Re: Gluten sensitivity: real or not?
Congratulations to BMJ editors. As all weekends, at library of our Surcolombiana University we have read, circled, checked, and underlined the most important of the last BMJ issue and we have thought, discussed and talked about one or two papers in order to reach conclusions and write a response. What difficult is for us after watching the issue to fill the blank sheet of paper that we face every week on Sundays.
Now at the end of 2012 year we want grateful acknowledge to you and your experts for preparing, writing, and publishing very exciting papers in the medical field. The wonderful subjects covered by you this year were so broad for us, that they were beyond our personal knowledge. Every professional in health, whether in training or in practice should be familiar with the weekly production of BMJ editors. He can read papers related with his daily clinical work. Each BMJ issue includes the most available and convenient information concerning the most relevant health problems around the world and today we don´t have exception. This week we have a very interesting problem related with reserve proteins of seeds or grains, which are daily used as main food for all people in several poor countries, mainly because of their bad economical situation.
With the increasing recognition of Biochemistry as the basic tool for understanding the natural biological processes, now there is a big research field directed to study seeds proteins for better understanding the true nature of gluten. Extraordinary progress in the understanding of the structure and function of physiology and biochemistry of seeds has been made in the past 30 years. Many of these achievements have been extremely important to nutrition.
The word gluten was introduced in the 17th century for calling any sticky, difficult or problematic substance and from 1803 it is used for naming the nitrogenous part of any seed or grain. When in Biochemist we speak about gluten we mainly refer to protein substances that give cohesiveness to dough.
In general we can say that a cereal or a leguminous seed is an extraordinary supramolecular complex that contains carbohydrates, lipids and several classes of nitrogenous compounds. All these compounds are very active during seed germination. The most abundant and very important for researchers in nutrition are the reserve proteins. Cereal and leguminous seeds contain from seven to sometimes 30% of those proteins. For their isolation from seeds were used several kinds of solvents, and each fraction was named accordingly the extraction method employed. For instance, proteins strongly fixed or attached to polysaccharides were called glutelins. Those were completely isolated using buffers with pH between 9, 5 and 9, 8 after the isolation of water soluble proteins.
Nowadays, at lab, all seed or grain proteins can be completely isolated using neutral saline solutions at pH 7.0. Until now the most studied are the reserve proteins of leguminous seeds. In those seeds there are two big protein fractions - globulins and albumins. The two globulin fractions are called Legumin – the major fraction and Vicilin – the minor one. There are not big differences between globulins and vicilins present in several leguminous plants. They are respectfully, very similar. Sometimes at papers for several kinds of seeds or grains they are named as proteins similar to Legumin or to Vicilin. Albumins are water soluble proteins and their concentration in seeds is very low. Reserve proteins are always accompanied by a little fraction of free amino acids, peptides, nucleic acids and other products of the seed nitrogen metabolism. Legumin and vicilin of several leguminous seeds have been purified and studied in vitro. They have a very complex quaternary structure and they have a low biological nutritional value. The percentage of reserve proteins taken into the digestive tract that is absorbed into our body is relatively low. Pepsin and other proteolytic enzymes are not capable of promoting the total digestion of those reserve proteins.
Cereal proteins isolated with saline buffers have been studied very few. They contain also two big fractions similar to those present in leguminous seeds, but accompanied with nucleic acids.
In order to understand the etiology and mechanism of celiac disease associated to gluten ingestion or the non celiac gluten sensitivity it´s necessary to know much more about the complexity of seeds structure. The long road is open.