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Bulletin #6 – Liver: Natural Iron

Liver has been a mainstay supple-ment for bodybuilders and power athletesfor years — and for good reason. Recently,endurance athletes have also realized theincredible nutritional value of liver. Liverprovides heme iron, high quality protein,and B vitamins, thereby meeting severalof the increased nutritional needs of ath-letes in a single blow. Heme iron is respon-sible for hemoglobin’s ability to carry oxy-gen in red blood cells. Heme iron is thebest absorbed — the most bio-available —of all iron sources (2,6). And liver isnature’s best source of heme iron (2).Your body generates energy bybreaking down foods and transporting thefood molecules to all the cells of the body.Inside the cells, the foods are burned in achemical reaction called “oxidation,”which simply means reaction with oxy-gen. (This is very similar to what happensto food when it burns in a fire.)  For foodsto be converted to energy, the cells haveto get plenty of oxygen.  This constantneed for energy is so critical that if tis-sues are deprived of oxygen for more thana few minutes they will die.As you know, red blood cells areresponsible for transporting oxygen to allthe tissues of the body.

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They do this  bybinding oxygen to hemoglobin, the red pig-ment in the blood.  Hemoglobin  is a pro-tein that includes a special chemical struc-ture known as heme—a complex of por-phyrin and iron.  And it’s the iron whichbinds oxygen in the lungs and subse-quently releases it in the muscles and otherperipheral tissues. Muscles contain myo-globin, an oxygen-carrying protein thatworks inside cells. Like hemoglobin, myo-globin also requires iron to bind oxygen.Without the iron, the whole oxygen trans-port system won’t work.  Not only that,but iron is also required by the enzymesin the electron transport chain—the se-ries of reactions in which oxygen is con-sumed in the cells. So iron is required notonly for transporting oxygen to the tis-sues but also for its use inside cells. Be-cause of its critical role in oxygen utiliza-tion, iron has earned its reputation foroccupying a central position in energymetabolism.Iron deficiency is widely recognizedas the most common nutritional deficiencyin the world (2, 3).  As many as 22% ofAmerican women are iron deficient, andthe number is as high as two-thirds in de-veloping countries (1, 2). The daily ironrequirement for women is 18 mg per day,while on average they obtain only 10-12mg per day (1). Men have lower daily ironrequirements, so are somewhat less proneto suffer from deficiency.

Among athletes,about 10% of males are iron deficient,compared to 22-25% of females (1). Manytimes a feeling of fatigue or low energy isthe result of an unrecognized iron defi-ciency (2, 3).Dietary iron sources are usually di-vided into two general categories: hemeiron and nonheme iron (2). Heme iron isiron which is already bound to heme—the red pigment in hemoglobin.  Goodsources of heme iron are red meat andliver. White meat chicken and turkeybreast also contain heme iron, but in loweramounts (2). The form of iron found inplants is not incorporated into heme andis therefore called nonheme iron. Ironfrom red meat and liver, in the form ofheme iron, is much easier for your bodyto absorb (6).Iron deficiency is associated withvegetarian diets (1). Some vegetables,such as beans, corn, and spinach, con-tain a significant amount of iron.  Unfor-tunately, iron from vegetable sources ispoorly absorbed (1).  Only 1.4% of ironfrom spinach is absorbed. Seven percentof iron from soybeans is absorbed, mak-ing it one of the best vegetable sources ofiron.Red meat provides much higheramounts of iron per serving than vegetablesources (2).  Additionally,  liver is an evenbetter source of iron than red meat. Fur-thermore, the iron from red meat andliver—heme iron—is much easier for yourbody to absorb (2, 6).

About 15-20% ofiron from red meat and liver is absorbed(2). The higher iron content of thesefoods, along with  the greaterbioavailability of heme iron, makes redmeat and especially liver much better di-etary iron sources.Another factor may also be involvedin explaining the association of iron deficiency with vegetarian diets. The effi-ciency of iron absorption depends on pro-tein intake (5).  Meat proteins improve theabsorption of heme and nonheme iron (5).Furthermore, the presence of heme ironalso improves the absorption of nonhemeiron (4). Athletes who do not eat red meator liver have an increased risk of devel-oping anemia (6).Anemic children and adults are of-ten thought of as backward or apathetic(2). Recently it has been realized that sub-clinical iron deficiency, less severe thananemia, can result in poor performanceon a variety of behavioral and cognitivetests (2). This effect is reversible and re-sponds to iron supplementation, depend-ing on the severity of the deficiency. Sometest scores of children improved after asingle iron injection, while in other ex-periments 11 or 12 weeks of iron therapyresulted in improvement. Several studieshave found a positive correlation betweenIQ and iron level: the higher the iron level,the higher the IQ (2).

Bear in mind, how-ever, these studies are concerned withdeficient children, and increasing iron lev-els in children with already sufficientamounts would not be expected to con-fer any advantage.It is well established that iron defi-ciency decreases work output and ath-letic performance (3, 6). This is prima-rily due to reduced oxygen carrying ca-pacity of the blood, but reduced aerobiccapacity of the muscle (due to tissue leveliron depletion) is involved as well (3). Ironsupplementation has been shown to beeffective at increasing productivity of irondeficient workers. Plantation workers andrubber tappers in Central America (2) andtea pickers in Sri Lanka (3) who wereiron deficient displayed decreased perfor-mance and work output.  Following ironsupplementation, productivity improved(2, 3). Also, iron deficient children andadults are much more likely to sufferfrom infectious diseases than those re-ceiving iron supplementation (2). Whiteblood cells need plenty of oxygen to killinvading bacteria. And having a good,strong immune response is critical tomaintaining optimum health.“Sports anemia” is induced by ex-ercise training and endurance athletes areespecially at risk (1, 3, 6). Many times,sports anemia is not associated with a trueiron deficiency. Skeletal muscle fibers aredamaged during intense exercise training,and this damage must be repaired duringthe recovery period following exercise.If dietary protein intake is inadequate, thebody will draw on red blood cells, hemo-globin, and plasma proteins as a sourceof protein to repair the muscles (3).  Ifprotein intake is limited, repair of muscletissue may soak up all of the incomingprotein and not leave enough left to re-build new red blood cells at the normalrate.  

Increased protein intake may be ef-fective in treating sports-induced anemia(1). Often times, an athlete experiences adecrease in red blood cell count and se-rum iron levels during the early phase oftraining (1). This could be due to the factthat aerobic training causes an increasein myoglobin (an oxygen carrying pro-tein) and cytochrome content of muscletissue and the protein and iron requiredfor their formation could be obtained fromdestruction of red blood cells (1, 3). Inother words, myoglobin may be increasedat the expense of hemoglobin if proteinintake is inadequate.Athletes with low hemoglobin lev-els do not perform as well at enduranceevents.  Interestingly, endurance athleteshave the highest incidence of sports ane-mia and also have the highest protein re-quirements. There seems to be an ironcost associated with exercise (3) and thereis no question that iron deficiency com-promises athletic performance (6). Stud-ies suggest that athletes have a higher thanusual incidence of iron deficiency, and thisis probably caused by iron depletion dur-ing exercise (3). Female athletes and en-durance athletes are especially at risk ofiron deficiency (1, 2, 3, 6).  

Iron defi-ciency anemia reduces maximal oxygenuptake, reduces work output, and in-creases the time required to recover be-tween workouts (1). Encouragingly, ironsupplements have been shown to be ef-fective in reversing the effects of irondeficiency and in restoring hemoglobinlevels (1, 2). Iron supplementation is ef-fective in improving athletic performanceand work output of deficient individuals(1, 3). It has been reported that ironsupplementation alone will not correct truesports anemia, which is reasonable whenconsidering it as a protein deficiency.However, since liver provides both highquality protein and heme iron it should bebeneficial to athletes suffering sports ane-mia. Liver may also be effective in pre-venting the iron deficiency induced byexercise training.Liver is the best source of hemeiron (2). Heme iron is damaged by cook-ing, reducing the bioavailability of iron byas much as 50% (5). Desiccated liversupplements thus represent probably themost bioavailable iron source. Parrillo Per-formance Liver-Amino Tablets™  aremade from de-fatted  liver, which meansyou don’t get all the fat and cholesterolthat comes along with liver and red meat.Plus we add predigested casein to fur-ther increase the protein content to 1.5grams per tablet. This is why we feelParrillo Performance Liver-Amino™  isone of the best supplements available forbodybuilders and endurance athletes: Itprovides heme iron, high quality protein,and B vitamins all in one.

REFERENCES

1.  Haymes; Proteins, Vitamins, and Iron; inErgogenic Aids in Sport; ed. Williams; Hu-man Kinetics Publishers; 1983; p.27-55.

2.  Scrimshaw, Iron Deficiency, ScientificAmerican, October, 1991, p. 46-52.

3.  Sherman and Kramer, Iron Nutrition andExercise, in: Nutrition in Exercise and Sport,eds. Hickson and Wolinsky, CRC Press,1989, p. 291-308.

4.  Steen, Nutrition Considerations for theLow Body Weight Athlete, in Sports Nutri-tion for the 90s, eds. Berning and Steen,Aspen Publishers, 1991, p. 153-174.

5.  Wapnir, Protein Nutrition and MineralAbsorption, CRC Press, 1990, p. 99-129.

6.  Whitmire, Vitamins and Minerals: A per-spective in Physical Performance, in SportsNutrition for the 90s, eds. Berning andSteen, Aspen Publishers, 1991, p. 129-151.

2018-03-13T11:10:39-04:00 May 7th, 2009|Technical Supplement Bulletins|

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