Many Americans May Be Taking Too Much Vitamin D – Study

Photo – Mizianitka – pixabay.com

Nutritionists and doctors recommend a daily intake of vitamin D at only 600 international units (IU) for adults aged 70 and younger while those over 70 are advised to ingest 800 IUs a day. New research suggests that more than three percent of American adults took more than 4,000 IUs of the vitamin daily – a figure that exceeds the upper limits of what is considered safe. As of 2016, there are 250 million Americans aged 18 years old above.

The study’s data show that more than seven million Americans are taking excessively high doses of the vitamins that are linked to an increased risk of fractures, falls, kidney stones, and certain cancers. The researchers reported their findings in the Journal of the American Medical Association in June 2017. ^[1]

The University of Minnesota study highlighted the 590 percent increase registered by the proportion of Americans that are taking vitamin D supplements at higher doses between 1999 and 2004. According to the people involved in the study, confusion is one of the reasons why many Americans are taking the supplement unnecessarily and dangerously. One of the authors of the study is Mary Rooney, a doctoral student at the U of M, who noted that one in five U.S. adults are consuming vitamin D supplements.

Rooney and her colleagues gathered data from the supplementation usage of 40,000 adults aged 20 or older who were recruited for the National Health and Nutrition Examination Survey (NHANES) for the years 1999-2000 and 2013-2014. ^[2] Here are the major findings of the study:

• 18.2 percent of the survey participants were taking vitamin D supplements of 1,000 IU or more in 2013-2014 compared with only 0.3 percent in 1999-2000

• 3.2 percent of the participants took daily vitamin D supplements of 4,000 IU or more in 2013-2014

• the use of exceptionally high doses was recorded by women (4.2 percent), whites (3.9 percent) and those 70 years older (6.6 percent)

The importance of vitamin D to bone metabolism was stressed by the study’s senior author Pamela Lutsey who is a public health researcher at the university. Lutsey mentioned the role of vitamin D supplementation in helping the body absorb calcium and maintain appropriate concentrations of phosphate in the blood. However, she warned that too much vitamin D is harmful and could lead to detrimental deposition of calcium in the heart and kidneys.

Long-term intakes of vitamin D above the upper limit recommended could lead to symptoms associated with vitamin D intoxication. ^[3] These symptoms include hypertension, loss of appetite, and weight loss. ^[4][5] Higher doses of vitamin D could also increase the risk of pancreatic cancers and cardiovascular events. ^[6]

Intake reference values for vitamin D and other nutrients are stated in the Dietary Reference Intakes developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of The National Academies (formerly National Academy of Sciences).

The recommended daily allowance (RDA) for vitamin D established by the FNB represents the daily intake the body needs to maintain bone health and normal calcium metabolism. The vitamin D RDAs are set on the basis of minimal sun exposure. See the table below on the RDAs for vitamin D:

0-12 months – 400 IU
1-13 years – 600 IU
14-18 years – 600 IU
19-50 years – 600 IU
51-70 years – 600 IU
Above 70 years – 800 IU

Most of the vitamin consumption of Americans comes from fortified foods since very few foods in nature contain vitamin D. Listed below are selected food sources of vitamin D and their IUs per serving.

Swiss Cheese, 1 ounce – 6 IU
Whole Egg, one large – 41 IU
Sardines, canned in oil – 42 IU
Fortified margarine – 46 IU
Nonfat milk – 80 IU
Cooked salmon – 154 IU
Cooked swordfish – 566 IU
Fortified Orange Juice – 137 IU
Fortified yogurt – 80 IU
Cooked liver – 42 IU

Further Reading:

Vitamin D Knowledge

12 Signs You Are Vitamin D Deficient (And How To Get More)