Life Extension Magazine®

Researcher taking notes for optimal vitamin D levels blood testing

New Study Warns Against Excessive Vitamin D Intake

New research has corroborated the blood-level range of 25-hydroxyvitamin D that was long ago established as protective against degenerative diseases. But the same scientists also found that excessive vitamin D levels may increase the risk of atrial fibrillation. Blood testing is strongly advised to achieve optimal levels of this important vitamin.

Scientifically reviewed by Dr. Gary Gonzalez, MD, in August 2023. Written by: William Faloon.

William Faloon
William Faloon
New Study Warns Against Excessive Vitamin D Intake

At the annual conference of the American Heart Association held near the end of 2011, a study was presented that measured 25-hydroxyvitamin D blood levels in a large group of Americans.1

The data corroborates previously published findings showing that people with higher vitamin D blood levels have lower risks of degenerative disease. For example, compared to people in the deficient range, those with higher blood levels of 25-hydroxy-vitamin D had significantly lower risk of heart failure, depression, coronary artery disease, and kidney failure.1

Those whose 25-hydroxyvitamin D levels ranged 81–100 ng/mL had a 36% reduction in hypertension incidence when measured against the deficient group.

There was a warning issued, however, when blood 25-hydroxy-vitamin D exceeded 100 ng/mL. These individuals showed a higher risk of atrial fibrillation.

Even though the data presented at the American Heart Association conference is not yet published, we immediately sent an advisory to our members to ensure they maintain sufficient 25-hydroxyvitamin D levels to protect their health, but not exceed upper limit levels long ago established by Life Extension® and other experts.

How This Study Compares to Life Extension’s Protocol

How This Study Compares to Life Extension’s Protocol

In the January 2010 issue of Life Extension Magazine®, we reported startling findings that 85% of our members had less than optimal levels of vitamin D in their blood (as measured by 25-hydroxyvitamin D).

Based on a large volume of published data, we recommended that the optimal range of 25-hydroxy-vitamin D to protect against disease is between 50–80 ng/mL. Yet the vast majority (85%) of our dedicated members were below 50 ng/mL.

As people age their skin converts less sunlight into vitamin D. For instance, a 70-year-old will make about 25% of the vitamin D that a 20-year-old will make given equal exposure to sunlight.2,3 There are also absorption problems aging people encounter that usually requires they supplement with 5,000–7,000 IU of vitamin D a day to get their 25-hydroxyvitamin D level over 50 ng/mL.4

In the study presented at the American Heart Association conference, 25-hydroxyvitamin D blood levels were measured in 132,000 patients. Out of this large group, a small number (291 or 0.22%) had 25-hydroxyvitamin D levels over 100 ng/mL. This level exceeds what Life Extension® (and most others) has long recommended.

Those whose 25-hydroxyvitamin D level exceeded 100 ng/mL had an atrial fibrillation incidence 2.5 times greater than people in the safe ranges (below 100 ng/mL).

Atrial Fibrillation and Excess Vitamin D Status

As the population ages, an increasing percentage develops an irregular rhythm in the upper chambers of the heart called atrial fibrillation. It is the most common type of heart arrhythmia and approximately 5% of persons over 65 years of age are expected to be diagnosed with it.5

The 132,000 subjects in this vitamin D study were defined by the following categories:

Definition of Vitamin D Status 25-Hydroxyvitamin D Levels
Low Less than 20 ng/mL
Low-normal Between 21–40 ng/mL
Normal Between 41–80 ng/mL
High-normal Between 81–100 ng/mL
Excess More than 100 ng/mL

In patients with low, low-normal, normal, and high-normal levels of vitamin D, there was no increased risk of atrial fibrillation. Those with excess levels (above 100 ng/mL) of vitamin D had 2.5 times greater risk of atrial fibrillation compared to those with lower levels.

The authors of this study recommended that people have their blood tested to ensure they are taking the proper dose of vitamin D.

We at Life Extension long ago noted wide dose-response variability with vitamin D and recommended 25-hydroxyvitamin D blood tests to ensure our members are in the optimal range of between 50–80 ng/mL.

Most members are surprised that even taking 5,000 IU a day (or more) of supplemental vitamin D does not always get them above 50 ng/mL. In rare instances, however, doses of less than 5,000 IU result in blood levels greater than 100 ng/mL.

These real world findings confirm the importance of checking one’s vitamin D blood status after initiating a daily dose significantly higher than 2,000 IU to establish how much vitamin D is individually needed to achieve optimal ranges (50–80 ng/mL) and not excess levels (over 100 ng/mL).

Atrial Fibrillation May Not Have Been Caused By Vitamin D

It is interesting to note that in patients with excess amounts (greater than 100 ng/mL) of 25-hydroxyvitamin D, a significant increase in hypothyroidism (sluggish thyroid function) was noted by the researchers who presented at the American Heart Association conference.

While hyperthyroidism (overactive thyroid function) is a well-known contributing factor in atrial fibrillation, in fact hypothyroidism is an underappreciated cause of heart disease, high cholesterol, and atrial fibrillation.

The high prevalence of hypothyroidism in those with excess 25-hydroxyvitamin D represents an underappreciated risk factor for atrial fibrillation in this observational trial. In other words, it may have been hypothyroidism that caused the increased incidence of atrial fibrillation and not the vitamin D.8-10 We nonetheless continue to recommend that members keep 25-hydroxyvitamin D levels below 100 ng/mL.

Symptoms, Concerns, and Causes of Atrial Fibrillation
Symptoms, Concerns, and Causes of Atrial Fibrillation

Atrial fibrillation is usually accompanied by symptoms related to a rapid heart rate. Rapid and irregular heart rates may be perceived as palpitations or exercise intolerance. Sometimes atrial fibrillation symptoms produce angina and shortness of breath (in response to strenuous activity) or edema. An electrocardiogram test can usually diagnose atrial fibrillation.

Some common (and often preventable) causes of atrial fibrillation are:6

  • Hypertension (high blood pressure)
  • Coronary artery disease
  • Mitral stenosis (rheumatic heart disease or mitral valve prolapse)
  • Mitral regurgitation
  • Hypertrophic cardiomyopathy
  • Pericarditis
  • Previous heart surgery
  • Excessive alcohol consumption (“binge drinking”)
  • Hyperthyroidism (excess thyroid hormone secretion)

The primary danger of atrial fibrillation is that it can cause an abnormal blood clot to form in the left atrial chamber that breaks away and travels up the carotid artery causing a stroke.7 Patients with atrial fibrillation are usually prescribed anti-arrhythmic and anti-coagulant drugs to reduce this risk.

Ideally, the underlying cause of atrial fibrillation is identified and corrected so the problem goes away. Some cases of atrial fibrillation resolve themselves and require no treatment, or the patient takes steps to correct lifestyle choices that bring on atrial fibrillation.

We would expect anyone who may have developed atrial fibrillation in response to excess blood levels of 25-hydroxyvitamin D would be able to reverse the problem by lowering their vitamin D dose. Since vitamin D is fat-soluble, we would recommend that someone who had been taking 10,000 IU a day of vitamin D and whose blood levels of 25-hydroxyvitamin D are over 100 ng/mL should reduce their dose to no more than 2,000 IU a day for two-three months and then take another 25-hydroxyvitamin D blood test. If 25-hydroxyvitamin D levels drop below 50 ng/mL, they may want to initiate supplementation with an additional 2,000 to 5,000 IU a day and re-check their blood within the next three months.

Excess Vitamin D Intake Relatively Rare

Life Extension meticulously tracks its members’ blood test results to look for trends that may indicate beneficial or detrimental events occurring in their bodies.

Before members started supplementing with higher doses of vitamin D, the majority (85%) had less than optimal levels, placing them at higher risk for contracting degenerative disease.

Since members have been taking higher vitamin D doses, this insufficiency has been largely corrected with relatively few results above 100 ng/mL, which can be easily reversed by reducing the daily dose of vitamin D.

The more common challenge is someone taking 5,000 IU (and higher) of vitamin D3 a day and still not being able to reach 50 ng/mL.

Since even conventional medicine’s upper limit reference range for 25-hydroxyvitamin D is 100 ng/mL, anyone who had their blood tested should have been able to adjust their vitamin D downward if their reading was above this level.

Critical Importance of Maintaining Optimal Vitamin D Status
Critical Importance of Maintaining Optimal Vitamin D Status

No other nutrient, drug, or hormone has gained more scientific credibility than vitamin D.

Insufficient vitamin D is linked to virtually every age-related disorder including cancer,11-20 vascular disease,21-25 and chronic inflammation.12,26-30 Adults (and children) with higher vitamin D levels contract substantially fewer cold, flu, and other viral infections.31-33

Numerous biological mechanisms have been identified to explain how vitamin D protects against so many human ailments.34-38 Aging humans who fail to maintain optimal vitamin D status face increased risks of premature disability and death.

Do You Know What Your 25-hydroxyvitamin D Level Is?

If you’ve had your blood tested through Life Extension’s convenient blood testing service and misplaced your results, just call us at 1-800-208-3444 and we will mail, email, or fax you a copy of your results.

If you are taking more than 2,000 IU of supplemental vitamin D and have never had your blood tested for 25-hydroxyvitamin D, we highly recommend it. The 25-hydroxyvitamin D test is so important we now include it in our popular Male and Female Panels.

Based on the findings reported at the American Heart Association conference, we have further confirmation that the optimal ranges of 25-hydroxyvitamin D (50–80 ng/mL) are safe and significantly effective in protecting against common age-related problems. There is now a basis (not yet published) to ensure that one does not exceed 100 ng/mL, which can be readily accomplished via low-cost blood testing.

Unique Blood Testing Services

No organization is more concerned about the health and longevity of its members than Life Extension. We have not heard of any other program that mines historical blood test data to notify individuals of new findings that can affect their health.

A benefit that many members may not realize is that our computer database readily enables us to go back and identify members whose results are in potentially unsafe ranges. So when a new finding appears that we can corroborate, such as where safe 25-hydroxyvitamin D levels should be; we can notify those who are above the range or below these ranges so they can take corrective actions.

Life Extension retains copies of its clients’ previous blood tests dating back to March of 2008 so we can quickly send these reports via email or in paper form at no charge to you or your doctor. I think many of you have endured the bureaucracy that occurs whenever you have to interact with the medical establishment, as they erect barriers to the simplest patient request.

It is sometimes important to review previous blood test results in order for your doctor to identify trends that may indicate either a benign situation or one that requires medical attention. I recall sitting at lunch with a member who called his doctor and asked to obtain a copy of previous blood tests results. This member was told the cost would be $250 and results would not be produced right away. I told this member he could call Life Extension anytime and obtain previous blood test results at no charge with a turnaround time of less than three days.

Sharply Discounted Blood Tests

Sharply Discounted Blood Tests

In 1996, we initiated a low-cost service whereby members could request their own blood tests.

A lot of people express surprise when their blood test results uncovers elevated glucose, triglycerides or the many other factors that predispose them to heart attack and stroke. These individuals often tell us “these blood markers never used to be this high.” We try to respond diplomatically, but our stark message is that “your blood has never been tested when you were this old.

The irrefutable fact is that younger individuals often have low levels of vascular disease markers (such as LDL, triglycerides, glucose, etc.), but these insidious killers creep up as one ages. When blood test results reveal disease markers to be out of balance, corrective actions can be taken before irreversible disease manifests.

Culprits that preclude Americans from having their blood properly tested are inconvenience, long waits at doctor’s offices, physician ignorance about what tests to prescribe, and high costs.

Life Extension long ago solved these impediments by enabling members to order comprehensive blood tests directly, go to a drawing station in their area usually with no appointment required, and obtain the critical blood tests they need at a fraction of the price charged by commercial laboratories.

Once a year, the price of the comprehensive Male or Female Blood Test Panel is sharply discounted so that members can ascertain their disease risk status and initiate preemptive measures before acute illness strikes.

This year we are including the 25-hydroxyvitamin D blood test in these comprehensive panels at no additional charge.

I encourage you to obtain your Male or Female Blood Test Panel soon. We send your requisition out immediately, but you can walk in for your blood draw at a time during normal business hours that is convenient to you. The next page describes the many unique tests that are included in Life Extension’s comprehensive panels.

To order the Male or Female Blood Test Panel at these once-a-year discounted prices, call 1-800-208-3444 (24 hours/day).

For longer life,

For Longer Life

William Faloon


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