On 23 August 2013 news headlines were “Red meat could raise Alzheimer’s risk.”
“Iron in red meat could raise the risk of Alzheimer’s” said the Daily Mail actual newspaper. On line we had a fuller headline: “Eating too much red meat could increase the risk of Alzheimer’s: Scientists warn build-up of iron may damage the brain.”
A quick check on line revealed that the story was making global headlines: “Is iron in steak to blame for risk of Alzheimer’s? Study suggests excess red meat bad for the brain” was the story on the Canadian Global News site.
The original article
The original journal article was published online on 21 June 2013 in The Journal of Alzheimer’s Disease. The full title of the article is “Increased Iron Levels and Decreased Tissue Integrity in Hippocampus of Alzheimer’s Disease Detected in vivo with Magnetic Resonance Imaging.”
This catchy title was inexplicably overlooked until a press release was issued on the 20 August 2013, on the main Journal of Alzheimer’s Disease web site, with the more media friendly headline: “UCLA study suggests iron is at core of Alzheimer’s disease.”
I haven’t paid $27.50 to get the full article, but I can confirm that the abstract (summary) of the article makes no mention of meat, or even diet, at all (you can read it for yourself on the link to the original journal article above).
The abstract tells us that the study hypothesised that “with age, iron accumulates in the brain and may contribute to the risk of developing age-related diseases such as Alzheimer’s Disease (AD).” Previous studies of AD have (according to the abstract) shown that an area of the brain called the hippocampus is heavily damaged with AD, while the thalamus seems to be resistant to AD damage.
The study set out to assess iron levels and evidence of tissue damage in the hippocampus and thalamus in 31 people with AD compared to 68 people without the disease. The participants undertook MRI scans to quantify (ferritin) iron levels in the two areas of the brain being studied. The results were that “compared with healthy controls, AD subjects had increased (ferritin) iron in the hippocampus but not in the thalamus.”
The study concluded: “The data shows that in AD, hippocampus damage occurs in conjunction with ferritin iron accumulation. Prospective studies are needed to evaluate how increasing iron levels may influence the trajectory of tissue damage and cognitive and pathologic manifestations of AD.” i.e. we assume that the hippocampus damage and ferritin iron levels are related and further studies are needed to understand how iron levels could be related to tissue damage.
Keywords for the study were “Alzheimer’s disease, chelation, dementia, ferritin, field dependent relaxation rate increase (FDRI), iron, magnetic resonance imagining (MRI), myelin, prevention, treatment.” And that was it. No mention of red meat, diet, ingestion of iron or anything related to the headlines that were to follow.
The press release
The press release is quite a technical introduction to current thinking on Alzheimer’s – that it’s related to two proteins that can disrupt signalling between neurons. This would have the effect of impacting the body’s messaging system and would explain the cognitive impairment observed with Alzheimer’s.
The PR note explained that the study by Bartzokis and his team hypothesised that iron could be a factor and not just these two proteins. Nothing in the continuing copy looks like it would excite the world’s media (“myelin”, “oligodendrocytesm”, “oxidative damage” etc, yawn, yawn). But then we have the wakeup call in the penultimate paragraph:
Bartzokis noted: “The accumulation of iron in the brain may be influenced by modifying environmental factors, such as how much red meat and iron dietary supplements we consume and, in women, having hysterectomies before menopause.”
Red meat! Oh how the media loves a good bit of red meat bashing:
The mention of red meat and an overlooked study published two months earlier suddenly appears in English newspapers published in Majorca (we picked this up while on holiday) and on Fox News.
The leaps to be made
For red meat to impact Alzheimer’s, as implied, ALL of the following need to hold true:
1) Alzheimer’s sufferers need to ingest and absorb excessive dietary iron from red meat;
2) Dietary iron needs to end up in the hippocampus (and not the thalamus) area of the brain;
3) This iron needs to cause tissue damage;
4) This tissue damage needs to be responsible for Alzheimer’s.
1) Alzheimer’s sufferers need to ingest and absorb excessive dietary iron from red meat.
The study falls at the first hurdle. We don’t even know if the 31 people with Alzheimer’s Disease consumed red meat. They could all have been vegan for all we know.
The study falls at the first hurdle on a population level. The 2011 UK average iron intake was 11.8mg (p28 of the Family Food Survey) The RDI (Reference Daily Intake) for iron is 18mg. There is thus no evidence for iron excess – it is rather iron deficiency that we should worry about.
The researchers could have taken blood iron levels of the participants to see if AD sufferers and/or control people had generally excessive or deficient iron levels. This would have been a crucial piece of information – excessive iron in the blood and in one part of the brain is a very different puzzle to deficient iron in the blood and ‘excessive’ iron in one part of the brain.
The study falls at the first hurdle for another, easily assessable, nutritional reason – red meat is a source of iron, but it is by no means the best source, let alone the only source. Here is iron intake per 100g of the following foods:
– Red meat 1.5mg
– Spinach 2.7mg
– Sardines 2.9mg
– Cocoa powder 13.9mg
The USDA all foods database will tell you that the richest sources of iron are thyme, parsley and marjoram with 124mg, 98mg and 83mg of iron per 100g of product respectively. We use spices in very small quantities, however, so we should continue down the list of highest providers of iron until we find a food that we would consume in 50-100g portions. This turns out to be fortified sugary cereals, with Kellogg’s oat bran flakes having 63mg of iron per 100g of product. That’s 45 times the iron levels of our sirloin steak!
The top 20 sources of iron, according to the USDA bible, are 7 spices, 9 fortified cereals, 2 baby foods and 2 meats – whale and seal. I don’t know about you but I’ve never eaten whale or seal. I have eaten baby food, fortified cereals (thanks mum) and spices. Beef or lamb spleen is the only other meat in the top 50 – baby food makes up most of the places from 21-50. Probably because iron is a pretty vital mineral to ingest.
So why was the headline not “Bran flakes could raise the risk of Alzheimer’s”? or “Baby food could raise the risk of Alzheimer’s.” Or even oily fish or spinach or high cocoa content dark chocolate? The simple answer is that red meat bashing is a media past time and the other products are not demonised in the same way.
Finally, hurdle 1 notes that iron not only needs to be ingested, but absorbed. Iron needs vitamin C for its absorption. Hence someone with high iron intake with insufficient vitamin C intake will have deficient iron levels due to impaired absorption. Someone with moderate iron intake and high vitamin C intake is likely to optimise their blood and body iron levels. How about “Too much vitamin C can cause Alzheimer’s”?!
Back to the four steps, which need to all hold true, to justify the world headlines:
2) Dietary iron needs to end up in the hippocampus (and not the thalamus) area of the brain.
The study did not try to show that dietary intake of iron had accumulated in any part of the body. The original journal article did not even consider dietary sources of iron. Notwithstanding that the study has already fallen at the first hurdle, it also falls at the second.
3) This iron needs to cause tissue damage.
The study does not claim that iron causes tissue damage, so it openly falls at the third hurdle.
The study concludes: “hippocampus damage occurs in conjunction with ferritin iron accumulation. Prospective studies are needed to evaluate how increasing iron levels may influence the trajectory of tissue damage and cognitive and pathologic manifestations of AD.” i.e. we observe iron levels and hippocampus damage together, but studies are needed to see how these could be related.
The opening of the article offers one mechanism: “Although essential for cell function, increased tissue iron can promote oxidative damage to which the brain is especially vulnerable.”
This probably should be the starting point for further research – why are higher levels of iron found in one part of the brain and not another? Are body iron levels higher generally in people with higher levels in the hippocampus? Does iron go to the damaged tissue to repair damage or did the iron cause the damage? There is a wealth of further research to be done before going anywhere near red meat.
Talking about areas for research, the press release said that two proteins, and their impact on neurons, are currently held by “most researchers” to be the cause of Alzheimer’s. A growing number of researchers are calling Alzheimer’s “type 3 diabetes” – the response of the brain to glucose, just as type 2 diabetes is the response of the body to glucose. That would be a worthy area for research.
4) This tissue damage needs to be responsible for Alzheimer’s.
Does Alzheimer’s damage tissue in the hippocampus (and not the thalamus) or does tissue damage in the hippocampus (and not the thalamus) cause Alzheimer’s?
Bartzokis needs to get some Roland Rats or Mickey Mouses and induce the same tissue damage and see if Alzheimer’s develops.
This is the kind of assessment that the media should have done – not just leap four unproven steps and join the red meat attackers.
Dear journalists. Please – I beg you – please don’t be part of the demonisation of the food that we have been eating for the longest time in human development. Surely – if it’s something new you’re after – NOT bashing red meat would be a refreshing change!