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Some people experience gas and bloating when consuming synbiotics. Those who experience these side effects may want to select a supplement that does not contain prebiotics ( 40). Summary Keeping a food diary including any headache symptoms you might experience can help clarify whether fermented foods are problematic for you. In rare cases, the bacteria or yeasts found in probiotics can enter the bloodstream and cause infections in susceptible individuals ( 41, 42, 43, 44). While studies suggest that most people with lactose intolerance can tolerate up to 400 mg of lactose in medications or supplements, there have been case reports of adverse effects from probiotics ( 35, 36, 37).
Since a small number of people with lactose intolerance may experience unpleasant gas and bloating when consuming lactose-containing probiotics, they may want to choose lactose-free products. When histamine levels rise, blood vessels dilate to bring more blood to the affected area. The vessels also become more permeable so that immune cells can easily get into the relevant tissue to combat any pathogens ( 22). It is estimated that only about one in one million people who take probiotics containing Lactobacilli bacteria will develop an infection. The risk is even smaller for yeast-based probiotics, with only about one in 5.6 million users getting infected ( 48, 49). This process creates redness and swelling in the affected area, and can also trigger allergy symptoms such as itching, watery eyes, runny nose or trouble breathing. Those at greatest risk for infection from probiotics include people with suppressed immune systems, prolonged hospitalizations, venous catheters or those who have undergone recent surgeries ( 45, 46, 47).
There is no "right dose" of probiotics
When a supplement contains both probiotic microorganisms and prebiotic fibers, it is called a synbiotic ( 39) . Some histamine-producing probiotic strains include Lactobacillus buchneri, Lactobacillus helveticus, Lactobacillus hilgardii and Streptococcus thermophilus ( 29, 30, 31). Summary Probiotics are safe for the vast majority of the population, but may not be the best fit for everyone.
More research is needed to determine whether or not amines can be direct triggers of headaches or migraines in some people. In addition to containing powerful probiotics, some supplements also contain prebiotics. These are plant fibers that humans cannot digest, but that bacteria can consume as food. The most common types are lactulose, inulin and various oligosaccharides ( 38). Normally, histamine that is produced in your digestive tract is naturally degraded by an enzyme called diamine oxidase (DAO). This enzyme inhibits histamine levels from rising enough to cause symptoms ( 23). However, the risk of developing an infection is very low, and no serious infections have been reported in clinical studies of the general population.Biogenic amines are substances that form when protein-containing foods age or are fermented by bacteria ( 13). Amines can excite the central nervous system, increase or decrease blood flow and may trigger headaches in people sensitive to the substance ( 15, 16).