Here in the UK we’ve had a distinct downturn in temperatures of late, and this is something that will make us more reluctant to venture out. And even if we do, we’re likely to be very well wrapped up and protected from the elements. The net results is that at this time of year we can run a bit short on sunlight, which may impact not only on our mood but also the vitamin D levels in our bodies. There is some evidence that vitamin D deficiency might be a factor in seasonal affective disorder, and mounting evidence links lower levels of this nutrient with heightened risk of chronic disease including cancer and cardiovascular disease. For more on this, have a look at the previous blog post here.
One of the studies cited in this particular blog post found that lower vitamin D levels are associated with an increased risk of cardiovascular disease [1]. This study found that compared to vitamin D levels of 15 ng/ml or more, levels of 10-<15 ng/ml and <10 ng/ml were associated with a 53 and 80 per cent increased risk of cardiovascular disease respectively.
This week saw the publication of a study which delved deeper into the relationship between vitamin levels and cardiovascular disease risk [2].
This paper’s authors details some of the potential mechanisms by which vitamin D deficiency might enhance cardiovascular disease risk. Vitamin D deficiency predisposes, for instance, to high blood pressure, diabetes, metabolic syndrome (which can precede diabetes) and inflammation. All of these states are considered to be risk factors for cardiovascular disease. The authors also write about how vitamin D deficiency which can lead to overactivity of the parathyroid glands, which in turn appears to have a number of effects in the body that might increase cardiovascular disease risk.
They also cite several studies (including the Wang reference below) that have found lower levels of vitamin D to be associated with an elevated risk of cardiovascular events or death from cardiovascular disease.
What the authors acknowledge is the fact that we don’t have evidence in the way of intervention studies that show that increasing vitamin D levels, say through supplementation, reduced cardiovascular disease risk. However, there is such a good amount of epidemiological evidence linking higher vitamin D levels with improved health outcomes (including a reduced risk of not just cardiovascular disease, but cancer too) that ensuring adequate vitamin D levels looks like a good bet for those interested in optimising their health.
The authors of this study also question the recommended daily amounts of vitamin D in the USA. These currently stand at 200, 400 and 600 IU for individuals aged <50 years, 50-70 years and older than 70 years respectively. However, they quote research [3] which suggests that 1000-2000 IU is what is required to satisfy most individual’s needs for vitamin D.
Some of this can be achieved through appropriate sun exposure. The authors state: The most potent sources of vitamin D are sunlight (about 3,000 IU vitamin D3 per 5 to 10 min of mid-day, midyear exposure of arms and legs for a light-skinned Caucasian). The authors also offer supplements as an alternative at a dose of 50,000 IU every 2 weeks, or 1000-2000 IU per day. The article also contains a list of some of the richer food sources of vitamin D, which I have reproduced below (food followed by the IU of vitamin D it contains in each serving).
Cod liver oil, 1 tablespoon 1,360
Wild-caught salmon, 3 oz 600″1,000
Farmed salmon, 3 oz 100″250
Mackerel, cooked, 3 oz 345
Tuna fish, canned in oil, 3 oz 200
Sardines (with bones), canned in oil, drained, 1 oz 250
Vitamin D fortified milk 1 cup 98
In individuals who have proven vitamin D deficiency (25(OH)D levels of less than 20 ng/ml), the authors recommend starting by loading individuals with 50,000 IU of vitamin D per week for 8 weeks.
References:
1. Wang TJ, et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation 2008;117(4):503-11
2. Lee JH, et al. Vitamin D Deficiency: An Important, Common, and Easily Treatable Cardiovascular Risk Factor? J Am Coll Cardiol, 2008; 52:1949-1956
3. Bischoff-Ferrari HA, et al. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes Am J Clin Nutr 2006;84:18-28.
