Probiotics are safe and helpful live bacterial strains, but that doesn’t mean they come without side effects for everyone. While the first two weeks might include unpleasant changes for some, you’ll surely welcome the long-term beneficial effects with open arms.* Here’s what you can expect.
Why you should take probiotics.
Your gut is intricately connected to every other part of your body, including your brain and immune system. While many people start taking probiotics to help support digestion, promote regularity, or ease bloat, these benefits only touch the surface.*
Not only are probiotics beneficial for overall gut health, but they may also improve your stress response, contribute to healthier skin, and even support healthy cholesterol levels.*
Probiotics also play a role in your metabolism. Robert Rountree, M.D., a renowned integrative physician, explains that certain bacteria are better at extracting nutrients and energy from foods than others. That means if you have more of these bacteria in your gut, you may find it easier to maintain a healthy weight.*
(You can read more about the range of benefits here.)
Potential short-term side effects.
In general, probiotics are considered safe to take and won’t cause major negative side effects if you’re healthy, according to the NCCIH. That said, as your body adjusts to the new bacteria, you may experience some mildly unpleasant changes before seeing improvements. Here are the most common short-term effects:
Gas and bloating
“The two most common side effects, gas and bloating are a normal response that happens when you introduce a new bacteria to your gut ecosystem,” explains Amy Shah, M.D., a double board-certified integrative doctor. As your gut microbiome adjusts, bacteria can produce gas as a byproduct—and trapped gas leads to bloating.
Probiotics can decrease transit time—or how quickly food and waste move through your digestive system.* While this is great news for anyone who perhaps goes too frequently, it may contribute to less regularity at first. As your body adjusts, this irregularity will typically resolve itself and you’ll have more regular bowel movements, but it can be uncomfortable in the beginning.
Some probiotic foods contain substances called amines, which can trigger headaches, especially in people who are sensitive to them. This side effect isn’t usually an issue with probiotic supplements but may develop if you suddenly increase your intake of probiotic-rich foods like sauerkraut and yogurt.
Positive side effects over time.
Once you get past the not-so-pleasant stuff, you may notice some awesome side effects you hope will stick around awhile.* OK, so maybe long-term benefits is a better term than side effects, but in many cases, you’ll notice positive changes in your health that you weren’t even expecting:*
You’ll feel less bloated.*
Increased bloating is a common side effect when you first start taking probiotics, but over time, the switch will flip and you’ll likely notice less bloating.* “Typically, bloating is caused by an imbalance of good-to-bad bacteria in your gut,” explains Shah. Adding more good bacteria to crowd out the bad contributes to less gas and less bloat.* “We do know that taking probiotics on a regular basis can support a healthy microbial balance in the gut, which can ease bloating,” says Shah.*
You might go to the bathroom more regularly.
The good bacteria in probiotics improve digestion, which may translate to more consistent bathroom visits.* While this may be a side effect that can be inconvenient at times, especially when you’re at work or out to lunch with your friends, your body and your belly will thank you once you start eliminating regularly.*
You’ll feel more energetic.*
Probiotics help your body properly utilize and absorb nutrients.* And when your body is actually getting the right amount of vitamins and minerals, that translates to more energy and just feeling better overall. This means you may find yourself spending less time on the couch watching TV and more time checking things off your to-do list.
Your immune system will thank you.*
“The longer you take a probiotic, the more diverse your microbiome will become, and the stronger your immune system and GI tract get,”* Bindiya Gandhi, M.D., an American Board Family Medicine–certified physician, previously told mbg. In other words, as your gut microbiome balances, your immune system is supported and strengthened.* In fact, did you know that over 70% of the immune system is located in your digestive tract?
How long do side effects from probiotics last?
How you feel—and how long you feel that way—really comes down to the current state of your gut health and how your body processes the different probiotic strains. According to Shah, everyone metabolizes probiotics differently, so there’s really no definitive time frame for everyone.
As a general rule, initial unpleasant side effects typically go away within the first two weeks, when your gut microbiome starts to reach its new state of balance. Many people start experiencing gut support benefits as soon as two days after taking probiotics, but it really depends on how imbalanced your gut is to start and which strains you’re taking.*
If you don’t see unpleasant side effects start to diminish in the first couple of weeks, it’s a good idea to check in with your doctor and make sure there isn’t something else going on underneath the surface. For example, if you have small intestinal bacterial overgrowth (SIBO) or irritable bowel syndrome (IBS), the side effects may be more intense and long-lasting.
As for the fringe benefits—like less bloating and more regular elimination—those should stick around for the long haul.*
Initially, probiotics can cause unwanted changes like gas, bloating, and occasional headaches, but if you stay consistent, these should subside in about two weeks. Once your gut becomes balanced, less bloating, increased energy, immune support, and bowel movement regularity will take their place.* If you don’t start to feel better after a couple of weeks, there may be something more serious going on underneath the surface that’s worth a checkup with your doctor.
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