If you’re one of the millions of Americans who have been told by their doctor take vitamin D, you’re not alone. In recent years, many doctors have jumped on the vitamin D bandwagon, prescribing the “sunshine in a bottle” at extremely high doses. In fact, I know one person who was prescribed 50,000 IU of vitamin D by his doctor—a dose that can be dangerously high.
As I’ll explain in a minute, taking too much vitamin D can be just as risky as taking too little—leading to increased risk for strokes and other cardiovascular events. So, I wanted to get the word out about why vitamin D is so important for your health and how to ensure you’re getting the right dose.
Why Do You Need Vitamin D?
We’ve long-known that vitamin D—which is actually a hormone rather than a “vitamin” —helps with the absorption of calcium and phosphorous, which are vital nutrients for bone health. That’s why vitamin D deficiencies are linked with rickets.
Now we know that vitamin D affects your immune system as well, modulating many activities in the body—including promoting anti-tumor activity. In fact, the number of health conditions linked with low levels of vitamin D is extremely long and growing. Having adequate levels of vitamin D can help to protect you from everything from type 2 diabetes, to dementia, and cancer.
One of the biggest bodies of research in support of vitamin D is the Nurses' Health Study (NHS). This enormous investigative initiative was started by Dr. Frank Speizer of Boston's Brigham and Women's Hospital way back in 1976, and found that:
- As vitamin D intake increased, the risk for colon polyps decreased,
- Vitamin D intake of 400+ IU/day has been associated with decreased risk for developing rheumatoid arthritis,
- Vitamin D intake of 400+ IU/day has been associated with decreased risk of developing multiple sclerosis.
Vitamin D is Also Critical for Heart Health
Vitamin D testing should be part of every cardiology workup. That’s because a number of studies have linked low blood levels of vitamin D with increased arterial stiffness and endothelial dysfunction, more fatal strokes, and even a higher risk of fatal cancer among patients with cardiovascular disease.
One of the biggest, and newest, studies on the correlation between vitamin D and heart health was conducted by researchers at Copenhagen University Hospital and the University of Copenhagen. They reviewed data from studies of more than 10,000 Danes and compared those with the lowest levels of vitamin D (less than 15 ng/mL) to those with the highest levels (more than 50 ng/mL).
What they found is that those with low levels of vitamin D (versus the optimal level) were 64% more likely to have a heart attack. Plus, they had a 40% higher risk of ischemic heart disease, a 57% increased risk of early death, and an 81% higher risk of dying from heart disease.
But Too Much Vitamin D Can Be Just as Harmful as Too Little
New research released in 2015 by the University of Copenhagen has found that taking too much vitamin D can be as risky as having a vitamin D deficit. For their study which was published in the Journal of Clinical Endocrinology and Metabolism, researchers followed the participants in the chronic obstructive pulmonary disease (COPD) study, which followed 250,000 people from 2004 to 2011.
What they found is that there was a J-shaped curve of mortality—which means that people with too much, or too little, vitamin D in their blood had a higher rate of mortality.
Deaths from a stroke or other cardiovascular event doubled when blood levels of vitamin D fell below 50 nmol/L. Deaths also increased by one-third when vitamin D levels in the blood rose to over 100 nmol/L. The ideal blood level of vitamin D was roughly between 50 to 100, with 70 nmol/L being the optimal level.
But while I do agree with their findings, there was a missing piece to this study—we don’t know if the research participants were also taking calcium supplements. This is an important detail because calcium supplements taken with high dose vitamin D can create coronary calcifications that can lead to cardiovascular disease.
How Much Vitamin D Should You Take?
Many people assume they’re getting enough vitamin D through their diet or through synthesis of sunlight by the skin. Our milk has also been “fortified” with vitamin D for years, leading people to the assumption that vitamin D deficiency is no longer a health concern in the Western Hemisphere. Unfortunately, though, vitamin D deficiency is still a widespread problem.
So, how much vitamin D should you take? As with all medications and other dietary supplements, vitamin D has a “sweet spot” when it comes to dosing. The current dietary guidelines still recommend 400 IU of vitamin D, but the research clearly shows that number is way too low.
The minimum recommended daily intake should be 1,000-3,000 IU daily if you are healthy. It’s also prudent to check your vitamin D level at least once a year to make sure you are in that sweet spot and getting all the benefit and none of the harm. If your vitamin D levels are low, you can take 5,000 to 10,000 IU a day for up to three months and recheck your levels.
Which Form of Vitamin D Should You Take, D2 or D3?
Vitamin D2 is found in some foods, and a lot of multivitamin formulas. But it’s less active than D3, which is the form of vitamin D your skin manufactures with exposure to UV light (sunshine). So, I prefer vitamin D3.
However, there’s one note of caution. People with adenoma of the parathyroid gland, granulomatous diseases, lymphoma, sarcoidosis, and tuberculosis need to be careful about taking vitamin D. That’s because people with these conditions often produce too much vitamin D, so you want to work closely with your doctor. But in general, many of us do not get enough vitamin D.
Now it’s your turn: Do you take vitamin D?
You May Also Be Interested In
Peter B. et al. Journal on Arteriosclerosis, Thrombosis and Vascular Biology 2012
Durup D. et al. Journal of Endocrinology and Metabolism 2015