by Craig Weatherby
According to the American Heart Association, more than 50 million Americans have metabolic syndrome—a cluster of signs linked to a greater risk of developing cardiovascular disease and type 2 diabetes or suffering a stroke.
Metabolic syndrome is defined as having three or more of these half-dozen metabolic signs, most of which are linked to junky diets and sedentary lifestyles, with genetic influences at play as well:
- Abdominal obesity (excessive fat tissue in and around the abdomen).
- High blood triglycerides, low HDL cholesterol and high LDL cholesterol: a state that fosters plaque buildups in artery walls.
- High blood pressure.
- Insulin resistance or glucose intolerance (i.e., the body can't properly use insulin or blood sugar).
- Sticky, “pro-thrombotic” blood that can promote dangerous clots (e.g., high fibrinogen or plasminogen activator inhibitor–1 levels in the blood).
- Pro-inflammatory state (e.g., elevated C-reactive protein in the blood).
And recent research suggests that lack of vitamin D may promote metabolic syndrome.
Ten years ago, researchers from Britain's Institute of Metabolic Science in Cambridge recruited 524 non-diabetic men and women aged 40-69 years, tested their blood chemistry, then tested it again 10 years later.
After adjusting for age and other risk factors, they found that the participants with the lowest vitamin D levels were the most likely to have developed two key components of metabolic syndrome—high blood sugar and insulin resistance— which are the key warning signs of developing diabetes (Forouhi NG et al. 2008).
Authors of new study put findings in public health perspective
The authors of a joint Anglo-Chinese study report that deficient levels of vitamin D may increase the risk of metabolic syndrome by 52 percent.
The study was conducted in 3,262 urban Chinese people from Beijing and Shanghai, aged between 50 and 70 years (Lu L et al. 2009).
An amazing 94 percent were vitamin D deficient or insufficient, and among this large majority of the participants, a whopping 42 percent also had metabolic syndrome.
Team leader Oscar Franco, M.D., Ph.D., noted that these results are consistent with the findings of other studies in Western populations and he suggests that vitamin D deficiency could become a global health problem:
“Vitamin D deficiency is becoming a condition that is causing a large burden of disease across the globe with particular deleterious impact among the elderly. Our results are consistent with those found in British and American populations. We found that low vitamin D levels were associated with an increased risk of having metabolic syndrome, and was also significantly associated with increased insulin resistance” (WU 2009).
Dr. Franco added that many factors help explain why older people have less vitamin D in their blood, including changes in lifestyle factors such as clothing and outdoor activity:
“As we get older our skin is less efficient at forming vitamin D and our diet may also become less varied, with a lower natural vitamin D content. Most importantly, however, the dermal [skin-based] production of vitamin D following a standard exposure to UVB light decreases with age because of atrophic skin changes. When we are older we may need to spend more time outdoors to stimulate the same levels of vitamin D we had when we were younger” (WU 2009).
He went on to say, “Vitamin D deficiency is now recognized as a worldwide concern and metabolic syndrome has become a global epidemic. More research is needed to find out why older people are more likely to have lower levels of vitamin D and how this is linked to the development of metabolic syndrome and related metabolic diseases” (WU 2009).
Dr. Franco could have also noted that you can get vitamin D from supplements and its only good food source, fatty fish.
Tuna and wild salmon provide about 200 IU (king salmon) to 600 IU (albacore tuna and sockeye salmon) per 3.5 oz (100 gram) serving, compared with the adult RDAs of 200 IU (birth to age 50) and 400 IU (aged 51-plus).
Most experts now urge the Institute of Medicine to raise the adult RDA to at least 1,000 IU... preferably 2,000 IU or even 4,000 IU.
According to all the published evidence, adults can very safely consume at least 10,000 IU per day.
The current officially recommended upper daily limit is 2,000 IU... a level vitamin D researchers decry as wholly unfounded and misleading. However, children should not exceed 2,000 IU per day unless approved by a doctor.
The National Institutes of Health defines deficiency as having blood levels below 15 nanograms per liter (ng/mL), it says that anything less than 20 ng/mL is inadequate for bone and overall health, and the NIH sets 30 ng/mL as the minimum needed for good overall health.
According to the NIH, up to 45 percent of Americans fall below the sufficiency level (20 ng/mL), and 50-78 percent have blood levels that fall below the recommended sufficiency level (30 ng/mL or more).
A team led by vitamin D expert Michael Holick, M.D., of Boston University recently recommended a target range of 30 to 100 ng/mL, based on the evidence showing that rates of major disease drop when blood levels rise into this region (Klein GL et al 2009).
Only blood levels that consistently test higher than 200 ng/mL (same as 500 nanomoles per liter)—are considered potentially toxic.
By itself, vitamin D is unlikely to prevent metabolic syndrome when a person's genetic profile and lifestyle strongly favor its development.
But given the associations found in epidemiological studies like this one, and the nutrient's broad, hormone-like effects, vitamin D could be one critical factor in the pre-diabetic developments collectively called metabolic syndrome.
Anyone who lacks enough of the “sunshine-and-seafood” vitamin is conducting an experiment... one that could threaten their own metabolic health.
- Forouhi NG et al. Baseline serum 25-hydroxy vitamin d is predictive of future glycemic status and insulin resistance: the Medical Research Council Ely Prospective Study 1990-2000. Diabetes. 2008 Oct;57(10):2619-25. Epub 2008 Jun 30.
- Klein GL et al. Standard multivitamin supplementation does not improve vitamin D insufficiency after burns. J Bone Miner Metab. 2009 Mar 17. [Epub ahead of print]
- Lu L et al. Plasma 25-hydroxyvitamin D Concentration and Metabolic Syndrome among Middle-aged and Elderly Chinese. Diabetes Care. 2009 Apr 14. [Epub ahead of print]
- Warwick Medical School (WU). Research says older people need more sun. May 11, 2009. Accessed at http://www2.warwick.ac.uk/fac/med/newsfront/research_says_older/