New findings add broad metabolic benefits to nutrient’s anti-diabetes potential
We all know that a sunny day can do wonders for your mood.
But time in the sun — and eating fatty fish like salmon or sardines — might also help you avoid metabolic syndrome, which promotes heart disease, diabetes, and other chronic conditions.
A person is said to suffer from metabolic syndrome or MetS when they have three or more of these risk factors:
- Central obesity (excessive fat tissue in and around the abdomen).
- High blood triglycerides
- Low HDL cholesterol
- High blood pressure.
- High blood sugar
And these two problems are sometimes included in the list of factors defining metabolic syndrome:
- A pro-inflammatory state (e.g., high blood levels of C-reactive protein).
- A "pro-thrombotic" state, which promotes blood clots (e.g., high blood levels of fibrinogen or plasminogen activator inhibitor–1).
The documented risk factors for metabolic syndrome, include age, family history, and lack of exercise.
Sadly, more than one-third (35 percent) of American adults have MetS, while half of those aged 60 years or older are estimated to have metabolic syndrome.
Dangers of metabolic syndrome (MetS)
Metabolic syndrome is linked to several serious, even life-threatening diseases:
- Heart attack
- Kidney issues
- Cardiovascular disease
- Peripheral artery disease
- Non-alcoholic fatty liver disease (NAFLD)
Prior research linked low vitamin D levels to greater risk for diabetes — see Vitamin D Seen to Stall Pre-Diabetic Syndrome, Vitamin D Deterred Decline to Diabetes, and Vitamin D Clinical Trial Detects Anti-Diabetes Benefits.
Recent studies from China, Japan, and Canada also linked vitamin D deficiency to risk for metabolic syndrome (Gagnon C et al. 2012; Pan GT et al. 2016; Akter S et al. 2016).
And that link between low vitamin D levels and higher risk for metabolic syndrome was recently confirmed by Brazilian researchers.
Following our summary of that research, you’ll see some basic information about ways to get vitamin D, and optimal dietary intakes.
Brazilian study links low vitamin D levels to metabolic syndrome
Scientists from Brazil’s São Paulo Medical School looked for possible links between vitamin D deficiency and risk for metabolic syndrome.
Their study included 463 postmenopausal between the ages of 45 and 75 who were not taking vitamin D supplements and did not have cardiovascular disease.
Women who had at least three of the following five criteria were diagnosed with metabolic syndrome:
- Waist circumference greater than 34.6 inches (88 centimeters)
- Triglyceride level equal to or greater than 150mg/dL
- HDL cholesterol level less than 50mg/dL
- Blood pressure equal to or greater than 130/85mmHg
- Blood sugar (glucose) equal to or greater than 100mg/dL
The Brazilian researchers categorized vitamin D levels equal to or greater than 30ng/mL as sufficient, levels between 20 and 29ng/mL as insufficient, and levels below 20ng/mL as deficient.
As it turned out, about one third of the women fell into each category of vitamin D status:
- 32 percent had sufficient vitamin D levels
- 32.6 percent had insufficient levels
- 35.4 percent were deficient in vitamin D.
And of the women whose vitamin D levels were either insufficient or deficient, 58% had metabolic syndrome.
In contrast, only 40% of the women with sufficient vitamin D levels had metabolic syndrome.
The Brazilian team calculated that — compared to women with sufficient vitamin D levels — the odds that a woman with insufficient or deficient levels of vitamin D had metabolic syndrome were nearly twice as high as the odds for a woman with sufficient vitamin D levels.
Likewise, women who had insufficient or deficient levels of vitamin D were also much more likely to have high triglyceride levels and low HDL cholesterol levels.
And, a woman’s vitamin D levels also reflected the number of components of metabolic syndrome found in their blood tests.
In other words, greater numbers of MetS components were mirrored by lower vitamin D levels, and vice versa.
Importantly, the Brazilian team’s calculation of the odds accounted for the known effects of various factors on the risk for metabolic syndrome: age, time since menopause, body mass index, smoking and physical exercise.
As the Brazilian researchers wrote, “Vitamin D deficiency in postmenopausal women was associated with a higher prevalence of MetS.”
In addition, low levels of vitamin D among these postmenopausal women were also associated with greater risks for high triglyceride levels and low HDL cholesterol levels.
Simple deterrent to a dangerous syndrome?
Needless to say, no one nutrient or lifestyle factor can prevent the cluster of conditions defined as metabolic syndrome.
And no single epidemiological study cannot prove a cause-effect relationship between a dietary or blood factor and the presence of a health condition such as metabolic syndrome.
However, several other such studies have found the same link, which strengthens the suspicion that vitamin D plays a role in reducing the risk for the components of metabolic syndrome.
And there’s good reason to take seriously the idea that higher vitamin D levels might reduce your risk for the disease is associated with metabolic syndrome.
We say that because a British study published in Diabetes Care found that people with optimal vitamin D levels (i.e., at or above 30ng/mL) were much less likely to die from any cause or be diagnosed with a heart -related condition:
- 67% less likely to die from heart disease
- 75% less likely to die from any health-related cause
- 76% less likely to be diagnosed with congestive heart failure
- 85% less likely to suffer from sudden cardiac death, which accounts for about half of all heart -related deaths
Conversely, studies have linked vitamin D deficiency to osteoporosis, weight gain, muscle weakness, digestive issues, aches and pains, and increased risk of falling.
Get your D every day
There are three simple ways to increase your vitamin D levels—sun, seafood and supplements.
Sunlight stimulates vitamin D production in the body — aim for 20-30 minutes of unprotected exposure (i.e. no sunscreen) to sunrays daily.
Aim for the higher end of that range if you have dark skin, and for the lower end if you’re light-skinned.
If you opt for the supplement route, aim for 2,000-4,000 IU of vitamin D3 daily (see “Vitamin D: Recommended forms, intakes, and blood levels”, below).
Fatty 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 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 D2 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 erred 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.
- Aguilar M, et al. Prevalence of the Metabolic Syndrome in the United States, 2003-2012. JAMA. 2015;313(19):1973-4.
- Akter S, Eguchi M, Kurotani K, Kochi T, Kashino I, Ito R, Kuwahara K, Tsuruoka H, Kabe I, Mizoue T. Serum 25-hydroxyvitamin D and metabolic syndrome in a Japanese working population: The Furukawa Nutrition and Health Study. Nutrition. 2017 Apr;36:26-32. doi: 10.1016/j.nut.2016.02.024. Epub 2016 Mar 16.
- Gagnon C, Lu ZX, Magliano DJ, Dunstan DW, Shaw JE, Zimmet PZ, Sikaris K, Ebeling PR, Daly RM. Low serum 25-hydroxyvitamin D is associated with increased risk of the development of the metabolic syndrome at five years: results from a national, population-based prospective study (The Australian Diabetes, Obesity and Lifestyle Study: AusDiab). J Clin Endocrinol Metab. 2012 Jun;97(6):1953-61. doi: 10.1210/jc.2011-3187. Epub 2012 Mar 22.
- Kalyani RR, et al. Vitamin D treatment for the prevention of falls in older adults: systematic review and meta-analysis. J Am Geriatr Soc. 2010;58:1299-1210.
- Menant JC, et al. Relationships between serum vitamin D levels, neuromuscular and neuropsychological function and falls in older men and women. Osteoporos Int. 2012 Mar;23(3):981-9.
- Milić S, et al. Non-alcoholic fatty liver disease and obesity: biochemical, metabolic and clinical presentations. World J Gastroenterol. Jul 28, 2014; 20(28):9330-7.
- Pan GT, Guo JF, Mei SL, Zhang MX, Hu ZY, Zhong CK, Zeng CY, Liu XH, Ma QH, Li BY, Qin LQ, Zhang ZL.Vitamin D Deficiency in Relation to the Risk of Metabolic Syndrome in Middle-Aged and Elderly Patients with Type 2 Diabetes Mellitus. J Nutr Sci Vitaminol (Tokyo). 2016;62(4):213-219
- Schmitt EB, et al. Vitamin D deficiency is associated with metabolic syndrome in postmenopausal women. Maturitas. 2018 Jan; 107:97-102.
- Thomas GN, et al. Vitamin D Levels Predict All-Cause and Cardiovascular Disease Mortality in Subjects With the Metabolic Syndrome. Diabetes Care. 2012 May;35(5):1158-64.