Most antacids contain at least one of four major ingredients. These include:

• Aluminum and magnesium. Aluminum salts dissolve slowly in the stomach and work gradually, providing longer-lasting relief. However, they may cause constipation. Magnesium salts act quickly to neutralize acids. In addition, they tend to act as a laxative. Because the effects of aluminum and magnesium balance each other so well, these types of antacids have long been considered an excellent treatment for digestive upset. However, in recent years there have been questions about the long-term safety of taking aluminum, which may deplete the body of phosphorus and calcium, increasing the risk of weak bones.
  
  
• Calcium carbonate. Also known as chalk, it acts quickly and neutralizes acids for relatively long periods of time. This ingredient is also beneficial because it provides calcium. Amounts of calcium usually range between 500 milligrams and 1,000 milligrams per dose. Calcium supplementation may be useful for those with osteoporosis. However, people should be sure not to exceed 2,000 milligrams per day, as it is possible to overdose on calcium.
  
  
• Sodium bicarbonate. Also known as baking soda, it works quickly to neutralize acid. People who belch after taking this antacid are releasing carbon dioxide gas. This is an indication that the antacid is working by neutralizing acid. However, taking too much bicarbonate can upset the body’s acid-base balance, leading to metabolic alkalosis (excess base in body fluids which can cause muscle spasms). In addition, the high level of sodium in this ingredient can cause problems for people with health conditions such as heart failure or high blood pressure (hypertension).

There are many varieties of antacids. They include: