Chemistry Reference
In-Depth Information
the current recommendation for adequate intake of fluoride is based on
fluoride normally received from human milk, 0.01 mg/d, an amount 10-50
times less than the estimated safe and adequate intake established in 1989
(0.1-0.5 mg/d) (Food and Nutrition Board: Institute of Medicine, 1997).
Excessive intake of fluoride causes fluorosis, characterized by mottling
of teeth (with hypomineralized and porous enamel), and sometimes the more
severe skeletal fluorosis with lower extremity pain and microfracture
(Hallanger Johnson et al., 2007). For infants, the lowest-observed-adverse-
effect level is 0.10 mg/kg/d for moderate enamel fluorosis. On this basis, the
upper limit of fluorine is 0.7 and 0.9 mg fluoride/d for infants aged 0-6
months and 7-12 months, respectively.
The mean concentration of fluoride in mature human milk is approxi-
mately 18 mg/l (Table 10.1). The fluoride content of bovine milk is variable
(Table 10.1). About 46-64% of the fluoride in bovine milk occurs as free
fluoride ions with the remainder bound to proteins (Esala et al., 1982).
Essentially 100% of fluoride ingested in the fasted state as fluoridated water
and 50-80% of fluoride ingested with food is absorbed from the gastrointest-
inal tract (Nielsen, 2006).
10.15.
Boron
Boron is a bioactive element of low molecular weight (atomic weight
ΒΌ
10.81 g
mol
1
) that is essential for all vascular plants (Loomis and Durst,
1992). There are four lines of evidence, derived in large part from research in
animal models, that dietary boron can have beneficial effects on humans:
(1) In amounts typically found in human and animal diets, boron improved
bone health (independent of vitamin D status) by increasing bone develop-
ment in frogs (Fort et al., 2000), bone breaking strength in pigs (Armstrong
et al., 2000), broilers (Rossi et al., 1993) and growing pullets (Wilson and
Ruzler, 1997) and bone calcium concentration in chicks (Hunt et al., 1994).
(2) Boron interacts with specific steroid hormones; it counteracts the dele-
terious effects of dietary vitamin D deficiency on body growth in chicks (Bai
and Hunt, 1996) and growth plate morphology in embryonic (King et al.,
1991) or hatched chicks (Hunt, 1989; Hunt et al., 1994). In addition, boron
increased the circulating concentration of 17
-estradiol in humans (Nielsen
et al., 1992; Naghii and Samman, 1997) and, together with injections of 17
-
estradiol, increased trabecular bone surfaces in ovariectomized rats (Sheng
et al., 2001). (3) Physiologic amounts of boron apparently reduce the
amount of insulin required to maintain plasma glucose in rats (Bakken
and Hunt, 2003). (4) Borate or borate analogs can inhibit the in vitro activity
of several enzymes in the eicosanoid pathway related to inflammation and
