MadSci Network: General Biology
Query:

Subject: How many calories (nutritionally) are in say, a litre, of blood?

Date: Sun Nov 8 14:20:59 2009
Posted by Jesse
Grade level: undergrad School: UofT
City: No city entered. State/Province: No state entered. Country: No country entered.
Area of science: General Biology
ID: 1257715259.Gb
Message:

Also, Why can't you survive on a diet of blood alone? I'm asking this because I
have to make a presentation on vampires--why they wouldn't be able to survive
from a biological perspective.



Response:


Re: How many calories (nutritionally) are in say, a litre, of blood?

Greetings Jessie,

Thanks for submitting your question about vampirism to the MadSci Network. I am 
pleased to let you know that questions related to yours have been answered 
on our site. Take a look at this answer : 
http://www.madsci.org/posts/archives/aug99/935553476.Me.r.html
and
http://www.madsci.org/posts/archives/2004-04/1081912776.Me.r.html
and
http://www.madsci.org/posts/archives/2004-02/1077578504.Gb.r.html

You can also use our search engine to locate answers containing the word(s) :
http://www.madsci.org/MS_search.html

In the first answer, you will see the the estimated caloric content of a pint of 
donated whole blood is 341.4 kcal (Calories). Note that one kilocalorie (lower-
case c) is equivalent to one Calorie (upper-case C). The Mayo Clinic site says
that the body burns 650 calories (0.65 kcal) in donating a pint of blood.

So, if 1 pint of blood contains 341 Calories, since 1 pint is 0.47 liters, then 
one liter of blood will contain 2.11 pints or 721.5 Calories. So, you would
have to drink 3 liters of blood to maintain a 2000 Calorie a day diet. However,
a diet of blood does not likely constitute a balanced diet so you likely won't 
get all of the Calories. There is definitely no fiber in a blood diet, and it will
likely be deficient in many vitamins. Humans are omnivores;we need to consume
a diet of fruits and vegetables in addition to protein and processed carbs. 

As for why vampires wouldn't be able to survive from a biological perspective;
since vampires are fictional characters, and magical characters at that, science
does not really pertain to them. There is no biological reason why vampires 
wouldn't be able to survive, because there is no biological reason why 
vampires should exist. This is to say that you can come up with ANY reason
why vampires should or shouldn't exist. Why does sunlight destroy vampires, 
or a stake through the heart, or holy water? Why do they live forever? There
are no scientific answers to these questions, because vampires are not the 
topic of science. 

If, after reviewing the previous answers, you still have a question, feel free to 
submit a new question, but please be sure to tell us that you have already 
searched the archives, along with what is not in the archives that you want to 
have additional information about, or what in the the archived answers you do 
not understand. This will help us to give you the best answer possible.

Cheers!

Steve Mack, Moderator MadSci Network

_______________________________________________________________
Also, Why can't you survive on a diet of blood alone? I'm asking this because I
have to make a presentation on vampires--why they wouldn't be able to survive
from a biological perspective.


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Re: How many calories (nutritionally) are in say, a litre, of blood?

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