Lack of vitamin D is a global health problem that increases mortality rates. At this point, many studies have shown that having adequate amounts of vitamin D in the blood can lower your risk of cardiovascular disease, which is the leading cause of death. In a new review article that is published in Nutrients, the authors look closer at vitamin D supplementation to see if it can prevent stroke and speed up rehabilitation. It is essential that vitamin D supplements have good bioavailability so they can optimize blood levels of the nutrient.
Vitamin D is a lipid-soluble vitamin that was discovered in 1913 by the two biochemists, Elmer McCollum and Marguerite Davis. Ever since, the vitamin has been subject to intense research.
Vitamin D is considered a steroid hormone that is converted in a two-step process. The precursor of vitamin D is cholecalciferol, which is synthesized when cholesterol in the skin is exposed to UV light from the sun. This is the form of vitamin D that is found in normal supplements. In the liver, cholecalciferol is converted into 25(OH)D, the type of vitamin D that is measured in blood tests. When vitamin D is needed in our cells, it is converted into the active form known as 1,25-dihydroxyvitamin D3. This conversion takes place in the kidneys and certain other tissues.
Vitamin D is important for our uptake and utilization of calcium and magnesium, and it is also involved in the regulation of different genes and cell functions by way of different on-off switches. Vitamin D is of vital importance to the prevention of osteoporosis and infections like influenza and coronavirus, autoimmune diseases, depression, cardiovascular diseases, type 2 diabetes, and cancer.
Around one billion people worldwide are believed to lack vitamin D, and the widespread deficiency contributes to a host of different diseases. In their new review article which is published in Nutrients, the authors wanted to look closer at vitamin D’s role in the cardiovascular system and brain. Also, they wanted to see if vitamin D supplementation could help patients recover from a stroke. They started by searching databases such as MEDLINE and EMBASE and analyzed 125 articles, including 54 meta-analyses published within the last 10 years.
- At our latitude, the sun during the summer is the primary vitamin D source
- A normal diet only provides limited amounts of the vitamin from sources like oily fish, cod liver, cod roe, eggs, and high-fat dairy products
- Factors that result in widespread deficiency include winter, spending too much time indoors, sun screen with sun factor, ageing processes, overweight, and type 2 diabetes.
Vitamin D’s role in the brain
Most cells in the brain have vitamin D receptors (VDR) which is not surprising, considering vitamin D’s role in neuron function, brain plasticity, cognitive functions, and the prevention of dementia, atherosclerosis, and stroke. The nutrient affects different mechanisms such as the regulation of transport molecules to the central nervous system, reduction of oxidative stress, reduction of pro-inflammatory cytokines, regulation of lipids such as cholesterol, and reduction of damage to blood vessels and neurons.
It has been seen that lack vitamin D in seniors may reduce the volume of their brain and hippocampus. A vitamin D deficiency may generally lead to a host of different harmful changes in different parts of the brain
- Ischemic stroke often follows in the wake of a minor blood clot in the brain, causing a failure in the blood supply to the surrounding tissue.
- Hemorrhagic stroke (bleeds) occurs when blood from an artery suddenly begins bleeding into the brain and causes a hematoma.
Vitamin D and the risk of stroke
Stroke is believed to be the second-most common cause of death globally, and it is also assumed that being vitamin D-deficient contributes to the problem. For example, a large Chinese study has shown that low blood levels of vitamin D are linked to an increased risk of ischemic stroke and even worsens the prognosis after a stroke.
On the other hand, high levels of vitamin D in the blood are able to lower the risk of atherosclerosis and cardiovascular disease, including stroke. Several recent studies have shown how important to take vitamin D to prevent stroke.
- Vitamin D is a lipid-soluble vitamin, which is why it is best to take the nutrient in capsules where it is bound to some sort of oil
- People have different needs for vitamin D. On the market, you can find high-dosed supplements that contain 20-100 micrograms of vitamin D
Vitamin D’s effect on rehabilitation following a stroke
Lack of vitamin D not only increases the risk of stroke and worsens the prognosis it may also contribute to the cognitive decline and impaired physical performance that often follow in the wake of a stroke. It even looks as if vitamin D supplementation after a stroke can reduce several of the harmful late effects. According to the authors, we need more studies with more than 1,000 patients that are followed for a five-year period.
It is also important to make sure the patients get vitamin D in a form that is easy to absorb and can optimize blood levels of the nutrient. Besides vitamin D, diet and lifestyle in general have a lot to say in terms of preventing and treating stroke.
The new review article is published in Nutrients.
Measuring vitamin D in the blood
- The lower threshold level is 50 nmol/L
- Levels above 75 nmol/L are considered to be adequate
- Many scientists believe optimal level are in the range of 100-200 nmol/L
- The upper threshold level is 160 nmol/L
Klaudia Marek et al. The Role of Vitamin D in Stroke Prevention and the Effects of Its Supplementation for Post-Stroke Rehabilitation: A Narrative Review. Nutrients 4 July 2022
Hassan Yahaya. Could vitamin D deficiency increase the risk of heart disease? MedicalNewsToday. January 6, 2022
Ang Zhou et al. Non – linear Mendelian randomization analyses support a role for vitamin D deficiency in cardiovascular disease risk. European Heart Journal. 05 December 2021.
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