The amount of calcium you need each day depends on
your age. Average daily recommended amounts are listed
below in milligrams (mg):
The safe upper
limits for calcium are listed below. Most people do not get amounts
above the upper limits from food alone; excess intakes usually come
from the use of calcium supplements. Surveys show that some older
women in the United States probably get amounts somewhat above the
upper limit since the use of calcium supplements is common among
reference values for vitamin D and other nutrients are provided in the Dietary
Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the
Institute of Medicine of The National Academies (formerly National Academy of
Sciences). DRI is the general term for a set of reference values used to plan
and assess nutrient intakes of healthy people. These values, which vary by age
and gender, include:
The FNB established an RDA for vitamin D representing a daily intake that is
sufficient to maintain bone health and normal calcium metabolism in healthy
people. RDAs for vitamin D are listed in both International Units (IUs) and
micrograms (mcg); the biological activity of 40 IU is equal to 1 mcg (Table 2).
Even though sunlight may be a major source of vitamin D for some, the vitamin D
RDAs are set on the basis of minimal sun exposure.
Vitamin D toxicity can cause non-specific symptoms such as anorexia, weight
loss, polyuria, and heart arrhythmias. More seriously, it can also raise blood
levels of calcium which leads to vascular and tissue calcification, with
subsequent damage to the heart, blood vessels, and kidneys .
The use of supplements of both calcium (1,000 mg/day) and vitamin D (400 IU) by
postmenopausal women was associated with a 17% increase in the risk of kidney
stones over 7 years in the Women's Health Initiative. A serum 25(OH)D
concentration consistently >500 nmol/L (>200 ng/mL) is considered to be
Excessive sun exposure does not result in vitamin D toxicity because the
sustained heat on the skin is thought to photodegrade previtamin D3
and vitamin D3 as it is formed. In addition, thermal activation of
previtamin D3 in the skin gives rise to various non-vitamin D forms
that limit formation of vitamin D3 itself. Some vitamin D3
is also converted to nonactive forms .
Intakes of vitamin D from food that are high enough to cause toxicity are very
unlikely. Toxicity is much more likely to occur from high intakes of dietary
supplements containing vitamin D.
Long-term intakes above the UL increase the risk of adverse health effects 
(Table 4). Most reports suggest a toxicity threshold for vitamin D of 10,000 to
40,000 IU/day and serum 25(OH)D levels of 500–600 nmol/L (200–240 ng/mL). While
symptoms of toxicity are unlikely at daily intakes below 10,000 IU/day, the FNB
pointed to emerging science from national survey data, observational studies,
and clinical trials suggesting that even lower vitamin D intakes and serum
25(OH)D levels might have adverse health effects over time. The FNB concluded
that serum 25(OH)D levels above approximately 125–150 nmol/L (50–60 ng/mL)
should be avoided, as even lower serum levels (approximately 75–120 nmol/L or
30–48 ng/mL) are associated with increases in all-cause mortality, greater risk
of cancer at some sites like the pancreas, greater risk of cardiovascular
events, and more falls and fractures among the elderly. The FNB committee cited
research which found that vitamin D intakes of 5,000 IU/day achieved serum
25(OH)D concentrations between 100–150 nmol/L (40–60 ng/mL), but no greater.
Applying an uncertainty factor of 20% to this intake value gave a UL of 4,000 IU
which the FNB applied to children aged 9 and older, with corresponding lower
amounts for younger children.