Can iron-rich food cause an overdose?

Question

Daily Value (DV) for iron for adults and children age 4 and older is 18 mg (Office of Dietary Supplements, NIH.gov). Can iron-rich foods cause an overdose of iron, if 150 % daily value (27 mg) is consumed in one day?

Like, let's say (theoretically):

Someone ate 3 1/2 boxes of cereal (12 cups/ box), in one day. Iron daily value is listed as 45% (8.1 mg) per 1 1/2 cup. What would happen?

or

Someone ate 9 leaves of kale (assuming that that's 1.5 lbs. or ~680 grams of kale), which contain 10 mg of iron in total, which is 55% Daily Value. What would happen?

I found similar questions online, but I'm wondering about an acute situation, and not supplements, but just food that contains iron (for example, kale).

Answer 1

The consumption of food that contains 150% Daily Value or 27 mg of iron only once by a healthy person should not result in any side effects.

This is because Tolerable Upper Intake Levels (maximum daily intake unlikely to cause adverse health effects) for iron for individuals age 0-13 is 40 mg and for those age 14 or older is 45 mg (Office of Dietary Supplements, NIH.gov).

Is acute iron overdose from food (not supplements) in healthy adults possible?

Not likely. According to Office of Dietary Supplements, NIH.gov:

Adults with normal intestinal function have very little risk of iron overload from dietary sources of iron.

and

acute intakes of more than 20 mg/kg iron from supplements or medicines can lead to gastric upset, constipation, nausea, abdominal pain, vomiting, and faintness.

For a 70 kg man, this is 1,400 mg of iron, which is virtually impossible to get from foods even highest in iron.

What happens with iron consumed in excess of the body needs?

Most of the excessive iron probably won't be absorbed (AJCN):

If an individual requires more iron, more iron will be mobilized from body iron stores and there will be an increase in intestinal iron absorption. However, if the body is iron replete, these processes will be downregulated.

According to vivo.colostate.edu:

Iron abundance states: iron within the enterocyte [intestinal lining cell] is trapped by incorporation into ferritin and hence, not transported into blood. When the enterocyte dies and is shed, this iron is lost.

Would a single ingestion of 150% Daily Value of iron be harmful for a person with hemochromatosis?

Not likely. According to the article The myths and realities of hemochromatosis (Canadian Journal of Gastroenterology):

Although dietary iron is the source of excess iron in hemochromatosis, a decrease in dietary iron has not been shown to decrease iron stores in hemochromatosis.