Liver consumption good or bad?

As of now we have to live in a world where all consumables, especially foods, are associated with hazardous compounds, which adversely affect our health. For example, not like during the ancient time, now we don’t have fresh and pure green harvest. There was a time when agriculture  didn’t use chemical fertilizer and pesticides; made available with industrialization. Not only fruits and vegetables, animal food resources are also contaminated with chemicals such as certain drugs and food additives in order to earn a big profit. 

Animal based foods are generally a solid source of protein. These days, people are more interested in organ meats because the latter promises good nutrition values such as a rich source of  vitamins and minerals including vitamin B, iron, phosphorus, copper, magnesium, vitamin A, vitamin D , vitamin E and vitamin K.
Among different kinds of organ meat, liver is the most nutrient dense meat and it is a powerful source of vitamin A. This vitamin is beneficial for eye health and for reducing diseases that cause inflammation, including everything from Alzheimer’s disease to arthritis. Moreover, the liver contains folic acid, iron, chromium, copper, and zinc and is known to be particularly good for the heart and for increasing hemoglobin level in the blood. As a result of these benefits, most of the people are willing to eat the liver of animals and fish. However, there are some health risks which are associated with frequent animal liver consumption. Liver is the largest organ in animals. It has three vital functions including detoxification, synthesis and storage.  It is true that the liver should not be consumed frequently because the liver is some sort of water and food filter, metabolizing nutrients, and accumulating these undesirable substances.

Toxicity due to antibiotics residue
During past few decades, poultry has gone through massive growth and due to the increase of production, farmers tend to use certain drugs and feed additives in order to prevent diseases, for treatment and growth promotion. However, the excessive use of antimicrobial drugs accumulate in the tissues and organs of treated animals as residues and eventually become part of the food pyramid. For example, studies have discovered higher concentrations of levamisole (drugs used to treat parasitic worms) residues in liver of broiler chicken compared with other body tissues, including thigh muscles, due to the lipid-soluble nature of the drug. The veterinary drug residues in poultry products can potentially be transmitted to humans via consumption of contaminated edible parts such as liver and it leads into serious public health hazards such as antibiotic resistant bacterial formation, allergic manifestations, or alteration of useful microflora of digestive tract to no microflora and/or harmful or non-healthy microflora. Moreover, Penicillin (Antibiotic) residues are considered as the most problematic because of the vulnerability of a large proportion of allergic people and residues of penicillin in poultry can lead to severe anaphylactic reactions while eggs containing residues of sulfonamides in higher concentrations cause skin allergies upon consumption. Furthermore, the residual levels of tetracycline (antibiotic) in meat consumed by human have been reported to lead to poor fetal development, staining of teeth in young children, gastrointestinal disorders, and pro-inflammatory, toxic to living cells and immuno-pathological effects. Likewise, residual amounts of tilmicosin (antibiotic) affect hematological; white blood cell (WBC), red blood cell (RBC), total protein, albumen, cholesterol, and triglyceride concentration. Most of veterinary drugs residual in animal based diet may produce toxic, mutagenic, or cancer effects, transmit antibiotic resistance among human gut microorganisms and also reproductive abnormalities or bone marrow toxicity. 

Toxicity due to mycotoxin
Mycotoxins are toxic metabolites produced by fungus under specific conditions. Among them, aflatoxins, dangerous toxicants and health hazards for both humans and animals is produced by toxigenic fungi mainly Aspergillusflavus, Aspergillusparasiticus and Aspergillusnomius. Aflatoxins, even in small amounts, are biologically active compounds that pose potential toxic, carcinogenic, mutagenic effects in human as well as in farm animals  due to poor quality feed. According to the previous research, Aflatoxins B1 was detected in chicken liver and gizzard samples confirming the poultry’s exposure through feed or feed ingredients.  Aflatoxins B1 is known as the most toxic and carcinogenic natural toxicant which may cause liver cancer. 

Toxicity due to growth of hormone residue
Besides antimicrobial drugs, hormones are extensively used for growth promotion because one of the major factors controlling the deposition of protein in an animal is the activity of the hormones circulating in its blood. The hormonal substances used in animal production are the naturally occurring steroids such as estradiol-17β, progesterone, and testosterone, as well as synthetic compounds including zeranol used to  improve meat quality by decreasing the deposition of fat, producing the lean meat that consumers desire, increase feed efficiency, thereby allowing more growth with less feed, increase lactation period in cows when injected with bovine growth hormone. Growth promoting hormones enhance endogenous estrogen production and growth.  In general, orally administered estradiol is inactive because it is metabolized and conjugated in the gastrointestinal tract and liver. Studies have shown that growth hormone residues in animal liver adversely affect human health including neurobiological, genotoxic and carcinogenic effects. There is a recent research evidence that the natural hormone 17β-oestradiol has to be considered as a complete carcinogen and it exerts both tumor initiating and tumor promoting effects. Estrogens bind to the estrogen receptor and subsequently stimulate cancer cell growth in breast, endometrial and ovaries. 

Toxicity due to heavy metals
There are two types of minerals namely essential and non-essential minerals whereas essential minerals are also toxic to our body if it exceeds the required limit. The metal level in many aquatic ecosystems has increased due to environmental pollution caused by human activities and fish in this ecosystem consume water which are contaminated with heavy metals. Eventually, it raises the concerns of metal bioaccumulation in human and related health hazards via food chain. The particular study in our country has discovered that affinity of heavy metals accumulation in fish liver is higher than in other parts of the fish such as muscle and gills. According to this study, most of fish’s muscle tissue is not an active organ for accumulation of heavy metals while their liver has more capacity to store metal ions by producing metallothioneins which appears as a metal detoxification mechanism within the body. Metallothioneins is a cystein rich protein in animals and their synthesis can be induced by a wide variety of metal ions such as cadmium, copper and zinc. Lead, cadmium and mercury are biologically non-essential metals and accumulation of these ions in human tissues is harmful to human health. 

Vitamin A toxicity
The potentially harmful effect of eating liver is vitamin A toxicity since liver is a good source for vitamin A. The body stores any vitamin A, which is not used for future use. Hence, we do not need to consume it every day.  As mentioned in research studies, eating too much liver can interfere with our bone density and contribute to fractures because of its high vitamin A content. Other effects of vitamin A toxicity include blurred vision, trouble with muscular coordination and birth defects. 
In conclusion, we have to avoid frequent consumption of liver meat since it has several adverse effects on our health eventhough liver meat is a more nutritious source of animal food.

(The writer is a medical laboratory technologist at a private hospital and holds a MSc. Degree in Industrial and Environmental Chemistry from the University of Kelaniya and BSc. Food Production and Technology Management Degree from the Wayamba University of Sri Lanka)