You can copy and paste this URL.
This URL will permanently link back to this page.
Postscript 1 May 2012 by the author:
In light of the facts revealed in this paper, published by Best Thinking in 2011, I am grateful to the USDA for deleting their misleading spread sheet from the Internet, which claimed that drinking Florida grapefruit juice would help humans to absorb two to four times as much iron from spinach as would otherwise be possible. I now have another request for the USDA: Given that a pregnant woman would need to eat at least 14 pounds or 6kg (yes 6kg!) of spinach every single day, to have the slightest chance of absorbing her recommended daily amount of iron from that source alone, isn't it about time that you ceased promoting spinach as a good source of iron in your nutrition tables? Otherwise, it appears that the USDA might well be promoting agricultural interests over those of individuals. This is an important issue because low iron levels is one of the major nutrition problems among women in the USA, leading to disability and early death. Moreover, the most common source of poisoning of children in the USA is from young children overdosing on iron pills in the home. If proper advice is not given regarding the best nutritional food sources of iron then it seems reasonable to hypothesise that more supplements will be taken - leading to more infants suffering from accidental iron overdose.
The main aim of the article is to reveal and explain why the United States Department of Agriculture (USDA) is publishing harmful counterknowledge on the Internet to promote spinach consumption.
The story in this article has never before been told and, because of the complexity of the subject matter, could fairly be described as long and involved. It is written and published in the public interest with the hope that it will bring influence to bear upon the USDA to cease promoting spinach as a good source of iron and to cease publishing potentially harmful counterknowledge about the benefits of vitamin C as an aid to iron absorption from spinach for those who are low in iron.
A personal anecdote
Last year I got married. In June 2010 my American in-laws, flew over from New York as guests for the wedding in Nottingham, England. Two of them, Elorie Stevens and Dawn Manning, are social work managers in Massachusetts. Both are black Jamaican American women. Both have low iron levels.
At a sunny back garden barbeque the week after the wedding Elorie and Dawn listened indulgently as the topic of conversation was humorously turned by my wife Elaine from serial killers to my crime research on the impact of bad data upon policymaking.
Elaine, with a curious mixture of pride outweighed by amusement, told how my latest research had dragged me out of my social science criminology comfort zone into the field of biochemistry myth busting about spinach (Sutton 2010a; 2010b). Elorie and Dawn were amused but also agog to hear that, contrary to popular belief, spinach is not a good nutritional source of iron. Both were advised by their primary health providers to eat spinach in order to get more iron from their diet, and both had been religiously eating it ever since.
“Good grief! Why?” I asked.
I told Elorie and Dawn that they had been fed a load of old bull and that they would be better off eating eggs, liver and red meat and perhaps – but I was not sure - dried apricots. What really annoyed me at the time, and to this day, is that I am a social science criminologist, not a medical doctor, nutritionist or biochemist, and yet I know more about iron nutrition than their general medical practitioners across the Atlantic. Surely that can’t be right.
As a criminologist, with no formal education in nutrition or bio-chemistry, I began my research in this area by studying scholarly work on nutrition written by orthodox experts who conducted scientific research and supported all of their assertions with verifiable references. It was, as they say, a steep learning curve.
Iron, I learned, is an essential part of most living organisms on Earth. Low iron is one of the most common nutrient deficiencies in the USA and in the world (Ackerman, 2003). A sufficient supply of iron in our diet is essential for human health, while too much is toxic. Overdosing on iron pills is a leading cause of childhood poisoning (Morris 2000; Tenenbein 2005). People who have low stores of iron in their body often feel tired, lack energy and may have spoon shaped nails.
In 2010, I published two articles that debunked a widely held belief in what turns out to be a long standing myth about spinach. In those articles I showed that what I call the Spinach Popeye Decimal Error Story (SPIDES) is a two-pronged myth. Firstly, because the cartoon character Popeye in fact ate spinach for vitamin A (Sutton 2010 a) and never for iron, and secondly because – despite what you might read on countless websites and in orthodox and authoritative academic textbooks and scholarly articles - there never was a 19th century typographical decimal error made in recording the iron content of spinach (Sutton 2010b), and furthermore there was no long-standing erroneous 19th Century data that remained influential in the 20th Century until German scientists re-checked the figures in the 1930’s.
With exquisitely excruciating unintended irony the SPIDES has been perversely used by orthodox experts for years as an example of the need for scholars to check their sources and facts, rather than merely citing the unsubstantiated work of others.
I first became embroiled in debunking the SPIDES by happenstance while fact checking it as a widely believed example of the impact of bad data on policymaking (see Sutton 2010a). When I started out, all I wanted was a reputable reference to support the story that I too believed was true. What I soon found, through conducting proper research, however is that it is a complete myth that is widely yet erroneously believed by top scientists and journalists publishing, amongst thousands of other examples, in the British Medical Journal (Hamblin 1981), The European Molecular Biology Organization (Weigman 2005), The New York Times (Emsley 2008), The Royal Society of Chemistry (Coultate 2009), Cambridge University Press (Gustavii, 2008), the British Broadcasting Corporation (BBC 2006) and The Guardian (Gabbatt 2009).
I hypothesise that when orthodox and respected sceptics believe, or disingenuously, use a myth to support the need to be sceptical that they brace-the myth – making it deeply entrenched and harder to eradicate (Supermyths 2010). By way of example, at the time of writing, despite all the verifiable and fully referenced evidence that I have carefully presented by way of my 2010 articles in this area – the Wikipedians in charge of editorial decisions on both the Spinach and Popeye pages in Wikipedia appear to find it impossible to accept that the SPIDES is a myth and it seems that, without so much as seeking to check the latest research, they have simply deleted any mention of it being debunked. For example, a page about the SPIDES itself was completely deleted by Wikipedia, but it can be found elsewhere, because on the Internet delete never actually means delete. See, for example, Wikibin (2010) and Annex Wikia (2010).
Such blind deletion and re-publishing of deleted content elsewhere on the Internet is something that appears to work both in favour of perverse censorship of scholarly myth busting and the mythmongering it seeks to correct; whether or not it favours one over the other is an area worthy of further research.
Next, I present the results of my research and my latest myth busting findings to reveal how the USDA is misinforming the general public and their nutritional advisors.
The USDA Began Publishing Misinformation About Spinach Over 100 Years Ago
Contrary to what we now believe to be true, the U.S.A. nutritionist H.C. Sherman advised at length in an early USDA publication that eating plants rather than meat, liver and eggs was the most effective way for us to get iron from natural dietary sources (Sherman 1907:57-58):
“The iron content of eggs is also high, but the cost of these is sometimes almost prohibitive for families of limited means, while present methods of drying and preserving tend to equalise the cost and increase the available variety of fruits and vegetables throughout the year. The ratio of iron to fuel value is also high in lean meat, but here, as has already been pointed out, the iron exists largely in the form of haemoglobin, which appears to be of distinctly lower nutritive value than the iron compounds of milk, eggs and foods of vegetable origin. Moreover, there is now a general agreement among medical authorities that little meat should be used in the dietaries of young children, where, as already explained, the supply of food-iron is of the greatest importance.”
We now know that advice was wrong, because subsequent research reveals that the most efficient and effective way to get easily absorbable iron from natural dietary sources is by eating liver, eggs and red meat - rather than nonheme iron from plant sources.
By 1935 it was quite widely known that scientists had discovered not only that the iron content of spinach was not as great as previously believed (see Sutton 2010a and 2010b) but that it was difficult for humans to absorb it from that hardy little plant. On 17th August 1935 the Society for Science and the Public (The Science News-Letter 1935) wrote:
“Science is coming to the defense of the youngster who refuses to eat his spinach.
Mother, it seems, is only partly right when she pleads with junior to “Eat your spinach-it’s good for you.”
“It’s good for him, but not nearly as good as its cracked up to be. It just can’t be spinach that enables Popeye the Sailor to perform those red blooded feats in the movies. For spinach contains iron, but new studies at the University of Wisconsin, carried on in those agricultural chemistry laboratories which have already made countless contributions to the knowledge of vitamins and minerals, show that 25 per cent of the iron in spinach is “available”, as scientists put it. That is, only one-quarter of it is in a form that is usable by the body. Other vegetables are no better than spinach in this respect.”
Today the US Government Office of Dietary Supplements (ODS 2007) advise that:
“Vegetarians who exclude all animal products from their diet may need almost twice as much dietary iron each day as non-vegetarians because of the lower intestinal absorption of nonheme iron in plant foods.”
The ODS and the USDA also recommend vegetarians to consider taking vitamin C to help absorb nonheme iron. But does research evidence support such confident advice?
In order to appreciate the significance of the question, it is important to understand exactly what the presence of oxalic acid in spinach means for those who believe that eating it with vitamin C will help to ensure they have enough iron in their diet. This is explained below.
The questionable benefit of vitamin C in this role is the central theme of this article and we will be returning to it shortly.
At this point, however, before examining the evidence for the iron absorption benefits of consuming it with vitamin C, it is a necessary exercise, given the huge popularity of spinach in the USA, to consider - for example - how many cans of Popeye brand spinach consumed on its own – or a similar standard can of spinach - will provide a person with enough daily iron to be healthy.
To answer this question we first need to know what experts recommended our daily intake of iron should be. This is known as our recommended daily allowance (RDA). There is, unfortunately, no one size fits all RDA for iron because it varies by age and gender. Pregnant women, for example, require far higher amounts of iron than any other group.
Iron RDA information is easy to find from official sources. The information in Table 1 is taken from ODS (2007).
Table 1: Recommended Dietary Allowances for Iron for Infants (7 to 12 months), Children (1 to 18 years), and Adults
7 to 12 months
1 to 3 years
4 to 8 years
9 to 13 years
14 to 18 years
19 to 50 years
USDA tables (2010) inform us that canned spinach, drained of the brine it is canned with, has 2.3 mg of iron per 100g. A standard 13.5 oz (383 gram) can once drained is equivalent to 10oz (283 grams) of such spinach. Rounding this drained figure up to 300 grams - to help us err generously on the iron in spinach-favourable side of caution - allows us to estimate with a fair degree of confidence that a standard can of spinach contains no more than some 6.6 mg of iron.
Taking things at face value
Working at face value on official US guidelines that vegetarians need to eat twice as much dietary iron as those who eat meat, if no other source of iron was available, that would mean that each day a man aged 19-50 should eat some two and a half 13.5 oz cans of Popeye spinach, a woman aged 19-50 should eat five and a half cans, and a pregnant woman should eat eight cans. But such face value calculations would be completely wrong. Because we should not forget that it is difficult for humans to absorb such nonheme iron. In fact, such canned quantities would be nowhere near enough spinach to meet the daily requirements of these 19-50 year old men and women, because experts (e.g. Harvard 2010; Akerman 2003) conclude that research shows that at best we can only absorb only between 2 and 20 percent of nonheme iron, and that iron from spinach is particularly difficult to absorb since spinach contains oxalic acid.
There are no definitive answers on the issue of exactly how much iron we can absorb from spinach
Research by McMillan and Johnston (1951) found the best case scenario was where their subjects were able to absorb 13 percent of the iron from spinach when they consumed it with other foodstuffs such as meat that aided absorption of nonheme iron. And an overview of later research by Campen and Welch (1980) found much lower figures than this for human subjects. In my calculations below, therefore, I am working on the “at best” assumption, from the research or the experts, that it is ordinarily possible for humans to absorb 15 percent of the iron from spinach – when in reality the figure is probably much lower.
All males aged 19-50 or, for example, pregnant female vegetarians reading the ODS (2007) advice, who are unaware of the effect of oxalic acids upon iron absorption from spinach, would be patently misled if they were to believe that by simply eating twice as much nonheme iron as heme iron that they need only eat 16, 36 or 54 mg, respectively, of iron in spinach. To repeat the point already made, they would be mistaken in this belief because we are all, are at best, able to absorb only 15 percent of the iron from spinach.
This means that current research suggests that we can absorb no more than 1 mg of the 6.6 mg of iron that is at most likely to be found in a standard 13.5 oz of spinach. This means that if no other source of iron is available, a man aged 19-50 would in fact need to eat at least eight cans of spinach every day to get his required level of iron, a woman of the same age would need to eat 18 cans and a pregnant woman would need to consume a nauseating 27, which - at 10 oz of solid matter when drained - is well over a stone (14 lb) of the stuff.
Yet the USDA tables tell us that spinach is high source of iron and quite amazingly, Campen and Welch (1980), of the USDA conclude that spinach should not be abandoned as a potentially valuable source of our dietary iron without further study.
The Ohio State University Online fact sheet (2010) describes what constitutes a “good source of iron”.
“A good food source of iron contains a substantial amount of iron in relation to its calorie content and contributes at least 10% of the U.S. Recommended Dietary Allowance (U.S. RDA) for iron in a selected serving size. The U.S. RDA for iron is the amount of the mineral used as a standard in nutrition labelling of foods, which is 18 milligrams per day for iron.”
I argue that there are two troubling elements in this official “good source of iron” classification system. Firstly and of least seriousness is that the RDA that everyone sees on all US food labelling is based on non pregnant females aged 19-50 – when men of the same age group need less then half as much and research shows that American men as a group consume too much iron on the whole (See: Ohio State University National Health and Nutrition Examination Survey (2010). Secondly, the most important problem with this classification is that a foodstuff, such as cooked spinach, is seen to be a good source of iron merely because of its iron content in proportion to its calorie content.
Surely, completely failing to take account of the fact that some 85 percent of iron in cooked or raw spinach cannot be absorbed by humans is bad science?
Let us begin by trying to give the USDA the benefit of the doubt on this one. Perhaps the reason why they recommend spinach for adults and children (USDA (2) as a good source of iron is because they hope it will be consumed with vitamin C to help with absorbing its iron? Here we can now turn at last to examine the big vitamin C question.
Researching the vitamin C question
As we have seen, current research clearly shows the difficulties of absorbing iron from spinach. And the US Government Office of Dietary Supplements (ODS) is clear about the difficulties of absorbing iron from such plant matter and advises that vitamin C is best taken to help absorb nonheme iron. The problem is they appear very foggy regarding exactly how much is required. Breaking the rule about avoiding repetition, let us revisit one last time that quotation from the ODS (2007):
“Total dietary iron intake in vegetarian diets may meet recommended levels; however that iron is less available for absorption than in diets that include meat. Vegetarians who exclude all animal products from their diet may need almost twice as much dietary iron each day as non-vegetarians because of the lower intestinal absorption of nonheme iron in plant foods. Vegetarians should consider consuming nonheme iron sources together with a good source of vitamin C, such as citrus fruits, to improve the absorption of nonheme iron.”
So what exactly is known about how vitamin C might aid iron absorption from spinach? Unfortunately, the official advice is so unspecific as to be, effectively useless. For example, this is what else the ODS (2007) Fact Sheet on Iron has to say on the matter:
“Absorption of heme iron from meat proteins is efficient. Absorption of heme iron ranges from 15% to 35%, and is not significantly affected by diet. In contrast, 2% to 20% of nonheme iron in plant foods such as rice, maize, black beans, soybeans and wheat is absorbed . Nonheme iron absorption is significantly influenced by various food components. Meat proteins and vitamin C will improve the absorption of nonheme iron. Tannins (found in tea), calcium, polyphenols, and phytates (found in legumes and whole grains) can decrease absorption of nonheme iron. Some proteins found in soybeans also inhibit nonheme iron absorption. It is most important to include foods that enhance nonheme iron absorption when daily iron intake is less than recommended, when iron losses are high (which may occur with heavy menstrual losses), when iron requirements are high (as in pregnancy), and when only vegetarian nonheme sources of iron are consumed.”
The problem is where eating spinach, or any other nonheme source of iron, is concerned we are not told how much vitamin C we should consume with it. At the time of writing, the USDA is similarly foggy when it comes to explaining exactly how much vitamin C is required to improve the otherwise, at best,15 percent absorption rate of iron from spinach. Presumably this is because nobody actually knows. And as for how much tea and coffee, soybeans and whole grains and legumes to avoid and how much meat to eat with your greens – you’ll get no answer from official sources.
As I am sure you will agree, this is no help at all. Anyone who wishes to maximise their iron absorption from spinach, or any other greens, reading current ODS information would not have a clue how to go about doing so.
In search of answers, in the summer of 2010, I undertook some mind numbingly extensive online research, which revealed exactly what I was looking for.
Using the search term “spinach iron” within the USDA’s Economic Research Service’s (ERS) website, I found a spreadsheet they published that extols the nutrient benefits of grapefruit juice (See: USDA 1).
Amongst all the USDA’s other data is a text box with the following statement:
“Seventy-seven percent of American women under the age of 50 are iron deficient.
Consuming citrus foods like grapefruit and grapefruit juice can help boost the absorption of the iron found in plants. So, if you drink a glass of grapefruit juice before you eat a spinach salad, your body absorbs two to four times as much iron.”
“Eureka!” I cried, because I was delighted at last to find such specific advice.
Every other official publication (e.g. USDA 2005) I had read on this issue failed to provide so much as a vague clue as to how much vitamin C rich food, or mg of vitamin C was required to help with any degree of iron absorption from spinach. But then I quickly realised that in providing their Grapefruit Spinach Salad Advice the USDA annoyingly neglects to say whether they mean a shot glass, wine glass or pint glass. Nevertheless, their positive advice is the most specific official advice I have found. I followed up on the reference used in support of their advice.
Scientific Research Suggests the USDA is Spreading Bull on the Internet
On their spreadsheet, the USDA cites the source of this positive information - another website called Floridajuice.com.
Floridajuice.com is the website of The Florida Department of Citrus (FDOC), which is an executive agency of the Florida government. The FDOC explains that they are:
“… charged with the marketing, research and regulation of the Florida citrus industry”, and that their mission is: ..” to grow the market for the Florida citrus industry in order to enhance the economic well-being of the Florida citrus grower, the citrus industry and the State of Florida.”
In doing so they write that they:
“… market both Florida citrus juices and fresh fruit with a focus on the health and wellness benefits the products have to offer. Marketing activities are conducted in the United States, Canada, Europe and Asia to reach consumers, key influencers and health professionals.”
Peculiarly, the FDOC appear much less sure than the USDA that a non-specific glass-sized quantity of citrus juice will empower you to absorb two to four times the amount of otherwise unavailable iron from spinach. With annoyingly familiar fogginess the advice of the FDOC is as vague as every other source I was able to find on this particular area of expert advice:
“Vitamin C can help increase iron absorption. Iron deficiency is one of the most common nutritional deficiencies worldwide and has been reported in 9%-16% of the adolescent and adult female population in the United States.Vitamin C can help boost the absorption of non-heme iron (the iron found in plants, not meat products). So including a glass of grapefruit juice before eating a spinach salad may help your body absorb more iron from the spinach. Vitamin C-rich foods should be included daily to get the most iron out of foods.”
Here seems like a good point to pause in order to, digest the information so far provided.
Of late I have taken to reading a little philosophy in order to try to make sense of complex issues regarding junk science and pseudo scholarship. Currently, one of my favourite essays is Harry Frankfurt’s (2005) “On Bullshit”. In this essay, Professor Frankfurt, a Princeton University moral philosopher, concludes that bull is worse and potentially more dangerous than lying because the liar cares that he is wrong and deliberately intends to mislead the recipient of his message, while the bullshitter cares not a jot for the truth and merely wishes to sound plausible in order to promote his own standing. Perhaps Frankfurt’s writing on bull is the key to what is going on with the USDA’s advice on spinach?
Could the USDA be bull-spreading world-wide?
Perplexed that the USDA referenced the vague advice of FDOC as the source of their more precise claim about the incredible powers of grapefruit juice, I looked for what evidence the FDOC cited to support its assertion on this issue.
‘Would a pint glass’, I wondered, amazingly ‘quadruple my absorption and a half pint glass double it?’ Did the USDA and FDOC know something more than scientists reporting their painstaking research findings on this subject in peer reviewed journals? What about the double-blind trials conducted by Hunt, Gallagher, and Johnson, L.K. (1994), which found that vitamin C did very little at all to help women to absorb iron from food? What about Cook and Reddy’s (2001) research that found no increase in nonheme-iron absorption during realistic long-term supplementation – as opposed to earlier experiments involving unrealistic prior fasting and one meal only? Perhaps the USDA had found evidence produced by the FDOC to refute the findings of Teucher, Olivares and Cori (2004),who found that to promote absorption of iron from food, in the presence of high levels of inhibitors, vitamin C needs to be added at a molar ratio in excess of 4:1 (which is rather impractical to say the least).
As it turned out, answers to my questions were not going to be easy to find. For a start, I was disappointed to discover that the USDA reference was not at all what it purported to be.
As far as I can tell, the FDOC has not conducted any research to support what the USDA write about the benefits of grapefruit juice as an aid to iron absorption from spinach. Even though the USDA reference the FDOC as the source of their super grapefruit juice knowledge, the reference provided by the FDOC to support their own recommendation that vitamin C – by way of citrus juice - may help with iron absorption from spinach turns out to be a hugely expensive two volume text book (Bowman and Russell 2006), which in its 9th edition retails for $110. These volumes entitled “Present Knowledge on Nutrition” are, I found, generally unavailable second hand for less than $75. Fortunately, as an academic, I was quickly and easily able to use my computer to order a copy on interlibrary loan from my university. Obviously, this is not something that members the general public are likely to go to the effort of doing. Most people have little choice, or inclination, to fact check expert health advice from a US Government department – they are going to take it on faith. Not me.
Twaddle cloaked in obscurity
Having ordered the books, I awaited eagerly their arrival in hope that they would reveal the scientific basis for the incredible effects of grapefruit juice upon spinach.By this point, however, I suspected that the shabby referencing might indicate the USDA is guilty of publishing pseudo scholarship counterknowledge about the benefits of spinach and vitamin C. Let me explain the source of my suspicions in this regard.
Thompson (2008) tells us that a common trick used by those who promote pseudoscience is to reference obscure sources and to tie readers up in a labyrinth of mind numbingly tangled information sources; something that David McKie (see: Wheen 2004) of the UK Guardian newspaper neatly describes as: “…twaddle cloaked in obscurity.”
Tellingly, the expensive two-volume texts “Present Knowledge in Nutrition” run to 967 pages and yet the USDA do not provide a page number for their assertion on this difficult and well obscured subject.
After two hours of wading through Bowman and Russell (2006), I was unable to find a single mention of spinach. After thoroughly reading and re-reading various sections of the books, especially those on iron and on vitamin C, I had what is probably the source of the bold USDA statement that: “… if you drink a glass of grapefruit juice before you eat a spinach salad, your body absorbs two to four times as much iron.” It is in the chapter on vitamin C by Carol S. Johnson (PhD) of the Department of Nutrition, Arizona State University. Dr Johnson has quite an expert mouthful to say on the subject (p.237):
“Iron absorption from test meals is enhanced 2-3 fold in the presence of 25 to 70 mg of vitamin C, presumably due to ascorbate-induced reduction of ferric iron to ferrous iron, which is less likely to form insoluble complexes with phytates. However, indices of iron status, including haemoglobin, serum ferritin, and percent transferring saturation, are generally not improved in iron deficient subjects consuming vitamin C-fortified diets.”
So it is clear from the outset that expert available scientific evidence suggests that taking vitamin C will not in fact help boost iron absorption in people who are low in iron.
Other key issues here, I determined as best as I could as a non-expert, from this difficult scientific text, are that Dr Johnson is referring to test meals – not any one specific source of food such as spinach. To check this, I needed to examine the research that Johnson cites to support her assertions (Garcia, Diaz and Rosaldo 2003). After all, the research subjects could have been fed meals entirely of spinach and nothing else. That said, even if they were, it is important not to forget that Dr Johnson tells us quite unambiguously that the extremely limited research in this area suggests that people who are low in iron do not benefit from taking ascorbic acid (AA) – otherwise known as vitamin C - with their food.
This is what Garcia et al (2003) – the obscure source of the USDA’s confident advice on the iron boosting wonders of Florida grapefruit juice – write that is pertinent to our enquiry about it:
“ Background: Although ascorbic acid (AA) increases dietary iron bioavailability, there has been no food-based community trial of its efficacy in improving iron status.
Objective: The objective was to assess the efficacy of 25 mgAA as agua de limón (limeade), consumed with each of 2 daily meals, in improving the iron status of iron-deficient women.
Design: Two rural Mexican populations were randomly assigned to an AA or a placebo group, each with 18 iron-deficient women.The AA group was given 500 ml limeade containing 25 mg AA twice a day, 6 d/wk, for 8 mo. The placebo group was given a lime-flavored beverage free of AA or citric acid. Beverages were consumed within 30 min of 2 main daily meals. Data were collected on morbidity (3 times/wk), dietary intake (on 6 d), socioeconomic status, parasites (twice), medical history, and response to treatment. Blood samples at 0, 2, 4, 6, and 8 mo were analyzedf or hemoglobin, plasma AA, plasma ferritin, transferrin receptors,and C-reactive protein.
Conclusion:“Increasing dietary AA by 25 mg at each of 2 meals did not improve iron status in iron-deficient women consuming diets high in phytate and nonheme iron.”
In sum, no mention is made of the specific action of vitamin C (ascorbic acid) on iron absorption from spinach. Presumably, this is why the USDA reference Dr Johns as the source of their bull, rather than citing Garcia et al directly. It appears to me that they sought to keep the bull hidden like the dangerous mythical Minotaur within a labyrinth of difficult to check sources.
And if that is not enough to shame the USDA for cloaking its pseudoscience spinach advice with misleading references, an expert overview of research, at the time of writing, reveals that we do not yet have anything even approaching a clear picture regarding the extent to which vitamin C improves iron absorption (Beard et al 2007).
Adopting Frankfurt’s (2005) philosophical distinction between lies and bull, only two possible conclusions can be drawn from all this. The first is that the USDA is spreading bull on the Internet. The second is that blatant and deliberate lies are being told by a person or persons within the USDA simply to encourage the consumption of home grown spinach and Florida grapefruit juice.
As I write these words, I wonder what would happen if I were to set up in business canning Texas spinach in Florida grapefruit juice instead of brine?
I could name my invention “Superspinach.” And, because nobody else has ever done it before, I could patent the concept and advertise internationally that the USDA has claimed that leading nutritional science proves that this new Superspinach provides between double and four times as much iron as ordinary spinach.
Superspinach might sell so well that I get rich at the expense of the health and wellbeing of others. But this is an evil pipe dream, because to knowingly do such a thing would be a crime against humanity in my opinion. And yet there are plenty of quackmongers and other charlatans with a stronger stomach than mine for profiteering from pseudoscience. This is a field, strangely ignored by criminologists, in need of further research.
In the USA, the official government advice is that spinach is a good source of iron. In the UK the official UK advice is the opposite. Perhaps experts in the British Food Standards Agency (FSA) were having a subtle dig at those within the USDA when they penned the following plain and simple, objective, advice on their website? (FSA 1):
“Some people think that spinach is a good source of iron, but spinach contains a substance that makes it harder for the body to absorb the iron from it.”
The USDA has erroneously promoted spinach for over 100 years – often in the teeth of scientific evidence against it. By way of contrast, the fully referenced and verifiable evidence presented in this article makes the case that the USDA should at once cease its promotion of junk science advice. The truth is that, contrary to USDA advice, cooked spinach – like raw spinach - is not a good source or iron.
Current scientific knowledge does not support the USDA claim that taking vitamin C (ascorbic acid) in any form significantly increases our iron absorption from Popeye’s favourite fast food.
As a non-expert who has studied the literature on this subject, I argue that officially encouraging spinach consumption with meat and perhaps accompanied by a vitamin C rich fruit juice – to maximise iron absorption from spinach - is dangerous pseudoscience. The amount of iron obtained from spinach is so low, even in these circumstances, that it is grossly misleading to tell people - who may need to increase their daily iron intake - that choosing cooked spinach will provide them with a good source of iron.
Many women in the USA and elsewhere in the world are low in iron. The danger with the current advice system on food labelling in the USA is that people may be relieved to believe that ½ a cup portion (60ml; 2 fl. oz.), or even an entire can of spinach, will conveniently provide a good dietary source of iron. Nothing could be further from the truth.The USA needs to ensure spinach products are properly labelled so as not to mislead the public on such an important area of nutrition. And the USDA should cease and desist publishing harmful spuriofacts.
At the time of writing, Allens Popeye Spinach – under the heading Nutrition Facts – has on the label that the 13.5 oz (383g) canned product will provide someone on a 2,000 calorie a day diet (which is in fact the recommended daily calorie intake for women) with 10 per cent of her recommended daily iron needs from one can. Yet , due to what science knows about iron availability problems with spinach, the can provides, at best, only 5.5 per cent of the recommended daily allowance (RDA) for a non-pregnant fertile woman aged 18 to 50 years of age and 3.7 per cent for a pregnant woman. To be fair to Allen's, who must have factored more conservative estimates of available iron into their labeling for this one group, the good news is that it provides, at very best, 12.5 per cent of the RDA for an older non pregnant woman.
Dr Mike Sutton
In my next paper “Spin@ge II USA” I examine the case of the most peculiar defense of spinach made by the US Council of Foods in 1937. In Spin@ge III (forthcoming 2011) I examine problematic science behind the promotion of spinach as a good source of beta carotene for the production of vitamin A and its possible consequences for nutrition policy in developing nations.
Ackerman, J. (Editor) (2003)Vitamin C and iron are great partners. Chow Line. Ohio State University. http://www.ag.ohio-state.edu/~news/story.php?id=2492
Annex Wikia (2010) Spinach Popeye Iron Decimal Error Myth. Available online: http://annex.wikia.com/wiki/Spinach_Popeye_Iron_Decimal_Error_Myth
BBC (2006) Spinach – The Truth. June 9th: http://www.bbc.co.uk/dna/h2g2/A11681912
Beard, J.L. Murray-Kolb, L.E. Haas, J.D. and Lawrence, F. (2007).
Iron Absorption Prediction Equations Lack Agreement and
Underestimate Iron Absorption. Journal of Nutrition. 137:
Bowman, B. A and Russell, R.M (eds) (2006) Present Knowledge in Nutrition. Ninth Edition. Washington, DC: International Life Sciences Institute.
Campen, R.V and Welch, R.M. (1980) Availability to Rats of Iron from Spinach: Effects of Oxalic Acid. Journal of Nutrition 110. 1618 -1621.
Cook, J. D. and Reddy, M. B. (2001) Effect of ascorbic acid intake on nonheme-iron absorption from a complete diet. The American Journal of Clinical Nutrition. Vol. 73, No. 1. 93-98. January
Coultate, T. (2009) Food the Chemistry of its components. 5th Edition. Cambridge. Royal Society of Chemistry Publishing;
Emsley, J. (2008) Nearly as Nature Intended: An exhibition of some curious molecules in the foods we eat. Oxford. Oxford University Press.
Frankfurt, H.G. 2005. On Bullshit. Princeton N.J.. Princeton University Press.
FSA (1) Healthy Diet: Iron : http://www.eatwell.gov.uk/healthydiet/nutritionessentials/vitaminsandminerals/iron/
Gabbatt, A. 2009. E.C. Segar, Popeye's creator, celebrated with a Google doodle. The Guardian 8th December: http://www.guardian.co.uk/technology/2009/dec/08/ec-segar-popeye-google-doodle
Garcia, O.P. Diaz, M. Rosado, J. I. and Allen, L. H. (2003) Ascorbic acid from lime juice does not improve the iron status of iron-deficient women in rural Mexico. American Journal of Clinical Nutrition, Vol. 78, No. 2, 267-273, August.
Gustavii, B. (2008) How to write and illustrate a scientific paper. Cambridge. Cambridge University Press.
Harvard University Health Services (2010). Iron Nutrition. http://huhs.harvard.edu/Resources/HealthInformationByTopic/Nutrition/IronNutrition.aspx
Hunt, J. R. Gallagher, S. K. and Johnson, L.K. (1994) Effect of ascorbic acid on apparent iron absorption by women with low iron stores. American Journal of Nutrition. 59 (6) 1381-5.
McMillan T. J, and Johnston, F.A. (1951) The absorption of iron from spinach by six young women, and the effect of beef upon the absorption. J Nutr. Jul;44(3):383–398
Morris, C.C. ( 2000). Pediatric iron poisonings in the United States. Southern Medical Journal. April. 93 (4) 352-8.
Ohio State University Extension Fact Sheet. Human Nutrition (2010): Iron HYG-5559-05. Available online: http://ohioline.osu.edu/hyg-fact/5000/5559.html
ODS (Office of Dietary Supplements) (2007). Dietary Supplement Fact Sheet: Iron. National Institutes of Health. Available online: http://ods.od.nih.gov/factsheets/iron.asp
Sherman. H.C. (1907). Iron in Food and Its Functions in Nutrition. Office of Experimental Stations Bulletin 185. May 25. p56.
Sherman, W.C., Elvehjem, C.A. and Hart.E. B. 1934. Further Studies on the Availability of Iron in Biological Materials. The Journal of Biological Chemistry. Vol. 107. N0. 3. pp383-394.
Supermyths (2010) The Discovery of Braced Myths: The most disastrous typo of all time? http://super-myths.blogspot.com/2010/09/most-disasterous-typo-of-all-time.html
Sutton, M. (2010a).Spinach, Iron and Popeye: Ironic lessons from biochemistry and history on the importance of healthy eating, healthy scepticism and adequate citation. Internet Journal of Criminology (Primary Research Paper series).http://www.internetjournalofcriminology.com/Sutton_Spinach_Iron_and_Popeye_March_2010.pdf
Sutton, M. (2010b) The Spinach, Popeye, Iron, Decimal Error Myth is Finally Busted. Best Thinking. Available Online: http://www.bestthinking.com/articles/science/chemistry/biochemistry/the-spinach-popeye-iron-decimal-error-myth-is-finally-busted
Teucher, B. Olivares, M. and Cori, H. (2004) Enhancers of iron absorption: ascorbic acid and other organic acids. International Journal of Vitamin Nutrition Research. 74 (6) 403-19.
Tenenbein, M. (2005) Unit-dose packaging of iron supplements and reduction of iron poisoning in young children. Pediatric Adolescent Medicine. June 1. 59 (6) 557-60
The Science News Letter. (1935). Spinach Over-Rated as Source of Iron Vol. 28, No. 749. Aug. 17, p. 110
Thompson, D. (2008) Counterknowledge: How we surrendered to conspiracy theories, quack medicine, bogus science, and fake history. London. Atlantic Books.
USDA (1) (Undated): Economic Research Service Grapefruit. http://www.ers.usda.gov/Data/FruitVegetableCosts/Grapefruit.xls
USDA (2) (Undated) Nibbles for health 24. Iron in Foods: Does my child get enough? Nutrition Newsletters for Parents of Young Children. Available online: http://www.fns.usda.gov/tn/resources/Nibbles/iron.pdf
USDA (2005) Dietary Guidelines for Americans. US Department of Health and Human Services. US Department of Agriculture.http://www.health.gov/dietaryguidelines/dga2005/document/pdf/DGA2005.pdf
Wheen, F. (2004). How Mumbo-Jumbo Conquered the World. London. Harper Perenial.
Weigman, K. (2005) The consequence of errors. European Molecular Biology Organization Report. April 6 (4) pp 306-309.
Wikibin (2010) Spinach Popeye Iron Decimal Error Myth. Available online at: http://wikibin.org/articles/spinach-popeye-iron-decimal-error-myth.html
Very many thanks for the feedback on this paper. I'm glad it was useful.
On the downside of heme sources (particularly liver) is the problem of it being a dietary cause of high levels of bad cholesterol. So it’s all about balance and moderation when it comes to consuming heme sources for non-vegetarians .
I’ve not researched it in depth but I’m led to believe that when we are low in iron we can more easily absorb iron from sources such as eggs, which are not a causal factor in high levels of bad cholesterol.
Another thing to watch out for is that some foods and beverages - such as bran and tea are iron blockers, which makes one wonder about why manufacturers add iron to bran flakes. Other iron fortified cereals – while often high in sugar and salt - are a good source of iron.
Personally I’d recommend canned sardines a couple of times a week (but not on wholegrain bread – as it might block iron uptake) Those with the bones left in are a wonderful source of calcium. http://www.medicalnewstoday.com/releases/8482.php
In light of the facts revealed in this paper, I am grateful to the USDA for deleting their misleading spreadsheet from the internet
This is the one I refer to:
USDA (1) (Undated): Economic Research Service Grapefruit. http://www.ers.usda.gov/Data/FruitVegetableCosts/Grapefruit.xls
Many other websites - including one run by MIT (http://web.mit.edu/athletics/sportsmedicine/wcrminerals.html) contine to boldly claim that vitamin C helps with iron absorption.
Since low iron levels - linked to poor diet - kill people in large numbers (see http://www.bestthinking.com/thinkers/science/social_sciences/sociology/mike-sutton?tab=blog&blogpostid=9942%2c9942 ) there should be more care taken to get the facts right.
Here are just few of the very many web sites that still promote the fallacy (or at least to promote vitamin C in this role when the evidence is inconclusive) some are giving advice on cancer - other are for children's diets... the list seems endless:
This new Article is not yet ready for syndication. Please check back in a few minutes.
This Article is not available for syndication. Contact BestThinking for details.
Enjoy high quality content through BestThinking's syndication program. Learn more and register as a publisher today!
Enhance your publication, blog or journal with high quality content from BestThinking. Whether you are looking for a single feature article, a stream of dynamic content or just a few pieces each month, BestThinking's unique, customizable syndication feeds provide rights-verified material from identity verified Thinkers.
To syndicate a Blog or Article, you’ll need to start by setting up a feed. Creating a feed is a 3-step process:
About the Author
Dr Mike Sutton is the author of 'Nullius in Verba: Darwin's greatest secret'.