Probiotics Side Effects: Should You Be Worried?

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    Like most supplements, probiotics do come with concern of side effects. While side effects are rare and mild, a discussion of these effects is still warranted.

    Top 7 Possible Probiotic Side Effects

    Your body naturally contains a variety of bacteria and other microorganisms. As one of the fastest-growing supplements in terms of popularity, the benefits of probiotics are quickly being revealed. But there may be some potential side effects that accompany these benefits. For most people, these side effects are minor (if they occur at all). Regardless, it is important to discuss the side effects that a person may experience after taking a probiotic.

    1. Gas and bloating

    Although you may be taking a probiotic to help relieve symptoms such as gas and bloating, these also happen to be the most common side effects. This is a normal occurrence that can happen when the body is adjusting to the new balance of beneficial bacteria in the gut. For those new to probiotics, it's important to remember that our gastrointestinal system may need time to adapt.

    To decrease these symptoms, consider beginning with smaller portions of probiotic-rich foods, or spacing out the frequency of probiotic supplements instead of taking them daily. Always monitor how your body responds and consult with your healthcare provider for guidance.

    2. Upset stomach

    Another side effect to be aware of is an upset stomach. According to this meta-analysis, this is more common in people who already have pre-existing digestive conditions, compared to those who don’t. Symptoms can range from upper abdominal discomfort to indigestion and nausea. These effects are generally temporary, but it’s still crucial to monitor them and discuss them with your healthcare provider if they do present themselves.

    3. Diarrhea

    There is strong and solid evidence that probiotics can help address antibiotic associated diarrhea. However, loose stool can also manifest as a sid e effect for some individuals depending on the potency of the probiotic and the ingredients present. This negative side effect is more common, particularly in individuals with histamine intolerance or sensitivity. The reason for this is that certain strains of probiotics can produce histamine within the digestive tract. So, if you are someone who is sensitive to histamine, taking these strains can exacerbate or trigger changes in the stool. The strains included in Care/of Probiotic blend are not associated with promoting histamine levels.

    4. Constipation

    For some people, certain strains of probiotics may actually lead to temporary changes in bowel movements, depending on their individual gut biome. When probiotics are introduced, they work to alter the existing microbiome environment. So, for those who naturally have a more rapid transit time through the gastrointestinal system, initially adding probiotic-rich foods or supplements can result in a noticeable shift in bowel movement patterns. This shift can be experienced as a feeling of constipation or a decrease in the frequency of bowel movements, but this usually balances out over time. But, as always, you should check with your doctor. Sudden changes in bowel movements like chronic or persistent constipation should not be experienced as a result of probiotics. If you do experience constipation, there are many potential causes (including but not limited to lack of fiber, lack of adequate hydration, or lack of movement, among other more serious underlying issues), so you should talk to your doctor about the concern.

    5. Headaches

    Although very rare, certain individuals may notice headaches when they begin eating fermented foods. This is often linked to the biogenic amines (including histamine) that are present in some probiotic-rich fermented food sources that can impact blood flow. For some, lactic acid may also be a trigger. This study found that Streptococcus thermophilus contributed to amine formation when making home-made yogurt. There is still significant research that needs to be done because there are mixed results from other studies regarding sensitivities to bioamines.

    Histamine and other amines function as chemical messengers in the body, and some are more sensitive to them than others. Factors such as individual immune responses, genetic predispositions, and environmental influences can all play a role in determining someone’s level of sensitivity.

    6. Adverse reactions to certain ingredients

    When it comes to probiotics, not all strains are created equal, and not all are suitable for everyone. Only your medical provider can truly determine what is safe for you. However, there are some items you can look out for. Firstly, if you are someone with food allergies or intolerances, it’s critical to always read the label of supplements and review the added ingredients.

    Additionally, particular allergens, such as those derived from cow’s milk, like lactose, or even eggs, may potentially be lurking in some formulas. So, anyone with known sensitivities or allergies needs to be vigilant when selecting a probiotic supplement.

    Lastly, as mentioned earlier, there are specific strains known to produce histamine, which can sometimes lead to reactions that mimic allergic reactions, even though they’re purely histamine-based. Strains that fall under this category include Lactobacillus buchneri, Lactobacillus helveticus, Lactobacillus hilgardii, and Streptococcus thermophilus.

    7. Reactions to prebiotics & synbiotics

    Prebiotics are non-digestible fibers that serve as a fuel source for beneficial gut bacteria, allowing them to thrive. Thus, there are many supplement formulations that include prebiotics and probiotics together in order to help provide the most benefit – these are referred to as synbiotics. These too come with their share of potential side effects.

    Adverse reactions to prebiotics and synbiotics may be similar to those experienced when taking probiotics. Again, those with food allergies or sensitivities should always review the ingredient labels carefully.

    Moreover, since prebiotics are fiber-rich foods, suddenly increasing the amount of high-fiber foods into your diet can lead to temporary digestive discomfort, especially if you’re not consuming enough fluids.

    Less common side effects and reactions to probiotics

    While most probiotics are generally well-tolerated, there are some less frequent side effects and reactions to be aware of:

    • Potential skin concerns: Some individuals reported an itchy rash of the skin in a study that was included in the systematic review. However, most research shows potential for benefits for skin health with use of probiotics. If you notice a new rash after starting any supplement, discontinue use and talk to your doctor.
    • Potential gut bacterial imbalance: In this study, participants who had brain fog, gas, and bloating took probiotics. But it turned out that their symptoms were caused by a small intestinal bacterial overgrowth (SIBO), and probiotics were not helpful. Each person and case is unique. Probiotics may not always be the solution to some digestive symptoms. So, if you take probiotics and notice you are feeling worse, this could be a sign that there is another underlying issue. As always, your best bet is to talk to your doctor.

    Outside of these specific reactions, probiotics might not be suitable for everyone, especially those with compromised immune systems or certain health conditions. Before integrating probiotics into your health regimen, it's always recommended to consult a physician, especially for anyone with existing health conditions or a history of sensitivities. The NCCIH highlights that there's a lack of solid information on the frequency and severity of side effects from probiotics. This can be an exciting area for researchers to further explore.

    What should I expect when I start taking probiotics?

    Before taking a probiotic, you should speak with your physician about the best way to begin. If you may benefit from a probiotic, your physician may recommend starting with bacteria-containing food–foods like yogurt and kefir. Your physician may also recommend that you start with a smaller dose (lower CFUs) when first starting out.

    Some of the most common initial experiences include temporary stomach and bowel changes (e.g. irregular bowel movements) since the bacteria directly impact your digestive and metabolic systems. Some people report temporary bloating or softer stools when starting a new probiotic, which is both normal due to the changes happening in your gut biome.

    The bottom line

    Probiotics have surged in popularity due to their various health benefits, particularly for digestive health. While they offer potential benefits for many, there is still a possibility to experience side effects. Most of these potential side effects are mild and temporary, stemming from the body's adjustment to a shifting balance of gut bacteria. It's important to recognize individual factors such as allergies, intolerances, or pre-existing health conditions, which can influence how you might react to probiotics, prebiotics, or synbiotics. Starting with a food-based approach and consulting a healthcare provider before diving into supplements can also be beneficial.

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    Diana Morgan, MS, CISSN
    Head of Scientific & Regulatory Affairs
    Diana Morgan is an innovative and entrepreneurial strategist with over 15 years of experience in the dietary supplement industry in areas such as Regulatory Affairs, Product Development, Technical Services and Sales coupled with a personal passion for nutrition & health.
    Jordana Tobelem, RD
    Freelance Contributor
    Jordana Tobelem is a Registered Dietitian who enjoys helping others become the best versions of themselves through proper nutrition education. Jordana is passionate about promoting lifestyle changes through nutrition, physical activity, and behavior to create a superior quality of life. She uses her experience in the clinical field of dietetics to provide consulting services to an array of healthcare brands and companies. Jordana loves finding the most current research in nutrition to create meaningful content to share with her clients. Jordana has been a member of the Academy of Nutrition and Dietetics since 2018 and also holds certifications in both Personal Training and Health Coaching.