Population study affirms prior indications that vitamin D may be one key to heart and mood health
by Craig Weatherby
Two new population studies add weight to the growing pile of evidence that vitamin D is a key player in heart health… and mood maintenance, too.
The sheer size of new cardiovascular study lends it added substance and certainty… and the pool for the depression investigation was pretty big, too.
Fish fit the vitamin D bill; Sockeye salmon stand out
In addition to getting vitamin D from supplements, certain fish rank among the very few substantial food sources of vitamin D, far outranking milk and other D-fortified foods.
Among fish, wild Sockeye Salmon may be the richest source of all, with a single 3.5 ounce serving surpassing the US RDA of 400 IU by about 70 percent:
Vitamin D per 3.5 ounce serving*
Sockeye Salmon 687 IU
Albacore Tuna 544 IU
Silver Salmon 430 IU
King Salmon 236 IU
Sardines 222 IU
Sablefish 169 IU
Halibut 162 IU
*For our full test results, click here.
Perhaps more importantly, the researchers had access to the participant’s blood tests for vitamin D and to their medical records, giving them a very reliable basis for analysis.
Recent years have witnessed many other studies that link low vitamin D to risk factors for heart disease, adverse cardiac events, depression, and cancer … for more on this, search our newsletter archive for “vitamin d”.
Today’s news comes from Utah-based researchers who presented two papers at the recent American Heart Association (AHA) Scientific Conference 2009 in Orlando, Florida.
Utah study adds weight to heart promise of vitamin D
A team of doctors from the Heart Institute at Intermountain Medical Center in Salt Lake City claim to have more firmly established a link between a lack of dietary vitamin D and heart disease.
For more than a year, the Intermountain Medical Center research team followed 27,686 people who were 50 years old at the outset, with no prior history of cardiovascular disease (Bair TM et al 2009).
The participants had their blood vitamin D levels tested during routine clinical care. They were divided into three groups based on their vitamin D levels (ng/mL means nanograms per milliliter):
- Normal—Over 30 ng/mL
- Low—Between 16 and 29 ng/mL
- Very low—Less than 15 ng/mL
The Utah team found that people with very low levels of vitamin D were 77 percent more likely to die, 45 percent more likely to develop coronary artery disease, and 78 percent more likely to have a stroke than those with normal levels.
They also found that participants with very low levels of vitamin D were twice as likely to suffer heart failure.
How much "D" is enough?
Most researchers involved in vitamin D studies recommend minimum blood levels ranging from 36 to 48 ng/mL (90 to 120 nmol/L)… which is the range the new diabetes study found helpful.
But the average American’s vitamin D level is a mere 25 ng/mL (60 nmol/L) or less, and the U.S RDAs (200 to 600 IU) are proven unable to raise blood levels into this range.
Though the current, official safe upper intake limit is only 2,000 IU per day, vitamin D intake is proven safe at daily levels some 25 times the current RDA for adults 51 to 70: that is, 10,000 IU per day vs. only 400 IU.
Most experts recommend taking at least 1,000 IU via food and supplements, and prefer an intake of 2,000 IU to 4,000 IU per day... unless most of your skin is exposed to 20 to 30 minutes of strong sunlight per day, which reduces the need for oral vitamin D.
Note: Darker skinned people, whose greater amount of skin pigment blocks the UV rays that make vitamin D, need either more sun exposure or more dietary vitamin D.
Leading vitamin D researcher Ronald Vieth, M.D., notes that normal human blood levels of vitamin D extend above 80 ng/mL (200 nmol/L).
Although it was not a controlled clinical study, this very large epidemiological study was conducted among a population pool well suited to detecting unexpected cardiac risk factors.
Because Utah has so many Mormon families, it has very low rates of tobacco and alcohol use, those strong “confounding” factors were not present to muddy the waters.
The results were very important, said study co-author Heidi May, Ph.D., M.S.:
“We concluded that among patients 50 years of age or older, even a moderate deficiency of Vitamin D levels was associated with developing coronary artery disease, heart failure, stroke, and death.
“This is important because Vitamin D deficiency is easily treated. If increasing levels of Vitamin D can decrease some risk associated with these cardiovascular diseases, it could have a significant public health impact. When you consider that cardiovascular disease is the leading cause of death in America, you understand how this research can help improve the length and quality of people's lives” (IMC 2009).
We couldn’t agree more.
Depression study puts vitamin D in mood-support spotlight
The same Utah team compared the vitamin D blood levels and medical records of 8,680 men and women diagnosed with cardiovascular disease, who were age 50 at the outset of the one-year study (May HT et al. 2009).
As in the heart study, they divided the people into three groups based on their vitamin D levels:
- Normal - Over 30 ng/mL
- Low -Between 15 and 30 ng/mL
- Very low - Less than 15 ng/mL
When compared to those with normal vitamin D levels, those with very low levels were more than one-third (35 percent) more likely to also have been diagnosed with depression.
Among those with no prior depression diagnosis (6,493), those with very low levels were 42 percent more likely to develop depression, and those with low levels were 31 percent more likely to develop depression.
These associations were stronger during winter.
As the authors wrote, “…levels of vitamin D were shown to be associated with depression. This was particularly evident among those with no prior incidence of depression. Though future studies are needed to further adequately establish a relationship, this study strengthens the hypothesis of the association between vitamin D and depression.”
It’s past time that the NIH funded large clinical trials testing the effects of vitamin D on major diseases.
Harvard study set the stage for new Utah results
Back in June of 2008, researchers from the Harvard School of Public Health reviewed the medical records and blood samples of 454 men between 40 and 75, selected from among 18,225 men who’d participated in the Health Professionals Follow-up Study (see “Vitamin D May Reduce Heart Attack Risk”).
The Harvard team found that men with low blood levels of vitamin D were more than twice as likely to have died from heart disease or suffered a heart attack, compared with men whose blood levels are considered sufficient, albeit suboptimal.
And even men with intermediate vitamin D levels were 60 percent more likely to have died from heart disease or suffered a heart attack, compared to men with the highest levels.
- Intermountain Medical Center (IMC). New study links vitamin D deficiency to cardiovascular disease and death. Nov. 16, 2009. Accessed at http://www.eurekalert.org/pub_releases/2009-11/imc-nsl111009.php
- Bair TM et al. Abstract 1147: Vitamin D Deficiency is Strongly Associated With Incident Death and Cardiovascular Disease in a General Healthcare Population. Circulation, Nov 2009; 120: S455.
- May HT et al. Abstract 1125: Associations of Vitamin D Levels to Depression Among a General Healthcare Population With Cardiovascular Disease. Circulation, Nov 2009; 120: S451.