#OTD 1901, Queen Victoria's funeral took place. Here's a little medical history THREAD (1/9) about one of Britain's longest reigning monarchs. 👇
"Queen Victorian on her death bed" by Emil Fuchs.
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Why do B12 and folate deficiencies lead to HUGE red blood cells?
And, if the issue is DNA synthesis, why are red blood cells (which don't have DNA) the key cell line affected?
For answers, we'll have to go back a few billion years.
2/
RNA came first. Then, ~3-4 billion years ago, DNA emerged.
Among their differences:
🔹RNA contains uracil
🔹DNA contains thymine
But why does DNA contains thymine (T) instead of uracil (U)?
https://t.co/XlxT6cLLXg
3/
🔑Cytosine (C) can undergo spontaneous deamination to uracil (U).
In the RNA world, this meant that U could appear intensionally or unintentionally. This is clearly problematic. How can you repair RNA when you can't tell if something is an error?
https://t.co/bIZGviHBUc
4/
DNA's use of T instead of U means that spontaneous C → U deamination can be corrected without worry that an intentional U is being removed.
DNA requires greater stability than RNA so the transition to a thymine-based structure was beneficial.
https://t.co/bIZGviHBUc
5/
Let's return to megaloblastic anemia secondary to B12 or folate deficiency.
When either is severely deficient deoxythymidine monophosphate (dTMP*) production is hindered. With less dTMP, DNA synthesis is abnormal.
[*Note: thymine is the base in dTMP]
https://t.co/AnDUtKkbZh
Why do B12 and folate deficiencies lead to HUGE red blood cells?
And, if the issue is DNA synthesis, why are red blood cells (which don't have DNA) the key cell line affected?
For answers, we'll have to go back a few billion years.
2/
RNA came first. Then, ~3-4 billion years ago, DNA emerged.
Among their differences:
🔹RNA contains uracil
🔹DNA contains thymine
But why does DNA contains thymine (T) instead of uracil (U)?
https://t.co/XlxT6cLLXg
3/
🔑Cytosine (C) can undergo spontaneous deamination to uracil (U).
In the RNA world, this meant that U could appear intensionally or unintentionally. This is clearly problematic. How can you repair RNA when you can't tell if something is an error?
https://t.co/bIZGviHBUc
4/
DNA's use of T instead of U means that spontaneous C → U deamination can be corrected without worry that an intentional U is being removed.
DNA requires greater stability than RNA so the transition to a thymine-based structure was beneficial.
https://t.co/bIZGviHBUc
5/
Let's return to megaloblastic anemia secondary to B12 or folate deficiency.
When either is severely deficient deoxythymidine monophosphate (dTMP*) production is hindered. With less dTMP, DNA synthesis is abnormal.
[*Note: thymine is the base in dTMP]
https://t.co/AnDUtKkbZh
I applaud the #EUCancerPlan *BUT* caution: putting #meat 🥩 (a nourishing, evolutionary food) in the same box as 🚬 to solve a contemporary health challenge, would be basing policy on assumptions rather than robust data.
#FollowTheScience yes, but not just part of it!
THREAD👇
1/ Granted, some studies have pointed to ASSOCIATIONS of HIGH intake of red & processed meats with (slightly!) increased colorectal cancer incidence. Also, @WHO/IARC is often mentioned in support (usually hyperbolically so).
But, let’s have a closer look at all this! 🔍
2/ First, meat being “associated” with cancer is very different from stating that meat CAUSES cancer.
Unwarranted use of causal language is widespread in nutritional sciences, posing a systemic problem & undermining credibility.
3/ That’s because observational data are CONFOUNDED (even after statistical adjustment).
Healthy user bias is a major problem. Healthy middle classes are TOLD to eat less red meat (due to historical rather than rational reasons, cf link). So, they
4/ What’s captured here is sociology, not physiology.
Health-focused Westerners eat less red meat, whereas those who don’t adhere to dietary advice tend to have unhealthier lifestyles.
That tells us very little about meat AS SUCH being responsible for disease.
#FollowTheScience yes, but not just part of it!
THREAD👇
\U0001f534LIVE \U0001f4c5Today \u23f012:00 CET
— EU_HEALTH - #EUCancerPlan (@EU_Health) February 3, 2021
We are presenting today the #EUCancerPlan as part of a strong \U0001f1ea\U0001f1fa#HealthUnion
Follow the presentation live here: https://t.co/Cr8ATvzNkg#WorldCancerDay pic.twitter.com/zdByuklWV6
1/ Granted, some studies have pointed to ASSOCIATIONS of HIGH intake of red & processed meats with (slightly!) increased colorectal cancer incidence. Also, @WHO/IARC is often mentioned in support (usually hyperbolically so).
But, let’s have a closer look at all this! 🔍
2/ First, meat being “associated” with cancer is very different from stating that meat CAUSES cancer.
Unwarranted use of causal language is widespread in nutritional sciences, posing a systemic problem & undermining credibility.
3/ That’s because observational data are CONFOUNDED (even after statistical adjustment).
Healthy user bias is a major problem. Healthy middle classes are TOLD to eat less red meat (due to historical rather than rational reasons, cf link). So, they
4/ What’s captured here is sociology, not physiology.
Health-focused Westerners eat less red meat, whereas those who don’t adhere to dietary advice tend to have unhealthier lifestyles.
That tells us very little about meat AS SUCH being responsible for disease.
