New benefits seen for the “sunshine-and-seafood” nutrient, which is depleted by darker days 11/09/2017
Claims for “super” supplements make great bait for online clicks.
And marketers make serious money by touting exotic supplements as the latest, greatest health remedy or enhancer.
People never cease searching for magic pills and panaceas to protect or improve their health — preferably without side effects.
As the term itself implies, “magic” pills don’t exist, but some supplements — such as omega-3s and vitamin D — come very close to deserving that designation.
Better still, certain natural sources — sunshine and seafood — provide as much or more vitamin D as you can get from pills.
Sadly, few people get enough, as we reported in World Panel Calls “D” Deficiency Rampant and Rising.
Because winter offers the least and weakest sunshine, now’s the time to ensure that you’re getting adequate vitamin D from foods and/or supplements.
To learn more about optimal vitamin D levels and intakes, see “Vitamin D: Recommended forms, intakes, and blood levels” below.
The vital nature of vitamin D
Vitamin D is exceptional in that it plays important roles in virtually every disease, body system, and aging-related condition.
Vitamin D appears to reduce your risk of premature death from all causes, yet most Americans remain woefully deficient in the “sunshine-and-seafood” nutrient.
Let’s take a look at seven reasons why getting ample vitamin D is a bright (excuse the pun) idea.
#1 – Vitamin D and blood sugar
Low levels of vitamin D have been strongly linked to blood sugar imbalances.
For example, diabetics who took 50,000 IU of vitamin D3 per week for eight weeks enjoyed significant improvements in their blood sugar and insulin levels.
Another study found that people with diabetes tend to have lower vitamin D levels and higher A1C (glycosylated hemoglobin) levels — a key marker of long-term blood sugar control—than people without diabetes.
Moreover, as vitamin D levels dropped, glycosylated hemoglobin levels rose, along with blood sugar levels.
#2 – Vitamin D for bone health
By now, everyone knows that vitamin D is critical to bone health.
In fact, it's more important than calcium – see Vitamin D Called More Critical for Bones than High-Dose Calcium.
And vitamin D can be more powerful when combined with other bone-building nutrients, such as various minerals and vitamin K.
That fact is reflected in a recent Norwegian study among older people suffering from hip fractures.
After drawing blood samples from hip fracture patients and a control group, the Norwegian team reported that the fracture patients had significantly lower levels of vitamins D and K, and they found a strong link between this twin deficiency and higher risk of hip fractures.
#3 – Vitamin D versus cancer
Many epidemiological (population) studies link low vitamin D levels to greater cancer risk.
Unfortunately, as we reported in Vitamin D Intakes Called Too Low to Nix Cancer, most Americans don’t have enough vitamin D to seriously dent their cancer risk.
The link between low vitamin D and greater risk for breast cancer has received a lot of attention, but the anticancer benefits of vitamin D appear far broader.
For example, see Vitamin D May Lower Risk of Ovarian, Breast, Kidney, and Colon Cancers.
Strong links exist between vitamin D levels and the risks for all invasive forms of cancer, as demonstrated in a study by researchers from the University of California, Ohio’s
Creighton University, and Grassroots Health — a consortium of vitamin D researchers.
They examined data from two studies:
- Lappe Cohort – 1,169 participants
- Grassroots Health cohort – 1,135 participants
They then compared the participants vitamin D levels to their risk of getting cancer over nearly four years.
The results showed that cancer rates were lower in people with higher vitamin D levels, and women who had vitamin D levels of 40 ng/mL or higher were 67% less likely to develop cancer, versus women whose vitamin D levels fell below 20 ng/mL.
The anti-sun position taken by some dermatologists — who fear that excess sun exposure causes skin cancer — ignores the ample, fast-growing evidence that the vitamin D produced by greater sun exposure helps prevent many common cancers.
As we reported in Vitamin D and Cancer: A Sunny Follow-Up Story, some dermatologists are now persuaded that the anti-cancer benefits of sun outweigh the cancer-promoting risks.
That tide began to turn more than 10 years ago, when the Associated Press published this quote from Allan Halpern, M.D., Chief dermatologist at Memorial Sloan-Kettering Cancer Center: “I find the evidence [that the benefits of sun outweigh the risks] to be mounting and increasingly compelling.”
Of course, you should keep your complexion in mind — people with fair skin have less protection — and avoid sunburn, which signals possible DNA damage in deeper layers of the skin.
And when picking a sunscreen, choose a high SPF factor product — e.g., SPF 30 or higher — that protects against both UVA and UVB rays.
#4 – Vitamin D may deflect dementia
Low levels of vitamin D have been shown to be associated with dementia risk.
For example, a 17-year Finnish study involving 5,010 men and women — whose brains were healthy at the outset — found that those with higher vitamin D levels were much less likely to have developed dementia by its conclusion.
Two years ago, researchers from UC Davis and Rutgers University reported the alarming results of a five-year study conducted among 382 older, racially and ethnically diverse men and women in Northern California.
At the outset of the Northern California study, the participants were either cognitively normal, or had mild cognitive impairment or dementia.
About one in four (26%) of the participants were vitamin D deficient, while 35% had higher but still insufficient levels.
Just over half (54%) of the white participants had low vitamin D levels, compared with almost three out of four (70%) of African-Americans and Hispanics.
That ethnic discrepancy — one seen in many other studies — is almost certainly caused by darker skin, which blocks more of the UV sunrays that stimulate production of vitamin D in our skin.
The rate of cognitive decline was two to three times faster in the vitamin D deficient participants in Northern California, compared with the rate of decline seen among people with adequate vitamin D levels.
Put another way, cognitive abilities among the vitamin D deficient participants declined as much in two years as they did after five years in those with adequate vitamin D levels.
Low vitamin D levels were linked to worse cognitive performance, including memory loss — mental deficits associated with greater risk for Alzheimer’s disease and dementia.
“We expected to see declines in individuals with low vitamin D status,” said Charles DeCarli, director of the UC Davis Alzheimer’s Disease Center. “What was unexpected was how profoundly and rapidly [low vitamin D] impacts cognition.”
Likewise, a four-year study from the Minneapolis VA Medical Center, conducted among 6,257 older women, linked lower vitamin D levels to higher risk for dementia — and a Wake Forest School of Medicine study among 2,777 older men and women found the same distressing link.
#5 – Vitamin D helps heart health
Vitamin D supports key aspects of cardiovascular health, including cholesterol profiles and blood pressure, and is linked to reduced risk for heart failure and heart attacks.
Earlier this year, researchers from China and Pennsylvania State University reported the results of a huge evidence review covering 34 studies with 180,667 participants,
The results of their “meta-analysis” linked higher blood levels of vitamin D to significantly lower risk for adverse cardiovascular events — such as heart attacks — and a lower risk of dying from cardiovascular disease.
Importantly, the evidence review revealed a “dose-response” effect that strengthens their conclusions: Every 10-ng/mL rise in vitamin D levels reduced the risk of adverse cardiac events by 10%, and the risk of dying from cardiovascular disease by 12%.
Further strengthening the findings of the Chinese/Penn State evidence review, they echoed the results of a similar 2012 review by scientists at Boston’s Brigham and Women’s Hospital.
The vitamin’s specific effects on heart disease were explored in a Turkish study involving 209 participants with coronary artery disease (CAD) and 102 healthy controls (average age of 63 years).
The Turkish team tested vitamin D’s effect on both the extent and the “complexity” of CAD in the participants.
They found that people with CAD had lower vitamin D blood levels than the healthy subjects, and that lower blood vitamin D levels were linked to higher blood pressure, higher inflammation levels, higher body mass index (BMI), and greater complexity in their disease.
Unsurprisingly, the Turkish researchers concluded that lack of vitamin D may promote coronary artery disease and worsen its severity.
#6 – Vitamin D’s critical importance to immunity
Vitamin D also plays an outsized role when it comes to immunity.
It’s a critical element in both our “innate” immune system and more sophisticated “adaptive” immune system — see Vitamin D Activates Two Key Immune Systems.
Fitting with that fact, low levels of vitamin D have been linked to greater risk for infections, including upper respiratory infections such as colds or flu.
The evidence that vitamin D wards off viral infections is encouraging but a bit mixed: see Flu and Colds Risk Linked to Vitamin D Lack, Vitamin D Cuts Flu Rate in First Clinical Trial, and Friendly Bugs Cut Colds; Vitamin D Defeated.
#7 – Vitamin D for weight control
Finally, vitamin D may even help us fight the anatomical “battle of the bulge”.
Researchers from Kaiser Permanente Northwest studied 4,659 women aged 65 or older, and found that those with higher vitamin D levels enjoyed less weight gain over the course of 4.5 years.
Consequently, they speculated that low vitamin D levels may predispose a person to accumulating more body fat.
Another study found that taking vitamin D may even help decrease body fat.
Nearly 80 overweight or obese women took either 25 mcg of vitamin D or a placebo for 12 weeks. The women taking vitamin D saw a significant cut in body fat mass, compared to the placebo group, and as vitamin D levels rose, body fat mass dropped.
How to dial up your D
Good, old-fashioned sunshine is people’s primary source of vitamin D.
But, the chances you are not getting — and can't easily get — enough sunshine to overcome a deficiency.
That’s why experts recommend eating foods high in vitamin D — fatty fish serve as the best food source, by far — and/or taking supplemental vitamin D3, which is the most efficient form for your body.
Depending on your current vitamin D status — as determined by a blood test — leading researchers recommend consuming from 2,000 to 4,000 IU per day from any combination of supplements and fatty fish.
If you’re unsure of your vitamin D status, you can safely take 4,000 IU daily until get your blood levels tested.
Fatty fish fill the vitamin D bill
Oily fish like salmon, tuna, and sardines rank among the very few substantial food sources of vitamin D, far outranking milk and other D-fortified foods.
Among fish, wild sockeye salmon rank as the richest source, with a single 3.5 ounce serving surpassing the US RDA of 600 IU.
Average Vitamin D level per 3.5 oz 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
Vitamin D: Recommended forms, intakes, and blood levels
It’s important to know that supplemental vitamin D comes in two forms: D2 and D3.
It’s pretty clear that vitamin D3 — the form found in seafood — is more beneficial per dose unit, versus the vitamin D2 found in mushrooms and other plant sources.
In the U.S., most milk is voluntarily fortified with about 100 IU of vitamin D per 8-oz glass, making it a substantial source, but nowhere near as good as fatty fish.
In 2010, an expert committee convened by the U.S. Institute of Medicine established higher RDAs and safe intake limits for vitamin D:
- Infants from birth to one year – 400 IU daily
- Ages one to 70 years – 600 IU daily
- Ages 71 or higher – 800 IU daily
- Tolerable Upper Intake Level (maximum safe intake) – 4,000 IU daily
Many expert vitamin D researchers say the evidence shows it’s safe to take up to 10,000 IU of supplemental vitamin D per day, but we’d recommend sticking with the IOM’s more conservative upper limit.
And, as we reported two years ago, four separate studies found that the IOM errred in its calculations of the optimal and safe dietary intakes — see Vitamin D RDA Deemed Much too Low.
As to adequate blood levels, the IOM recommends maintaining at least 20 ng/mL (IOM 2011).
In contrast, an expert task force convened by the Endocrine Society recommends maintaining vitamin D levels of at least 30 ng/mL (Holick MF et al. 2011).
Let’s be clear. Vitamin D’s long-overlooked value relates to the beneficial effects of sharply lifting the alarmingly low blood levels found in most Americans.
And it’s neither more healthful — nor necessarily wise — to get more dietary vitamin D than you need to raise blood levels into the optimal range.
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