Vitamin D can help you maintain a healthy blood pressure, partly through its effects on calcium metabolism. Vitamin D may also have independent beneficial effects on blood pressure through its many hormone actions and its ability to interact directly with your DNA to switch certain genes on and off.
Vitamin D reduces blood pressure
Researchers from the University of Edinburgh have found that sensible sun bathing can reduce your blood pressure by boosting vitamin D levels and by generating and releasing a substance called nitric oxide which dilates blood vessels.
After exposing your skin to sunlight for twenty minutes, you produce enough nitric oxide to lower your blood pressure for at least one hour. The heart health benefits of sunlight are likely to outweigh the risk of skin cancer, but if you prefer to avoid the sun then researchers at Brigham and Women’s Hospital in Boston have found that taking moderate doses of vitamin D (between 1000 iu and 4000 iu) can contribute to lower BP but different people need different doses to achieve these benefits.
Vitamin D protects against stroke
A well as helping to lower blood pressure, vitamin D appears to decrease the risk of ischemic stroke by improving blood flow throughout the brain. A large analysis of data from 10 studies, involving over 58,000 people, showed that as blood levels of vitamin D increased, the risk of stroke fell in a stepwise manner. As a result, those with the highest vitamin D levels were up to 82% less likely to experience a haemorrhagic stroke than those with the lowest levels.
In fact, studies performed throughout Europe and the US, involving over 26,000 people aged 50 plus showed that those with the highest vitamin D levels were 57% less likely to die from any medical cause over the course of the study follow-ups than those with the lowest levels. So it seems pretty clear – to help lower your blood pressure and maintain optimal health, you need a good vitamin D status.
Sensible sun exposure for vitamin D
You make vitamin D in your skin on exposure to sunlight when the UV index is greater than 3. In many countries this only occurs during certain months of the year. If you live at a latitude of 520N (which passes through the centre of the UK and Canada) you are not exposed to enough UVB radiation to make vitamin D between October and April, for example.
If you live at a latitude of 420N (which forms the northern limit of Spain and part of the border between Canada and North America) you are unable to synthesis vitamin D in your skin between November to February. Low vitamin D status is therefore widespread at northern latitudes, and, with the exception of Norway (where intakes of vitamin-D rich fish are high) most Europeans have low vitamin D levels during winter. Vitamin D levels are also low in those who habitually wear clothes that cover most of their skin, or who stay indoors most of the time.
Even when the sun is shining, though, not everyone produces vitamin D efficiently. A fascinating study involving 93 fit, healthy surfers in Hawaii found that more than half had low vitamin D levels despite getting 29 hours of sunshine exposure per week! This is partly due to genetic factors and partly due to the fact that, after 15 to 20 minutes UV exposure, the vitamin D you’ve made in your skin is rapidly broken down and destroyed by excess UV radiation.
Usual advice is to obtain no more than 20 minutes sun exposure to face, arms, hands and/or back, without sunscreen, two or three times a week, when the UV index is greater than 3, but avoid the hottest sun between 11am and 3pm. Longer exposures than this don’t provide additional benefit as vitamin D is rapidly broken down by excess UV radiation and, at the same time, your risk of skin cancer will increase.
Vitamin D and sun screen
When used properly, a sunscreen with a sun protection factor of 8 reduces vitamin D production in your skin by 95%, while SPF15 reduces vitamin D production by 99%. But most people use less sunscreen than they need, and if you develop a tan this means enough UVB radiation is still striking your skin to stimulate production of both melanin pigment (produced in response to UV damage) and some vitamin D regardless of sunscreen use. So, after you’ve achieved your recommended sun exposure, cover up and apply sufficient sunscreen according to in-pack instructions.
Vitamin D synthesis and your age
The efficiency with which you synthesise vitamin D reduces with age so that, by the time you are in your mid-60s, you make at least 50% less vitamin D in your skin as you did in your mid-20s.
One study found that people aged 62 to 80 years synthesised four times less vitamin D than those aged 20 to 30 years. Over the age of 50 you also absorb less vitamin D from your diet due to reduced secretion of enzyme-rich juices within the stomach, intestines, pancreas and bile. This double-whammy means it’s important to maintain good dietary intakes of vitamin D as you get older and also consider taking supplements.
The age-related decline in vitamin D production is now believed to contribute to the age-related increase in blood pressure that occurs as you get older. While supplements are important when you have hypertension, diet should always come first.
Food sources of vitamin D include oily fish, fish liver oils, animal liver, eggs, butter plus fortified brands of milk, margarine and cereals. Mushrooms also contain some vitamin D2 made when they are exposed to the sun.
Vitamin D and statin drugs
If you have significant hypertension, your doctor may recommend that you take a statin drug to reduce your long-term risk of heart disease and stroke. Because vitamin D3 is made in your skin from an interaction between ultra-violet rays and a cholesterol derivative (7-dehydrocholesterol), taking a statin can significantly reduce your ability to make vitamin D. Studies show that statin users are likely to be deficient in vitamin D – and one symptom of deficiency is muscle pain, which affects at least one in ten people on statin medication.
When 134 people who were both vitamin D deficient and intolerant to statins because of muscle pain, took high dose vitamin D supplements, their blood levels came back into the normal range. They then took their statin again, while still taking vitamin D supplements, and over 88% were able to tolerate the statin for six months without a recurrence of the muscle side effects. After two years, almost all (95%) were tolerant of the statin while taking vitamin D supplements.
Vitamin D self test kits
If you want to know your vitamin D status, accurate home test kits are available which involve sending a fingerprick sample of blood to a laboratory. These results will tell you if you need a vitamin D3 supplement, and usually suggest a dose to take based on your readings.
Vitamin D supplements
The recommended daily amount (RDA) for vitamin D is based on the old understanding that vitamin D was only involved in calcium absorption and maintaining bone strength. These levels (typically 5 mcg (200 iu) to 10 mcg (400 iu) are not enough if you have high blood pressure.
An intake of 25mcg (1000 iu) is more appropriate for optimum heart, brain and immune health in adults in their 40s to 50s.
A higher intake of at least 50mcg vitamin D3 may be appropriate for over 50s to offset lower production in the skin and reduced dietary absorption. In the United States, for examples, researchers have found that an intake of 100 mcg (4000 IU) is needed to maintain vitamin D levels in all older women. This intake is equivalent to the currently suggested EU Upper Safe Level.
Vitamin D3 supplements are available as tablets or capsules, as oral sprays or as a vitamin D3 topical cream that is absorbed via the skin. As it is fat soluble, vitamin D is best taken in an oil-based form, or taken with a meal that contains some fat.
NB When taking supplements, select one providing vitamin D3 (cholecalciferol) as this is more effective in maintaining blood vitamin D levels than the plant-based form, vitamin D2 (ergocalciferol).
Doses higher than the daily upper safe level for long-term use (100mcg or 4,000IU ) are best taken under medical supervision. Taking too much can lead to side effects associated with high calcium levels, such as demineralisation of bone, kidney stones, headache and weakness. If in doubt, consult your doctor.
If your blood pressure is borderline or raised, self-monitoring is key to maintaining good control.
Click here for advice on choosing a blood pressure monitor to use at home.
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