選單

雞蛋和膽固醇:我們站在哪裡?

長期以來雞蛋一直是世界各地的主食,不僅被認為是經濟和營養的蛋白質來源,而且還是富含膽固醇的來源。因此在主流媒體以及旨在降低血液中膽固醇水平和心血管疾病風險的國際營養指南中,關於它們對心血管健康產生影響的資訊不一。1 儘管如此,該領域的研究近年來取得了很大進展。我們今天的立場是什麼呢?以下是對於此問題相關的知識和建議的簡單概述。

研究現況

最近大規模研究的證據並不一致,但大多數得出了類似的結論:中度或更高的雞蛋攝取量(相當於每週 7 個雞蛋或更多)似乎與心血管疾病的風險和總體死亡率的增加無關。1,2,3,4 另一方面,2021 年發表的一項大型研究報告稱,多吃雞蛋與膽固醇與心血管疾病和癌症等各種原因導致的死亡率升高相關聯。5 然而,這些相互矛盾的發現在科學界引起了爭論,科學界指出該研究的一些重要局限,目前無法在大範圍內得出明確的結論。6,7

另一個問題必須被提及。與干預性研究不同,這些研究大多都基於觀察,從本質上並不能建立因果關係。事實上,正常的人類飲食通常由許多不同的食物組成,這使得很難在飲食模式之外評估單一成分(例如雞蛋)對健康的影響。因此這些結果無法證明多吃雞蛋是否會增加患心血管疾病的風險,因為後者可能同時受到許多其它生活方式因素的影響。

事實上,儘管有些人可能是“高反應者”,但膳食膽固醇似乎對血液内膽固醇水平的影響不大。這意味著膽固醇攝入對這些人体内膽固醇水平的影響可能比對普通人更大。而更廣為人知的是,已知的其它食物成分,例如飽和脂肪酸和反式脂肪酸,對於膽固醇水平的影響更大。8,9

營養指南

國際和各國的營養建議也反映了這些近期的發現。當前(FAO/WHOa)10針對全球人口發佈的官方指南,以及美國 、歐盟 、英國 、加拿大 、澳大利亞、新西蘭 、中國 和臺灣11,12,13,14,15,16,17等各國家地區,並不設定膳食膽固醇的營養素參考值,儘管情況並非總是如此。18,19美國膳食指南的上一個版本(2015-2020)強調,取消之前每天攝取300毫克膽固醇的限制並不一定意味著不再考量膳食膽固醇的攝取量。20保持盡可能低的膽固醇攝取量仍然是大多數建議中的常見方法。

儘管如此,也有一些例外如日本的狀況,根據日本動脈粥樣硬化學會(Japan Atherosclerosis Society)的指導方針,建議每天最多攝取 200 毫克的膽固醇,以防止出現嚴重的血脂異常(即血液脂質水準異常)。21,22 此外,歐洲心臟學會(European Society of Cardiology)和歐洲動脈硬化學會(European Atherosclerosis Society)建議每天應攝入低於 300 毫克膳食膽固醇,以管理血脂異常(尤其是血清膽固醇水平高的族群),9 以及英國國家健康與照顧卓越研究所(UK National Institute for Health and Care Excellence)針對心血管疾病高風險或患有心血管疾病的個人亦做此建議。23,24

事實上,儘管有些人可能是“高反應者”,但膳食膽固醇似乎對血液内膽固醇水平的影響不大。

膳食膽固醇的來源

雞蛋因其高膽固醇含量而經常被作為一個例子,但您可能知道膽固醇也天然存在於一系列其它產品中,植物性產品除外。膳食膽固醇的主要食物來源包括雞蛋、肥肉(例如一些塊狀肉品,如肋眼牛排、排骨、羊肩)、加工肉類(如碎豬肉、香腸、義大利臘腸)、內臟(如小牛腎、甜麵包、豬頰肉) 、全脂牛奶和衍生乳製品(例如普通乳酪、優酪乳、奶油)、動物脂肪(例如黃油、豬油、培根脂肪)和海鮮(尤其是貝類)。1,8,9,25

雖然有些食物的膽固醇和飽和脂肪酸含量都很高,例如肥肉、加工肉類、全脂乳製品和動物脂肪。其它食物雖然膽固醇含量很高,但飽和脂肪含量卻不高,雞蛋、貝類和某些內臟(例如甜麵包、雞肝)就屬於這種状況。1,8 根據美國和法國的食物營養成分表,作為指標物,一個中等大小的雞蛋含有 185-200 毫克膽固醇,但平均只含 1.3-1.6 克飽和脂肪(即低於飽和脂肪提供的預估每日 2000 大卡能量值的 1%)。26,27

我可以吃幾個雞蛋?

許多人仍在向自己或他們的健康顧問提出的這個問題,也已在媒體上進行了詳細討論。然而大多數飲食建議並沒有設定特定的雞蛋消費頻率。只有一些專家組和國家提出了對健康的個體和患有某些疾病或易患心血管疾病的高風險族群的限制。以下列出了一些範例:

  • 美國心臟協會 (American Heart Association,AHA):作為健康飲食的一部分,健康人每天最多食用 1 個雞蛋,膽固醇水準正常的老年人每天最多 2 個雞蛋。另一方面,AHA 建議血脂異常患者(尤其是二型糖尿病患者或有心力衰竭風險的患者)應謹慎對待飲食中的膽固醇攝取量;1
  • 澳大利亞和紐西蘭國家心臟基金會(National Heart Foundations of Australia and New Zealand):對於沒有心血管疾病或二型糖尿病的人來說,攝取雞蛋可以作為健康飲食模式的一部分。相比之下,為二型糖尿病、心血管疾病或心臟病高危人群設定的標準為每週最多攝取 7 個雞蛋;28,29
  • 中國國家膳食指南:健康個體每週最多攝取7個雞蛋;30
  • 臺灣飲食指南:健康個體每天最多 1 個雞蛋,但心血管疾病風險較高(如高膽固醇血症、肥胖症)或患有心血管疾病的人每天應攝取少於 1 個雞蛋。31

有益心臟健康的飲食

值得注意的是,與簡單地限制雞蛋消費相比,一些生活方式的改變可能對心血管疾病風險和血脂異常的預防和管理產生更大影響。雖然減少膽固醇的攝取量並不是最強烈的建議之一,但這裏有一些關於心臟健康飲食的關鍵建議,您可能可以記住:

  • 透過攝取全麥產品、蔬菜、水果、豆類和堅果來增加膳食纖維攝取量;
  • 限制食用富含飽和脂肪酸的食物(全脂乳製品、肉類脂肪切塊、動物脂肪和含有熱帶植物油的產品,如椰子油和棕櫚油),多吃魚、去皮家禽和植物性來源的蛋白質,如豆類和豆製品;
  • 選擇不飽和脂肪的來源,例如植物油(來自橄欖、油菜籽、向日葵、大豆等)、堅果(例如杏仁、核桃、榛子)和種子(例如南瓜子、亞麻籽);
  • 盡可能限制反式脂肪酸的攝取量,尤其是工業來源的反式脂肪酸,即在加工食品中發現的部分氫化脂肪酸,如一些煎炸油、餅乾、糕點、零食等。9,32

結論

儘管攝取雞蛋對心血管疾病風險的影響尚未完全被瞭解,但作為多樣化和健康飲食的一部分,雞蛋仍然是一種營養選擇。雞蛋是含有所有必需氨基酸的完整 蛋白質 來源 ,因此適用於雜食和乳蛋素食者。雞蛋還含有大量的維生素 A、維生素 D、維生素 B12、鐵、鋅和一系列有益於健康的其它營養素。26,28

除了有益於心臟健康飲食的主要建議外,在研究結果更加明確之前限制膽固醇攝取量可能更安全,特別是對於易患心血管疾病的高風險族群或已患有心血管疾病者。切記在決定最適合您和您的身體狀況的飲食前,通常建議諮詢您的醫生或營養師。最後與任何其它食物一樣,適度和平衡才是關鍵。

最後更新時間:2021 年 6 月

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參考

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