New study reveals that fluoride – while protecting teeth – can damage the microbial intestine in high doses, stressing the need to review long -term exposure limits.
Effect of fluoride on the gut: a systematic review. Credit Picture: Ledyx / Shutterstock
In a recent study published in the magazine Eating reviewsResearchers in the United Kingdom investigated the effects of fluoride on bowel microbes.
The work of the human germ said that more than two -thirds of the human microbiome are in the gastrointestinal (GI). Progresses in computational methods and molecular sequence have given an understanding of how the gut gutters coincidentally operates with the host and contributes to metabolism, nutrition, intestinal architecture and immune response.
In addition, lifestyle interventions aimed at the microbiotic intestine lead to significant changes in its composition. Fluoride is known for its role in reversing and prevention of caries. It is added to water, salt, milk and dental products to prevent caries. However, the effects of fluoride on the microbial intestine are poorly understood.
For the study
In the present study, the researchers investigated the correlation of the fluoride report with changes in the composition of germs of the bowel. First, they searched for bibliography in six databases: Web of Science, Pubmed, Embase, Cinahl, Medline and Scopus. Eligible studies were detailed studies, quantitative and laboratory studies. All studies of animals or people of any sex and age exposed to different doses and forms of fluoride were selected.
Studies also included in vitro models from bowel or stool samples. After the search for the literature, the studies were relegated and examined by eligibility criteria. The summaries/titles were examined, followed by the review of the full texts. The relevant data was extracted from studies included, such as identifiers, authors, publishing year, magazine, study design, study duration, results, statistical methods and results.
The quality of the studies was evaluated using the mixed methods tool. The intervention or exposure was fluoride in all sources and forms: systematic (eg diet) and topical (eg dental products). The result was the evaluation of the synthesis of germs after exposure to fluoride, including wealth, prevalence of bacterial taxonomic and their functions.
Findings
The search for the literature yielded over 1,000 hits. Following deduplication, 590 articles were examined at the abstract/title level, followed by the full text exam of 63 records. In total, 49 studies were included in the analyzes. Studies included 39 randomized testing tests (RCTS, including animal studies), six experimental or laboratory studies, two-case-case studies, a coach study and one non-RCT.
Most studies were conducted in Asia (90%), followed by Australia (4%), the United States (4%) and Brazil (2%). Three studies used in vitro models, 42 are involved in animals and four had human individuals. Animal models included birds, fish and rodents. The size of the sample in animal studies ranged between six and 900 animals. Human studies had 15 to 114 people.
Sixteen animal studies and all human studies included analysis of germs. The rest of the animals were based on other tissues as biomarkers. The composition of gut germs was assessed using different sequence flows in studies: RRNA gene sequence of RRNA, quantitative chain polymerase (QPCR) chain with 16s RRNA and QPCR sequence in real-time with 16S RRNA-Specifically.
The total size of the sample in animal and human studies was 3,249 and 217, respectively. Most studies (73%) used sodium fluoride (NAF) as a source of fluoride in diet or water as intervention. Three studies used hyperfo -alkyl fluorine (eg sodium fluorooxic and hyperfoocytic acid) and an explored polyphlimated sulphonic ether. The effects of fluoride vary depending on the form of fluoride used, with systematic and local sources showing different effects of germs on some studies. Most animal studies (83%) reported long -term correlations, while a human study and some animal studies reported short -term results.
In addition, 79% of studies were of high quality and the risk of selection bias was low. An increase or decrease in alpha diversity indicators in groups performed by fluoride compared to witnesses have shown that fluoride affects the structure of the microbial community. Nine studies also examined the differences of beta diversity. Two found no differences, and four reported significant differences after exposure to fluoride.
It is important that a two -phase response was observed in some in vitro studies, where low doses of fluoride (0.1 mm NAF) promoted the growth of bacteria and enzymatic activity. Compared, the high doses (up to 100 mm) inhibited growth, especially Lactobacilli.
A human study observed that low -dose NAF did not result in significant differences in abundance of gender and race Lactobacillus and Stupid. Conversely, the high doses of NAF (up to 1200 mg/l in animal studies) increased the abundance of the protection. Specifically, the review found that the doses ≤ 2 mg/l NAF appeared harmless or even beneficial to intestinal microbiotoma, while doses ≥ 50 mg/l NAF caused constant disorders in the synthesis of germs, including reductions in Protevite.
Overall, the results of human studies have shown that high exposure to fluoride modified the composition of germs of the intestinal, disrupting the balance between beneficial and pathogenic germs.
However, the limited number of human studies (4 in total) emphasizes the need for further research to confirm these findings. In all animal studies, consistent exposure to high -dose fluoride has led to disorders in the gut microflora and the most affected genera or Phyla differ between animal types. The findings vary between animal species, fluoride forms and tissues analyzed, indicating that the effects of fluoride on the microbial intestine are complex and dependent on species.
Findings from in vitro models suggested a two -phase response with bacterial growth that causes fluoride at low dose (0.1 mm NAF), with a dramatic increase in growth and enzymatic composition. The increase in dose (up to 100 mm) suspended the growth of germs, especially Lactobacilli.
In a human study, low and high doses of fluoride did not affect the production of short chain fatty acids (SCFAS). In rodents, 100-150 mg/l NAF for up to six months of reduced SCFAS, digestive enzymes, P62 proteins, antioxidant enzymes and metallos. Fluoride also reduced the levels of gastropin, glutathione and follicle hormone. In addition, the fluoride stimulates the production of pre-inflammatory cytokines, secretory immunoglobulin A and Malianiomedialdehyde.
Conclusions
Findings indicate that in vitro or in vivo Fluoride intervention can modify the microbial intestine and its activities. The low dose fluoride did not show results in the microbial intestine. The doses ≤ 2 mg/l NAF were identified as possible safe or beneficial, while doses ≥ 50 mg/l NAF disrupts microbial diversity, altered metabolism and shifted the balance of specific bacterial taxonomic.
While the effects on high doses were inconsistent, there were changes in total microbial diversity, metabolism and the relative abundance of specific taxonomic. Shifts to these aspects of the germ could lead to impact on health. Further, the variability of the results depending on the species, form, duration of fluoride exposure and special tissues studied highlights the need for more standardized research approaches.
Therefore, further studies are needed to understand the impact of the long -term low -dose fluoride exposure to basic gut microbial communities.
This systematic review is recorded under Prospero CRD42022347357.
