Processed meat là gì

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IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Red Meat and Processed Meat. Lyon (FR): International Agency for Retìm kiếm on Cancer; 2018. (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, No. 114.)


4.1. Digestion & metabolism

The composition of red meat và processed meat, as well as their potential contaminants, is described in detail in Section 1 of this Monograph. Red meat & processed meat are sources of high-chất lượng protein, fat in highly variable amounts, and a range of micronutrients. The impact of the digestion of protein & fat, and the modifications that these macronutrients may undergo in the processing of meat, is addressed in this section. The specific components of red meat and processed meat, including haem iron, lipid oxidation products, heterocyclic aromatic amines (HAAs), polycyclic aromatic hydrocarbons (PAHs), và N-nitroso compounds (NOCs), that are potentially involved in carcinogenesis are discussed in Section 4.5.

After the hydrolytic breakdown of dietary proteins by the activity of proteases, và the absorption of the resultant amino acids và dipeptides in the proximal gut, fermentation of excess proteins may yield toxic compounds. The amount of protein that enters the colon depends on the protein nội dung of the ingested food and the protein digestibility (Windey et al., 2012). Digestibility of dairy and animal proteins exceeds 90%, và is generally higher than the digestibility of plant proteins (70–90%). Storage and processing of meat before consumption may alter its protein digestibility. Cooking of beef affected bovine myofibrillar protein susceptibility lớn proteases in vitro, with increased or decreased rates depending on the nature of the proteases, and the time và temperature parameters (Santé-Lhoutellier et al., 2008). Similarly, Bax et al. (2012) reported that ageing và mincing had little impact on the in vitro digestion of pig muscle proteins, but heat treatment had temperature-dependent effects. At 70 °C, the proteins underwent denaturation, enhancing the tốc độ of pepsin digestion by increasing enzyme accessibility to lớn protein cleavage sites. At above 100 °C, the proteins underwent oxidation-related aggregation, slowing the speed of pepsin digestion, but improving overall meat protein digestibility. In a study of miniature pigs fed meat from a calf, the true ileal protein digestibility averaged 95%, & was not affected by cooking temperature or by the level of meat intake (Bax et al., 2013). Chemical oxidation of pig myofibrillar proteins has been shown lớn reduce protein digestibility in vitro (Santé-Lhoutellier et al., 2007). Overall, the impact of thermal denaturation & oxidation of meat proteins during processing và storage on their digestibility, as well as the formation of carcinogenic compounds during digestion, is not well known.

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On a normal mixed diet, the amount of protein rather than the source determines the quantity that reaches the colon (Silvester & Cummings, 1995). Hence, high-meat, low-fibre diets may stimulate protein fermentation in the colon, producing short- and branched-chain fatty acids, ammonia, phenolic và indolic compounds, and hydrogene sulfide (O’Keefe, 2008). Bacterial proteases và peptidases are more active sầu when pH is neutral lớn alkaline. In the proximal colon, pH is more acidic due to the production of short-chain fatty acids, primarily from carbohydrate fermentation, but also from reductive deamination of many amino acids. In more distal parts of the colon, pH is higher and protein fermentation becomes more prominent. In relation khổng lồ meat intake, ammonia and hydroren sulfide are the most critical compounds because of their known toxicity (Attene-Ramos et al., 2007; Windey et al., 2012). Meat is rich in sulfur-containing amino acids, possibly leading to higher hydrogene sulfide concentrations in the colon. However, hydroren sulfide in the gut originates from both the fermentation of sulfur-containing amino acids và dietary sulfate.

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A diet high in red meat or processed meat may contain high levels of fat. The digestion of food lipids consists of a series of enzyme-catalysed steps resulting in absorbable components, whereby the release of bile from the gallbladder is essential. It has been suggested that dietary fat promotes the development of cancer of the colorectum (Boyle et al., 1985; Reddy, 1992). Several mechanisms have sầu been postulated to explain this association, including the stimulating effect of high-fat intake on the secretion of secondary bile acids in the gut; this proposed mechanism has received the most attention. These bile acids may promote tumour formation by acting as aggressive sầu surfactants on the mucosa, thus increasing cell loss and proliferation (Bruce, 1987; Owen, 1997; Bernstein et al., 2005). Other proposed mechanisms for the promoting role of dietary fat include an increase in the amount of không tính phí fatty acids in the colonic lumen, which may damage the colonic epithelium & induce cell proliferation, & an augmented risk for obesity (Calle & Kaaks, 2004). Dietary fat intake is also associated with peroxidation of unsaturated fatty acids (see Section 4.5.2).

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