Trace Minerals: Fluoride and Iodine – Functions, Sources, Deficiency, and Toxicity

Trace Minerals: Fluoride and Iodine

Fluoride (F)

Fluoride is an essential trace mineral that plays a significant role in maintaining dental health and bone integrity. It is required in small amounts and is commonly found in water supplies and dental products.

• Main Bodily Functions:

  • Enhances mineralization of bones and teeth.

  • Prevents dental caries (tooth decay).

  • Protects against acid in bacteria that erode tooth enamel.

• Absorption: Fluoride can be absorbed directly from water, food, and dental products.

Food Sources, Deficiency, and Toxicity

Food Sources	Deficiency	Excess/Toxicity
Fluoridated municipal water, seafood, bottled water, dental products (toothpaste, mouthwash)	Dental caries (tooth decay)	Fluorosis (pitted, stained enamel); increased bone mass & stiffness

Main dietary concern: Insufficient fluoride leads to increased dental caries. Excessive intake can cause dental fluorosis (white spots, mottling).

Key Points

• Fluoride is not abundant in most foods; water fluoridation is the primary source for most populations.

• Deficiency: Increased risk of dental caries.

• Toxicity: Dental fluorosis and, in severe cases, skeletal fluorosis.

Example

• Children who drink non-fluoridated water are at higher risk for cavities compared to those who consume fluoridated water.

Iodine (I)

Functions and Importance

Iodine is a vital trace mineral necessary for the synthesis of thyroid hormones, which regulate metabolism, growth, and development.

• Main Bodily Functions:

  • Required for the synthesis of thyroid hormones (thyroxine/T4 and triiodothyronine/T3).

  • Supports normal growth, neurological development, and metabolic regulation.

Food Sources, Deficiency, and Toxicity

Food Sources	Deficiency (Name)	Excess/Toxicity
Iodized salt, seafood, seaweed, dairy	Goiter: Enlargement of the thyroid gland Cretinism: Congenital hypothyroidism in infants, leading to mental retardation and stunted growth	Impaired hormone production

Main dietary concern: Iodine deficiencies are largely eliminated through the introduction of iodized salt.

Key Points

• Iodine is essential for thyroid hormone production, which controls metabolic rate and development.

• Deficiency: Can cause goiter and, in severe cases, cretinism (especially in infants).

• Toxicity: Excessive iodine intake can impair thyroid hormone production.

Example

• Populations with access to iodized salt have significantly lower rates of goiter and congenital hypothyroidism.

Review Questions and Answers

• True/False: Seafood and iodized salt are the best sources of iodine. True.

• True/False: Fruits and vegetables are good sources of fluoride. False. (Fluoride in foods is not readily absorbed.)

• Which conditions are prevented through the use of iodized salt?

  • Goiter and congenital hypothyroidism.

• Which of the following is a function of iodine?

  • Thyroid hormone synthesis.

Additional info:

• Thyroid hormones regulate energy metabolism, protein synthesis, and are critical for fetal and infant brain development.

• Recommended Dietary Allowance (RDA): Fluoride 3-4 mg/day; Iodine 150 μg/day (adults), 1100 μg/day (UL).