Hearts Have Higher Taurine

Why Hearts Have Higher Taurine

If you are a dedicated cat parent who wants keep your kitty as healthy as possible, you’ve likely already read about the benefits and necessity of feeding your little feline food containing taurine. Furthermore, you may already know that turkey hearts, chicken hearts, and duck hearts are exceptionally high in taurine. What you probably don’t know, however, or know in detail, is why this is true. Why are hearts so high in taurine? We answer this question in detail below and we also explain why bird hearts have more taurine than most mammalian hearts.

A Bit Of Relevant History

On August 14 1987, the Los Angeles Times reported that tens of thousands of domestic cats had died from heart disease due to a nutritional deficiency in commercial brand cat foods. Specifically, these beloved feline members of American households had died from dilated cardiomyopathy (DCM) due to the lack of taurine. Basically, their hearts became too weak to meet their metabolic demands.

Cat lovers were understandably shocked and dismayed by this startling revelation. With the spotlight now on this issue, Purina and other major cat food manufacturers quickly reformulated their commercial cat foods to contain taurine. However, there has been ongoing concern ever since over the quantity, and perhaps more importantly, the quality of the taurine in highly processed commercial cat food. As a result, many cat parents look for ways to supplement their cat’s diet with healthier and more trusted sources of taurine. Feeding their cats raw hearts as a highly nutritious treat has become a popular way to ensure they are getting enough taurine.

The timing of the Los Angeles Times’ article was spurred by a scientific research article published in the top-rated journal Science that same month in 1987. However, this national attention addressed an issue that had actually plagued domestic cats since at least the 1970s. It had been known in the scientific community since the 1970s that a lack of taurine in a cat’s diet can cause retinal degradation, often leading to blindness. In fact, kittens born to cat mothers deficient in taurine can be born completely blind! However, even though the cat food industry had been aware of the taurine issue since at least 1981, they failed to add taurine to their cat food formulas until they received national media attention.

The Hardest Working Muscles Contain the Most Taurine

In general, the harder a muscle works, the more taurine it contains when eaten as food. The hardest working muscle in the body by far is the heart… no other muscle even comes close! Therefore, the heart contains the highest concentration of taurine! Following this same “rule,” skeletal muscles that get worked harder contain more taurine than skeletal muscles that don’t get used as much. In birds, the dark meat corresponds to the skeletal muscles that get worked the hardest, and therefore, they contain more taurine than the white meat.

Just How Hard Does a Heart Work?

To give some perspective on how hard a heart works, a human heart pumps a minimum of 2500 gallons of blood a day, according to the University of Chicago Medicine. Furthermore, a human heart beats about 115,000 times a day, about 42 million times a year, and about three billion times over the course of a lifetime! This is non-stop work all day every day until you die! Bodybuilder biceps pale in comparison!

What’s even more amazing to consider is the fact that the hearts in certain other animals, namely birds and mice, actually work much harder than the human heart! Compare the resting heart rate (beats per minute) of the various animals listed below:

Mouse: 450–750
Hamster: 300–600
Adult Chicken: 250–300
Chick (baby chicken): 350–450
Domestic Turkey (Broad Whites): 298-309
Tufted Duck (a diving duck) Floating On Water: 260
Common Pochard (a diving duck) Floating On Water: 158
Cat: 120–140
Dog: 70–120
Sheep: 70–80
Goat: 70–80
Dairy Cow: 48–84
Horse: 28–40
Elephant: 25–35

The Higher the Heartbeat the More Taurine the Heart Contains!

Across all animals, there is a direct correlation between how fast the heart beats, i.e. how hard the heart works, and how much taurine will be found in each gram of heart tissue! This is because a faster beating heart needs more taurine than a slower beating heart to function properly. There’s also more taurine in the skeletal muscles of animals with higher heart beat rates. This makes sense because animals that have a higher metabolic rate need a corresponding higher heart rate.

Looking at the heart rates above, you will notice two particular standouts: rodents and birds! This is why there is so much taurine in rodent and bird hearts, and of course, rodents and birds (and bugs) just happen to be the favorite foods of most frisky felines!

Birds have an extremely high metabolism, even at rest, and therefore have a heart that beats very fast and is exceptionally high in taurine. Birds also often engage in activities over an extended period of time that require their hearts beat even higher than a mouse. For example, if you’ve ever watched ducks on the water, you know they can be very energetic beasts! Dabbling or diving for food, diving to escape danger (eagle or human approaching), and taking off in flight from the surface of the water all require a tremendous amount of energy. Duck hearts are designed to handle these intense bursts of energy and their heart rate can skyrocket in mere seconds! In fact, ducks give new meaning to the old expression, “working your heart out!”

In 1979, there was a very interesting experiment conducted with Tufted Ducks and Common Pochards, two types of diving ducks. This experiment clearly illustrated just how fast a duck’s heart rate can escalate when they dive. It also showed that even at rest, ducks have an exceptional high heart rate. To collect their data, the scientists surgically implanted a radio transmitter inside the ducks that would constantly record their heart rate and respiratory rate. They then allowed the ducks to roam free within a 20 meter x 20 meter range (one meter equals 1.09 yards) and observed their behaviors while receiving heart rate data.

Just before a spontaneous dive, Tufted Ducks went from an average heart rate of 260 beats per minute to 395 beats per minute! This astounding increase in heart rate was accomplished in only a split second! Common Pochards went from a heart beat of 158 beats per minute to 285 beats per minute. Usually too, the ducks would dive several more times before their heart rate returned back to where it was before the first spontaneous dive so this incredibly elevated heart rate was sustained for a long time. When diving specfically for food, the heart rate went up even more. When being chased by a “predator,” in this case a human with a big net, the Tufted Ducks’ average heart rate went up to 532 beats per minute and the Common Pochards’ average heart rate went up to 482 beats per minute. These ducks are true olympians!

Since ducks can double their already exceptionally high resting heart rate within a few seconds, they have to store plenty of taurine inside their heart tissue to accomodate these herculean feats! This is also why duck skeletal meat is so dark. Remember, the darker the poultry skeletal meat, the more taurine it contains. Even slower birds, like chickens and domesticated turkeys, have very high metabolic rates due to their heritage and their continued need to be able to produce a great burst of energy for flight and other activities like escaping eagles and foxes coming into the barn yard!

Relative to their body size, birds also tend to have a larger heart than mammals and they pump out more volume of blood with each beat. As you can see from studying the heart rate data above, mice and other rodents are a major exception to this trend. This is because rodents are exceptionally energetic compared to other mammals, and therefore, have an exceedingly high heart rate, high metabolism, and copious amounts of taurine stockpiled in their tissues.

What Does Taurine Do Inside the Heart?

Over the last few decades, it has become abundantly clear that taurine plays a key and integral role in the transport of positively charged calcium ions in the heart. Taurine also plays an equally important role in controlling how sensitive heart cells are to the calcium ions they encounter. In other words, taurine plays a pivotal role in the normal functioning of the electrical system of the heart. In performing this crucial role, taurine can be thought of as the master switch for one of the most fundamental elements of life: the heartbeat!

Without an adequate supply of taurine stored inside each heart cell, the heart will fail to beat properly. This was suspected by many scientists long before it was absolutely proven. Moreover, this is now a well-proven scientific fact. If taurine levels fall too low, heart contractions may become too weak to supply the body with the oxygenated blood it needs to flourish and too weak to remove toxins. It has also been proven that an irregular heartbeat can be induced by reducimg taurine and this same irregular heart beat can then be cured by restoring taurine back to normal levels. Further, the outer and inner membranes of each heart cell will deteriorate without proper taurine levels.

Taurine is so important to the normal functioning of the heart, it is stored in great quantities inside a membranous structure called the sarcoplasmic reticulum inside each heart cell. However, the exact mechanisms by which taurine controls the life-giving tasks are not entirely understood yet, even by the scientists actively studying these biochemical reactions. However, this is an area of very active scientific research because taurine supplementation (or increased taurine in diet) is thought to hold great promise in preventing, and even reversing, many heart disorders, diabetes, and other common life-compromising ailments in both people and pets. Look for taurine to become an increasingly important part of the conversation in health conscious circles, natural pet forums, and in the medical/veterinary community.

Cats Instinctively Hunt For Taurine

All members of the cat family, from the smallest member to the largest member, are instinctively drawn to hunt for prey that contain high levels of taurine and/or they prefer to eat the parts of their prey that have more taurine.

When big cats like leopards make a kill, they almost always eat the heart first! When lions hunt in groups, the socially dominant members eat first and they almost always start with the heart. This is usually followed by eating other internal organs high in taurine like the liver and lungs. Only then do they move on to the skeletal muscle meat, and here too, they show a clear preference for skeletal muscle meat that contains the most taurine. Again, muscles that work the hardest contain the most taurine so they usually eat the romp and hind quarters before they eat less worked skeletal muscles. This way, if they get chased off by hyenas or disturbed in any other way, they will have eaten the parts of the prey that contain the most taurine.

For survival purposes, smaller cats like wildcats are instinctively drawn to prey items that contain the most taurine. These include mice, rats, birds, insects, scorpions, and marine arthropods like shrimp and crab when available.

When food is limited, cats will eat an entire mouse head first, tail and all. They will also eat an entire bird when food is less abundant, except perhaps the beak and largest feathers of the wing. However, when food is plentiful and/or they aren’t very hungry, small cats have a tendency to eat the parts containing the most taurine and leave the rest! This includes the heart, the head (because brain and eyes are exceptionally high in taurine), and other internal organs. This is why so many people find partially eat corpses around if they have outdoor cats, most often with the heads and/or the heart missing!

Cats instinctively target taurine in their hunting strategies — and the heart is their #1 prime target across all species of cats, big and small! This is because hearts have more taurine! To optimize your companion cat’s health, feeding them raw hearts to mimic what what wild cats target in nature, is always an excellent option. To learn more, you can read our article on why raw hearts are better than cooked hearts.

Raw Hearts Are Better Than Cooked Hearts

Raw Hearts Provide Cats With The Taurine To Thrive

Companion cats are essentially domesticated African Wild Cats! As such, their physiology functions basically the same. This means they are obligate carnivores and need a diet of mostly animal meat and internal organs to survive and thrive. Moreover, they need quality food containing taurine that is bioavailable or they will develop serious health issues. Feeding raw hearts daily, or at least weekly, can prevent these issues because taurine levels are exceptionally high in raw hearts, and equally important, taurine is more bioavailable in raw hearts than cooked hearts (see below for more information).

With Low Taurine Intake, Cats Can Develop Serious Health Issues

One of the most common health issues in taurine deprived cats is retinal degeneration which can quickly progress to complete blindness. Another medical problem often seen in cats with low a taurine diet is dilated cardiomyopathy. This is where the heart muscle, starting in the left ventricle, becomes too weak to pump blood properly. Dilated cardiomyopathy does not always show obvious symptoms until it is too late so many cats die from it. This heart disease can also occur in dogs and ferrets if their diet is too low in taurine, especially as they age. Low taurine causes many other health issues as well including reproductive failure, decreased kidney function, decreased motor function, and a compromised immune system.

Cats Need Between 50-60nm/mL of Blood Plasma Taurine For Optimal Health

According to the latest (2006) “Nutrient Requirements of Dogs and Cats” report by the National Research Council, a division of the National Academy of Sciences, the minimal safe blood plasm concentration of taurine in cats is 40 nm/mL. This recommendation is based in part on studies that show cats with dilated cardiomyopathy often have taurine levels below 40 nm/mL in their blood plasma. It is also based on the fact that dilated cardiomyopathy can be induced in cats when they are intentionally fed a diet that allows their blood plasma taurine levels to fall below 40 nm/mL. This minimal 40 nm/mL blood plasma taurine concentration is substantiated in numerous other academic references. However, many experts now recommend an even higher blood plasma taurine level, 50-60 nm/mL minimum, to maintain optimal health in cats.

Experiments Show Freeze-Dried Raw Hearts Provide Cats With High Levels Of Taurine

Several experiments have been performed that compare the effect of cooked cat food versus raw food on a cat’s blood plasma taurine levels. These experiments clearly show that raw food (previously frozen) easily maintains adequate taurine levels in the blood plasma while heat-processed canned food does not (commercial cat food). Two of the best of these experiments were conducted by a team of scientists in the School of Veterinary Medicine at the University of California at Davis and published in peer reviewed journals. They have also been re-tested so the results can be trusted.

In the UC Davis taurine experiments, the taurine blood plasma concentrations are compared between cats fed a heat-processed can cat food versus a raw food (previously frozen) with the same exact ingredients. Besides the variation in how their food is processed (cooked versus raw), the cats tested are kept in exactly the same conditions: same space provided, same constant temperature, same constant water, same 12 hours of light/day, same 12 hours of darkness/day, and same slight air currents. The experiment is set up this way to ensure that the difference in the food is the only variable, i.e. the only thing different between the two groups of cats.

The cooked cat food and raw cat food contain exactly the same ingredients: liver and meat by-products being the top two ingredients with some smaller amounts of ground corn, animal fat, and dried skimmed milk (12% crude protein total). In the cooked version, the cat food is preserved by heating it to 120 degrees Celsius (248 degrees Fahrenheit) and then canning it. This is similar to how all commercial can cat foods are preserved and made “shelf stable” so they can sit in a warehouse or grocery store shelf for years without spoiling. The raw food version was frozen to minus 20 degrees Celsius (minus 4 degrees Fahrenheit) after preparation. It was maintained at this temperature until it was thawed and fed to the cats receiving raw food.

The results were dramatic!

The taurine levels in the blood plasma of the cats fed the heat-processed diet dropped to only 5 nm/mL. This is well below the minimum required for good health by anyone’s standard. On the other hand, the taurine levels in the blood plasma of the cats fed the raw diet averaged nm/mL! This is well above the minimum level needed to maintain good health.

Freeze Dried, Raw Hearts Provide More Bioavailability In Cats’ Diets

It should be emphasized that even though the heat-processed canned food was supposed to contain adequate taurine levels for cats, in fact almost double the recommended amount for that year (1070 mg/kg dry matter determined by analysis), it was evidently processed in a way that the cats could not fully utilize it, i.e. it was not entirely bioavailable to the cats even though they were eating it. However, the taurine in the previously frozen raw diet, containing the exact same ingredients, was bioavailable and the cats who received this diet maintained healthy taurine levels, well above the threshold needed to survive.

By also measuring the carbon traced back to the taurine (by looking for carbon-14 they included in the taurine) in their respiratory carbon dioxide, urine, and feces, the scientists were able to study how a cat processes taurine from cooked food versus raw food. It was concluded that the taurine from the heat-processed food was not able to be absorbed fully by the small intestine, probably due to a substance being released in the cooking process that made taurine transport through the cell membrane difficult. They further deduced that the gut flora found in the large intestines broke down the taurine that was not absorbed in the small intestine into inorganic substances that were not useful to the cat and he or she simply defecated it out.

Cooked, Heat-Processed Food Have Less Bioavailable Taurine For Cats

These experiments, as well as several others, clearly show that taurine becomes far less bioavailable when it is heat-processed in a manner consistent with how commercial cat food is normally processed. This is why pet food manufacturers often add synthetic taurine to their foods after they have been heat-processed, even when the food contains ingredients that are naturally high in taurine. On the other hand, these experiments also clearly show that subjecting taurine to freezing temperatures does not affect the bioavailability of the taurine significantly.

And…. this is the primary reason why raw hearts are better than cooked hearts! If you want to ensure your cat, dog, or ferret is receiving adequate amounts of natural bioavailable taurine in his or her diet, one of your best bets is to feed them freeze-dried hearts.

Selected References:

THOMAS H. MAUGH II. Thousands of Cat Deaths Traced to Pet Food Deficiency. Los Angeles Times. August 14, 1987.
http://articles.latimes.com/1987-08-14/news/mn-805_1_cat-food

Pion PD, Kittleson MD, Rogers QR, Morris JG. Myocardial Failure In Cats Associated With Low Plasma Taurine: A Reversible Cardiomyopathy. Science 1987; Aug 14;237(4816):764-8.
http://www.ncbi.nlm.nih.gov/pubmed/3616607

Hickman M.A., Rogers Q.R., Morris J.G. Effect of Processing on Fate of Dietary Taurine in Cats. J. Nutrition 1990; 120: 995-1000.

Merck Veterinary Manual. Online Edition Revised March 2012.
http://www.merckvetmanual.com/mvm/appendixes/reference_guides/resting_heart_rates.html

L. M. Krista, Ray E. Burger and P. E. Waibel. Blood Pressure and Heart Rate in the Turkey as Measured by the Indirect Method and their Modifications by Pharmacological Agents. Poultry Science (1963) 42 (3): 646-652.
http://ps.oxfordjournals.org/content/42/3/646.full.pdf

P. J. Butler AND A. J. Woakes. Changes In Heart Rate and Respiratory Frequency During Natural Behavior of Ducks, With Particular Reference To Diving. J Exp Biol 79, 283-300.
http://jeb.biologists.org/content/79/1/283.full.pdf+html

Harris Ripps and Wen Shen. Review: Taurine: A “Very Essential” Amino Acid. Mol Vis. 2012; 18: 2673–2686.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3501277/

Stephen W Schaffer, Chian Ju Jong, Ramila KC, and Junichi Azuma. Physiological Roles Of Taurine In Heart and Muscle. J Biomed Sci. 2010; 17(Suppl 1): S2.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2994395/

Laura Della Corte, Ryan J. Huxtable, Giampietro Sgaragli. Taurine 4: Taurine and Excitable Tissues. ‎2006.
https://books.google.com/

James J. Kocsis, S.I. Baskin, Stephen W. Schaffer. The Effects of Taurine on Excitable Tissues: Proceedings of the 21st Annual A. N. Richards Symposium of the Physiological Society of Philadelphia. 2012.
https://books.google.com/

Michelle T. Bernard. Raising Cats Naturally: How To Care For Your Cat the Way Nature Intended. January 1, 2003.

Hickman M.A., Rogers Q.R., Morris J.G. Effect of Processing on Fate of Dietary Taurine in Cats. J. Nutrition 1990; 120: 995-1000.
http://jn.nutrition.org/content/120/9/995.full.pdf

Nutrient Requirements of Dogs and Cats. Report By the National Research Council. Washington, DC: The National Academies Press, 2006
URL #1: http://www.nap.edu/openbook.php?record_id=10668
URL #2: https://books.google.com/books?

Gregory M. Douglass, Edward B. Fern, Androbert C. Brown. Feline Plasma and Whole Blood Taurine Levels as Influenced by Commercial Dry and Canned Diets. 1991; J. Nutr. 121: S179-S180,
http://jn.nutrition.org/content/121/11_Suppl/S179.full.pdf

James G Morris, Quinton Ray Rogers, Linda M Pacioretty. Taurine: An Essential Nutrient For Cats. J. Small Anim. Pract. 2008; 31(10):502 – 509.
http://www.researchgate.net/publication/229771636_Taurine_an_essential_nutrient_for_cats