Chapter Thirteen – Kiwifruit and Mineral Nutrition第十三章獼猴桃與礦物質(zhì)營養(yǎng)

Chapter Thirteen - Kiwifruit and Mineral Nutrition第十三章獼猴桃與礦物質(zhì)營養(yǎng)

Abstract
Dietary minerals are essential nutrients that drive key cellular and physiological functions. Each mineral is absorbed in the gut via unique, complex pathways that can involve a cascade of receptors and binding proteins. Foods can both provide dietary minerals and contain components that impact the bioavailability of minerals in the digestive system. Kiwifruit exceeds most other fruits in its content of key micronutrients including potassium, phosphorus, magnesium, calcium, iron, and folate. It also contains exceedingly high levels of ascorbic acid, which increases the bioavailability of nonheme iron and can impact on calcium absorption. Recent research in cells, animals, and humans has demonstrated that kiwifruit, particularly the gold variety, can increase the uptake and retention of the essential dietary minerals iron, calcium, phosphorus, and magnesium.

▲A kiwi orchard with abundant fruits

摘要
膳食礦物質(zhì)是驅(qū)動關(guān)鍵細(xì)胞和生理功能的必需營養(yǎng)素。每種礦物質(zhì)都通過獨特而復(fù)雜的途徑被腸道吸收，這些途徑可能涉及一系列受體和結(jié)合蛋白。食物既能提供膳食礦物質(zhì)，又含有影響消化系統(tǒng)礦物質(zhì)生物利用度的成分。獼猴桃在鉀、磷、鎂、鈣、鐵和葉酸等關(guān)鍵微量營養(yǎng)素的含量上超過了大多數(shù)其他水果。它還含有極高水平的抗壞血酸，這增加了非血紅素鐵的生物利用度，并可能影響鈣的吸收。最近對細(xì)胞、動物和人類的研究表明，獼猴桃，特別是黃金品種，可以增加對必需膳食礦物質(zhì)鐵、鈣、磷和鎂的吸收和保留。

▲Kiwi Pollination

Introduction
Dietary minerals are inorganic elements that are required in small quantities but are essential for health. They have a number of functions within the human body. Some, such as copper and magnesium, stabilize the structure of proteins and DNA. Other minerals, such as calcium and phosphorus, are themselves important structural components of bone. A number of minerals are enzyme cofactors or are involved in redox reactions and electrical gradients (Fleet, Replogle, & Salt, 2011). Key dietary minerals include iron, magnesium, calcium, copper, and potassium. Even people who consume high-energy Western diets may be deficient in minerals such as iron and calcium, while illness can contribute to deficiencies in potassium and magnesium. New research continues to refine and evolve our understanding of the mechanisms through which dietary minerals are independently or synergistically absorbed and utilized in the body.

▲Red kiwifruit

Mineral uptake is dependent on the level in the diet and the needs of the body but is also modulated by other factors. Dietary minerals must be bioavailable: that is, they must be present in a form in which the digestive system is able to remove them from food and absorb them into the bloodstream for use in the body. Antinutritional factors can lower the bioavailability of a mineral by chelating it and making it insoluble; conversely, some food components can enhance bioavailability by making favorable changes to the gut microenvironment (Hunt et al., 1995, Hurrell, 2003, Lopez et al., 2003, Record et al., 1996, Song et al., 2012). Similarly, processing, refinement, and cooking or storage procedures used on a food can affect its mineral content and bioavailability (Kimura and Itokawa, 1990, Reddy and Love, 1999). In addition, interactions occur between minerals in the body so that a deficiency or excess of one mineral can affect the status of another mineral (Lonnerdal, 2010, Pepin and Shields, 2012).
Kiwifruit both contain minerals and impact the absorption of several dietary minerals. These include iron, magnesium, calcium, copper, and potassium, which are discussed individually in more detail below.

▲水楊桃苗

介紹
膳食礦物質(zhì)是少量必需的無機元素，但對健康至關(guān)重要。它們在人體內(nèi)具有多種功能。一些，如銅和鎂，可以穩(wěn)定蛋白質(zhì)和DNA的結(jié)構(gòu)。其他礦物質(zhì)，如鈣和磷，本身就是骨骼的重要結(jié)構(gòu)成分。許多礦物質(zhì)是酶輔因子或參與氧化還原反應(yīng)和電梯度（Fleet、Replogle和Salt，2011）。關(guān)鍵的膳食礦物質(zhì)包括鐵、鎂、鈣、銅和鉀。即使是食用高能量西方飲食的人也可能缺乏鐵和鈣等礦物質(zhì)，而疾病也可能導(dǎo)致鉀和鎂的缺乏。新的研究繼續(xù)完善和發(fā)展我們對膳食礦物質(zhì)在體內(nèi)獨立或協(xié)同吸收和利用的機制的理解。
礦物質(zhì)吸收取決于飲食水平和身體需求，但也受到其他因素的調(diào)節(jié)。膳食礦物質(zhì)必須具有生物可利用性：也就是說，它們必須以消化系統(tǒng)能夠?qū)⑵鋸氖澄镏星宄⑽盏窖褐幸怨w內(nèi)使用的形式存在?？?fàn)I養(yǎng)因子可以通過螯合礦物質(zhì)并使其不溶來降低礦物質(zhì)的生物利用度；相反，一些食物成分可以通過對腸道微環(huán)境進行有利的改變來提高生物利用度（Hunt等人，1995，Hurrell，2003，Lopez等人，2003，Record等人，1996，Song等人，2012）。同樣，食品上使用的加工、精煉、烹飪或儲存程序會影響其礦物質(zhì)含量和生物利用度（Kimura和Itokawa，1990，Reddy和Love，1999）。此外，體內(nèi)礦物質(zhì)之間會發(fā)生相互作用，因此一種礦物質(zhì)的缺乏或過量都會影響另一種礦物的狀態(tài)（Lonnerdal，2010，Pepin和Shields，2012）。
獼猴桃既含有礦物質(zhì)，又影響幾種膳食礦物質(zhì)的吸收。這些包括鐵、鎂、鈣、銅和鉀，下文將分別詳細(xì)討論。

▲KiwiPollen

Essential Dietary Minerals
The human body contains 2–4 g of iron (Bothwell, Charlton, Cook, & Finch, 1979). The majority of this iron is found in hemoglobin, the erythrocyte protein responsible for transporting oxygen from the lungs to the body's tissues. Much of the remaining iron in the body is found in myoglobin, a protein important for the storage of oxygen in muscle tissue. Iron acts as a transport medium for electrons in cells and is an important component of many enzymes, playing a role in oxidative metabolism and
Mineral Absorption in the Digestive System
The pH of the digestive system differs in each compartment, and the mechanisms and locations of a mineral's absorption are partly determined by the pH at which the mineral is soluble. Some minerals, such as magnesium and calcium, are soluble within a wide pH range and thus remain as free ions through the entire digestive system. Others, such as iron and copper, are soluble only under acidic conditions and form insoluble precipitates in nonacidic compartments of the digestive system (Powell,

▲準(zhǔn)備開始加工獼猴桃花粉的鮮花

Iron
Dietary iron is found in two well-characterized forms: heme and nonheme iron. Heme iron is found in red meat, chicken, and fish. Heme iron is well absorbed (15–35% absorbed from meals), with dietary factors and an individual's iron status having only a small effect on absorption (Gibson, Donovan, & Heath, 1997). Most dietary iron is in the form of nonheme iron, which is present in meats, eggs, cereals, legumes, pulses, fruit, and vegetables. However, the absorption of nonheme iron is poor
必需膳食礦物質(zhì)
人體含有2-4g鐵（Bothwell，Charlton，Cook，&Finch，1979）。大部分鐵存在于血紅蛋白中，血紅蛋白是負(fù)責(zé)將氧氣從肺部輸送到身體組織的紅細(xì)胞蛋白。體內(nèi)剩余的大部分鐵存在于肌紅蛋白中，肌紅蛋白是一種對肌肉組織中氧氣儲存很重要的蛋白質(zhì)。鐵在細(xì)胞中充當(dāng)電子的運輸介質(zhì)，是許多酶的重要組成部分，在氧化代謝和
消化系統(tǒng)中的礦物質(zhì)吸收
消化系統(tǒng)的pH值在每個隔室中都不同，礦物質(zhì)吸收的機制和位置部分取決于礦物質(zhì)可溶的pH值。一些礦物質(zhì)，如鎂和鈣，在很寬的pH范圍內(nèi)是可溶的，因此在整個消化系統(tǒng)中保持游離離子狀態(tài)。其他物質(zhì)，如鐵和銅，僅在酸性條件下可溶，并在消化系統(tǒng)的非酸性室中形成不溶性沉淀物（Powell，
鐵
膳食鐵有兩種特征明顯的形式：血紅素鐵和非血紅素鐵。血紅素鐵存在于紅肉、雞肉和魚中。血紅素鐵吸收良好（從膳食中吸收15-35%），飲食因素和個人的鐵狀態(tài)對吸收的影響很?。℅ibson，Donovan和Heath，1997）。大多數(shù)膳食鐵以非血紅素鐵的形式存在，存在于肉類、蛋類、谷物、豆類、水果和蔬菜中。然而，非血紅素鐵的吸收較差
Minerals in Kiwifruit
Kiwifruit is popular with consumers because it has a pleasant taste and texture, and because, being approximately 90% water, it is low in energy. It is also viewed as a “healthy” food: it is nutrient dense, containing complex carbohydrates and dietary fiber, as described in earlier chapters of this volume. Kiwifruit are relatively rich in minerals and other nutrients compared with other fruits. (Note: In this chapter, “kiwifruit” generally refers to green kiwifruit, Actinidia deliciosa cv.

▲Kiwi Pollen

獼猴桃中的礦物質(zhì)
獼猴桃之所以受到消費者的歡迎，是因為它有著令人愉悅的味道和質(zhì)地，而且因為它含有約90%的水分，能量低。它也被視為一種“健康”食品：它營養(yǎng)豐富，含有復(fù)合碳水化合物和膳食纖維，如本卷前幾章所述。與其他水果相比，獼猴桃富含礦物質(zhì)和其他營養(yǎng)物質(zhì)。（注：在本章中，“獼猴桃”一般是指綠色獼猴桃，美味獼猴桃品種。
Kiwifruit Components Facilitate Mineral Uptake
For an individual to obtain all the essential nutrients, it is recommended that nutrient-dense foods are included in the diet. Components in food may influence dietary mineral absorption. Ideal foods are both nutrient dense and contain bioactive factors that enhance mineral absorption.
The mechanism by which ascorbic acid enhances iron absorption is well established (Fairweather-Tait, 1995). As kiwifruit is a rich source of ascorbic acid, consuming kiwifruit with a dietary source of iron has the

▲collecting anthers

獼猴桃成分促進礦物質(zhì)吸收
為了使個人獲得所有必需營養(yǎng)素，建議在飲食中加入營養(yǎng)豐富的食物。食物中的成分可能會影響膳食礦物質(zhì)的吸收。理想的食物既營養(yǎng)豐富，又含有增強礦物質(zhì)吸收的生物活性因子。
抗壞血酸增強鐵吸收的機制已經(jīng)得到很好的證實（Fairweather-Tait，1995）。由于獼猴桃富含抗壞血酸，食用含有鐵的獼猴桃會產(chǎn)生
Conclusions
Kiwifruit is a nutrient-dense food, containing nutritionally significant amounts of several key micronutrients often found to be deficient, even in high-energy Western diets. High levels of ascorbic acid in kiwifruit have been shown to aid mineral uptake and retention both in vitro and in vivo. Consumption of kiwifruit can therefore make an important contribution to an individual's diet and health.

結(jié)論
獼猴桃是一種營養(yǎng)豐富的食物，含有大量營養(yǎng)豐富的幾種關(guān)鍵微量營養(yǎng)素，即使在高能量的西方飲食中也是如此。獼猴桃中高水平的抗壞血酸已被證明有助于體外和體內(nèi)礦物質(zhì)的吸收和保留。因此，食用獼猴桃可以對個人的飲食和健康做出重要貢獻。

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