는경우에는혈청콜레스테롤수준에큰영향을미치지않으나콜레스테롤섭취량이증가할수록 LDL-콜레스테롤수준이증가하였으며, 특히함께섭취하는지방의종류에따라그영향이달라질수있음을강조하였다. 포화지방산은간의 LDL 수용체의활성을감소시켜간으로 LDL-콜레스테롤이이동되는것을억제하여혈액중콜레스테롤의농도를높이게되며, 19 포화지방산의섭취가적으면간에서의지단백합성이감소되어혈액중의 LDL이간으로이동되어담즙을거쳐소장을통해배설되어혈액중의 LDL 양을감소시키는역할을하게된다. 16 에너지원으로포화지방산의섭취가 1% 증가하면혈액중의총콜레스테롤치가 2.7 mg/dl 상승되어포화지방산의섭취가혈액중콜레스테롤수준에미치는영향이큰것으로보고되고있다. 28 혈액중콜레스테롤은섭취량뿐만아니라다양한유전인자의조절에의해영향을받기때문에섭취하는콜레스테롤에대한반응은개인에따라다르게나타나며, 콜레스테롤흡수율은개인에따라 20~80% 로다양한것으로보고되고있다. 1 일반적으로인구의 75% 이상은콜레스테롤섭취량에따라혈액중콜레스테롤량이크게증가하지는않으나 25% 정도는콜레스테롤섭취량에예민하게반응하는것으로주장되고있다. 1 Apo E4형유전자는혈액콜레스테롤, LDL, apo B 증가와관련되고, Apo E2형유전자는혈액콜레스테롤, LDL, apo B 감소와관련되는것으로보고되었다. 34 콜레스테롤대사에대한반응정도가다른그룹을대상으로콜레스테롤섭취량증가에따른혈액콜레스테롤생성량을비교한연구에서대상자의특징에따라콜레스테롤합성정도가달랐으며, 콜레스테롤의종류에따라서도합성량이다른것으로보고되었다. 30 콜레스테롤에대해민감하게반응하는사람의경우에 100 mg의콜레스테롤을섭취했을때 LDL-콜레스테롤생성량은 2.84 mg/dl, HDL- 콜레스테롤생성량은 0.69 mg/dl였으며, 민감하지않은사람의 LDL-콜레스테롤생성량은 0.76 mg/dl, HDL-콜레스테롤생성량은 0.50 mg/dl으로콜레스테롤생성량이달랐으며특히 LDL-콜레스테롤생성량에차이가있었다. 30 식이콜레스테롤 500 mg을흡수하게되면더이상체내에서콜레스테롤이합성되지않거나혈액의콜레스테롤수준이상승하지않는다고보고되었으나 3 동맥벽에축적되는 LDL-콜레스테롤을간과할수없을것이다. 하루에 3,100~3,400 mg 의콜레스테롤을섭취한사람의간에서콜
390 / 계란의영양적특성 레스테롤이 62% 증가하였고, 혈청콜레스테롤농도는 19% 증가하였다고보고되어간이나조직에콜레스테롤이축적될수있음을암시하였다. 3 그러나정상적인식사로는하루 3,000 mg 이상의콜레스테롤을섭취하기어렵기때문에이러한연구결과에대한논란이제기되기도하였다. 콜레스테롤섭취량이많으면 LDL-수용체감소, HMG- CoA reductase 감소, 간의콜레스테롤양증가등을통하여체내콜레스테롤수준을조절하고, 반대로콜레스테롤섭취량감소, 흡수율감소, 배설량이증가하게되면 LDL-수용체증가, HMG-CoA reductase 증가, 간의콜레스테롤양감소등을통하여체내콜레스테롤수준을조절하게된다. 체내콜레스테롤의수준조절은혈청의기본콜레스테롤수준, 콜레스테롤대사정도등에따라민감성이다르고, 혈액의콜레스테롤수준이크게증가하지않았다고해도간이나조직의콜레스테롤축적등을통하여조절이될수있기때문에콜레스테롤섭취량과혈액수준의관계를명확히설명하기가어렵다. 3 혈액콜레스테롤, 심혈관질환, 계란섭취와의관련성혈중 LDL-콜레스테롤농도는심혈관질환의주요위험인자로서콜레스테롤섭취는심장병의중요위험으로간주되고있다. 4 콜레스테롤섭취량과심장병발생위험도와의상관관계는여러역학조사에서다양한연구결과가제시되고있다. 5.6 Ireland-Boston Heart Study, 35 Zutphen Study, 36 Framingham Study, 37 Nurses Health Study 38 등의연구에서는콜레스테롤섭취량 (2,000 kcal 에너지섭취량기준으로콜레스테롤 416~466 mg 섭취함 ) 이심장병발생위험도와상관관계가없는것으로발표하였으나, Honolulu Heart Study 39 에서는 1,000 kcal 에너지섭취당콜레스테롤섭취량이 241 mg일경우 (2,000 kcal 기준시 482 mg 정도콜레스테롤섭취하는경우 ) 심장병발생위험도가 1.2배로증가하였으며, Western Electric Study 40 에서는심장병발생위험도가 1.9배로증가하였다고발표하였다. 심혈관질환발생에대한계란의관련성은계란의높은콜레스테롤함량 ( 난황 1개의콜레스테롤함량 : 215 mg, 난황 100 g 당 1,280 mg) 때문으로, 계란을섭취하면혈액중의콜레스테롤수준에영향을미칠수있을것이다. 특히, 혈청콜레스테롤이 1% 증가하면심장병발생위험도는 2% 로증가할수있는것으로보고되어계란을많이섭취하면심장병발생위험도가증가할것으로주장되고있다. 3 그러나계란과혈청콜레스테롤이관련성이있다고해도심장병의위험요인으로서계란의여러성분중콜레스테롤만별도로구분하여관련성을제시하기에어려움이있으며, 난황에는콜레스테롤함량이높음에도불구하고불 포화지방산의함량이높아다른동물성지방에비해혈액의콜레스테롤수준이섭취한만큼증가되지않는다고주장되기도하였다. 41 미국심장협회 (AHA) Step 1 diet에계란을매일 1, 2, 4개씩추가 ( 총콜레스테롤섭취량 128~858 mg) 했을때, 식이콜레스테롤 100 mg 당혈청콜레스테롤증가량은 1.46 mg/dl로비교적혈청콜레스테롤증가량이적었으며, 이러한결과는포화지방산이낮은 AHA Step 1 diet를기준으로계란을추가한식이를공급한결과라고발표하였다. 19 우리나라의농촌과중소도시에서 40대이상성인의식품섭취패턴과질병유병률을살펴본결과에서도계란을포함하는식사패턴이계란을포함하지않는식사패턴보다만성질환 ( 당뇨, 대사증후군, 비만등 ) 의발생위험도가낮은것으로조사되었다. 42 또한채식을많이하는사람에게계란콜레스테롤을공급했을때, 섭취량에따라혈청콜레스테롤수준이변하지않은것으로보고되었다. 43 채식을많이하는사람에게하루계란콜레스테롤섭취량을 387 mg 증가시켜저콜레스테롤식이 ( 콜레스테롤섭취량 165 mg) 와고콜레스테롤식이 ( 콜레스테롤섭취량 603 mg, 계란콜레스테롤 387 mg 포함 ) 의혈액지질수준을비교한결과혈청콜레스테롤수준에유의적인차이가없었다. 43 또한채식남자와일반식사를하는남자의혈액지방을비교했을때, 채식을하는남자의혈액중총콜레스테롤, LDL-콜레스테롤, 중성지방의수준이더낮았으며, 특히채식위주의식생활을하는사람의경우에는계란의섭취량보다는총지방량이혈액에미치는영향이더크다고주장하였다. 44 계란섭취량과심장병발생위험도와의관련성을조사한대규모역학조사결과를살펴보면 27 그결과에일관성이없으며, 연구방법및연구내용, 조사대상자의특성에따라상반된연구결과가제시되고있다. Framingham Heart Study 9 에서 16년간의추적조사결과, 일주일에계란을 2.5 개미만으로섭취하는남자에비해 7개이상섭취하는남자의심장병발생위험도에차이가없었으며, Nurses Health Study & Health Professional Study 6 에서도일주일에 1개미만의계란을섭취하는남, 녀에비해 7개이상섭취하는사람의심장병발생위험도에차이가없었으며, 이태리여성을대상으로한 case-control study에서도 1주일에 1개미만, 1~2개, 2개이상의계란을섭취한경우계란섭취와심장병과는상관관계가없는것으로보고하였으며, 10 Nakamura 등이 14년동안추적조사한일본의대규모 cohort study에서도계란섭취와심장병, 사망률과의관계가없는것으로보고하였다. 11 그러나 Framingham Heart Study 9 에서여자의경우에는일주일에계란을 1.5개미만으로섭취하는사람에비해 5개이상섭취하는사람의심장병발생위험도가
Journal of Nutrition and Health (J Nutr Health) 2014; 47(6): 385 ~ 393 / 391 Table 6. The effects of egg consumption to coronary heart disease risk Study, year (reference) Egg consumption levels compared (per week) Relative risk Adjustment factors Dawber et al., 1982 9 men, <2.5 vs 7 1.3 none Hu et al., 1999 6 men, <1 vs 7 1.08 lifestyle variables women, <1 vs 7 0.82 lifestyle variables Gramenzi et al., 1990 10 women, <1 vs >2 0.8 age Djousse et al., 2008 45 men, 1< vs 7 0.92 lifestyle variables Jones, 2009 43 men, 1< vs 7 1.08 lifestyle variables women, <1 vs 7 0.82 lifestyle variables Burke et al., 2007 7 <2 vs 2 2.59 * gender Mann et al., 1997 8 <1 vs 6 2.68 ** gender, lifestyle variables *: p < 0.05 **: p < 0.01 1.3배높았으며, 일주일에 2개이상의계란을섭취하는호주원주민의심장병발생률을 14년동안추적조사한결과심장병발생률이 2.6배증가하였고, 7 영국인을대상으로한연구에서는일주일에 6개이상계란을섭취하는경우에 1개미만으로섭취하는사람에비해사망률이 2.7배증가한것으로보고하여 8 계란섭취와심장병발생의관련성을제기하기도하였다 (Table 6). 정상인과달리당뇨환자의경우에는계란의섭취정도와심장병위험도와관련성이높은것으로조사되었다. 정상인이계란을일주일에 7개이상섭취했을때심장병위험도가 1.27배로증가한반면, 당뇨환자는일주일에 5~6개이상섭취했을때심장병발생위험도가 2.48배로증가하는것으로보고되어당뇨환자나당뇨위험도가높은사람은계란섭취에주의를기울어야한다고강조하였다. 45,46 콜레스테롤이풍부한식품은총콜레스테롤, LDL-콜레스테롤, apob 수준을증가시키는것으로알려져있으나, 이러한반응은한끼식사에서섭취하는콜레스테롤의양, 식이콜레스테롤과포화지방산섭취와의관련성, 함께섭취하는불포화지방산이나다른식품등의영향에의해달라지기때문에이에대한지속적이연구가필요할것이다. 식생활에서계란의의미 계란은고콜레스테롤식품으로서심장병발생과의관련성을간과할수는없지만여러영양소를동시에공급할수있는우수한영양공급원으로서경제적인육류대체식품이될수있다. 특히영양상태가불량하기쉬운노인, 저소득층, 임신부, 영유아, 저열량다이어트를하는사람, 양질의단백질이필요한간질환이나신장질환자의경우에훌륭한영양공급원으로이용되기도한다. 계란을콜레스테롤이많은단일급원식품으로인식하여 좋은식품 또는 나쁜식품 으로규정하기보다는식생활패턴에서계란의건강성, 의미를찾는것도중요할것이다. 미국심장협회 (AHA) 에서는심장병예방을위해하루콜레스테롤섭취량을 300 mg 이하로섭취할것을권장하였으나최근에는식사에서콜레스테롤의양을줄인다면하루 1개의난황을섭취할수레시피를제공하기도하였다. 47 이는다른동물성식품의섭취를줄이는대신계란을섭취하고채소를풍부히섭취하여콜레스테롤흡수를감소시키고배설을증가시킨다면계란에함유된양질의영양성분을섭취할수있기때문이다. 그러나미국심장협회 (AHA) 는심장병환자의경우에는일주일에계란노른자를 2개이하로섭취할것을권장하였고, 계란노른자보다는흰자를많이섭취할것을권장하였다. 47 일본의 18세이상성인의콜레스테롤상한목표량은남자 750 mg, 여자 600 mg 미만으로서 48 정상적인식사에하루계란한개정도를더섭취할수있는수준을제안하고있으며, 우리나라는한국영양학회에서하루콜레스테롤목표량을 300 mg 이하 15 로권장하고있다. 모든대상에게계란을섭취할수있는권장수준을일률적으로적용하기는어려울것이다. 그러나계란이우리의식생활에서기여도가높은식품임에는틀림없다. 지금까지다양한국내외연구결과를비교분석한결과에의하면, 특별한건강문제가없는사람들의경우에는다른동물성식품의섭취를줄이는대신풍부한채소섭취와함께적절하게계란을섭취하는것은건강상이점이있을것으로생각된다. 또한이용목적에따라서는난황과난백을구분하여효과적으로이용한다면계란의우수한영양성분을섭취할수있을것이다. References 1. Herron KL, Fernandez ML. Are the current dietary guidelines regarding egg consumption appropriate? J Nutr 2004; 134(1): 187-
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