Weil's Vitamin D recommendation Hope this helps

[Guest guest]

I am raising my recommendation of 1,000 IU of vitamin D per day to

2,000 IU per day. Since 2005, when I raised it from 400 to 1,000 IU,

clinical evidence has been accumulating to suggest that a higher dose

is more appropriate to help maintain optimum health.

We have known for many years that we need vitamin D to facilitate

calcium absorption and promote bone mineralization. But newer research

has shown that we also need it for protection against a number of

serious diseases. In recent years, scientists have discovered that it

may help to prevent several cancers, cardiovascular disease, autoimmune

disorders, psoriasis, diabetes, psychosis, and respiratory infections

including colds and flu.

To focus particularly on cancer prevention, two recent meta-analyses

(in which data from multiple studies is combined) conducted by the

s Cancer Center at the University of California at San Diego and

colleagues suggested that raising blood levels of vitamin D could

prevent one-half of the cases of breast cancer and two-thirds of the

cases of colorectal cancer in the U.S. Discussing the breast cancer

analysis, study author Cedric Garland, Dr.P.H., stated that " The serum

level associated with a 50 percent reduction in risk could be

maintained by taking 2,000 international units of vitamin D3 daily

plus, when the weather permits, spending 10 to 15 minutes a day in the

sun. "

A 50 percent reduction in breast cancer deaths would have saved the lives of

more than 20,000 American women in 2009.

As these meta-analyses suggest, vitamin D deficiency is widespread.

Aside from breast cancer, it is quite likely that hundreds of thousands

of cancers of various kinds worldwide might be prevented each year if

we all were getting enough.

We can get vitamin D through foods such as fortified milk and

cereals as well as eggs, salmon, tuna and mackerel, but the amounts are

not nearly sufficient to lift blood concentrations to optimal levels.

Sun exposure is the best way to get it; ultraviolet rays trigger

vitamin D synthesis in the skin. Factors that decrease the body's

ability to make vitamin D include dark skin, heredity, obesity and

certain medications, including some anti-seizure drugs (check with your

pharmacist). Most significantly, sunscreen blocks vitamin D synthesis

in the skin, and in northern latitudes (above that of Atlanta, Georgia)

the sun is at too low an angle for half the year to provide sufficient

UV radiation.

Low levels of vitamin D in the population as a whole suggest that

most people need to take a vitamin D supplement. This may be especially

true for seniors, as the ability to synthesize vitamin D in the skin

declines with age. Always take your vitamin D with a fat-containing

meal to ensure absorption.

Don't be concerned that 2,000 IU will give you too much. With

exposure to sunlight in the summer, the body can generate between

10,000 IU and 20,000 IU of vitamin D per hour with no ill effects. In

addition, no adverse effects have been seen with supplemental vitamin D

intakes up to 10,000 IU daily.

If you decide to have your vitamin D levels tested, look for results

in the normal range, from 30.0 to 74.0 nanograms of 25-hydroxy vitamin

D per milliliter (ng/mL) of blood. If you are found to be deficient,

your physician can advise you on the best way to raise your blood

concentration into the normal range.

Weil, M.D., is the founder and director of the Arizona Center for

Integrative Medicine and the editorial director of www.DrWeil.com. Become a fan

on Facebook, follow Dr. Weil on Twitter, and check out Dr. Weil's Daily Health

Tips blog.

Wiki on overdose

Overdose

For more details on this topic, see hypervitaminosis D.

Vitamin D is stored in the human body as calcidiol (25-hydroxy-vitamin D) which

has a large volume of distribution and a half-life of about 20 to 29 days.[16]

Ordinarily, the synthesis of bioactive vitamin D hormone is tightly regulated,

and prevalent thinking is that vitamin D toxicity usually occurs only if

excessive doses (prescription forms or rodenticide analogs) are taken.[49] Serum

levels of calcidiol (25-hydroxy-vitamin D) are typically used to diagnose

vitamin D overdose. In healthy individuals, calcidiol levels are normally

between 32 to 70 ng/mL (80 to 175 nmol/L), but these levels may be as much as

15-fold greater in cases of vitamin D toxicity. Serum levels of bioactive

vitamin D hormone (1,25(OH2)D) are usually normal in cases of vitamin D

overdose.[3]

The exact long-term safe dose of vitamin D is not known. In 1997 the U.S.

Dietary Reference Intake Tolerable Upper Intake Level (UL) of vitamin D for

children and adults was set at 50 micrograms/day (2,000 IU)[50], but this is

viewed by some researchers as outdated and overly restrictive.[51] A 2007 risk

assessment was made by two employees of the dietary supplement trade association

Council for Responsible Nutrition,[51] that represents companies including

Amway, Bayer AG and GlaxoKline,[52] and their two colleagues, who declared

that they had no personal or financial conflicts of interest. They suggested

that 250 micrograms/day (10,000 IU) in healthy adults should be adopted as the

tolerable upper limit.[51] In adults, sustained intake of 1250 micrograms/day

(50,000 IU) can produce toxicity within a few months.[3] For infants (birth to

12 months) the tolerable UL is set at 25 micrograms/day (1000 IU), and vitamin D

concentrations of 1000 micrograms/day (40,000 IU) in infants has been shown to

produce toxicity within 1 to 4 months. Other sources indicate that the threshold

for vitamin D toxicity in humans is 500 to 600 micrograms per kilogram body

weight per day. " [53] In rats an oral LD50 of 619 mg/kg is noted.[54] All known

cases of vitamin D toxicity with hypercalcemia have involved intake of over

1,000 micrograms/day (40,000 IU)[55].

Although normal food and pill vitamin D concentration levels are far too low to

be toxic in adults, people taking multiples of the normal dose of codliver oil

may reach toxic levels of vitamin A, not vitamin D,[56] if taken in an attempt

to increase the levels of vitamin D. Most officially-recorded historical cases

of vitamin D overdose have occurred due to manufacturing and industrial

accidents.[55] In the United States, overdose exposure of vitamin D was reported

by 284 individuals in 2004 (a randomly selected year), leading to 1 death.[57]

Some symptoms of vitamin D toxicity are a result of hypercalcemia (an elevated

level of calcium in the blood) caused by increased intestinal calcium

absorption. Vitamin D toxicity is known to be a cause of high blood

pressure.[58] Gastrointestinal symptoms of vitamin D toxicity can include

anorexia, nausea, and vomiting. These symptoms are often followed by polyuria

(excessive production of urine), polydipsia (increased thirst), weakness,

nervousness, pruritus (itch), and eventually renal failure. Other signals of

kidney disease including elevated protein levels in the urine, urinary casts,

and a build up of wastes in the blood stream can also develop.[3] In one study,

hypercalciuria and bone loss occurred in four patients with documented vitamin D

toxicity.[59] Another study showed elevated risk of ischemic heart disease when

25D was above 89 ng/mL.[60] Vitamin D toxicity is treated by discontinuing

vitamin D supplementation, and restricting calcium intake. If the toxicity is

severe blood calcium levels can be further reduced with corticosteroids or

bisphosphonates. In some cases kidney damage may be irreversible.[3]

Exposure to sunlight for extended periods of time does not normally cause

vitamin D toxicity.[55] This is because within about 20 minutes of ultraviolet

exposure in light skinned individuals (3–6 times longer for pigmented skin) the

concentration of vitamin D precursors produced in the skin reach an equilibrium,

and any further vitamin D that is produced is degraded.[15] According to some

sources, endogenous production with full body exposure to sunlight is

approximately 250 µg (10,000 IU) per day.[55] According to Holick, " the skin has

a large capacity to produce cholecalciferol " ; his experiments indicate that,

" [W]hole-body exposure to one minimal erythemal dose of simulated solar

ultraviolet radiation is comparable with taking an oral dose of between 250 and

625 micrograms (10 000 and 25 000 IU) vitamin D. " [15]

http://en.wikipedia.org/wiki/Vitamin_D#Overdose