Meat nutritional composition and nutritive role in the human diet

TL;DR: The present review attempts to sum up meats role and importance in human nutrition as well as examine some pejorative beliefs about meat consumption.

About: This article is published in Meat Science.The article was published on 2013-03-01 and is currently open access. It has received 547 citations till now. The article focuses on the topics: B vitamins & Saturated fat.

Summary

2. The role of meat in human evolution

• Anthropology has previously recognized the importance of food and diet variations among time periods.
• Gastrointestinal tract features can also aid in determining dietary preferences considering that the gut of herbivores and pure carnivores suffered different physiological and metabolic adaptations.
• This aminoacid has shown several important biological functions such as acting like an antioxidant and anti-inflammatory agent which can be related to cardiovascular disease prevention and is almost exclusively found in animal products (Wójcik et al., 2010).

3. Meat nutritional composition

• In European legislation, the term meat refers to the edible parts removed from the carcass of domestic ungulates including bovine, porcine, ovine and caprine animals as well as domestic solipeds; poultry; lagomorphs; wild game; farmed game; small and large wild game (European Comission, 2004).
• It is particularly rich in high biological value protein, as well as micronutrients like iron, selenium, zinc and vitamin B12.
• Offal meats like liver are also crucial sources of vitamin A and folic acid (Biesalski, 2005).

3.1. Meat protein content and protein value

• It is also important to note that this protein has high digestibility scores as determined by the Protein Digestibility-Corrected Amino Acid Scores .
• Additionally, meat proteins have been distinguished by their essential amino acids content.
• Even if these non essential amino acids can be produced by the human body, it is mandatory to have all the raw materials necessary for their production.
• Vegetarians have to combine cereal and legumes to get all the essential amino acids.

3.2. Fat content

• Fat content differs significantly among retail beef cuts, poultry and other meat products such as offal and specialties like sausages, ham, etc.
• Table 2 sums up some of the main differences that can be observed among several cuts.
• Chicken and turkey breasts have similar fat contents while turkey legs tend to have higher fat contents than chicken legs (INSRJ, 2006).
• Cooking can have a major influence in meat fat content and fatty acid composition.

3.2.1. Fatty acid composition

• For several decades, dietary guidelines have recommended avoiding saturated fat in order to prevent cardiovascular disease (Krauss et al., 2000) leading to a significant decrease in the consumption of animal products especially meat.
• The mechanisms through which saturated fat exert pejorative effects in cardiovascular and general metabolic health are diverse, Kennedy, Martinez, Chuang, Lapoint, and Mcintosh (2009) have proposed that an excessive consumption of saturated fatty acids could promote white adipose tissue expansion and hypertrophy leading to apoptosis.
• Ruminant intrinsic digestive characteristics affect meat fatty acid composition.
• Arachidonic acid is the precursor of thromboxane A2 which begins plaque aggregation, the primary phenomena in thrombosis development (Gabrielsen et al., 2010).

3.3. Vitamins and minerals

• Red meat provides around 25% of the recommended dietary intakes for riboflavin, niacin, vitamin B6 and pantothenic acid per 100 g and practically two thirds of the daily requirement (DR) of vitamin B12 in the same serving (Williams, 2007).
• Meat is also one of the best sources for zinc, selenium phosphorus and iron.
• It is important to consider the influence of cooking techniques on vitamin and trace element contents considering that humans rarely eat raw meat.
• Some studies have shown that cooking in general produces significant losses of B vitamins (Lombardi-Boccia, Lanzi, & Aguzzi, 2005).
• Several data suggest that B12 and thiamin are among the most affected B vitamins in compared with riboflavin and niacin which show lower decreases (D'Evoli et al., 2009; Riccio, Mennella, & Fogliano, 2006).

3.3.1. Meat, a valuable iron source

• Iron has a crucial role in human health and iron deficiency leads to an impairment of several biological functions as well as disturbances in child growth and development (Grantham-McGregor & Ani, 2001; Lozoff & Georgieff, 2006).
• There are also obligatory losses through skin, intestines, urinary tract, airways and menstrual bleeding in women.
• For these reasons, there is a tolerable upper intake level which represents the highest intake that does not provoke adverse health effects.

3.3.2. Vitamin B12 in meat

• Meat is a valuable source of complex B vitamins, especially B12, the most complex and largest vitamin.
• Then it is taken into lysosomes where cobalamin is released and metabolized to its methyl and deoxyadenosyl forms.
• The absorption of IF-B12 significantly determines the dietary vitamin B12 bioavailability (Quadros, Nakayama, & Sequeira, 2005).
• It is also strongly associated with high levels of blood homocysteine which is a cardiovascular disease risk factor (Green & Miller, 2005).
• There are some controversies around meat consumption and vitamin B12 status.

3.3.3. Other vitamins — vitamin A, folic acid, zinc and selenium

• Meat and meat products are also important sources of other micronutrients which are vital in human health.
• Liver, especially from pigs, is a great source of folic acid supplying 81% of DR while calf liver supplies 87% of DR.
• Within vegetable sources, pinto beans and enriched wholegrain breakfast cereals are the best accomplishing 85% and 53% of DR (INSRJ, 2006; USDA, 2011).
• Adequate zinc intake is essential for human health considering its functional roles in enzymatic systems, cell division and growth, gene expression, immune and reproductive functions.
• Finally, selenium is an essential trace element in human nutrition being the component of selenoproteins which have antioxidant functions in cardiovascular disease and cancer prevention (Rayman, 2000).

4. Concluding remarks— the role of meat in human evolution and a healthy diet

• The growing incidence of several chronic diseases such as cancer and cardiovascular diseases has motivated extensive research into the foods associated with increased risk.
• Recently, research has started to demystify this negative health image and has helped to point out the crucial role of meat in human evolution, especially red meat.
• Fat content, a matter of concern regarding meat consumption, is highly variable depending on species, origin, feeding system and the cut.
• Leaner cuts like pork or beef loin do not differ significantly from skinless turkey or chicken breast and the nutritional richness justifies their inclusion in a well balanced diet.
• Removing this component from diet could increase the risk of severe nutritional deficiencies and impair human health and nutritional status.

Figures

Table 2 Nutritional composition of several meat cuts (INSRJ, 2006).

Table 3 Comparison of meat and vegetable based diets.

Table 1 Essential amino acids and non-essential amino acids (Wu, 2009).

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Meat nutritional composition and nutritive role in the human diet" ?

In this paper, the authors show that although some epidemiological data has revealed a possible association between its consumption and increased risk of several forms of cancer, cardiovascular and metabolic diseases, meat consumption has been important in human species evolution. 

Q2. What is the main absorption site of stearic acid?

Rumen microbial enzymes promote isomerisation and hydrolysis of unsaturated fatty acids leading to an increase in stearic acid concentration reaching the small intestine, the main absorption site. 

Q3. What is the role of arachnidonic acid in thrombosis?

Arachidonic acid is the precursor of thromboxane A2 which begins plaque aggregation, the primary phenomena in thrombosis development (Gabrielsen et al., 2010). 

Q4. Why is the small intestine the prominent organ in the human gastrointestinal tract?

The fact that the small intestine is the most prominent organ in the human gastrointestinal tract is due to the need for adaptation to a varied diet, including nutritionally dense foods, with great volume and conducive to being digested in the small intestine (Milton, 1999). 

Q5. What is the main advantage of meat based diet?

Meat continues to supply nutrients and plays a vital role in human life because of its high biological value protein, iron, zinc, selenium and vitamin B12 contents being a crucial component of a well balanced diet. 

Q6. What is the main source of omega 3 fatty acids?

Meat is an important arachnidonic acid source, an omega 6 polynsaturated fatty acid which increases the risk of thrombosis (Christophersen & Haug, 2011; Mann, Johnson, Warrick, & Sinclair, 1995). 

Q7. What is the important part of a healthy balanced diet?

Meat and meat products can contribute up to 18% of iron daily requirements (Geissler & Singh, 2011) which makes it important in a healthy balanced diet and crucial in preventing one of the most common nutritional deficiencies (WHO/ UNICEF/UNU, 2001). 

Q8. What are the effects of inflammatory proteins on the body?

These phenomenawould promote the release of inflammatory proteins like cytokines and chemokines inducing inflammation and insulin resistance, thus increasing the risk of cardiovascular disease and metabolic syndrome (Haffner, 2006; Willerson & Ridker, 2004). 

Q9. What is the role of selenium in the prevention of cancer?

selenium is an essential trace element inhuman nutrition being the component of selenoproteins which have antioxidant functions in cardiovascular disease and cancer prevention (Rayman, 2000). 

Q10. Why is it a common cause of anemia in elderly people?

However it can also be due to absorptive process impairments provoked by gastric atrophy and malabsorption from food, quite frequent in elderly people (Allen, 2008). 

Q11. What is the main source of vitamin B12?

Animal foods are considered the major dietary sources of vitamin B12, however, it can also be found in certain types of algae (Watanabe, 2007). 

Q12. What is the reason why primates have large brains?

Considering their body size, primates in general and humans in particular, have metabolically expensive large brains which are due to the so called encephalisation process (Aiello, 1992). 

Q13. What is the role of taurine in the prevention of cardiovascular disease?

Despite the fact that taurine is not incorporated in proteins, this aminoacid has shown several important biological functions such as acting like an antioxidant and anti-inflammatory agent which can be related to cardiovascular disease prevention and is almost exclusively found in animal products (Wójcik et al., 2010).