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.
"It's most likely a hamburger not a bacterial infection," is
basically the message, says Dr. Paul O'Connor, renal physiologist in the
MCG Department of Physiology at Augusta University and the study's
corresponding author.
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," O'Connor says.
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.
"It sets the whole system up to fail basically," O'Connor says.
Clinical trials have shown that a daily dose of baking soda can not only
reduce acidity but actually slow progression of the kidney disease, and
it's now a therapy offered to patients.
"We started thinking, how does baking soda slow progression of kidney disease?" O'Connor says.
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.
"The shift from inflammatory to an anti-inflammatory profile is
happening everywhere," O'Connor says. "We saw it in the kidneys, we saw
it in the spleen, now we see it in the peripheral blood."
The shifting landscape, he says, is likely due to increased
conversion of some of the proinflammatory cells to anti-inflammatory
ones coupled with actual production of more anti-inflammatory
macrophages. The scientists also saw a shift in other immune cell types,
like more regulatory T cells, which generally drive down the immune
response and help keep the immune system from attacking our own tissues.
That anti-inflammatory shift was sustained for at least four hours in
humans and three days in rats.
The shift ties back to the mesothelial cells and their conversations
with our spleen with the help of acetylcholine. Part of the new
information about mesothelial cells is that they are neuron-like, but
not neurons O'Connor is quick to clarify.
"We think the cholinergic (acetylcholine) signals that we know
mediate this anti-inflammatory response aren't coming directly from the
vagal nerve innervating the spleen, but from the mesothelial cells that
form these connections to the spleen," O'Connor says.
In fact, when they cut the vagal nerve, a big cranial nerve that
starts in the brain and reaches into the heart, lungs and gut to help
control things like a constant heart rate and food digestion, it did not
impact the mesothelial cells' neuron-like behavior.
The affect, it appears, was more local because just touching the spleen did have an effect.
When they removed or even just moved the spleen, it broke the fragile
mesothelial connections and the anti-inflammatory response was lost,
O'Connor says. In fact, when they only slightly moved the spleen as
might occur in surgery, the previously smooth covering of mesothelial
cells became lumpier and changed colors.
"We think this helps explain the cholinergic (acetylcholine)
anti-inflammatory response that people have been studying for a long
time," O'Connor says.
Studies are currently underway at other institutions that, much like
vagal nerve stimulation for seizures, electrically stimulate the vagal
nerve to tamp down the immune response in people with rheumatoid
arthritis. While there is no known direct connection between the vagal
nerve and the spleen -- and O'Connor and his team looked again for one
-- the treatment also attenuates inflammation and disease severity in
rheumatoid arthritis, researchers at the Feinstein Institute for Medical
Research reported in 2016 in the journal Proceedings of the National
Academy of Sciences.
O'Connor hopes drinking baking soda can one day produce similar results for people with autoimmune disease.
"You are not really turning anything off or on, you are just pushing
it toward one side by giving an anti-inflammatory stimulus," he says, in
this case, away from harmful inflammation. "It's potentially a really
safe way to treat inflammatory disease."
The spleen also got bigger with consuming baking soda, the scientists
think because of the anti-inflammatory stimulus it produces. Infection
also can increase spleen size and physicians often palpate the spleen
when concerned about a big infection.
Other cells besides neurons are known to use the chemical
communicator acetylcholine. Baking soda also interact with acidic
ingredients like buttermilk and cocoa in cakes and other baked goods to
help the batter expand and, along with heat from the oven, to rise. It
can also help raise the pH in pools, is found in antacids and can help
clean your teeth and tub.
The research was funded by the National Institutes of Health.
- Sarah C. Ray, Babak Baban, Matthew A. Tucker, Alec J. Seaton, Kyu Chul Chang, Elinor C. Mannon, Jingping Sun, Bansari Patel, Katie Wilson, Jacqueline B. Musall, Hiram Ocasio, Debra Irsik, Jessica A. Filosa, Jennifer C. Sullivan, Brendan Marshall, Ryan A. Harris, Paul M. O’Connor. Oral NaHCO3 Activates a Splenic Anti-Inflammatory Pathway: Evidence That Cholinergic Signals Are Transmitted via Mesothelial Cells. The Journal of Immunology, 2018; ji1701605 DOI: 10.4049/jimmunol.1701605
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