Are You Taking Too Much Vitamin D?
Vitamin D isnecessary for bone metabolism, helping the body to absorb calcium and maintain adequate levels of calcium and phosphate in the blood. Starting in 2002, there was an uptick in research on vitamin D.
A2011年医学研究所（IOM）报告suggested the benefits of vitamin D with regards to bone health only. There are some ongoing trials looking at possible benefits of vitamin D on other health parameters. The IOM was clear on the impact of服用过多的维生素D(including hypercalcemia and calcifications in soft tissue and blood vessels) which makes it important to take the right dose.
A June2017年美国医学协会杂志study建议许多人服用过高的剂量。换句话说，这是一个“太多好事”的情况。本研究指出，1999年至2014年间的维生素D的摄入量增加了增加。剂量范围在1000 IU和4000 IU之间。从中收集数据National Health and Nutrition Examination Survey (NHANES), a program of studies that was designed to evaluate the health and nutrition status of children and adults in the U.S. The date in the NHANES was obtained in the form of questionnaires. It is a well-regarded data set, and used or referenced in numerous studies.
The researchers analyzed data involving 39,243 subjects with a mean age of 46.6 years old. About half the participants were women, and 69.7 percent self-reported as non-Hispanic white. The analysis also showed:
Prevalence of taking 1000 IU or more of vitamin D was 18.2 percent during 2013-2014
Prevalence of taking 1000 IU or more of vitamin D was 0.3 percent during 1999-2000
Prevalence of taking 4000 IU or more of vitamin D was 3.25 percent during 2013-2014
Prevalence of taking 4000 IU or more of vitamin D was less than 0.1 percent during 2005-2006
在2013 - 2014年,落脚ke of 4000 IU or more was highest among women (4.2 percent), among non-Hispanic white (3.9 percent), and among individuals 70 years or older (6.8 percent).
在所有参与者中，大约3％超过了4000 IU“安全”限制。总体而言，在研究中列出的后期表现增加的剂量增加，所有年龄组织，所有种族和各种各样的人都会发现。
目前，这维生素D的推荐膳食津贴（RDA）is 800 IU for adults aged 70 years or younger and 600 IU for adults over age 70. The upper limit for daily intake is 4000 IU. At this level, an individual may begin to develop complications.
It should be noted that this study did not take into account the “updated”Daily Value (DV)for vitamin D, which is 800 IU. Thisnew DV will be used by vitamin makerswhen they meet the new — and unfortunately delayed — deadline for the labels, mandated by the Federal Drug Administration (FDA).
要清楚，RDA是“推荐的每日津贴”或摄入健康个体应遵循。RDA是由美国国家学院医学研究所的食品和营养委员会开发的。RDA因年龄而异，生命环境（怀孕或护理母亲）不同。
DV or Daily Value is established by the FDA and are used on food and dietary supplement labels as a percentage. There is one DV for each nutrient for everyone over the age of four years old. DVs usually exceed RDAs. If the DV for vitamin D is 800 IU, then a vitamin that offers 400 IU of vitamin D is offering 50 percent of the DV.
The researchers stress that, despite the perceived benefits and the need for specific vitamin D daily goals, taking higher than recommended doses in combination with calcium can encouragekidney stones。另一项研究表明，高于推荐的维生素D剂量可以增加骨折和落下的风险。
On the other hand, too-low levels of vitamin D interfere with the bone metabolism of otherwise healthy women in their childbearing years. Too-low levels are linked to an increased risk of diabetes, neuromuscular disorders, and immune, skin, renal, and heart disease.
Limitations of the study include the fact that it was not a controlled research project designed to look at the risks and benefits of different amounts of vitamin D, and the fact that the accuracy of the data depended on subjects' recall.
Thebest sources of vitamin Dinclude: Sunlight, fatty fish, canned tuna, Portobello mushrooms,fortified milk或牛奶替代品，强化橙汁，蛋黄，强化谷物，鳕鱼肝油和补充剂。
It’s important to have a discussion with your health professional regarding the对您的维生素D的最佳水平。Make sure to account for food sources before using supplements. In most cases, taking 1000 - 2000 IU daily is considered safe for most adults.
