The new VITAMIN CRITERIA is most adamant about NO IRON multiples for everyone. WHY?
Iron is like fire. In a controlled fire pit, it has benefits for warmth and cooking foods. But, uncontrolled, it is capable of great destruction. ref
The body has developed a method to help control iron. It combines it with a protein called ferritin which lowers its reactive potential. Plus, the absorption of iron is regulated to just small amounts. Iron is very reactionary with radicals, like ROS, reactive oxygen species. Food sources of iron are usually sufficient and better able to contain the possible iron /ROS reactions. Once absorbed, the body does not like to give iron up. In fact, every seven years, the body completely exchanges all the minerals in the body with new ones. The last mineral molecule to be exchanged is usually an iron. 
Why is it necessary to control iron?
Rust. Automobiles rust, and outdoor barbecues, water pipes and storm drains. This rust action also affects the body. Unprotected iron leads to "body rust." In the presence of oxygen, Iron readily oxidizes and forms radicals called ROS, reactive oxygen species. Increased amounts of ROS are capable of damaging cell structures and DNA. They are neutralized by antioxidants to protect against any DNA destruction. And yes, a controlled amount of ROS is needed and used by the body for beneficial actions.
But we need iron for red blood cell production. Why the dilemma?
It's a mystery of nature. The goal is to get just the right amount of iron and keep it protected. Only with a loss of blood do you also eliminate iron. Even when the body breaks down old red blood cells, it often recycles the iron into new red blood cells.
Iron oxidizes and creates rust. Eating red meat increases iron. In fact, the red meat itself is a dilemma. It appears the protective mechanisms of the body to prevent excess iron intake are hindered when iron arrives in red meat. High red meat eaters may assimilate too much iron.
Type 2 diabetes is increased by 28% when iron levels are high. Even though supplements have low absorption rates, non red meat food sources are best since they allow the wisdom of the body to dictate how much to absorb.
Note: Of course, if your Doctor tested and found you anemic, he would recommend an iron supplement. Unfortunately, Doctors usually say to take ferrous sulfate at 325 mg. This is NOT 325 mg of iron, it is only 67 mg of elemental iron. At 325 mg, iron could do immense damage to the body. ref This sulfate iron combination is hard on the body and constipation often results. Supplement sources are available in forms that are easier on the system and often result in quicker increases in blood counts, even though they contain much lower amounts of iron. Could be due to the inclusion of vitamins C, B12, folic acid, and a little copper which work synergistic with iron. Floradix Iron tonic is quite effective even though very low iron. A liquid liver cap also works quite well from Enzymatic Therapy. These observations are from use of these products during chemo and surgery recovery times to maintain blood iron counts so drugs or treatments would not have to be postponed.
SPECIAL NEEDS DURING PREGNANCY
Obviously there are extraordinary demands on iron reserves when a fetus is growing inside a woman. Increased blood building demands greater iron for Red blood cell production. Nature gives iron priority to the fetus and if not enough iron is in the diet, the woman suffers. Iron deficiency (ID) and iron deficiency anemia (IDA) are major problems around the world. Iron is typically supplemented as ferrous sulfate. While this tends to work, there are many side effects from ferrous sulfate supplements at the amounts needed. For over ten years now in research studies, the supplement lactoferrin with 30% infused iron has been compared to ferrous sulfate. ref And the results have all been favorable with equal or better red blood cell building and iron reserves plus reduced if any gastrointestinal side effects. An added bonus is that lactoferrin reduces inflammation while ferrous sulfate increases inflammation, most likely from elevated ROS actions. Infants gain the advantage of lactoferrin from breast milk.
SIDEBAR: From Wikipedia on lactoferrin, copied here: "Lactoferrin is one of the transferrin proteins that transfer iron to the cells and control the level of free iron in the blood and external secretions. It is present in the milk of humans and other mammals,[8] in the blood plasma and neutrophils and is one of the major proteins of virtually all exocrine secretions of mammals, such as saliva, bile, tears and pancreas.[13
The latest study by a team of researchers in Italy revealed another unexpected but welcomed discovery, reduced miscarriages in the lactoferrin iron treated women. ref Yes, this needs expanded studies, but the simple blood work up results are pretty compelling that benefits are real. New 2015 research from India for lactoferrin including fight against parasites. ref
Here is part of the report from the preceding ref: "Iron-saturated lactoferrin protein has been shown to generate many free radical ions (ROS) which can be helpful for inhibiting a variety of tumors, intracellular parasites, and microbes." This is representative of how and where the body uses just the right amount of free radicals for positive actions before stepping in and neutralizing them to prevent radical damage to DNA and body tissues. In this case, iron-saturated lactoferrin generates ROS to stimulate immune blood cells called macrophages to surround and destroy parasites and microbes before they can grow to numbers capable of generating disease. This process is called phagocytosis.