# item.guide
Side-by-Side Comparison Essential Vitamins & Minerals

Iodine (Elemental I) vs. Vitamin B9 (Folate & Folic Acid)

Comparing 2 standards across 9 specifications. 9 key differences identified.

Comparing:
Iodine (Elemental I)
Vitamin B9 (Folate & Folic Acid)

Iodine is an essential halogen trace element required exclusively as an essential structural component of thyroid hormones thyroxine (T4) and triiodothyronine (T3), regulating metabolic rate, cellular respiration, and fetal neurodevelopment. Adult RDA is 150 µg, with an Upper Limit of 1,100 µg/day.

View full Iodine (Elemental I) spec sheet →

Vitamin B9 comprises natural dietary folates (polyglutamates) and synthetic folic acid (monoglutamate). Adult RDA is 400 µg DFE, with a Tolerable Upper Limit of 1,000 µg/day synthetic folic acid, essential as a single-carbon donor in thymidylate DNA synthesis and neural tube closure.

View full Vitamin B9 (Folate & Folic Acid) spec sheet →

Specification Comparison Table

9 Parameters
Parameter / Spec
Nutrient Type
Essential Trace Halogen Element Water-Soluble Pteroylglutamate Vitamin
Adult RDA / RDI
150 µg / day (220 µg pregnancy / 290 µg lactation) 400 µg DFE / day (600 µg DFE pregnancy / prevents neural tube defects)
Tolerable Upper Limit (UL)
1,100 µg / day (Avoid Wolff-Chaikoff thyroid autoregulatory shutdown) 1,000 µg / day (Synthetic folic acid only; masks B12 deficiency neuropathy)
Chemical Forms
Iodide (I- / Potassium Iodide KI, Potassium Iodate KIO3 in iodized salt), Molecular Iodine (6S)-5-Methyltetrahydrofolate (5-MTHF, active circulating form), Tetrahydrofolate (THF), Folic Acid (Pteroylmonoglutamic acid, synthetic)
Primary Biological Function
Constituent of Thyroxine (T4, 4 iodine atoms / 65% by weight) and Triiodothyronine (T3, 3 iodine atoms / 59% by weight) 1-Carbon transfer reactions, dUMP -> dTMP methylation (Thymidine DNA synthesis), Methionine-Homocysteine cycle, Erythropoiesis
Deficiency Condition
Endemic Goiter (Compensatory thyroid enlargement), Congenital Hypothyroidism / Cretinism (Permanent neurodevelopmental impairment), Maternal miscarriages Neural Tube Defects (Spina bifida, anencephaly in fetuses), Megaloblastic Macrocytic Anemia, Elevated Homocysteine
Top Whole Food Sources
Kombu Kelp, Nori Seaweed, Atlantic Cod, Eastern Oysters, Iodized Table Salt, Greek Yogurt, Dairy Milk, Eggs Beef Liver, Spinach, Asparagus, Brussels Sprouts, Roman Lentils, Chickpeas, Fortified Flours
Iodized Salt Public Health Impact
Universal salt iodization (45–75 mg KI / kg salt) is hailed as one of the greatest global public health achievements, eradicating cretinism worldwide
MTHFR Genetic Polymorphism
Homozygous MTHFR C677T variant reduces folate reduction activity by ~70%, benefiting from direct 5-MTHF supplementation