Scientific evidence is accumulating that shows that vitamin D not only maintains the calcium balance and prevents bone deformation (rickets, osteomalacia and osteoporosis), but has many other functions in the human body (Mahan et al, 2012).
Research reported in the Arbor Clinical Nutrition Updates in 2006 indicated that adequate levels of vitamin D may counteract calcification of the arteries, prevent stroke and reduce high blood pressure.
A Japanese study found that in renal patients on dialysis, who are generally at risk of vitamin D deficiency because of renal failure, vitamin Dsupplementation significantly reduced the risk of death from heart disease.
Another study conducted in the USA with more than 8 000 adults, showed that subjects who had high vitamin D levels were significantly less likely to develop metabolic syndrome than subjects who had low vitamin D levels.
Metabolic syndrome is a cluster of conditions or derangements of normal metabolism, which include obesity (particularly abdominal obesity), insulin resistance or type 2 diabetes, hypertension, and arteriosclerosis.
It was also found that patients with congestive heart failure responded positively to a vitamin D supplement of 50 microgram a day, which they received together with a calcium supplement (Arbor, 2006).
Even more recently, a study conducted in Germany for a period exceeding 9 years with more than 9 900 older adults with ages ranging from 50 to 74 years, revealed that 59% of the subjects had inadequate vitamin D levels. These individuals had a significantly increased risk of 27% for cardiovascular disease and a 62% increased risk for these events to be fatal (Medscape, 2013).
Read: Tips to counteract the metabolic syndrome
The link between an adequate vitamin D intake or adequate levels of vitamin D in the body, and heart disease, hypertension and stroke was evident for some time before specific research studies were performed.
Researchers noticed that people living in countries far from the equator, where exposure to sunlight (which permits the formation of vitamin D in the human body) is low, were more prone to heart disease and hypertension than people living in countries where sun exposure is high.
A link between seasons, vitamin D levels and heart disease was also identified. Winter in the northern hemisphere, when sunshine is limited to a few hours a day and the cold prevents exposure of bare skin to sunlight, is associated with a higher incidence of heart disease and hypertension than the summer months.
Once these so-called epidemiological studies pointed the way towards a link between vitamin D and certain diseases, a number of well-controlled scientific studies were carried out to investigate the relationship in more detail.
A study conducted in the UK identified that a lack of vitamin D is associated with biomarkers for cardiovascular disease (e.g. interleukin-6 and C-reactive protein) and inflammation in older persons who suffered from a vitamin D deficiency.
The leader of the research team, Dr Mary Ward of the University of Ulster, stated that, “The results suggest that older adults with a deficiency in vitamin D may be at risk of having a more proinflammatory immune profile … which in itself may be a risk factor for chronic disease development.” Chronic diseases included cardiovascular disease, osteoporosis, and cognitive dysfunction (Medscape, 2014).
Read: The sun and vitamin D
What does this mean to South Africans?
Most South Africans are particularly susceptible to heart disease, hypertension and stroke – all three of which claim thousands of lives every year.
White South Africans and urbanised black South Africans are prone to heart disease, while hypertension and stroke are reaching epidemic proportions amongst black South Africans.
Although many factors play a role in these diseases (e.g. genetic predisposition, unhealthy diets, lack of exercise, smoking), evidence from other parts of the world indicate that either having an adequate dietary intake of vitamin D, or manufacturing enough vitamin D by exposing the skin to at least 20 minutes of sunlight a day to enable the body to manufacture its own supply of vitamin D, may be important in preventing heart disease, hypertension and stroke.
It would seem that countries that have abundant sunshine such as South Africa should not experience a problem with vitamin D. This may be true for South Africans who spend some time every day in the sun, but what about those of us who sit in offices or in schoolrooms all day, and no longer work or play in the sun?
In addition, people with darker skins or those who cover their bodies completely with clothing (e.g. Muslim women or swaddled babies), are less likely to produce sufficient vitamin D in their bodies.
When a winter is particularly cold and most South Africans are bundled up with only their faces and hands exposed to the ultraviolet rays of the sun – the majority are thus not manufacturing much vitamin D.
Quiz: Am I at risk for hypertension?
Tips to ensure adequate vitamin D
The simplest way to ensure that you are making some vitamin D is to expose your body to the sun for about 20 minutes a day, particularly in winter. This should also apply to infants and young children.
If you are home- or office-bound and never see the sun, it may be advisable to ask your medical doctor’s advice about taking a vitamin D supplement at least every second day.
In the USA, nutrition authorities recommend that infants should have 400 IU (International Units) or 10 microgram/day and children and adults 600 IU or 15 microgram of vitamin D per day (Mahan et al, 2012). Because excessive intakes of vitamin D can also be harmful, it is advisable not to take vitamin D supplements unless prescribed by your medical doctor.
While researchers determine exactly what effect vitamin D has on our health, including on heart disease, we can make sure that we get some sun exposure every day, and that we eat foods rich in vitamin D (egg yolk, liver, and vitamin D-enriched milk, margarine and soy milks). If you are concerned about your lack of sun exposure, ask your doctor if you need to take a vitamin D supplement.
(Arbor Clinical Nutrition Updates (2006). Vitamin D and cardiovascular disease. June 2006, No 254:1-3; Mahan LK et al (2012). Krause’s Food and the Nutrition Care Process. 13thEdition. Elsevier, Missouri, USA; Medscape (2010). Vitamin D may lower colon cancer risk. Medscape, Jan 25, 2010; Medscape (2013). Vitamin-D deficiency linked to fatal CVD. Medscape, Dec 23, 2013; Medscape (2014).Lack of vitamin D linked to CVD biomarkers, inflammation. Medscape, Feb 27, 2014).
(Photo of sunset heart from Shutterstock)
10 tips that will save you from heart trouble
Diets that protect the heart
Races respond differently to low vitamin D