Liver as Food: Nutrition, Diet and Cooking by R.Borgacci

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What is the liver?

The liver, as a food, is one of the most well-known offal on Italian tables. The types of liver most commonly found on the market are: bovine liver, pork liver, equine liver, sheep's liver, goose liver and chicken liver - or chicken livers.

Technically speaking, the liver, despite being considered a meat product, belongs to the whole of the fifth quarter of the animal - edible parts other than skeletal muscle tissue, such as organs, glands, rind, bones and particular cuts such as diaphragm. Also read "Heart as Food".

From a nutritional point of view, the liver is part of the first fundamental group of foods. Contains high biological value proteins, minerals and vitamins specific to this set of foods; moreover, it seems to be characterized by the significant contribution of:

  • Water-soluble vitamins different from those typical of the food group
    1. Folic acid
    2. Vitamin B12 or cobalamin
  • Fat-soluble vitamins:
    1. Vitamin A or retinol
    2. Vitamin D or calciferol
  • Other minerals: for example zinc, selenium and phosphorus
  • Cholesterol
  • Purines.

Note : the liver also contains small amounts of carbohydrates, consisting of reserve glycogen, respectively, and vitamin C.

The liver should be part of the eating habits of any healthy person; it is characterized by almost unequaled nutritional supplies and allows to easily reach some of the most hostile recommended rations - for example, bio-available iron for pregnant women - while maintaining a certain balance between energy macronutrients.

However, we must not forget that, due to the metabolic functions - which we will analyze better in the next paragraph - the liver also has more delicate health and hygiene aspects than muscle meat.


The etymology of the term "liver" derives from the Latin iecur ficatum - which in turn comes from the Greek - which literally means "liver with figs" - food of the classical epoch obtained by supercharging the pig with figs.

From the gastronomic point of view, the type of liver most used as a food is that of bovine, more precisely of calf - thanks to the best organoleptic and gustatory characteristics - even if in terms of edibility, nutritional properties and hygienic characteristics no significant differences emerge.

Did You Know That ...

In addition to offal of land animals, those of some fish such as tuna heart, cod liver, monkfish tripe etc. are also highly appreciated.

Outline of liver physiology

The liver is the largest gland in the body and proportionally plays most of the metabolic functions of the body, both in humans and in animals. The specialization of this organ is due to the wide range of enzymes and organelles of the specific parenchymal tissue, supported by the surrounding stroma. Among the various tasks performed by the liver we remember:

  • Proteosynthesis: synthesis of lipoproteins, coagulation factors, plasma proteins, etc. For this reason, the liver is rich in all the essential amino acids - even more than meat, given the metabolic function of protein synthesis
  • Production and storage of fats: fatty acids, triglycerides, cholesterol, phospholipids, etc. The production of triglycerides occurs especially through the conversion of energy molecules (glucose-amino acids) present in excess in the blood; on the contrary, cholesterol follows a quite linear and continuous cycle of uptake / release / synthesis
  • Production, conversion and storage of glucides for glycemic regulation: neoglucogenesis, glycogenolysis, glycogenosynthesis, conversion of fructose and lactose into glucose. It also performs an excellent storage function for glycogen - about 33% of the total in the body
  • Vitamin storage: especially some of the B group - such as cobalamin - vitamin A and vitamin C - and mineral salts - mainly iron
  • Endocrine gland: produces angiotensinogen, IGF-1 etc.
  • Exocrine gland: produces digestive bile juices
  • In the fetus, hematopoiesis: production of red blood cells
  • Blood purification and chemical conversion gland: deamination, transamination, urea cycle, disposal of circulating hormones, disposal of red blood cells - especially in the absence of the spleen - disposal of drugs, disposal of compromised immune cells, disposal of nerve molecules, disposal of drugs toxic agents etc.

Below we will analyze with greater precision how the various functions of the liver can characterize their nutritional values ​​and / or compromise their food safety.

Nutritional Properties

Nutritional properties of the liver as a food

The liver, as we anticipated above, is a product that belongs to the first fundamental group of foods - nutritional source of essential amino acids, mineral salts and specific vitamins.

It has a medium energy supply, mainly provided by proteins, followed by lipids and finally by few carbohydrates.

Peptides have a high biological value, that is they contain all the essential amino acids in the right quantities and proportions with respect to the human protein model; the amino acid profile of the liver is largely made up of: glutamic acid, aspartic acid, leucine and lysine.

The liver can be excessively rich in fats, in this case triglycerides, only if the animal suffers a forced overeating - fatty liver or fatty liver fatty tissue - see goose fat liver. The lipid profile of the liver changes significantly between terrestrial and aquatic animals. In terrestrial creatures there is a prevalence of unsaturated on saturated, even if the latter are still rather significant and if the fraction of polyunsaturated is not particularly high. In contrast, in aquatic animals, in addition to the prevalence of unsaturated fats, a quantity of semi-essential omega three - docosahexaenoic acid DHA and eicosapentaenoic EPA - is also very significant.

The carbohydrates it contains are complex, more precisely glycogen; when compared to foods of animal origin, which are almost without them, the fresh liver is therefore rich in carbohydrates.

The liver does not contain fiber, but is very rich in cholesterol; unlike triglycerides, the concentrations of this nutritional factor are always high, even in the lean animal. It is devoid of the most common molecules object of food intolerance: lactose, gluten and histamine. Like all offal, the liver is also very rich in purines. Fairly good phenylalanine level.

From the vitamin point of view, the liver is distinguished by the excellent concentration of soluble molecules of group B, in particular thiamine (vit B1), riboflavin (vit B2), niacin (vit PP), pantothenic acid (vit B5), pyridoxine (vit B6), biotin (vit B8 or vit H), folic acid and cobalamin (vit B12); interesting is the presence of ascorbic acid (vit C), however contained in marginal percentages compared to first-rate nutritional sources. The intake of liposoluble vitamins: retinol (vit A) and calciferol (vit D) are remarkable, indeed extremely significant.

Note : some vitamins are thermolabile, which is why even containing interesting levels, requiring deep cooking, the liver is not considered a relevant specific nutritional source.

As for minerals, the liver is an excellent source of: bioavailable iron, zinc, phosphorus, selenium, potassium, copper and molybdenum.


Hygienic aspects of the liver as food

After a long series of positive aspects - cholesterol and purines apart - we now present a hygienic-food "risk factor".

By virtue of its metabolic and purifying efficacy - closely linked and shared with the kidneys - against the circulatory stream, the content of unwanted molecules in the liver is certainly superior to that of muscle meat. Obviously the excess of pharmacological residues in the liver substantially depends on the lifestyle led by the beast; a living creature in the wild or naturally raised is never subjected to pharmacological treatments - such as antibiotics - or hormones - especially anabolic for growth. It is therefore appropriate to carefully select the supply sources of offal in general, especially of the liver or kidney which, at best, must come from excellent quality farms. As far as pollutants - such as heavy metals and dioxins - are concerned, this may be different. All creatures, in one way or another - due to contamination of feed or environmental pollution - expose themselves to environmental contamination. In this sense, it may be helpful to prefer creatures that are not too old and come from ecologically safe areas. Note : all regularly marketed foods, the liver in particular, are subject to regular veterinary inspections to ensure food fitness.

A final observation is also necessary as regards the zoological safety of the food. The liver is an organ potentially subject to parasitosis; the most statistically present and potentially harmful organisms are Echinococcus (hepatic echinococcosis) and Fascicola hepatica (hepato-biliary dystomatosis), even if they are not the only ones. For this reason, once again it is suggested to prefer guaranteed and traceable foods, with veterinary certification; buying a liver taken from domestic animals - almost never declared - significantly increases the risk of contracting this kind of disease.


Liver as a food in the diet

The liver is a food that should have a place in the diet of all healthy subjects. Economical and very nutritious, this food favors the achievement of many of the most hostile recommended rations to satisfy.

With its average energy intake, the liver lends itself to any nutritional regime. Obviously, to be able to insert it also in the slimming diet, it is necessary to guarantee that this remains normolipidic hypocaloric. For this reason it is advisable not to use more than one teaspoon of oil (about 5 g) for each portion of the liver to be cooked.

As far as the lipid profile is concerned, the liver can be considered very or little recommended in the case of certain metabolic pathologies. The liver of terrestrial animals - bovine, porcine, ovine, equine, chicken - is not recommended in case of hypercholesterolemia. This does not depend so much on the ratio of fatty acids (saturated: unsaturated = <1), which although not being the best is not even too unbalanced, as much as on the content of cholesterol; in a medium portion of the liver more than 60% of the recommended daily cholesterol ration is contained and almost 100% of that suggested for a hypercholesterolemic. Also the liver of peach products is rich in cholesterol, but on the other hand it contains a very advantageous ratio between fatty acids, thanks to the very high content of polyunsaturated fats. In this case, the liver of aquatic animals, and especially of the cold seas, provides very high quantities of omega three semi-essential EPA and DHA types. These have a very positive global impact on the metabolism and in particular on blood pressure and lipemia - despite the omega three are more effective in reducing triglyceridemia rather than cholesterol - for this reason the fish liver is considered more suitable than the animal in the diet against certain replacement diseases.

The liver, like the rest of foods of animal origin, is instead a highly recommended food to ensure the supply of essential amino acids. Conditions that determine an increased protein requirement are: pregnancy and lactation, growth, extremely intense and / or prolonged sporting practice, third age - due to an eating disorder and a tendency to malabsorption - malabsorption, recovery from specific or generalized malnutrition, debasement.

The liver contains good amounts of phenylalanine, therefore it is not among the foods given or recommended in the case of phenylketonuria.

It is considered the best nutritional source of bio-available iron. Inserting it regularly in the diet facilitates the coverage of the recommended ration, greater - with a tendency to iron deficiency anemia - in fertile women, especially pregnant women; marathon runners, vegetarians and especially vegans may also be anemic. The liver also favors the coverage of phosphorus requirements, abundant in the body both in bones and in phospholipids - contained in cell membranes and in nervous tissue. It has a wonderful content of zinc and selenium, two minerals with antioxidant power; zinc is also essential for hormonal and enzymatic production, selenium for the health of the thyroid gland. It is not a primary source of potassium, but still contributes to the coverage of specific needs - greater in case of increased sweating, for example in sports, increased diuresis and diarrhea; the deficiency frequently leads to the onset of cramps and weakness. It is an alkalizing agent necessary for the functioning of the membrane potential which can be useful in the fight against high blood pressure.

Rich in B vitamins, coenzymatic factors of great importance in cellular processes, the liver could be considered an excellent nutritional source for the correct functioning of all tissues. The content of vitamin D, rare in food and necessary for the functioning of the immune system and for bone metabolism, is remarkable and very useful. The liver can therefore support the diet of the growing subject and also the preventive osteoporosis. It is also very rich in vitamin A; this nutrient, essential for visual function, cell replication, reproductive function, etc., is however rarely scarce in the diet. Furthermore, given and considered the potential teratogenic effects linked to the nutritional excess of this vitamin, it is advisable for pregnant women not to overdo the frequency of consumption.

Interesting the content of vitamins normally absent or present only in traces inside the products of animal origin, especially folic acid - necessary for the replication of nucleic acids and very important in pregnancy - and vitamin C - antioxidant and essential for the immune system. It is however necessary to specify that the liver is a food that - due to hygienic, organoleptic and gustatory reasons - needs a deep cooking that reaches the heart of the food with temperatures higher than pasteurization. Since folic acid and ascorbic acid are two factors that are very sensitive to high temperatures, the liver cannot therefore be considered an important nutritional source.

The liver contains very significant levels of purines, it is therefore not recommended for those suffering from hyperuricemia - especially with gouty attacks - and for those who tend to kidney stones or uric acid lithiasis.

It has no contraindications for lactose intolerance, for celiac disease and for histamine intolerance. It is not allowed in the vegetarian and vegan diet. Relevance in religious nutritional regimes depends almost always on the animal of origin.

Due to the hygienic aspects we discussed in the previous paragraph, it is necessary that subjects with compromised immune system or in special conditions - for example pregnant women - pay particular attention to the cooking of the liver, which must be total, and to the choice of source of supply, which must necessarily be regular and certified.

The average portion of liver is 100-150 g (about 140-210 kcal).


Advice for liver purchases

It is essential to be able to distinguish a "good" liver from an old food of dubious quality; the necessary requirements are few and well distinguishable:

  1. Bright, turgid and NOT dehydrated appearance
  2. Typical color (depending on the species) and NOT pigmented or spotted.

The liver is highly perishable and must be kept refrigerated or frozen.

Culinary aspects of the liver

The liver is an exclusively cooked food to eat. The preferred cooking methods are those for conduction, more precisely in the pan or casserole. Recently some chefs enjoy the use of animal liver in vacuum-packed cooking or in vasocottura, a system that allows the organoleptic and gustatory characteristics of the food to be altered as little as possible. In the tradition of central Italy, with particular reference to the Apennine area, sheep's liver is also cooked grilled, often flavored with laurel and covered with retina or omentum.

The liver of land animals and aquatic animals are very different. The former differ mainly due to the sweet taste and the bitter aftertaste - above all that of pork - with a characteristic flavor. The latter, on the other hand, have particularly strong hints of fish.

The most famous recipe of the whole peninsula is, in all probability, the Venetian liver (floured liver and cooked with butter and onion).

Goose Fat Liver: Moral and Ethics

Finally, a final comment on "goose fat liver" is a must; this food, besides being taken from deliberately sick animals - since fatty liver steatosis can be considered a pathology or a clinical sign, even if with a metabolic etiology and NOT transmissible - represents a form of barbarism from which the consumer should abstain. First of all, due to its lipid profile, goose fat liver is a decidedly unhealthy food (and there is no organoleptic and gustatory characteristic that can justify its intake); secondly, the animal husbandry / feeding system involved is totally devoid of moral and professional ethics. The birds in question are forcibly fed by swelling and fattening excessively the liver due to the growing steatosis; it is a behavior completely disrespectful not to be encouraged and, on the contrary, to be condemned.