I have always respected your posts so when I saw your title was about iron deficiencies I was buckled in. You know that old adage, “when the newspaper reports on your area of expertise it’s crap, and yet you believe the rest of it”—I always pay special attention to what people I trust/respect say about things I know a lot about, especially when there’s a lot of misinformation out there.
I have just completed the requirements for a bachelor’s degree in Nutrition with a focus in biochemistry. I am not a dietitian and will freely admit I know less about iron than you do after this lit review. But what you said makes sense and is scientifically grounded and dovetails with the stuff I know “formally”. tl;dr I am thrilled to know that I can trust all your future posts.
I did recently write a draft blog post about iron aimed at a general audience as part of an internship, and I think a few of the things I say in there will provide useful context and background.
And yes, menstruating is definitely the reason why women are recommended more—I found the original paper where that recommendation comes from and that’s what they talk about.
One thing I have to add - ‘black stools’ are also a common side effect of iron supplementation, as well as constipation, that doesn’t mean you have iron toxicity. But taking “chelated iron” avoids that side effect.
Before I start talking about iron, I want to take a step back and talk about two concepts in nutrition that are often not well communicated to the public: the RDI and the EAR.
You’ve probably seen food labels that talk about the “% RDI” of different nutrients, and you might even know that it stands for “recommended dietary intake”. There’s another concept that goes along with it that you won’t find on nutrition labels: the EAR, or “estimated average requirement”. The RDI is the daily intake that will be enough for 97.5% of people, and is used when checking if an individual is consuming enough of a nutrient. The EAR is the intake that will be enough for 50% of people, and is used in nutrition research to check if a population is consuming enough of a nutrient.
These numbers are pretty close for most nutrients, but for iron they can be very different. The iron RDI for adult men is 8 mg/day and the EAR is 6 mg/day. Similarly, the RDI for post-menopausal women is 8 mg/day and the EAR is 5 mg/day. So the RDI and EAR are 2-3 mg apart. In comparison, for women who menstruate, the RDI is 18 mg/day and the EAR is 8 mg/day — a 10 mg difference!
To put that in concrete terms, imagine 100 women of childbearing age in a room (and none are pregnant or breastfeeding). 50 of them would be perfectly healthy consuming 8 mg or less of iron a day. 48 would need between 8 mg and 18 mg a day. And two of them would need even more than 18 mg!
So, even though the food labels recommend 18 mg of iron for women in this age range, half of them will have enough iron eating less than half the recommended amount — and 2% will need even more than the recommendation! This is why some people will have low iron levels, and other people who eat almost identical diets will have good levels. There’s a lot of variation in iron needs in this particular group and it comes down to variability in menstrual losses: for example, some women in this age group don’t menstruate at all and some may experience very heavy periods.
I’ve noticed this in the vegetarian community: a lot of people will say vegetarians don’t need to take iron supplements because their own iron levels are great, citing spinach or some other iron-rich vegetable as the reason for this. A cup of raw spinach contains 0.8 mg of iron, and the RDI is 18 mg. A typical daily “women’s multivitamin” contains around 5 mg of iron, the equivalent of 6 cups of raw spinach, every single day! For comparison, 100g of tofu contains about 3 mg of iron and 100g of beef contains about 3.5 mg of iron. It is most likely that people claiming that they don’t need iron supplements happen to be ‘lucky’ and need lower intakes.
On the subject of vegetarianism, contrary to popular belief, vegetarians and vegans tend to consume about the same amount of iron as people eating a typical western diet and are at similar risk of deficiency (https://academic.oup.com/ajcn/article/70/3/353/4714844 and https://www.mja.com.au/journal/2013/199/4/iron-and-vegetarian-diets ). However, due to the reduced absorption of iron from plant foods (18% is absorbed from a mixed western diet but only 10% from a vegetarian diet), it is recommended that vegetarians consume 80% more iron.
This is because there are two types of iron: heme iron, from animal sources, and non-heme iron, from plant sources. Heme iron is more easily absorbed, which is why vegetarians need more iron. A misconception about heme and non-heme iron is that all iron in meat is heme, but in fact, more than half of iron in meat is non-heme. So, 100g of beef would contain about 2 mg of non-heme iron and 1.5 mg of heme iron, while 100g of tofu contains 3 mg of non-heme iron. Non-heme iron absorption can be improved by consumption of vitamin C, which is abundant in most vegetarian and vegan diets.
So, where does all that leave us?
The only way to be sure of your iron status is to have a blood test, as I recommended in the previous article [unpublished; basically a much simpler version of the OP]. If your levels are low, you may want to incorporate more iron-rich foods in your diet, and ensure you consume vitamin C around the same time. You may also want to consider a supplement, especially if you have heavy periods. Whatever you do, you should get follow-up blood tests to ensure that it is working.
Iron supplements can often cause dark stools and constipation, so you may want to try several brands to find one that works for you. Some iron supplements contain “chelated iron”, which is more gentle on the stomach. [plug for advertised product removed]. For treatment of deficiencies under appropriate medical supervision, high-dose Ferrograd-C is available from pharmacies [in Australia]—though this contains non-chelated iron.
Finally, do not take high doses of iron supplements outside of medical supervision: they can be dangerous.
I mean, you don’t? You can look it up but recent advice was something like 10 days after first symptoms is when contagiousness reduces.
Anecdotally, my husband was sick on Friday and took rapid tests on Friday and Saturday (when he was very sick) and got negative. Then on Monday his rapid test was positive (followed by a positive PCR on Tuesday). So he was no doubt contagious on two days when he gave negative tests.