Vitamin D has come in for a lot of attention in recent months because of its role in protecting against Covid-19 infection.
In September, we reported on a study in the journal Nutrients, which showed that severe vitamin D deficiency is associated with increased risk of severe Covid-19 infection and death; and that most Covid-19 patients have a vitamin D deficiency.
But vitamin D also has other functions in addition to immune protection. As well as reports about its efficacy in protecting against infection, we’ve reported on its links to sound mental health and to proper weight management.
Now a new study out of Australia is showing that the vitamin may have an essential role to play in the health of our hearts.
Vitamin D and heart health
What is vitamin D?
Vitamin D is perhaps most appropriately classified as a steroid hormone rather than a vitamin. It is derived either through the action of ultraviolet light on the skin, which causes a particular form of cholesterol to convert into a form of vitamin D, or through dietary sources, including supplementation.
Although the prevalence of vitamin D deficiency, which generally used to be associated with rickets (a disease that causes softening of the bones), was reduced in the United States by programs including milk fortification, physicians have noted an increase in deficiency in recent decades, including a return of rickets in children.
In China, studies have led to estimates that around 40% of the population suffer from vitamin D deficiency in winter, and a similar percentage is suggested for the global population.
While vitamin D can be consumed through dietary sources, most experts agree that it is difficult to reach the recommended daily amounts through diet alone. As a result, exposure to sunlight or supplementation is necessary to consume enough.
With regard to sunlight exposure, the time of year, time of day, geographic latitude, cloud cover, pollution, skin melanin content (i.e. skin darkness), and sunscreen use all affect UV radiation exposure and vitamin D synthesis. For many, as a result, it will be necessary to supplement with vitamin D to ensure recommended daily amounts are met.
Scientists from the UniSA’s Australian Centre for Precision Health at SAHMRI have identified genetic evidence, the first of its kind, for a role of vitamin D deficiency in causing cardiovascular disease.
The study shows that people with vitamin D deficiency are more likely to suffer from heart disease and higher blood pressure, than people with normal levels of vitamin D.
For participants with the lowest concentrations the risk of heart disease was more than double that seen for those with sufficient concentrations.
Cardiovascular diseases (CVD) are the leading cause of death worldwide, causing an estimated 17.9 million deaths a year.
In Australia, where the research took place, CVD accounts for one in four deaths and is estimated to cost the Australian economy five billion dollars each year – more than any other disease.
Worldwide, vitamin D deficiency is thought to occur in as much as 40% of the population.
Chief investigator, UniSA’s Prof Elina Hyppönen says appreciating the role of vitamin D deficiency for heart health could help reduce the global burden of cardiovascular disease.
“Severe deficiency is relatively rare, but in settings where this does occur it is very important to be proactive and avoid negative effects on the heart. For example, deficiency can be a problem for people living in residential care who may have limited exposure to sun,” Prof Hyppönen says.
“We can also get vitamin D from food, including oily fish, eggs and fortified foods and drinks. This said, food is unfortunately a relatively poor source of vitamin D, and even an otherwise healthy diet does not typically contain enough.
“If we don’t get any vitamin D through the sun, this is one of the rare nutrients for which we sometimes need to take a daily supplement to keep up with the requirements.
“Understanding the connection between low levels of vitamin D and CVD is especially important, given the global prevalence of this deadly condition.
“Our results are exciting as they suggest that if we can raise levels of vitamin D within norms, we should also affect rates of CVD. In our study population, by increasing vitamin D-deficient individuals to levels of at least 50 nmol/L, we estimate that 4.4 per cent of all CVD cases could have been prevented.”
This large-scale Mendelian study used a new genetic approach that allowed the team to assess how increasing levels can affect CVD risk based on how high the participants actual vitamin D levels were. The study used information from up to 267,980 individuals which allowed the team to provide robust statistical evidence for the link between vitamin D deficiency and CVD.
“It is not ethical to recruit people with vitamin D deficiency to a randomised controlled trial and to leave them without treatment for long periods.” Prof Hyppönen says.
“It is exactly this type of difficult setting which demonstrates the power of our genetic approach, given we can show how improving concentrations affects the risk in those most in need, without exposing participants to any harm.
“Those with the lowest concentrations are likely to have the strongest effects, yet a population-wide approach to eradicate vitamin D deficiency could reduce the global burden of CVDs.”
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