The human body should never absorb proteins---only amino acids. The way the system is supposed to work is that stomach acid breaks proteins into amino acids. The amino acids go downstream, are absorbed, and the body makes its own proteins.
When you don't have stomach acid, whole proteins get absorbed. The immune system recognizes that it didn't make those proteins and assumes they are viruses. It makes antibodies to these food proteins. Soon you are allergic to the foods you most commonly eat. You have a "mini-flu" after every meal as your body attacks your food and thus you feel tired about 30 minutes after you eat.
The system tries to isolate these proteins and often stores them in fat---thus you gain weight.
The antibodies make your blood sticky. This increases your risk of blood clots and makes it hard for the blood to pick up and deliver oxygen. As your body oxygen levels drop, your metabolism gets worse and anaerobic microorganisms begin to grow.
This process often starts with GERD (gastro-esophageal reflux disease). When you don't make enough stomach acid, you develop gas as your stomach tries to digest your food. These gas bubbles are surrounded by stomach acid. The bubbles float up into your esophagus and you belch. You taste stomach acid and your esophagus burns. Thus you think you have too much stomach acid when the real problem is that you have too little.
Your stomach feels better when you take antacids and/or drugs that shut down your stomach acid. However, this insures that you will develop chronic disease! You will become allergic to your protiens. In addition, the body cannot absorb zinc without stomach acid. Without zinc, you cannot make neurochemicals like serotonin, so you become depressed. Zinc is also necessary for over 360 known biochemical reactions including proper prostate function.
Stomach acid is your "front door". It is intended to help kill infectious things like bacteria, fungus and parasites. Without it, they have an open invitation to invade your body. It is like removing the front door to your home so anyone that wants to can enter your home and do whatever mischief they wish.
These problems begin when you can't make enough stomach acid. Making stomach acid requires iodine, zinc, and vitamin B1 as well as water, salt, and CO2. Almost everyone is deficient in iodine and about 80% of the population is deficient in zinc. Many are deficient in the B vitamins. Thus we have another reason for so many to be depressed and tired from reacting to their foods and obese as well.
The solution is to correct your stomach's ability to make stomach acid by correcting these deficiencies. This usually takes 3-4 months. During that time, you must take a pill that acts like stomach acid. It is called Betaine it is available at health food stores. You should eat a few bites of food before you take it so it won't aggravate your stomach. Take it with each meal until you have time to correct your iodine, B1 and zinc levels.