Wednesday, September 15, 2010

Calories in Human Blood

As of Nov 2016 >15,000 visits have been made to this post on calories in human blood. "Article Directory by Category" lists other health-related topics, such as recovering from donating blood (March 2011) or statistics on dying while exercising (Sept 2011).

CALORIES HUMAN BLOOD or HUMAN BLOOD CALORIES:  The standard U.S. blood donation is 500 ml and weighs a tad under 1.2 pounds. Nutritionists tell us that losing one pound is equivalent to losing 3,500 calories. Does this mean that donating blood is a good way to start a diet? The answer is "No," because blood is mostly water, and thus not 3,500 calories per pound. To cut to the chase - a donation contains roughly 450 calories. Details of the math:

Blood tests always include hematocrit - the percent of blood that is cells versus the percent that is liquid, determined by spinning a tube of blood in a centrifuge to pack the cells to one end. Whatever percentage that is not packed cells is plasma. Men's blood has a lower plasma content (55%) than women's blood (60%) because men have more red blood cells, i.e., a higher hematocrit than women.

First calculate calories for plasma. Blood is denser than water by six percent, so multiply that 500 ml donation times 1.06 to get to grams (because calorie content will be calculated from grams). Multiply that by 55/100 for men or 60/100 for women to get to grams of plasma. Now, multiply that by .07, because plasma is only 7% protein, to get to grams of protein. Finally, multiply that result by four to get protein calories. Answer in the 80’s? Good.

Now for sugar in plasma. Normal fasting blood sugar is around 0.09 grams per 100 ml of plasma (more familiarly expressed as 90 mg/dl). Multiply the amount in grams time 2.75 for men or 3.00 for women, i.e., equal to how many hundreds of mls of plasma there are in 500 ml of blood, and then times four to get to calories. Result should be one calorie. Blood is not sweet!

As an aside here, for most people only 20 calories' worth of glucose (sugar) is circulating in the blood at any given moment, with the exception of after a meal, when there is a bump up for a few hours.. Muscle and other organs are constantly adding or withdrawing glucose to maintain this constant amount. For people with diabetes, excess sugar is poorly removed from circulation, leaving the sugar molecules to inappropriately attach to proteins, i.e., glycosylation, causing cumulative damage. Measuring blood sugar gives a real-time picture. Measuring hemoglobin A1C - glycosylation of a blood component - assesses long-term control.   

For plasma calories from fat, use 0.5 grams per 100 ml of plasma, times hundreds of mls of plasma, times nine - for calories from grams of fat - to get to calories. The 0.5 g/100 ml covers triglycerides and fatty acids in lipoproteins but not cholesterol, as cholesterol is not metabolized for energy. Result is roughly 12 calories.

Next comes calories from red blood cells. RBCs are mostly water and protein, the protein almost entirely hemoglobin. Hemoglobin does not conform to the rule of four calories per gram because the heme portion of the molecule is not metabolized for energy. Use average hemoglobin values of 160 g/L for men or 140 g/L for women, multiplied by 0.5 to get to the blood donation volume of 500 ml, multiplied by 0.96 to correct for using only the non-caloric heme portion of the hemoglobin molecules, then multiplied by four to get to calories. But wait! Hemoglobin is only 90% of the dry weight of RBCs. Multiply one-tenth the amount of the hemoglobin weight in 500 ml times six (see below for why six) and add that to red blood cell calories.

Finally, estimate calories for the other types of cells. Of the 500 ml blood donation, roughly one percent will be white blood cells and platelets. Figure five grams, times one-third to get to dry weight, times six, to get to an estimated 10 calories. The "times six" is because some of the dry weight is protein or carbohydrates, which both have four calories per gram, and some is fat, which is nine calories per gram.

Add everything up. The total should be approximately 425 calories for women and 460 for men. Anemia would result in a lower value. Use of EPO or NESP, drugs which unethical athletes can use to increase their red blood cell count and thus their oxygen transporting capacity, would result in a higher value.

All in all, the calories removed in a unit of donated blood are less than the equivalent of one normal-sized meal. The actual energy cost of making new blood will be higher than this calculated calorie content, as synthesis is not 100% energy efficient. But keep in mind that even without a blood donation, the body replaces about 1% of red blood cells every day. So the excess energy needed to replace a donation of roughly 10% of one's blood supply is not large, and takes place over four to eight weeks.

During prolonged vigorous exercise it is possible to deplete the easy to access stores of energy in the form of glycogen - a precursor for glucose - and not be able to metabolize fat or protein fast enough to keep up with demand. The transition from fueled to empty is quick and the consequences dramatic. In the U.S. the condition is referred to as 'bonking,' or 'bonked.' Marathon runners used to call it 'hitting the wall.' When circulating blood sugar drops, the brain, which relies solely on blood sugar, crashes. Recovery is slow, because even if the athlete stops moving and rests, any sugar being made by muscles or liver tends to get used locally before it gets to the brain.   

BLOOD AS FOOD: Blood, human or otherwise, can not be considered a nutritionally complete or balanced food for humans, as it is lacking in essential fatty acids and sufficient carbohydrates, has too much protein, and does not provide sufficient vitamins, minerals or fiber. Vampire bats get by, but to do so they have to consume more than a third of their body weight in blood every night. And pee a lot. As for vampire calorie requirements, if vampires have the same caloric needs as (living) humans then it would take five units a day (a night?) to keep a vampire in caloric balance. But given that vampires have no resting metabolism calorie requirements (they’re dead, remember?) calorie needs are probably much lower.

Non-human blood is featured in many traditional dishes from around the world. Blood sausage combines blood with grain and spices. Note that boudin blanc the popular Cajun sausage uses pork livers and hearts, rice and spices, but not blood. The boudin noir version uses blood. Blood is used as a soup ingredient in many cultures. In Eastern Asia, blood is allowed to congeal in shallow trays and then cut into squares. This is called “blood tofu” and used in many stir-fry dishes.

Calvin Trillin, renowned food writer, oft told of his frustration at being in a Chinese restaurant in the U.S. and not knowing what the choices meant on the Chinese-language parts of the menu. When he tried pointing at the entries the waiter typically replied "You no like." So if you see 血豆腐 on the Specials menu, likely, you no like. It translates as pig's blood tofu.

Wednesday, February 24, 2010

Marble/Whitney/Parmenter Farm

Click on photo to enlarge
Let’s start with the witch trial connection. In 1692 Joseph Marble, resident of Andover, posted bond for his two nieces accused of witchcraft. Abigail Faulkner, his wife’s sister and their mother, had already been convicted of witchcraft and sentenced to be hanged. Her execution was deferred because she was pregnant. By the spring of 1693 the witch hunt frenzy was over. Abigail was pardoned, her daughters never brought to trial. Subsequently, records show Joseph Marble buying 140 acres of land in Sudbury in 1704. Exactly what land Joseph bought and from whom has not been researched, but a good guess is from William Brown and at the northeast border of what is now Maynard. When Stow incorporated in 1683 this section remained part of Sudbury (Joseph is recorded as attending Sudbury town meetings). Not until 1730 did Joseph’s son John Marble and his neighbors successfully petition to switch their land to Stow. In 1871 the same land was included in the creation of Maynard. Thus, over the years the Marble/Whiney/Parmenter homestead was part of three towns, and connected to Marble family history, Whitney family history and Parmenter family history. All three of these historic New England families immigrated from England during the 1630's as part of the "Great Migration."

The Marble family line at the homestead was as follows: starting some time after 1704 with Joseph Marble, then his son John, John’s son John, and that John’s son John. John-the-last is buried in Glendale cemetery with his wife Lois. Their daughter Sarah Marble married Daniel Whitney and they inherited the house. Their daughter Mary Whitney married Joel Parmenter. Mary and Joel lived in Sudbury until Daniel Whitney died in 1871, then back to the homestead, making it the Parmenter house until Joel died in 1919. Mary’s and Joel’s son Harry owned half of the house and none of the farm by the time the house burned to the ground in 1924. The house was never rebuilt and the barns (spared by the fire) are long gone. The land is owned by the town of Maynard.

A few highlights: The original immigrants John and Judith Marble, John and Elinor Whitney and John and Briget Parmenter all arrived in New England in the 1630’s as part of the Puritan Great Migration. Joseph’s “witch” sister-in-law gave birth to Ammi Ruhamah Faulkner in 1693. His name was derived from Hebrew and translates as “my people have been saved” – apt for a child who’s pregnancy saved his mother’s life! Around 1740 Ammi moved to South Acton and bought the mill. His home is now the historic Faulkner Homestead. His first cousin John Marble was already in residence at the Marble homestead, a mile down the road. The Stow Lower Village Cemetery is full of Whitneys, including Daniel Whitney’s great-grandfather Richard Whitney, Richard’s wife Hannah, and Richard’s second wife, also Hannah. They are lined up Richard, Hannah #1, Hannah #2. Our local Whitneys were related to all the famous Whitneys: Eli Whitney, Whitney museum, horse-racing Whitneys, owner-of-the-Mets Whitneys… Joel Parmenter bought his way out of the Civil War draft, but his great-grandfather Deliverance Jr. fought in the Revolutionary War and his grandsons Joel F. Parmenter and Daniel L. Parmenter served in the U.S. Army in WWI and are listed on the monument in Maynard’s Memorial Park.

House and barns before the fire of 1924
What Maynard owns is a 28’ x 32’ house foundation and surrounding property of what was one of the first households in Maynard. Granite steps descend into what had been the basement. The Marble family had built an imposing, Georgian colonial style house plus large horse barns. In April 2009 Maynard’s Boy Scout Troop #130 cleared the site and installed a post and chain fence. This was an Eagle Scout project by Jason Schomacker. A plaque at the site shows an undated photo of the house and barns. The site borders the future Assabet River Rail Trail. With good hiking shoes it is possible to walk 0.8 miles on the trail from Maplebrook Park (south end of Maple Street) to the farm site. Or drive to Rockland Avenue and park in the driveway of the boarded-up white house, just past the site.

Behind the story: In January 2010 the Maynard Historical Society newsletter published an expanded (4000 word) version of this history. The long version is also in the 2011 book "MAYNARD: History and Life Outdoors" (available via Amazon). Visit the site during daffodil season for an additional treat!

Tuesday, February 2, 2010

Avoid Overhydration and Hyponatremia

Also see May 2013: "Water - How Much to Drink?"

This article is about the perils of overhydration - rarer than dehydration - but with its own adverse consequences. 

DO plan to drink during any endurance event such as a 100 mile (century) bicycle ride. Under warm & dry conditions an athlete can lose a quart (two pounds) of water an hour. According to a study by T.D. Noakes, of 2,135 athletes completing endurance events found that 50% were dehydrated at the finish, defined in the study as having lost more than 3% of pre-event body weight. [Proc Natl Acad Sci 2005;102:18550-55].

Weight losses of up to 2% are not expected to affect performance. Long training rides can be used to learn how much to drink to keep weight loss in the 0% to 2% range. There does not appear to be any advantage to pre-loading fluids before the start, and not doing so may save you time lost waiting in line at the Port-O-Potties at the first rest stop of a century. Be mindful that lack of urine production is not necessarily a sure sign of dehydration (see below).

DON'T overhydrate before, during, or after the ride. The popular dogma is “Drink before you are thirsty.” The dogma is wrong and potentially dangerous. With today’s cult of hydration, 5% to 20% of people completing endurance events will weigh more at the end than when they started! Studies have shown that when athletes drink to satisfy thirst they tend to replace only about 75% of the water they are losing during the endurance event. This, rather than drinking to not lose any weight, appears to be the safer target. Full recovery from the mild, event-related dehydration will take place after the event is over. Overhydrating, measurable as gaining weight during the course of the event, does not improve performance.

The health risk from overhydration is that it lowers sodium concentration in the blood. The scientific term for this is hyponatremia. In that study mentioned above, 10% of the athletes had gained weight by the end of the event, 3% had blood sodium below the normal range, and 1% had symptoms associated with low sodium. While puffy hands and ankles are not a serious health problem, swelling of the brain is! The problem here is that the brain is encased in a rigid container – the skull – and cannot expand.

From mild to severe, the signs and symptoms of overhydration can include one or more of the following: headache, nausea, puffiness (face, ankles, hands), dizziness, confusion, agitation, vomiting, respiratory distress, stupor, coma, seizures, and (very, very rarely) death.

Sports drinks do not contain enough sodium to prevent hyponatremia.

Contributing to the incidence of overhydration is that fact that for some people, prolonged exercise turns off urine production even if they are overhydrated. The effect can continue for hours after exercise stopped. Thinking that “No pee” means dehydration, these people continue drinking water and sports drinks in an attempt to trigger urine production. The best protection is to check post-event weight against pre-event weight, and not drink anything more than small amounts of fluids if you are heavier afterwards compared to before.

The International Marathon Medical Directors Association recommends athletes drink to satisfy thirst. The IMMDA also recommends that for marathon participants any post-event weight gain constitutes justification for a medical consultation. [Clin J Sport Med 2006;16:283-92]. The same thinking would apply to bicyclists.