In the early part of the 20th century, when vitamin D was discovered, scientists found that it prevented rickets. Since then, low levels of vitamin D have been implicated in a range of health conditions. Researchers have suggested that supplementation could help prevent osteoporosis (Calcified Tissue International, online Sep. 28, 2019). Supplements have not been shown to prevent other conditions, unless the patients already are deficient in the vitamin. But what dose of vitamin D is appropriate? We heard from a reader on a very high dose.

Is the Prescribed Dose of Vitamin D Too High?

Q. My doctor told me to take 5,000 IU of vitamin D in the morning and 5,000 IU of vitamin D in the evening. Is this dose of vitamin D OK?

A. According to the National Institutes of Health Office of Dietary Supplements, the RDA for vitamin D (ages 1-70) is 600 IUs.  The experts established 800 IUs as the RDA for individuals older than 70. We think that is low, but your intake of 10,000 IUs is very high. According to the experts, the upper limit should be 4,000 IU a day.

Since your doctor prescribed this dose of vitamin D, however, we trust that she or he is monitoring your progress on a regular basis. When you have reached a level of 25 hydroxyvitamin D that is sufficient, presumably your physician will lower the dose. People apparently respond to supplementation in divergent ways, probably due to genetic differences (Journal of Diabetes Research, online Sep. 8, 2019). 

Vitamin D to Boost Your Mood:

Some people have found that too little vitamin D is associated with a low mood. Here is one reader’s story:

Q. During a very cold winter, I began to feel more SAD than usual, as well as fuzzy, forgetful and achy. This worried me enough to send me to the doctor.

All my blood tests were fine except for my vitamin D, which was very low. Some high-dose supplements eventually caught me up, but apparently my ordinary multivitamin hadn’t been working.

Now I am reading that low vitamin D has been linked to breast cancer, immune problems and other conditions as well as seasonal affective disorder. If I couldn’t get enough sun exposure to make vitamin D where I live below the Mason-Dixon line, what about people in the north? Can older people who don’t go outside get enough vitamin D?

How Can You Get Enough Vitamin D?

A. Research links low circulating levels of vitamin D to seasonal affective disorder (SAD) and depression (Psychiatry Research, May 30, 2015; Journal of Postgraduate Medicine, Apr-June 2019). It seems that supplements may boost mood. In addition, you should try to avoid very low levels of this vitamin. Ask your doctor to monitor your blood level of 25-hydroxyvitamin D. The meta-analysis did not specify the best dose of vitamin D to counteract depression, unfortunately.

Vitamin D deficiency has also been associated with conditions such as cancer, hypertension, arthritis, osteoporosis, diabetes and multiple sclerosis (Nutrition Journal, Dec. 8, 2010). Older people with inadequate vitamin D levels may have less hand strength and walk more slowly (PLoS One, Aug. 21, 2018).

You are correct that people in northern states may have difficulty getting enough vitamin D. In fact, the National Health and Nutrition Examination Survey showed that 29 percent of Americans were deficient in vitamin D and another 41 percent had low levels (British Journal of Nutrition, April 28, 2018). An extremely high dose of vitamin D can lead to serious toxicity, however (Multiple Sclerosis, Aug. 2019).

Learn More:

Finally, you can learn more about optimal vitamin D levels to boost your mood and your bone strength, as well as vitamin supplements in our Guide to Vitamin D Deficiency. It provides more information on the pros and cons of this nutrient.

Related People's Pharmacy Health Guide

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