diseases that are associated with an iodine deficiency include: intellectual disabilities, hypothyroidism, and goiter. there is also a risk of various other growth and developmental abnormalities. folate folate (as a fortification ingredient, folic acid) functions in reducing blood homocysteine levels, forming red blood cells, proper growth and division of cells and preventing neural tube defects (ntds). in many industrialized countries, the addition of folic acid to flour has prevented a significant number of ntds in infants. two common types of ntds, spina bifida and anencephaly, affect approximately 2500-3000 infants born in the us annually. research trials have shown the ability to reduce the incidence of ntds by supplementing pregnant mothers with folic acid by 72%. niacin niacin (a form of vitamin b3) has been added to bread in the us since 1938 (when voluntary addition started), a program which substantially reduced the incidence of pellagra. pellagra was seen amongst poor families who used corn as their main dietary staple. although corn itself does contain niacin, it is not a bioavailable form unless it undergoes nixtamalization (treatment with alkali, traditional in native american cultures) and therefore was not contributing to the overall intake of niacin. diseases associated with niacin deficiency include pellagra which consisted of signs and symptoms called the three d's-"dermatitis, dementia, and diarrhea." others may include vascular or gastrointestinal diseases. common diseases which present a high frequency of niacin deficiency include alcoholism, anorexia nervosa, hiv infection, gastrectomy, malabsorptive disorders, certain cancers and their associated treatments. vitamin d since vitamin d is a fat-soluble vitamin, it cannot be added to a wide variety of foods. foods that it is commonly added to are margarine, vegetable oils and dairy products. during the late 1800s, after the discovery of curing conditions of scurvy and beriberi had occurred, researchers were aiming to see if the disease, later known as rickets, could also be cured by food. their results showed that sunlight exposure and cod liver oil were the cure. it was not until the 1930s that vitamin d was actually linked to curing rickets. this discovery led to the fortification of common foods such as milk, margarine, and breakfast cereals. this took the astonishing statistics of approximately 80–90% of children showing varying degrees of bone deformations due to vitamin d deficiency to being a very rare condition. diseases associated with a vitamin d deficiency include rickets, osteoporosis, and certain types of cancer (breast, prostate, colon and ovaries). it has also been associated with increased risks for fractures, heart disease, type 2 diabetes, autoimmune and infectious diseases, asthma and other wheezing disorders, myocardial infarction, hypertension, congestive heart failure, and peripheral vascular disease. fluoride main article: water fluoridation although fluoride is not considered an essential mineral, it is useful in prevention of tooth decay and maintaining adequate dental health. in the mid-1900s it was discovered that towns with a high level of fluoride in their water supply was causing the residents' teeth to have both brown spotting and a strange resistance to dental caries. this led to the fortification of water supplies with fluoride in safe amounts (or reduction of naturally occurring levels) to retain the properties of resistance to dental caries but avoid the staining caused by fluorosis (a condition caused by excessive fluoride intake). the tolerable upper intake level (ul) set for fluoride ranges from 0.7 mg/day for infants aged 0–6 months and 10 mg/day for adults over the age of 19.