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Low serum iron -- is this, or is this not, problematic for male CR practioners?


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Dear colleagues,


Below is a list of the last eight measurements of my serum iron levels:


Standard Range

Iron 45 - 170 ug/dL 10/12/14 4/2/15 10/29/15 5/23/16 12/23/16 6/9/17 11/13/17 3/5/18


130 63 92 93 62 95 32 33


Notice that the standard range is 45 - 170 ug/dL; my last two readings -- 11/13/2017 and 3/5/2018 -- were

well below this. (All readings prior to 10/12/2014 were in the normal range).


I felt faint early last Monday, but managed to teach my 9-10:15AM and 2-3:15PM courses. Between courses,

I went to Urgent Care in the medical group where my primary physician (specialized in gerontology) works.

Blood was drawn. Serum iron was 33 ug/dL -- low. I received a note from another NP who works in the same office,

suggesting an iron supplement.


I should note that I felt much better the next day, and the problem hasn't recurred. Although I have had a tendency to feel fatigued

for the last few years -- might this be a side effect of CR, aging, and/or low serum iron?


I thought I would check the high expertise of some of our members.


-- Saul

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Disclaimer: I'm not a doctor, so the following is my layman's opinion! But unless you have anemia, there really shouldn't be any connection between low serum iron and your feeling faint/weak. More interesting would be to find out what your ferritin levels are, that way one can see what your long term iron storage is, apart from serum fluctuations. If your ferritin is within range, then the low serum iron is not a long term issue. Has you diet or drug regimen changed in recent months such that it could explain why your iron is low?

FWIW, I think in general, people on CR have issues with iron. I remember years ago Dean P. had to re-jigger his diet to allow his body to absorb more iron - I've had a very similar issue. Again, I think you should check your ferritin level. Supplementing with iron is a last resort, and one should do it as sparsely as possible - iron is a nasty thing in excess. 

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FWIW, here is Michael Rae's statement on iron (for vegetarians/vegans):




Milligram-for-milligram, iron absorption from vegetarian diets is only about half of that from meat-based ones, and in some strict and traditional vegetarian diets may dip to less than one-third, for several reasons.[xviii] The iron in plant foods is much less bioavailable than the heme iron that predominates in meat; meat itself actually increases nonheme iron absorption, so that a mixed omnivorous meal increases the absorption of the plant-based iron; and because vegetarian diets tend to be higher in phytic acid and other inhibitors of iron absorption.  Therefore, has long been a concern that vegetarians might be at risk for iron-deficiency anemia.


Counterbalancing this reduced bioavailability is the fact that absolute iron levels in self-selected Western vegetarian diets tend to be significantly higher than those in omnivorous diets. Additionally, studies show that the body does adapt over time to reduced intake of readily-absorbed iron by actively increasing absorption and retention.[xix],[xx]


Tests performed in free-living vegetarians have generally found that while iron status does tend to be lower in vegetarians than in omnivores, the prevalence of actual iron deficiency is no higher in most Western vegetarian populations than in their omnivorous neighbors. The main exceptions to this generalization has been in Asian immigrant communities and macrobiotic dieters,[xxi],[xxii] due in part to their high intake of phytic acid-rich foods such as brown rice and unleavened chapattis, and possibly high-tannin teas.


And there is an upside to getting most of your iron in the highly-bound forms that predominate in vegetarian diets, and to the resulting historical tendency toward low-normal iron status in Western vegetarians: by reducing the formation of lipid hydroperoxides by free radical reactions catalyzed by the breakdown of heme iron in the gut,[xxiii] and the age-related increase in non-heme iron body burden,[xxiv] it may contribute substantially to the lower rate of cardiovascular mortality and possibly other diseases in ‘average’ vegetarians.


However, you certainly don’t want this favorably-low iron status to slide into iron-deficiency anemia, as it certainly can. Indeed, ironically, many of today’s more health-conscious vegetarians may be actively compromising their iron status as an unintended consequence of trying to further improve their diets with ‘superfoods.’ Well-known inhibitors of iron absorption in “health foods” (and pseudo-health foods) include phytic acid (present at high levels in unleavened whole grains), fiber, and complex polyphenols (‘tannins’) present in red wine, cocoa (and especially high-flavanol raw and undutched cacao), and a variety of novel ‘antioxidant superfoods’ like açai and goji berries.[xxv]


Bioavailability of nonheme iron can be boosted through the intake of organic acids in ‘acid-ash’ foods such as fruits (especially citrus) and most vegetables; by increasing vitamin C intake at meals; by sprouting, soaking, and fermenting seeds, grains, and legumes; and by  avoiding the intake of absorption-inhibiting foods at mealtime, such as cocoa and black tea.


With so many factors playing into an individual vegetarian’s functional iron status, it can be difficult to know with confidence that you are getting all the iron you need for long-term health. An important first step is to track your intake of iron with your nutrition software,  bearing in mind that because of the lower bioavailability of vegan iron, the RDA indicated by default in such software will not be enough to reliably meet your functional needs. For this reason,  the IOM has set an RDA for iron intake in vegetarians of 15 mg for men and postmenopausal women, 32 mg for younger adult women,  and a whopping 50 mg for pregnant and lactating women, instead of the 8, 18, and 27 mg (respectively) for the general population.xviii Fortunately, iron is again one of the relatively few nutrients for which well-established markers of functional status exist. While a panel of iron markers can be useful in some cases, a blood test for ferritin (using the lab’s reference range, and remembering the likely advantages of low-normal ferritin) should reliably establish your iron status.


If your levels are low, a supplement is in order in the short term, along with any engineering of your diet that you can do to correct the underlying deficiency. Despite health-food-store hype, there’s little evidence to support the superiority of iron amino acid chelates or other ‘special’ forms over more common iron sulfates or gluconate; after the first month, however, if you haven’t clearly recovered after dietary tweaks and supplementation, a more long-term supplement is required,  and you may want to switch to  iron protein succinylate (available as IronSorb from Jarrow or Iron Protein Plus from the Life Extension Foundation), which seems to take longer to initially restore iron status but does a better job of maintaining it long-term and as is less likely to cause constipation or other GI problems.[xxvi]


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And here is an excerpt from  "Becoming Vegan: Comprehensive Edition: The Complete Reference to Plant-Base Nutrition" by Brenda Davis and Vesanto Melina.


Iron in Perspective


In the past, nutrition texts rated nonheme iron from plant foods as inferior to heme iron in meat, because the body generally absorbs a lower percentage of nonheme iron. We’re now aware that relying on nonheme iron gives the body more control over absorption efficiency, by allowing it to adjust uptakes to suit its needs. If its iron reserves are low, the body absorbs more iron from plant foods; if iron reserves are abundant, the intestines can absorb a lower proportion of nonheme iron. (Food preparation and combinations also affect absorption of nonheme iron.) 2,29,36– 40


The heme form of iron found in meat and blood tends to be more readily absorbed— even when the body doesn’t need any iron. Once iron has been absorbed, the body has limited mechanisms for ridding itself of any excess. Because iron is a prooxidant, too much in the body may damage DNA and other molecules. New research also indicates that high iron intakes and a burden of excess iron in the body have been associated with Alzheimer’s and Parkinson’s diseases, arthritis, type 2 diabetes, cardiovascular disease, and colorectal and other cancers. To avoid iron overload, consuming the nonheme form found in plants is recommended. 2,29,36– 40


Although the oxidative stress of excess iron is best avoided, the body does need enough for vital functions. Iron-deficiency anemia is no more prevalent among vegans and other vegetarians than among nonvegetarians. Yet iron deficiency is the primary nutritional deficiency worldwide for people on any diet, especially for women of childbearing age, infants, and teens. In the United States, the prevalence of iron-deficiency anemia among youths and adults is estimated at 2 to 5 percent among females and 1 to 2 percent among males. 2,29,38,41


Function and Losses


As a constituent of red blood cells, iron plays a central role in transporting oxygen throughout the body, releasing this life-giving substance where needed, and carrying away the metabolic waste product, carbon dioxide. In myoglobin, iron delivers oxygen to working muscles. As part of many enzyme systems, iron is a key element in the production of cellular energy, in immune system functioning, in detoxification, and in the mental processes surrounding learning and behavior. 20


The body continuously breaks down red blood cells and builds new ones, efficiently recycling the iron reclaimed from spent red blood cells. However, each day tiny amounts of iron are lost in cells sloughed from the skin and from the inner lining of the intestine; these losses must be replaced from food or supplements.


Other causes can contribute to iron deficiency. Women of childbearing age have menstrual iron losses in the range of an extra 30 to 45 mg each month, making their dietary requirements higher than those of men. Growth and the building of new cells can deplete the small reserves of iron in infants and children. Teens experience the challenges of a powerful growth spurt and notoriously poor eating habits; in addition, girls have menstrual losses. Young obese women on poorly designed weight-loss diets are another group at risk for iron deficiency. People with blood loss for any reason (such as ulcers or blood donation) have an increased need for iron. Athletes have somewhat higher requirements due to increased oxygen demands and greater iron losses (see chapter 13). 38,49


Recommended Intake


The RDAs for men and postmenopausal women are set at 8 mg of iron per day and for women of childbearing age at 18 mg of iron per day. Although a separate RDA hasn’t been set for vegetarians (including vegans), the Institute of Medicine (IOM) advises aiming for 1.8 times as much iron as nonvegetarians due to the lower bioavailability of nonheme iron from plant foods. Following this guide, vegetarian women of childbearing age are advised to get 32.4 mg of iron per day, and other adults are urged to get 14.4 mg of iron. For other ages, see page 447 and multiply recommended intakes for iron by 1.8.29,38,42,43,49


The higher recommendation for vegetarians is controversial, because it was based on a single poorly designed study. In this study, participants consumed vegetarian diets low in components known to enhance iron absorption (such as vitamin C and organic acids from fruits and vegetables) and high in substances known to interfere with iron absorption (such as tannins). In addition, the study wasn’t conducted on vegetarians or vegans, who typically develop lower serum ferritin levels that optimize absorption. Vegans who include vitamin C– rich foods as part of their meals and who don’t routinely include tea, coffee, or calcium supplements with meals are less likely to need this suggested level of iron intake. Still, there’s widespread agreement that vegetarians, including vegans, should aim for more iron than nonvegetarians. 29,38,42,43,49


Vegan Intakes and Iron Status


Research has shown vegans have average iron intakes that are similar to or higher than those of nonvegetarians and higher than the RDA, though they don’t generally reach the higher levels of 32.4 mg iron per day suggested for vegetarian women of childbearing age. Studies have shown vegan women in the United States have average intakes of about 22 to 23 mg iron daily, higher than those of nonvegetarian controls; vegan women in Germany had average intakes of 20 mg iron daily. Average iron intakes of vegan men in the United States were significantly higher than those of nonvegetarians. For both genders, the average iron status of vegan groups— as shown by hemoglobin, hematocrit, and ferritin levels— was adequate and, where reported, compared favorably with nonvegan controls. 29,30


Laboratory Tests for Iron


A number of routine laboratory tests reflect iron status. These include hemoglobin (showing the amount of this iron-containing protein), hematocrit (indicating the concentration of red blood cells), and serum ferritin (a measure of the amount of stored iron). Vegetarians typically have lower serum ferritin levels than nonvegetarians. This common situation doesn’t affect how a person feels and isn’t an issue if a person’s diet continues to replenish lost iron. Unless a period of starvation occurs, there’s no apparent benefit to having more than minimal iron stores.


In fact, lower levels of serum ferritin may be an advantage and are linked with better insulin sensitivity and reduced risk of type 2 diabetes. 2,36,36,40,44 Researchers also are exploring the possibility of links between lower serum ferritin and reduced risk of coronary artery disease, colon cancer, and inflammatory conditions. 2,29,45 With iron depletion, however, there can be a decrease in other indicators of iron status. A tired feeling and sensitivity to cold may develop. Iron-deficiency anemia occurs when blood hemoglobin drops below the normal range. When the body’s oxygen-delivery system is impaired, people are likely to feel exhausted, irritable, and lethargic and have headaches; the skin may appear pale. Iron deficiency is easily diagnosed; doubts can be resolved with a blood test, and progress can be tracked as the situation is remedied. 46


Dietary Sources


Legumes are good plant sources of iron. They provide 3 to 6 mg of iron per 1 cup (250 ml) of beans or lentils or per ½ cup (125 ml) of soybeans or tofu (see table 6.2 on page 204). A serving of fortified breakfast cereal can supply as much as 18 mg of this mineral. Iron intake can quickly reach recommended levels with an assortment of vegetables, oatmeal or other whole grains, pumpkin seeds, and dried fruit. Dark chocolate or molasses (especially blackstrap) offer sweet ways to increase iron intake. Because molasses can also be a concentrated source of pesticides, organic brands should be chosen. Finally, when acidic foods (such as tomato sauce) are prepared in iron cookware, the sauce takes up some iron from the pan. 2


Special Issues


The percentage of nonheme iron absorbed from plant foods varies, based on the body’s needs, on food preparation methods, and on the food and beverage combinations eaten. Although iron (and zinc) deficiencies are associated with marginal plant-based diets of impoverished people in some parts of the world, this isn’t the situation in regions where the food supply and variety are sufficient. 1,2,6,8,38,47,48


As noted in the section on phytates (page 181), soaking, fermenting, yeasting, and sprouting plant foods increases the body’s absorption of iron and other valuable minerals. 48 Oxalate appears to have a variable, and sometimes minimal, impact on iron availability from calcium- and iron-rich foods such as spinach, for example, because its calcium is preferentially bound. 15,16


Absorption from iron-rich plant foods increases markedly when foods high in vitamin C (such as red bell peppers or strawberries) are eaten at the same time because iron is converted from a ferric form to a more readily absorbed ferrous form. The citric acid in citrus fruits also enhances iron absorption. Obsolete food-combining rules that insist fruit must be eaten separately from other foods can be ignored, especially by consumers low in iron. The beta-carotene in yellow, red, and orange foods also aids iron absorption. 2,6


Vegans eat plenty of fruits and vegetables, and typically get more than one and a half times as much vitamin C as nonvegetarians— a clear advantage when it comes to iron absorption. For example, 5 ounces (150 ml) of orange juice containing 75 mg of vitamin C has been shown to increase the absorption of iron from foods eaten at the same time by a factor of four. Other studies show 50 mg of vitamin C to enhance iron absorption sixfold. Eating ¾ cup (185 ml) of any of the following provides 50 mg of vitamin C: broccoli, Brussels sprouts, cauliflower, collard greens, bell peppers, snow peas, cantaloupes, citrus fruits and juices, guavas, papayas, strawberries, and vitamin C– fortified juices; so does having a kiwifruit, ¼ cup (60 ml) of sweet red bell pepper, or a big salad.


Even after cooking, some vitamin C remains; for example, vegetables retain about 85 percent of their vitamin C when microwaved, 70 percent when steamed, and 50 percent when boiled. (Losses vary with cooking time and temperature.) A large baked potato retains 30 mg of vitamin C after baking. 2,49– 51


 Onions and garlic can increase the availability of iron (and zinc) from grains and legumes by 50 percent, further boosting iron intake. 52

In contrast, absorption of dietary iron decreases in the presence of tannins and other polyphenols in black tea, coffee, cocoa, and red wine. Calcium supplements also inhibit iron absorption. 2,6 To maximize iron absorption, it’s wise to consume these inhibitors an hour apart from iron sources.




For people whose blood tests show they’re anemic, iron supplements or iron as part of a multivitamin-mineral supplement can be helpful. However, excessive amounts of this prooxidant mineral in supplements are best avoided. When the deficiency has been resolved, a diet that features good plant sources of iron— combined with vitamin C– rich foods— is a better choice for long-term maintenance. 46


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Hi Saul,


Feeling faint and fatigued could have many causes with anemia certainly being one of them, especially for someone such as yourself following a restricted, largely plant-based diet.


Serum iron level isn't the best way to test for anemia. You should get a standard CBC test done, and look at hematocrit and hemoglobin. Those measure the number of red blood cells in your blood and their ability to carry oxygen.


I can't imagine you got a serum iron test without also getting a CBC, particularly if you complained of feeling faint. If you've got the numbers from your CBC, it would really help rule out (or in) a diagnosis of anemia.


Ferritin is also a useful measure, but it is what you would call a "lagging indicator", measuring long-term iron stores in your blood.


If your hemoglobin is low and has dropped from previous tests, then you should definitely consider changing your diet and/or supplementing with iron. Anemia is both bad for your long-term health and saps your quality of life.



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Hi Tom, Sibiriac and Dean!


Thanks for your timely responses!


Here are some the recent numbers:


RBC 4.2 MIL/uL 4.6 - 6.1 MIL/uL

Hemoglobin 13.9 g/dL 13.7 - 17.5 g/dL

Hematocrit 40 % 40 - 51 %

Platelets 196 THOU/uL 150 - 330 THOU/uL

Folate 8.5 ng/mL >=4.6 ng/mL

Transferrin 255 mg/dL 200 - 360 mg/dL

Iron 33 ug/dL 45 - 170 ug/dL

Ferritin 87 ng/mL 20 - 250 ng/mL


Some details: Almost all of these numbers are consistent with my past measurements.


The exceptions: Folate and Transferrin simply haven't been tested before; the numbers are good, but there's nothing to compare them with.


Iron is the other exception: My current measurement, and the one made in November, 2017 (which showed 32), are markedly lower than the many tests done in the past (including as late as June 9, 2017), which were well in the normal range.


So serum iron may be technically low -- as correctly noted by all three of you, this lower number probably should be of no concern for those of us (all of us) who practice a plant-based diet -- whether or not minimally omnivorous.


My guess (I think) for my unusual tiredness last Monday: I had had a very bad night the night before: almost no sleep. I'd been inordinately worried about something that I had to teach in an elementary calculus course that I would teach the next morning.


Monday morning, my wife (who is an ANP specialized in gastroenterology), and an NP (an FNP) in my primary's office both noted that I looked very pale -- also suggesting anemia.


I should note that, my numbers above -- as well as past numbers -- DO imply, technically, that I have anemia. My CR friendly nephrologist, who writes the scripts for my semi-annual bloodwork (but not the ones just done), does write in his notes that I have cronic anemia.


I've explained to him, and he understands, that this is common among CRONnies. Nevertheless, he is happiest when my RBC is higher -- but it's always well below normal.


(My sodium levels are also always below normal -- but sometimes get very close to low normal -- when again my nephrologist is happiest. However, he has noted that I have a serum sodium setpoint that is lower than FDA guidelines -- which he claims may not be relevant for me -- by extension, probably not for other serious CR practitioners as well.)


-- Saul

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Thanks Dean. That had been my thought, too. Definitely, consistent with previous posts to the old CR email list, it would be a big mistake for me to supplement iron, as the ANP that I saw thought.


But I'll hash this out with my CR friendly nephrologist at URMC, when I see him in May.

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thanks a lot for so many useful posts here! am really appreciating it all as i am also a sufferer of low serum iron! here i found some very good tips and advices but i still wanted to ask you if i may ask you some questions as i'm new here and i'm not sure.. thanks!

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