Exploring the sense and nonsense of food and health

Too Much Vitamin D?

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Vitamin D

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Despite 91%* jump in sales, experts cautious about “benefits” of high levels, the headlines reads:

Vitamin D is most likely the hottest supplement today due to reports and claims that it not only supports bone health but also can prevent heart disease and cancer.

The problem is that most of these claims have not been thoroughly researched.  In addition, just how much vitamin D along with calcium should we be getting daily to maintain a healthy level.  And what is a healthy blood level?  I’ve seen differing reports on what is safe and effective.

A team of researchers selected by the Institute of Medicine Academy of Sciences set out to answer these questions due to the plethora of studies that suggested vitamin D in itself was good to prevent just about any disease.  The research team examined thousands of studies to see what support for the claims existed.

Their primary conclusion?   It appears that the only claim with sufficient research was that vitamin D and calcium does support bone health, a fact that has been known for years.  They admitted that the research for other claims is exciting, but dose-response data for humans has not yet been examined to pinpoint what is the optimal intake for protection of these diseases for most people if it exists at all.

Two recent reports exemplify this lack of knowledge.  The first one is entitled “Pancreatic Cancer Patients More Likely to Lack Vitamin D”.  Researchers compared 451 pancreatic cancer patients with 1,267 healthy controls and found that the average blood levels of vitamin D in cancer patients were lower than those without the cancer.  This is an observational study with no association between cause and effect. Compared to participants with the lowest levels of vitamin D, people with sufficient or only slightly low levels were at 30% lower risk of pancreatic cancer.  Very high levels of the vitamin, however, offered no additional risk-reduction benefits.

The second study looked at vitamin D and heart disease and concluded that the healthiest level of vitamin D may be neither high nor low but a value somewhere in between.  Researchers found that increasing blood levels of vitamin D are associated with decreasing amounts of a marker of inflammation called C-reactive protein (CRP).  Inflammation is linked to a greater risk for heart disease.  However, any increase in vitamin D above what is considered a low range of normal (21 nanograms per mlllilter of blood actually were associated with CRP increasing again.

So it may be that too much of a good thing like vitamin D may actually be harmful.  Some people are taking huge amounts of supplemental vitamin D.  Each 100 IU of supplemental vitamin D raises blood levels by about 1 nanogram/mL, according to the American Journal of Cardiology.

With that in mind, the Institute of Medicine did revise their recommendations for daily intake, suggesting that people from ages 1 to 70 get 600 international units (IU) per day and those over age 71 should get 800 IU.  No one should get more than 4,000.  Too much vitamin D and calcium can result in heart rhythm problems or kidney stones.

What does that mean?  Basically, a couple of glasses of milk or juice fortified with vitamin D and about 15 minutes a day in the sun provides most of us all the vitamin D we need.

The idea of “more is better” doesn’t apply here, could be dangerous. Check with your doctor before taking any supplements, especially vitamin D with its high propensity for toxicity problems.  Have your doctor measure your vitamin D levels. The consequence of overdose can include:

  • Mental retardation in young children
  • Abnormal bone growth and formation
  • Nausea, diarrhea, irritability, weight loss
  • Deposition of calcium in kidneys, liver and the heart

Vitamin D sources in foods are scarce.  Fortified foods like milk as well fish, eggs, and mushrooms are the best.  Go out in the sun for about 15 minutes a day.  Vitamin D is made from cholesterol in skin cells exposed to sunlight. Poor vitamin D status is prevalent in all age groups, especially those who live in Northern latitudes.  Breast-fed infants with little sun exposure benefit from vitamin D supplements, but check with your doctor first.


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One thought on “Too Much Vitamin D?

  1. I think they could be right, it’s vital that we get more research done on this topic but the only problem is without the press to hype up these supplements the study simple never gets enough attention, I think many people overdose on this vitamin thinking if they take more they will get a better benefit but that couldn’t be farther from the truth, I think we need better education and warnings when it comes to supplements, wouldn’t you agree?


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