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Protein Digestion

Protein Digestion

Protein digestion begins in the stomach, where the highly acidic environment can easily disrupt protein structure by exposing the peptide bonds of polypeptide chains. After polypeptide chains are broken into individual amino acids by a series of digestive enzymes, the amino acids are transported to the liver via the bloodstream to produce energy.

Protein Absorption

Protein Absorption

Proteins in the gastrointestinal tract typically come from food, but they can also originate from disintegrated cells or secreted enzymes. In the stomach, the enzyme pepsin breaks down these proteins into polypeptides. The fragments then move into the duodenum as a semi-fluid mass called chyme. Pancreatic proteases, such as trypsin and chymotrypsin, and intestinal brush border enzymes like carboxypeptidases further dismantle the polypeptides into tripeptides, dipeptides, and free amino acids.

Physiology of the Gastrointestinal System II: Digestion and Absorption

Physiology of the Gastrointestinal System II: Digestion and Absorption

The gastrointestinal (GI) tract, extending from the mouth to the anus, plays a pivotal role in the digestion and absorption of nutrients. This process involves both mechanical and chemical actions facilitated by various enzymes.
Digestion begins in the mouth, where food undergoes mechanical breakdown by chewing and combines with saliva. Salivary amylase, an enzyme in saliva, starts the breakdown of starches into maltose. The food then travels down the esophagus to the stomach.
In the stomach, a...

What is Monogastric Digestion?

What is Monogastric Digestion?

The human body contains a monogastric digestive system. In a monogastric digestive system, the stomach only contains one chamber in which it digests food. Several other animal species also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter, however, focuses on the human digestive system.

Intestinal Phase of Digestion

Intestinal Phase of Digestion

The intestinal phase of digestion is the third and final stage of the digestive process, occurring after the cephalic and gastric phases. It begins when chyme, a partially digested mixture of food and digestive enzymes, enters the small intestine from the stomach. This phase is crucial for nutrient absorption and involves complex hormonal and enzymatic interactions.
The arrival of the chyme in the small intestine distends the duodenum, which triggers the enterogastric reflex. This distension...

Carbohydrate Digestion

Carbohydrate Digestion

Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. Carbohydrate digestion starts in the mouth during mastication, or chewing. The masticated carbohydrates remain intact in the stomach. Digestion resumes in the duodenum of the small intestine, where pancreatic alpha-amylase and brush border enzymes of the microvilli convert complex carbohydrates to monosaccharides. Finally, the monosaccharides...

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Goat milk protein digestibility in relation to intestinal function.

Sindhu Kashyap¹, Nirupama Shivakumar¹, Veerasamy Sejian²

¹Division of Nutrition, St. John's Research Institute, St. John's National Academy of Health Sciences, Bangalore, India.

The American Journal of Clinical Nutrition

|March 7, 2021

Summary

Goat milk protein digestibility in South Indian women is high, comparable to European adults. This suggests milk protein is a valuable nutrient source for women in low- and middle-income countries.

Keywords:

amino acid absorption dual-isotope tracer technique intrinsic labeling lactulose to mannitol ratio milk protein

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Area of Science:

Nutritional Science
Gastroenterology
Biochemistry

Background:

Milk is a vital protein source in low- and middle-income countries (LMICs).
Previous studies show high milk digestibility in French adults.
Individuals in LMICs may have lower milk protein absorption due to environmental enteropathy risk.

Purpose of the Study:

To determine the true ileal indispensable amino acid (IAA) digestibility of goat milk protein in South Indian women of reproductive age (WRA).
To measure intestinal absorption of amino acids and inert sugars in the same participants.
To assess potential impacts of environmental enteropathy on nutrient absorption.

Main Methods:

Utilized intrinsically labeled goat milk protein and dual-isotope tracer techniques.
Administered labeled milk protein to WRA with normal BMI.
Measured urinary lactulose and mannitol recovery to assess intestinal permeability.
Employed L-allo-isoleucine and dual-sugar assays for amino acid and sugar absorption.

Main Results:

True ileal IAA digestibility of goat milk protein was 94.0 ± 2.9%.
Allo-isoleucine and phenylalanine absorption indices were 88.4 ± 3.8% and 24.5 ± 1.6%, respectively.
Lactulose/mannitol ratio (LMR) correlated with allo-isoleucine absorption (rs = -0.93, P = 0.008).

Conclusions:

Goat milk protein digestibility in South Indian WRA with normal intestinal function is high.
Findings are comparable to earlier estimates in healthy French adults.
Goat milk protein is a well-absorbed nutrient source in this population.