A daily dose of baking soda may help reduce the destructive inflammation of autoimmune diseases like rheumatoid arthritis, scientists say.

They have some of the first evidence of how the cheap, over-the-counter antacid can encourage our spleen to promote instead an anti-inflammatory environment that could be therapeutic in the face of inflammatory disease, Medical College of Georgia scientists report in the Journal of Immunology.

They have shown that when rats or healthy people drink a solution of baking soda, or sodium bicarbonate, it becomes a trigger for the stomach to make more acid to digest the next meal and for little-studied mesothelial cells sitting on the spleen to tell the fist-sized organ that there's no need to mount a protective immune response.

Mesothelial cells line body cavities, like the one that contains our digestive tract, and they also cover the exterior of our organs to quite literally keep them from rubbing together. About a decade ago, it was found that these cells also provide another level of protection. They have little fingers, called microvilli, that sense the environment, and warn the organs they cover that there is an invader and an immune response is needed.

Drinking baking soda, the MCG scientists think, tells the spleen -- which is part of the immune system, acts like a big blood filter and is where some white blood cells, like macrophages, are stored to go easy on the immune response. "Certainly drinking bicarbonate affects the spleen and we think it's through the mesothelial cells.

The conversation, which occurs with the help of the chemical messenger acetylcholine, appears to promote a landscape that shifts against inflammation, they report.

In the spleen, as well as the blood and kidneys, they found after drinking water with baking soda for two weeks, the population of immune cells called macrophages, shifted from primarily those that promote inflammation, called M1, to those that reduce it, called M2. Macrophages, perhaps best known for their ability to consume garbage in the body like debris from injured or dead cells, are early arrivers to a call for an immune response.

In the case of the lab animals, the problems were hypertension and chronic kidney disease, problems which got O'Connor's lab thinking about baking soda.

One of the many functions of the kidneys is balancing important compounds like acid, potassium and sodium. With kidney disease, there is impaired kidney function and one of the resulting problems can be that the blood becomes too acidic, O'Connor says. Significant consequences can include increased risk of cardiovascular disease and osteoporosis.

That's when the anti-inflammatory impact began to unfold as they saw reduced numbers of M1s and increased M2s in their kidney disease model after consuming the common compound.

When they looked at a rat model without actual kidney damage, they saw the same response. So the basic scientists worked with the investigators at MCG's Georgia Prevention Institute to bring in healthy medical students who drank baking soda in a bottle of water and also had a similar response.