Did you know low vitamin D levels could be impacting your heart health? We talk to experts about how and why this nutrient may be a factor in preventing strokes.

How is vitamin D related to heart health?

By helping to regulate the deposition of calcium in bones, vitamin D reduces the amount of calcium laid down in artery walls. This not only helps to improve blood pressure control but helps to maintain healthy blood flow to important organs such as the heart and the brain. As a result, people with optimal vitamin D levels are also less likely to experience a heart attack or stroke than those with a low vitamin D level.

Vitamin D and stroke

Stroke is the second leading cause of death among people aged 60 years and over, and the underlying cause is hardening of the arteries. This increases blood pressure, which may contribute to a burst blood vessel in the brain (haemorrhagic stroke) and limits blood flow, leading to loss of brain cells due to lack of oxygen (ischaemic stroke).

A study involving 15,000 adults confirmed that those with the lowest vitamin D levels were 30% more likely to have high blood pressure than those with optimal levels.1 By lowering blood pressure and improving blood flow, vitamin D also helps to protect against stroke.

Data from 10 studies, involving over 58,000 people found a clear, increasing risk of stroke with decreasing vitamin D blood levels. Those with the highest levels were up to 82% less likely to have a haemorrhagic stroke than those with low levels.2 Another analysis of 19 studies, found that those with the lowest vitamin D levels were 62% more likely to experience a stroke than those with the highest levels.3 This makes it important to maintain good vitamin D levels in later life, especially if you are among the one in three adults with high blood pressure.

In fact, studies carried out in eight countries, and involving over 26,000 men and women aged 50 or over, showed that people with the highest vitamin D levels were 57% less likely to die from any medical cause, including heart attack and stroke, during the study follow ups than those with the lowest levels.4

How to obtain more vitamin D

Diet should always come first, but it’s difficult to get enough vitamin D from your food unless you eat two servings of oily fish (eg salmon, mackerel, herrings, sardines) per week and regularly include some liver products, egg yolks, butter and fortified products such as cereals. Even so, the typical UK diet only provides around a tenth of most people’s daily needs.

You can also make vitamin D3 in your skin on exposure to sunlight when the UV index is greater than 3 which, in the UK, is usually during spring and summer months. If you use a sunscreen with a sun protection factor of SPF15 to guard against skin cancer, however, that will reduce your vitamin D production by 99%.

If you are over the age of 50, your ability to synthesise vitamin D in your skin also reduces by at least half between the ages of 20 to 80 years – often more. In one study, researchers found that people aged 62 to 80 years synthesised four times less natural vitamin D than those aged 20 to 30 years.5 This makes a vitamin D supplement particularly important for older people, for whom low levels of vitamin D may contribute to an increased stroke risk.

Did you know? According to Public Health England, 23% of adults aged 19 to 64 years, 21% of adults aged 65 years and above and 22% of children aged 11 to 18 years have low blood levels of vitamin D.

How much vitamin D do you need?

The EU RDA is 5 mcg (200 IU) per day, although Public Health England now recommend that everyone takes a supplement providing 10mcg vitamin D, at least during the cold months of the year. This is very much a minimum to prevent deficiency diseases such as rickets, osteomalacia (softening bones) and osteoporosis (brittle bones due to reduced calcium absorption).

For heart health benefits, I believe that most adults would benefit from taking 25mcg (1.000 IU) per day, increasing to 50 mcg (2,000 IU) per day from the age of 50 onwards to offset lower production in the skin and reduced dietary absorption.

What is the safe upper intake?

The European Food Safety Authority recently suggested a tolerable upper intake level of 100mcg per day (4000 IU).6

What to look for in a supplement

There are two types of vitamin D supplement available - vitamin D2 (ergocalciferol, the plant form) and vitamin D3 (cholecalciferol – the animal form). Research shows that vitamin D3 is superior at maintaining blood vitamin D levels, which is not surprising as we are not plants!

You can take vitamin D3 supplements as tablets, capsules, gummies or as an oral spray. Studies have confirmed that a vitamin D3 oral spray is equally effective at raising blood vitamin D concentrations as taking it in capsule form.

For more information on how to keep your heart healthy, see our heart health hub.


References
1Martins, D (2007). Prevalence of cardiovascular risk factors and the serum levels of 25-hydroxyvitamin D in the United States: data from the Third National Health and Nutrition Examination Survey, Arch Int Med
2Brøndum-Jacobsen, P (2013). 25-hydroxyvitamin D and symptomatic ischemic stroke: an original study and meta-analysis, Ann Neurol
3Zhou, R (2018). Lower Vitamin D Status Is Associated with an Increased Risk of Ischemic Stroke: A Systematic Review and Meta-Analysis Nutrients, NCBI
4Schöttker, B (2014). Vitamin D and mortality: meta-analysis of individual participant data from a large consortium of cohort studies from Europe and the United States, BMJ
5Heaney, RP (2006). Barriers to Optimizing Vitamin D3 Intake for the Elderly, J Nutr.
6(2012). Scientific Opinion on the Tolerable Upper Intake Level of vitamin D, EFSA Journal

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.

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