Zinc  鋅   男人少不了 女人不可少

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鋅是一種必需的微量礦物質，具有約 300 種不同酵素的一部分功能。 因此，鋅幾乎在所有生化途徑和生理過程中都發揮作用。 人體 90% 以上的鋅儲存在骨骼 (30%) 和肌肉 (60%) 中，但幾乎所有身體組織中也含有鋅。 鋅最豐富的飲食來源是海鮮（尤其是牡蠣）、肉、魚、蛋和家禽。

· Wound healing 促進傷口癒合

· Immune system support 支持免疫系統

· Reduces length and severity of colds (in lozenge form) 減少感冒的天數和嚴重度(口含錠)

· Supports a healthy prostate gland (prevents benign prostatic hyperplasia – BPH) 預防攝護腺肥大

· Increases fertility (sperm production) 增加精子數

由於鋅是近300 種不同生化途徑的重要組成部分，因此可以針對該營養素在多種過程中的作用進行結構/功能聲明，包括消化、傷口癒合、能量產生、生長、細胞修復、膠原蛋白合成、骨骼強度、認知功能、碳水化合物代謝（葡萄糖利用和胰島素產生）和生殖功能。 即使是輕微的鋅缺乏也會導致免疫力下降、精子數量減少和記憶力受損。 也許最近對鋅最流行的說法是它在免疫中的作用，鋅可能會幹擾感冒病毒（鼻病毒）的複製。

當然有足夠的證據支持使用鋅含片來減少感冒的持續時間和嚴重程度。 雖然濃縮鋅含片可以幫助殺死口腔和喉嚨中的感冒病毒，但重要的是在感冒症狀出現後儘快開始使用它們（最好是在最初的 24-48 小時內）。 試管研究表明，鋅可以阻止感冒病毒的複製，並且可以幫助人體的自然免疫防禦系統「快速啟動」殺死病毒。 大多數關於鋅含片（通常是葡萄糖酸鋅或醋酸鋅）對普通感冒的影響的研究表明，與服用補充劑的受試者相比，服用補充劑組的受試者往往有更少的“症狀」天數（平均少生病2-3 天）。安慰劑（以咳嗽、喉嚨痛、鼻塞和頭痛來衡量）。 有時，建議糖尿病患者服用高劑量的鋅補充劑。 這類患者通常會遭受鋅流失增加和體內鋅儲存減少的困擾。 高劑量的鋅已被證明可以模仿胰島素在降低血糖和促進傷口癒合方面的作用。 然而，這些影響應該被考慮為初步的，並且除非得到私人醫生的建議，否則不建議糖尿病患者服用高劑量的鋅補充劑。 運動表現也與充足的鋅含量有關——尤其是對於那些避免紅肉、飲食過多集中在碳水化合物或遵循過度限制飲食習慣的運動員。 鋅攝取量低（每天 3 毫克）與紅血球中一種稱為碳酸酐酶的含鋅酶（幫助紅血球將二氧化碳從組織運輸到肺部並呼出）的活性降低有關。 輕度至中度缺鋅會導致高強度運動期間吸收和使用氧氣、清除二氧化碳和產生能量的能力顯著降低。 鋅也與增強骨質形成和減少骨質流失有關——無論是單獨使用還是與植物異黃酮（如染料木黃酮）結合使用。 當與異黃酮一起使用時，鋅會增強異黃酮類化合物對骨骼的作用，並可能在預防骨質流失方面發揮有效作用。

短期使用治療劑量的鋅來緩解感冒（見下文）被認為是安全的，長期補充當前 RDA 水平 2-3 倍的鋅不應預期會造成任何明顯的不良副作用。 然而，由於擔心免疫系統抑制、幹擾銅吸收以及其他長期健康影響（例如增加心臟病風險），不建議服用高劑量鋅超過兩週。 高劑量的鋅（克水平）會導致噁心、腹瀉和嘔吐。

如果您曾經嘗試過市場上的一些鋅錠劑，請準備好接受鋅的獨特風味，這是眾所周知的，任何級別的調味劑和甜味劑都很難掩蓋這種味道。 然而，對許多人來說，鋅含片在嘴裡留下的輕微金屬味只是為了更快緩解感冒症狀而付出的很小的代價。

鋅的每日攝取量為每天 15 毫克，這水平足以支持骨骼代謝和最佳身體功能。 然而，作為感冒治療，需要更高的劑量——每 2 小時服用 13-23 毫克（含片形式），持續不超過 2 週，可有效減少感冒症狀的持續時間和嚴重程度。 盡量選擇不含山梨醇（甜味劑）、檸檬酸（調味料）和甘露醇（甜味劑）等賦形劑的含片，因為這些成分可能會與口腔中的鋅結合，降低其生物利用度和有效性。 另外需要注意的是，其他補充劑，特別是高含量的鈣和鐵，會降低鋅的吸收，同時與各種胺基酸（如甘胺酸、組胺酸和天門冬胺酸）或其他有機化合物（如葡萄糖酸鹽或吡啶甲酸）螯合可能會增加鋅的生物可利用性。

Because zinc is an essential part of nearly 300 different biochemical pathways, structure/function claims can be made for the nutrient’s role in a wide variety of processes including digestion, wound healing, energy production, growth, cellular repair, collagen synthesis, bone strength, cognitive function, carbohydrate metabolism (glucose utilization and insulin production), and reproductive function. Even mild zinc deficiency has been associated with depressed immunity, decreased sperm count and impaired memory. Perhaps the most popular claim for zinc lately is for its role in immunity, where zinc may interfere with the replication of the cold virus (rhinovirus). 

There is certainly sufficient evidence supporting the use of zinc lozenges in reducing the duration and severity of colds. Although concentrated zinc lozenges can help kill cold viruses in the mouth and throat, it is important to begin using them as soon as possible following the onset of cold symptoms (ideally within the first 24-48 hours). Test tube studies have shown that zinc can block the cold virus from replicating – and effect that could help the body’s natural immune defenses "get a jump on" killing the viruses. Most studies of the effect of zinc lozenges (typically zinc gluconate or zinc acetate) on the common cold have shown that subjects in the supplement group tend to have fewer "symptomatic" days (on average 2-3 fewer sick days) compared to subjects receiving a placebo (measured in terms of coughing, sore throat, nasal congestion and headache). Occasionally, high dose zinc supplements are recommended to diabetic patients. Such patients commonly suffer from increased loss of zinc and reduced body stores of zinc. High doses of zinc have been shown to mimic the effects of insulin in reducing blood sugar and promoting wound healing. These effects, however, should be considered preliminary and high dose zinc supplements are not recommended for diabetics except on the advice of their personal physician. Exercise performance has also been associated with adequate zinc status – especially in athletes who avoid red meat, concentrate their diets too much on carbohydrates or follow an overly restricted dietary regime. Low zinc intake (3mg/day) has been linked to reduced activity of a zinc-containing enzyme in red blood cells called carbonic anhydrase (which helps red blood cells transport carbon dioxide from tissues to the lungs to be exhaled). Mild to moderate zinc deficiency can lead to significant reductions in ability to take up and use oxygen, remove carbon dioxide and generate energy during high intensity exercise. Zinc has also been linked to enhanced bone formation and reduction of bone loss – both alone and in combination with plant isoflavones such as genistein. When used together with isoflavones, it appears that the isoflavonoid effect on bone is enhanced by zinc and may have a potent role in prevention of bone loss. 

The short-term use of zinc at therapeutic doses for cold relief (see below) is assumed to safe and chronic supplementation with zinc at levels 2-3 times the current RDA should not be expected to pose any significant adverse side effects. However, high doses of zinc are not recommended for periods of more than two weeks due to concerns of immune system depression, interference with copper absorption and other long-term health effects such as increased risk for heart disease. High doses of zinc (gram levels) can cause nausea, diarrhea, and vomiting. 

If you’ve ever tried some of the zinc lozenges on the market – get ready for the distinct flavor of zinc – which is notoriously difficult to cover with any levels of flavorings and sweeteners. For many people, however, the slightly metallic taste that zinc lozenges can leave in your mouth is a small price to pay for the quicker relief from cold symptoms. 

The Daily Value for zinc is 15mg per day – a level that should be adequate for support of bone metabolism and optimal physical performance. As therapy for colds, however, higher levels are required – with levels in the range of 13-23mg (in lozenge form) taken every 2 hours for no more than 2 weeks effective for reducing duration and severity of cold symptoms. Try to select lozenges that are free from excipients such as sorbitol (a sweetener), citric acid (a flavoring) and mannitol (a sweetener) as these ingredients may bind zinc in the mouth and reduce its bioavailability and effectiveness. It is also important to note that other supplements, particularly high levels of calcium and iron can decrease zinc absorption, while complexation (chelation) with various amino acids (such as glycine, histidine and aspartate) or other organic compounds (such as gluconate or picolinate) may increase zinc bioavailability.