MadSci Network: Medicine

Re: What is the calorie content (not weight) of a pint of blood?

Date: Tue Aug 24 22:56:55 1999
Posted By: Mark Fung, MD/PhD, Post-doc/Fellow, Laboratory Medicine, Washington Univ at St Louis
Area of science: Medicine
ID: 934846191.Me

Dear Barbara,

This is a very interesting question!

Here are some considerations I made in calculating the number of calories 
in a pint of blood.   The strategy is to express the components of blood in 
terms of grams of protein, lipid and carbohydrate.  Then convert the grams 
to calories.  An alternative and more direct way of determining the number 
of calories in a donated pint of blood would be to dry it down (to remove 
the water), and then burn it in a calorimeter to calculate how much heat is 
generated from the blood.

I can calculate a reasonable number for calories associated with the plasma 
(non-cellular portion) of the blood, but I can only make a rough 
approximation of the calories obtained from the red blood cells.

1.  A blood donation usually is 400 to 495 ml (for calculations I will use 
500 ml).  

2.  Assume an average hematocrit of 40% for a woman (40% red blood cells, 
60% plasma by volume).

500 ml x 40% = 200 ml (plasma volume)

*Plasma glucose:

The average plasma glucose concentration is 90 mg/dL (or 0.9 mg/ml). 

200 ml x 0.9 mg/ml = 180 mg of glucose in plasma portion of donated blood
                   = 0.18 gm of glucose

Caloric content of glucose is 3.4 kcal/g, 
therefore 0.18 gm of glucose = 0.612 kcal

*Plasma protein:

The average plasma total protein concentration is 7 g/dL (or 70 mg/ml)

200 ml x 70 mg/ml = 14,000 mg of protein in plasma portion of donated blood
                   = 14 gm of protein
Caloric content of protein is 4.0 kcal/g,
therefore 14 gm of protein = 56.0 kcal

*Plasma lipid:

The average plasma total lipid concentration is 600 mg/dL (or 6 mg/ml).

200 ml x 6 mg/ml = 1,200 mg of lipid in plasma portion of donated blood
                  = 1.2 gm of lipid

Caloric content of lipid is 9.0 kcal/g (long chain fatty acids),
therefore 1.2 gm of lipid = 10.8 kcal

**Therefore total calories in donated plasma = 0.6 + 56 + 10.8 = 61.4 kcal 

Calories derived from red blood cells:
I will make the assumption that the predominant component of RBC's is 
hemoglobin, which is a protein.  Therefore:

Whole blood hemoglobin in females averages around 14 g/dL (or 140 mg/ml)

The donated whole blood volume is 500 mls so 

500 ml x 140 mg/ml = 70,000 mg of protein (hemoglobin) from donated RBC's
                   = 70 gm of protein

Caloric content of protein is 4.0 kcal/g,
therefore 70 gm of protein = 280 kcal

*****EQUALS = 280 (from RBCs) + 61.4 (from plasma) = **341.4kcal****

Clinical Diagnosis & Management by Laboratory Methods by J.B. Henry, 18th 
Edition (1991), page 1366-1372

Facts and Formulas by R.C. Rollings, (1984) page 61

I hope this answers your question!

....mark fung, md/phd

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