铁是必不可少的矿物。
但是，像许多其他营养素一样，它的大量有害。
实际上，铁是如此的毒性，以至于其从消化道中的吸收受到严格控制。
For the most part, this minimizes the harmful effects of excess iron.
It is when these safety mechanisms fail that health issues arise.
本文讨论了消耗太多铁的潜在有害影响。
Iron is an essential dietary mineral, mostly used by red blood cells.
它是血红蛋白的关键部分，血红蛋白是在红细胞中发现的蛋白质。血红蛋白负责向所有人体细胞输送氧气。
There are two types of dietary iron:
- 血红素铁：This type of iron is only found in animal foods, mostly inred meat。它比非血红素铁更容易吸收。
- 非血红素铁：大多数饮食铁是非血红素形式的。它在动物和植物中都发现。可以用有机酸（例如维生素C）增强其吸收植物。
饮食中几乎没有血红素铁的人会增加铁缺乏症的风险（
许多人是铁不足的，尤其是女性。实际上，铁缺乏是世界上最常见的矿物质缺乏（
Bottom Line:铁是一种必不可少的饮食矿物质，在整个人体中运输氧气中起着重要作用。铁缺乏症在女性中很常见。
There are two reasons why iron levels are tightly regulated within the body:
- 铁是一种重要的营养素，在许多基本身体功能中起作用，因此我们必须获得一个小数量。
- 高水平的铁有可能有毒，因此我们应该避免too much。
The body regulates iron levels by adjusting the rate of iron absorption from the digestive tract.
肝素是人体的铁调节激素，负责使铁储存保持平衡。它的主要功能是抑制铁的吸收。
Basically, this is how it works (
- High iron stores -> Levels of hepcidin increase -> Iron absorption decreases.
- Low iron stores -> Levels of hepcidin decrease -> Iron absorption increases.
在大多数情况下，该系统运行良好。但是，一些抑制肝素产生的疾病会导致铁超负荷。
On the other hand, conditions that stimulate hepcidin formation may cause iron deficiency.
铁平衡也受我们饮食中铁的影响。随着时间的流逝，铁的饮食含量低可能会导致缺乏。同样，过量的铁补充剂可能会导致严重的铁中毒。
Bottom Line:消化道的铁吸收速率受激素肝素严格调节。但是，几种铁超负荷疾病可能会破坏这种脆弱的平衡。
铁毒性可能是突然的或逐渐的。
Many serious health problems may be caused by accidental overdoses, taking high-dose supplements for a long time, or chronic iron overload disorders.
在正常情况下，几乎没有自由铁在血液中循环。
It is safely bound to proteins, such as transferrin, which keep it from causing harm.
但是，铁毒性可以显着增加体内“游离”铁的水平。
Free iron is a pro-oxidant – the opposite of anantioxidant- 并可能对细胞造成损害。
Several conditions may cause this to happen. These include:
- 铁中毒：Poisoning can occur when people, usually children, overdose on iron supplements (
5 ,6 ）。 - Hereditary hemochromatosis:A genetic disorder characterized by excessive absorption of iron from food (
7 ）。 - 非洲铁超载：食物或饮料中的高水平铁引起的一种饮食过载。它最初是在非洲观察到的，在铁锅中酿造自制啤酒（
8 ）。
Acute iron poisoning happens when people overdose on iron supplements. Single doses as low as 10–20 mg/kg may cause adverse symptoms. Doses higher than 40 mg/kg require medical attention (
同样，重复的高剂量铁补充可能会导致严重问题。确保遵循有关铁补充剂的说明，并且切勿比医生推荐的更多。
Early symptoms of iron poisoning may include stomach pain, nausea and vomiting.
逐渐地，过量的铁在内部器官中积聚，从而对大脑和肝脏造成潜在的致命损害。
长期摄入大剂量补充剂可能会逐渐引起类似于铁超负荷的症状，以下更多讨论。
Bottom Line:铁毒性是指多余铁的有害作用。当1）服用过量的铁补充剂时，可能会发生这种情况，2）服用高剂量补充剂过长或3）患有慢性铁超载障碍。
铁超负荷是指体内过多铁的逐渐堆积。这是由于人体的调节系统无法将铁水平保持在健康的限制之内。
对于大多数人来说，铁超负荷不是问题。但是，对于那些在遗传上易于过度吸收铁中的铁的人来说，这是一个问题。
The most common iron overload disorder is hereditary血色素沉着病。This leads to the build up of iron in tissues and organs (
Over time, untreated hemochromatosis increases the risk of arthritis, cancer, liver problems, diabetes and heart failure (
身体没有简单的方法来处理额外的铁。摆脱过量铁的最有效方法是失血。
Therefore, menstruating women are less likely to experience iron overload. Likewise, those who donate blood frequently are at lower risk.
If you are prone to iron overload, you can minimize the risk of health problems by:
- Reducing your intake of iron-rich foods, such as red meat.
- 定期献血。
- 避免将维生素C与富含铁的食物一起服用。
- 避免使用铁炊具。
但是，如果您尚未被诊断出铁超负荷，通常不建议减少铁摄入量。
Bottom Line:Iron overload is characterized by excessive amounts of iron in the body. The most common disorder is hereditary hemochromatosis, which may lead to many health problems. This is not a concern for most people.
毫无疑问，铁超载可能导致动物和人类的癌症（
看来定期捐献或失血可能会降低这种风险（
Observational studies suggest that a high intake of heme iron may increase the risk of colon cancer (
人类的临床试验表明，补充剂或红肉的血红素铁可能会增加消化道中引起癌症的N-硝基化合物的形成（
The association of red meat and cancer is a hotly-debated topic. Although there are some plausible mechanisms explaining this link, most of the evidence is based on observational studies.
Bottom Line:铁超负荷障碍与患癌症的风险增加有关。研究还表明，血红素铁可能会增加结肠癌的风险。
Both iron overload and iron deficiency appear to make people more susceptible to infection (
There are two reasons for this (
- 免疫系统使用铁杀死有害细菌，因此需要一些铁才能抵抗感染。
- 游离铁的水平升高刺激细菌和病毒的生长，因此铁可以具有相反的作用，并且增加the risk of infections.
几项研究表明，补充铁可能会增加感染的频率和严重程度，尽管一些研究发现没有影响（
遗传性血色素症患者也更容易感染（
For patients at a high risk of infection, iron supplementation should be a well-grounded decision. All potential risks should be taken into account.
Bottom Line:铁超载和高剂量铁补充可能会增加某些人感染的风险。
