Fluorine/Fluoride

Fluorine is found as an anion within nature and is therefore called fluoride.¹ The practice of fluoridation within the U.S. water supply began in the 1940s and is used to promote dental health, especially in children. The majority of fluoride within the diet is not within foods but in fluoridated water, toothpaste, and mouthwash.¹

Absorption and Excretion:  The fluoride found in water or soluble fluoride is absorbed well into the body compared to fluoride bound to proteins.¹ Fluoride is absorbed mostly within the stomach but also in the intestines, and it rapidly enters into the blood and reaches peak levels within approximately 30 minutes.¹ Fluoride is excreted within urine and minimally within feces.¹

Circulation and Storage: Blood levels of fluoride are very low within the parts per billion range.¹ Fluoride is found in bones and teeth. 

Functions:  

Fluoride functions within bones and teeth. Within teeth, fluoride protects enamel from damage by incorporating itself into hydroxyapatite crystals during teeth development or when displacement in mature hydroxyapatite crystals occurs.¹ The substitution of fluoride into hydroxyapatite crystals (specifically within the hydroxyl groups) hardens and stabilizes the crystals, creating a stronger enamel.¹ The same occurs within bones. 

Dietary Reference Intake (DRI) - The Adequate Intake (AI) of fluoride for males aged 19 years old and older is 3 milligrams per day.² For females aged 14 years old and older is 4 milligrams per day.²

Deficiency/Toxicity- Fluoride toxicity is rare but can occur. The Tolerable Upper Intake Level (UL) is 10 milligrams per day for males and females 9 years old and older.² If fluoride in teeth and bones exceeds 3,000 micrograms per gram of tissue, fluoride deposits into soft tissues.¹ Excess fluoride can cause mottled teeth and deformed bones.¹ Other toxicity symptoms include respiratory failure, cardiac failure, and muscular weakness.¹ Metabolic issues such as inhibition of fatty acid oxidation, glycogen breakdown, and Acetyl CoA formation may occur in the presence of fluoride.¹ 

Dietary Sources of Fluoride 

Fluoride concentration in food is low and is considered a poor source. The main source of fluoride in the diet is fluoridated water. Fluoride is added to water in the forms of sodium fluoride and sodium fluorosilicate at approximately 1-2 parts per million.¹

However, trace amounts can be found in some plants and animal sources based on the amounts in the soil and water supply.¹ Examples of foods containing fluoride include:

Fruits/Vegetables - raisins, potatoes, corn, asparagus, apple, avocado

Dairy - cottage cheese, yogurt, cheese, milk

Meats/Seafood/Animal Products - shrimp, pork, chicken, beef

Beverages - tea, coffee

Grains - oatmeal, rice

Source(s):

1. Denise M Medeiros and Robert E.C. Wildman, Advanced Human Nutrition, 4th ed. (Burlington, MA: Jones & Bartlett, 2019).

2. https://ods.od.nih.gov/factsheets/Fluoride-HealthProfessional/