myoglobin that provides oxygen to muscle . The remaining iron is stored in the protein-bound form of ferritin or hemosiderin in the liver , spleen and bone marrow . Transferrin is the main protein in blood that binds to iron and transports it throughout the body . Menstruating women and those who are pregnant or lactating lose iron specific to these conditions which explains the higher RDAs noted in table 1 .
Although the literature is not clear on the subject , there is some evidence to suggest that the elderly well , males and females , have higher levels of stored iron than iron deficiency . 2 ( This information was abstracted from the Framingham Heart Study and is therefore limited to white males and females .) Higher levels of stored iron were linked to cardiac arrythmias also general fatigue and probably represent one of the factors impacting osteoporosis .
A healthy , balanced diet and dietary supplements , where appropriate , will usually provide adequate iron . The greatest food source is meat , particularly red meat ( heme-iron ). Iron is also present in vegetables , particularly dark leafy greens and legumes , and fortified grains ( non-heme iron ). The amount of iron we can absorb from these sources is termed the bioavailability . For example , the bioavailability of iron from red meat is about 40 %. From non-meat sources it ranges from 2-20 %.
As food labelling has assumed greater prominence in recent years , one can identify the amount of iron in processed foods ranging from the increasingly popular breakfast / energy bars to plant-based meat substitutes and ubiquitous breakfast cereal . Some of these labels identify the available iron in milligrams ( mg ) only , percentage DRV only , or both together . For example , I use a particular brand of farro , a type of wheat , as a side dish – a substitute for potatoes or rice . The labelling on the particular brand that I use indicates that each serving provides 2mg iron which is listed as 10 % DRV . This equation would therefore have 20mg as 100 % DRV . For me and my husband , 2mg per serving is actually 25 % of our daily iron requirement . Beyond Beef is a brand of plant-based meat substitute . Our son introduced us to this on a recent trip to San Francisco . We enjoyed the beef patties on brioche buns . I found the same products at our local market when we returned . I read the food label before buying . Each pattie contains 3.7mg iron which is listed as 20 % DRV . Thus 18.5 mg would be 100 %. The brioche buns contain 0.5mg iron listed as 2 % DRV . Thus 25mg would be 100 %. Whole Grain Cheerios , the favorite cereal of our grandson in San Francisco , contains 18mg iron per serving , listed clearly as 100 % DRV . Referring back to table 1 we see that this amount is the daily allowance only for adult menstruating females , no other group .
So the conundrum continues . A salient question would be whether or not the iron added to processed foods is 100 % absorbed after ingestion . To date I have found no source ( s ) to help determine this . Another salient question would be whether the individuals supervising the addition of iron to foodstuffs understand iron metabolism . The third salient question – in my mind – “ Does it really matter ?”
The National Institute of Health ( NIH ) indicates that probably no harm will come to us if we occasionally ingest up to 40mg of iron . This apparently includes infants . Frequent intake of 20mg or more may cause nausea , vomiting and / or abdominal pain . 3 Iron absorption is modified by many other things we ingest on a daily basis . Ascorbic acid / vitamin C enhances iron absorption . Polyphenols , frequently found in fruits and vegetables and other substances , reduce iron absorption . Therein lies my personal solution to the conundrum . I will continue my life-long habit of multiple cups of tea daily and chow down on Multi Grain Cheerios for the occasional breakfast with our grandson . Dinner , whether plant based or meat based , will include red wine . Each of these beverages is known to be high in polyphenols . Lucky me .
References :
1
National Institutes of Health , Office of Dietary Supplements https :// ods . od . nih . gov
2
Iron Status of Free-Living Elderly Individuals : DJ Fleming et al . American J Clin Nutr . 2001 Mar ; 73 ( 3 ): 638-646
3
Aggett P J .; Iron ; Present Knowledge in Nutrition 11 th . ed . Cambridge , MA : Elsevier ; 2020 : 375-392
Editor ’ s Note : Vitamins advertised as “ Stress Vitamins One a Day for Men ” have zero iron , typically – read the label though !
Dr . Amin is a retired diagnostic radiologist .
We are always welcoming new writers on these topics and so much more ! Please reach out to Kathryn Vance at kathryn . vance @ glms . org if you ’ d like to share your thoughts in an upcoming issue .
LOUISVILLE MEDICINE UPCOMING THEMES
April – Life After Medicine ( due 3 / 1 )
Of course there is life after medicine ! Have you retired yourself – if so , what are you doing now ? If you ’ re not retired yet , what do you plan to do in your life after medicine one day ?
May – Annual Report / No Theme ( due 4 / 1 )
As we look back on the last Presidential year and all that we have accomplished , we invite you to write on any topic of interest in this issue of Louisville Medicine . Medical or not , we want to hear what ’ s going on in your specialty and what ’ s on your mind !
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