Fluoride in the body: benefits, risks of excess and where it is found

Fluoride is a trace element found in the body in very small quantities, but it has a significant impact on dental and bone health. An adult's body contains approximately 2 to 4 grams of fluoride, with approximately 99% of this amount found in bones and tooth enamel. It is in these tissues that fluoride is "integrated" into the crystal lattice, affecting its strength and resistance to acids. [1]

Modern expert organizations emphasize that fluoride is not a vital nutrient in the classical sense, like calcium or iron. Its absence does not lead to the development of specific systemic diseases. However, optimal fluoride intake significantly reduces the risk of caries and chronic oral diseases. Therefore, fluoride is considered a beneficial factor in caries prevention, rather than a vitamin or essential element. [2]

The key feature of fluoride is the narrow range between beneficial and potentially harmful levels. Moderate consumption reduces the risk of dental caries, while chronic excess increases the risk of dental fluorosis and, at even higher doses, bone and joint damage. The World Health Organization and European regulators believe that benefits and risks should be balanced within a single concentration range, particularly in drinking water. [3]

Fluoride enters the body from several sources: drinking water, food, toothpastes and other hygiene products, topical fluoride preparations, and, in some countries, food supplements and fluoridated salt. The contribution of each source depends on local conditions and habits. In countries with low fluoride content in water, the main contributors are toothpastes and food; in regions with high natural mineralization of water, water becomes the primary factor of consumption. [4]

In recent years, the potential impact of chronic fluoride excess on the nervous system and cognitive functions of children has been actively discussed. The European Food Safety Authority updated its risk assessment in 2025 and established new safe intake levels, based, among other things, on the protection of the developing nervous system of the fetus and child. At fluoride concentrations in drinking water below 1.5 milligrams per liter and within the general upper daily intake limits for the population of the European Union, no serious risks were identified. [5]

Table 1. Quick facts about fluoride in the body

Parameter	Meaning
Total body count	About 2-4 grams in an adult [6]
Main depot	Bones and teeth - up to 99% of all fluoride [7]
Biological status	Not a classic “essential” nutrient, but an important factor in the prevention of dental caries [8]
The main beneficial effect	Reducing the risk of caries with moderate intake [9]
The main risk in excess	Dental fluorosis and, at high doses, bone damage [10]

The Biological Role of Fluoride: Teeth, Bones, and More

Fluoride accumulates in tooth enamel, replacing some of the hydroxyl groups in the hydroxyapatite crystal structure, forming fluorapatite. This structure is more resistant to the acids released by plaque bacteria when they process sugars. As a result, enamel becomes less susceptible to demineralization and the formation of cavities. [11]

In addition to its structural role, fluoride influences enamel remineralization processes. At low fluoride concentrations in saliva and on the tooth surface, remineralization of demineralized areas occurs more rapidly, crystals become more stable, and early carious lesions can be partially "inhibited." This is why regular topical fluoride exposure from toothpaste and mouthwash is so important for caries prevention. [12]

In bone tissue, fluoride is incorporated into the mineral matrix and can partially alter its properties. With a slight increase in fluoride intake, bone density can increase, but with chronic, significant excess, the bone structure becomes more fragile and its elasticity is impaired. This underlies skeletal fluorosis, which occurs in regions with very high natural fluoride concentrations in water. [13]

Some of fluoride's effects are mediated through saliva. Fluoride ionizes in saliva and on the enamel surface, creating a protective film that promotes remineralization. Fluoride also influences the activity of plaque bacteria, reducing their ability to produce acids. Frequent exposure of small amounts of fluoride to the tooth surface is essential, rather than high, single oral doses. [14]

Fluoride's specific beneficial role for other organs and systems has not been proven. Unlike calcium or iodine, its absence does not lead to significant endocrine or metabolic pathologies. Therefore, international organizations cautiously conclude: fluoride is not recognized as essential, but when administered correctly, it is an effective tool for preventing caries at both the individual and population levels. [15]

Table 2. Main effects of fluoride at moderate intake

Direction	What does fluoride do?
Tooth enamel	Strengthens the crystal lattice, increases resistance to acids [16]
Remineralization	Accelerates the restoration of early lesions, slows the progression of caries [17]
Bacterial flora of the oral cavity	Reduces the activity of cariogenic bacteria and acid production [18]
Bone tissue	With moderate intake it supports mineral metabolism, with excess there is a risk of bone fluorosis [19]
Prevention of dental caries at the population level	Reduction in dental caries incidence with optimized fluoride levels in water and hygiene products [20]

Sources of fluoride and consumption standards

Fluoride enters the body from several primary sources. In most countries, this primarily includes drinking water, including bottled and tap water, as well as foods and beverages prepared with this water. Additional sources include toothpastes, mouthwashes, topical fluoride gels, fluoridated salt, and, less commonly, medications or dietary supplements. [21]

Fluoride levels in water vary greatly: in most regions of Europe, concentrations are below 0.3 milligrams per liter, while in some areas with naturally high levels, they can exceed 1.5 milligrams per liter. The World Health Organization recommends a limit of 1.5 milligrams per liter for drinking water, based on the balance between the prevention of dental caries and the risk of fluorosis. Some countries set a lower "optimal" level for artificial water fluoridation, usually around 0.7 milligrams per liter. [22]

The European Food Safety Authority (EFSA) previously proposed an adequate daily fluoride intake (ADI) of 0.05 milligrams per kilogram of body weight per day for children and adults, including pregnant and breastfeeding women, from all sources. This value is interpreted as a benchmark that achieves caries prevention while maintaining a sufficient safety margin for the risk of fluorosis. [23]

In 2025, EFSA updated its risk assessment to take into account new data on the potential effects of fluoride on the nervous system of the fetus and child. For pregnant women, a safe level of total daily intake of approximately 3.3 milligrams per day was proposed, at which the risk of adverse effects on nervous system development is considered low, even at fluoride concentrations in water reaching 1.5 milligrams per liter. For other age groups, the upper limits were clarified, but no significant risk was identified for the European Union population at current fluoride concentrations in water. [24]

In practical terms, this means that with normal fluoride concentrations in water and moderate use of toothpaste and other hygiene products, most people do not need to take separate fluoride supplements or specifically monitor every milligram. Two points are really important: avoiding prolonged, uncontrolled exposure to high levels of natural fluoride in the water and avoiding combining high fluoride loads (water, toothpastes, and mouthwashes) with the uncontrolled use of fluoride tablets. [25]

Table 3. Main sources of fluoride and their contribution

Source	Peculiarities
Drinking water	Major background source; concentrations vary greatly by region, local assessment is important [26]
Food	Tea, fish, seafood, some mineral waters, products prepared with fluoridated water [27]
Toothpastes and rinses	Main source of local fluoride on enamel; adds systemic burden when swallowed, especially in children [28]
Fluoridated salt and other food carriers	Used in some countries for additional prevention of dental caries when fluoride levels in water are low [29]
Medicines and supplements	Prescribed for individuals with high risk of caries and low fluoride exposure; require strict dose control [30]

Insufficient fluoride intake and the risk of dental caries

Classic "fluoride deficiency" as a distinct systemic syndrome has not been described. The body does not experience a complete breakdown of metabolism with low fluoride intake. However, in regions with very low fluoride levels in water and the absence of other fluoride sources, the incidence of dental caries in children and adults is significantly higher than in areas with optimal levels. This is confirmed by numerous studies and large public health programs. [31]

Adding fluoride to drinking water at a level of approximately 0.7 milligrams per liter or regularly using fluoride toothpastes and rinses significantly reduces the risk of dental caries. Meta-analyses show a reduction in the incidence of dental caries in children and adolescents in areas with optimal fluoride levels compared to areas without water fluoridation. Moreover, the likelihood of serious side effects when maintaining the upper limit for water remains low. [32]

In families where children rarely use fluoride toothpaste, frequently consume sugary drinks and carbohydrates, and where the fluoride content in the water is low, the risk of early childhood caries is particularly high. In such cases, dentists may recommend individualized measures: early introduction of fluoride toothpastes in small amounts, professional applications of fluoride gels, and sometimes short courses of fluoride tablets if the fluoride level in the water is low. [33]

It's important to understand that fluoride alone is not enough to prevent tooth decay. Oral hygiene, limiting free sugar intake, regular dental checkups, and a healthy diet remain key factors. Fluoride enhances the effects of these measures and offsets some of the negative effects of acid-producing bacteria, but it cannot counteract the harm caused by constant sugary snacks and infrequent tooth brushing. [34]

At the population level, inadequate fluoride intake most often manifests itself in high rates of dental caries in children and adolescents, a large number of extracted teeth, and a high demand for restorations. Controlled water fluoridation programs and the widespread use of fluoride pastes are considered by the World Health Organization to be effective measures to reduce this burden, provided that concentrations are monitored and the population is informed. [35]

Table 4. Comparison of zones with different levels of fluoride in water

Fluoride levels in water	Expected impact on caries	Comments
Very low (below about 0.3 mg per liter)	High risk of caries, especially with poor hygiene and excess sugar [36]	Emphasis on fluoride pastes and other measures is often required
Optimal (usually around 0.7 mg per liter)	Significant reduction in the risk of caries, good benefit-risk balance [37]	Used in most fluoridation programs
Moderately elevated (closer to 1.5 mg per liter)	There is little additional benefit in terms of caries, and the risk of mild fluorosis increases [38]	Control of other fluoride sources is required.
Very high (above 2-3 mg per liter)	Dental fluorosis is possible, and with prolonged exposure there is a risk of skeletal fluorosis [39]	Measures are needed to reduce fluoride in water

Excess fluoride: dental fluorosis and bone damage

Chronically exceeding safe fluoride intake levels first leads to changes in enamel, then—at higher doses and over a longer period—to bone and joint damage. The earliest and most sensitive marker of excess fluoride is dental fluorosis: the appearance of white, chalky spots, streaks, or matte areas on the enamel, and in more severe forms, brown spots and surface defects. This is due to disruption of enamel mineralization during its formation. [40]

The risk of fluorosis is especially significant for children up to about 8 years of age, when the enamel of permanent teeth is forming. During this period, it is critical to avoid a combination of high levels of fluoride in water, systemic fluoride supplements, and regular ingestion of large amounts of toothpaste. Mild fluorosis, manifested as thin white lines or spots, is often cosmetic and does not affect dental function, but severe forms lead to enamel destruction. [41]

At higher and longer-term doses, skeletal fluorosis develops. Excess fluoride accumulates in the bones, altering the structure of bone tissue, making the bones stiffer and less elastic, and joints losing mobility. Clinically, this manifests as joint and spinal pain, limited mobility, and deformities. The most severe forms have been described in regions where fluoride concentrations in water are many times higher than 3-6 milligrams per liter and can reach over 10 milligrams per liter. [42]

A separate topic of discussion is the possible impact of chronic excess fluoride on the nervous system and cognitive functions of children. A number of studies have shown a link between high fluoride exposure and certain indicators of nervous system development, but the results are inconsistent, the methodology is often limited, and the influence of associated factors is not always accurately assessed. For this reason, EFSA and other regulators have revised safe levels taking into account the precautionary principle, but have not declared the universal optimal level of fluoride in water to be unsafe when observing the limit of 1.5 milligrams per liter. [43]

When assessing risk, the overall "balance"—the total fluoride intake from water, food, toothpaste, and medications—is important. In Europe, consumption analysis showed that even with the maximum permitted fluoride concentration in water, the general population does not exceed the new safe daily intake levels. Increased risk arises primarily in localized pockets of natural excess fluoride in water and with the uncontrolled use of fluoride tablets against a background of already high background levels. [44]

Table 5. Fluoride intake ranges and potential effects

Level	Characteristic	Main effects
Low intake	Below adequate levels, low fluoride in water and food	Increased risk of dental caries, especially with poor hygiene [45]
Optimal intake	About 0.05 mg per kg of body weight per day, a moderate level of fluoride in water	Maximum prevention of caries with minimal risk of fluorosis [46]
Borderline high	Intake is closer to the upper permissible levels, water up to 1.5 mg per liter	Mild fluorosis may occur with long-term exposure in children and is controlled by limiting other sources [47]
High chronic	Water 2-3 milligrams per liter and above, additionally other sources	Frequent dental fluorosis, risk of bone changes [48]
Very high	Water more than 6-10 milligrams per liter for a long time	Skeletal fluorosis, bone deformities, severe disability [49]

Fluoride in water, toothpastes and supplements

Fluoride in drinking water can be naturally occurring or added artificially as part of public health programs. For artificial water fluoridation, a target of approximately 0.7 milligrams per liter is typically chosen, which provides a consistent anti-caries effect and does not lead to significant fluorosis when properly controlled. Water with fluoride concentrations above 1.5 milligrams per liter is considered potentially unsafe, requiring a reduction in fluoride levels or the selection of an alternative water source. [50]

Adult toothpastes typically contain fluoride at concentrations of approximately 1,000 to 1,500 parts per million, or milligrams per kilogram of toothpaste. This is considered the standard range for effective cavity prevention. Children's toothpastes for younger children may contain lower concentrations to reduce the risk of ingesting excess fluoride. The key is to apply a small amount of toothpaste, a "pea" or strip no longer than the length of a child's fingernail, and teach the child to spit out the toothpaste after brushing. [51]

Fluoride rinses, gels, and varnishes are used in dentistry for individuals at increased risk of dental caries, including those undergoing orthodontic treatment, with multiple fillings, dry mouth, and in patients with enamel development disorders. These products provide additional local fluoride delivery, while the systemic load is relatively low unless the patient ingests significant amounts of the solution. The prescription and frequency of use are determined by the dentist. [52]

Fluoride tablets and drops as systemic medications have been used more cautiously in recent years than before. Current recommendations recommend prescribing them only after assessing all fluoride sources, the fluoride level in drinking water, and the individual's risk of dental caries. Effective doses for children typically amount to tenths of a milligram per day, and exceeding these doses is unacceptable. The use of such medications without a doctor's prescription is not recommended. [53]

An important point is the combined effect. If a child lives in a region with fluoride concentrations in the water near the upper limit, swallows toothpaste, and also takes fluoride tablets, the combined intake may exceed the safe limit. Therefore, monitoring should be comprehensive: knowledge of the water's composition, selection of the appropriate toothpaste and the amount used, caution with additives, and close collaboration with the dentist and pediatrician. [54]

Table 6. Fluoride in water and hygiene products

Source	Typical levels and features
Tap water in most European countries	Most often below 0.3 mg per liter, sometimes naturally higher in certain regions [55]
Optimized water fluoridation	Typically around 0.7 mg per liter, aimed at preventing dental caries [56]
Water with increased natural fluoride	May exceed 1.5-3 mg per liter; requires intervention and monitoring [57]
Toothpastes for adults	Approximately 1000-1500 parts per million of fluoride is effective against cavities when used correctly [58]
Children's toothpastes	Lower fluoride concentration, designed for lower weight and risk of ingestion [59]

Practical recommendations and a brief FAQ

The first practical step is to know the approximate fluoride level in your local drinking water. This information is usually available from your water supplier or health department. If the concentration is significantly below the optimal range, the emphasis should be on regular use of fluoride toothpaste and professional preventative treatments. If the water is close to or above the upper limit, it is necessary to discuss possible measures to reduce the overall load with your doctor and dentist. [60]

The second step is proper toothpaste use. For adults, it's recommended to use toothpaste with at least 1,000 parts per million fluoride, brush twice daily, and spit out the toothpaste after brushing without necessarily rinsing vigorously. For younger children, it's important to use a children's toothpaste with a lower fluoride concentration, apply it sparingly, and ensure the child doesn't swallow most of the toothpaste. [61]

The third step is to exercise caution with fluoride tablets and other systemic forms. Their use is only justified in cases of a high risk of dental caries and low fluoride exposure in water and hygiene products. The decision on administration, dosage, and duration of treatment should be made by a physician or dentist after assessing the complete exposure profile. Self-medication with fluoride tablets, especially in children, can lead to fluorosis. [62]

The fourth step is comprehensive prevention of caries and bone disease. Fluoride enhances dental protection, but it is only part of the overall plan: limiting free sugars, regular oral hygiene, flossing and brushing, adequate calcium, vitamin D, and protein intake, and avoiding tobacco and alcohol. A healthy lifestyle and diet help reduce the need for aggressive interventions and reduce the overall burden on the body. [63]

The fifth step is an individualized approach for vulnerable groups. It is especially important for pregnant women, young children, and people with chronic kidney disease to stay within the safe daily fluoride intake limits. The new EFSA guidelines are relevant for pregnant women, stricter upper levels are relevant for young children, and for patients with impaired renal function, limiting systemic fluoride sources under medical supervision is recommended. [64]

Brief FAQ

Does everyone need fluoride or just children?

Fluoride is useful for preventing dental caries in both children and adults, but is especially important during the period of enamel formation in permanent teeth. In adults, topical fluoride also reduces the risk of dental caries and slows the development of early enamel lesions. [65]

Is it possible to do without fluoride altogether if you brush your teeth well?

Theoretically possible, but in practice, a combination of good hygiene, sugar restriction, and fluoride provides the most lasting results. Without fluoride, even with good care, the risk of caries remains higher, especially in people with a predisposition and unfavorable saliva composition. [66]

Is fluoridated water dangerous when consumed long-term?

At fluoride concentrations within the limits recommended by the World Health Organization and national regulators (usually no higher than 1.5 milligrams per liter) and when general daily intake limits are observed, serious risks are low. At concentrations above this level, especially over a long period, the risk of fluorosis and possible skeletal effects increases. [67]

Should you be afraid of fluoride toothpastes?

No, when used correctly, fluoride toothpastes are considered safe and effective for preventing cavities. It is important not to swallow the toothpaste, monitor the amount used in children, and choose the fluoride concentration based on age and dentist recommendations. [68]

What should I do if the fluoride concentration in my local water is higher than 1.5 milligrams per liter?

The situation should be discussed with a doctor and dentist. Possible measures include using alternative sources of drinking water, limiting fluoride supplements, and, if necessary, revising local prevention plans. In some regions, fluoride reduction technologies are being implemented at the municipal water supply level. [69]