Nutrients: The Diverse Forms of Lactose Intolerance and the Putative Linkage to Several Cancers

open access

Abstract

 Lactase-phlorizin hydrolase (LPH) is a membrane glycoprotein and the only β-galactosidase of the brush border membrane of the intestinal epithelium. Besides active transcription, expression of the active LPH requires different maturation steps of the pro-peptide through the secretory pathway, including N- and O-glycosylation, dimerization and proteolytic cleavage steps. The inability to digest lactose due to insufficient lactase activity results in gastrointestinal symptoms known as lactose intolerance. In this review, we will concentrate on the structural and functional features of LPH protein and summarize the cellular and molecular mechanism required for its maturation and trafficking. Then, different types of lactose intolerance are discussed, and the molecular aspects of lactase persistence/non-persistence phenotypes are investigated. Finally, we will review the literature focusing on the lactase persistence/non-persistence populations as a comparative model in order to determine the protective or adverse effects of milk and dairy foods on the incidence of colorectal, ovarian and prostate cancers. 

 

Keywords:

lactase-phlorizin hydrolase; alactasia; adult type of hypolactasia; lactose intolerance; colorectal cancer; ovarian cancer; prostate cancer

1. Introduction

The main sources of energy in our daily diet are carbohydrates, like starch, sucrose or lactose. The breakdown of starch molecules requires preliminary digestion by salivary and pancreatic amylases......

 Colorectal, ovarian and prostate cancers are the most common cancer types in which a protective or adverse effect of milk and dairy foods has been investigated and discussed for a long time [104,105,106,107].

 .....On the other side, several publications are found that do not support a correlation of milk consumption with ovarian cancer......