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Vitamin D benefits and supplements

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 4 minutes read

Vitamin D is essential for strong bones, teeth, and healthy muscles and has many other benefits to keep you in tip-top health. We can get it from sunny summer days and some food. It’s easy to become deficient, so we need to take supplements in the darker months or depending on our ethnicity. Let’s take you through why it’s important and how you can boost levels.

What are the benefits?

Vitamin D has benefits across multiple body systems and organs and even has a role to play in helping mental health. Here are just some of its proven functions:

  • keeping bones and teeth strong by helping us absorb calcium and phosphorus from our food
  • maintaining healthy muscle function – too little vitamin D and muscles can become sore and weak
  • keeping blood glucose levels constant by regulating insulin, and therefore helping prevent you from getting diabetes, or helping if you have been diagnosed
  • keeping our heart and circulation healthy - vitamin D keeps belly fat and fat around internal organs in check by improving insulin sensitivity and reducing insulin resistance, plus it reduces high blood pressure and cholesterol, keeping the risk of heart disease at bay
  • it's essential for a healthy immune system, and some studies show that it may help in fighting respiratory infections and reducing the severity of colds and flu
  • it may help low mood and depression – the exact mechanism is not yet understood, but the brain has been found to have lots of vitamin D receptors, and some think it may regulate mood-related hormones such as dopamine and serotonin

Who needs supplements?

Your skin is the great vitamin D factory, using direct sunlight to convert it to a useful form in the body. To a lesser extent, certain foods contain vitamin D, such as oily fish, egg yolk, red meat, and some cereals and margarine, where they artificially add vitamin D.

Unfortunately, both of these sources have pitfalls. There's not enough sunshine in the winter months in northern countries and in northern states in the US. And dietary sources provide only a small amount of the vitamin D we need to keep us in optimum health. That’s where supplements are essential, especially between October and April.

Some people are at higher risk of deficiency, and it's recommended they take supplements all year round. These include those who don’t get outdoors much or cover their face and neck when they go out, the elderly, and those with darker skin, such as Asian, African, or Caribbean backgrounds. This can lead to osteoporosis.

Pregnant or breastfeeding women have higher vitamin requirements, so they should take supplements before and throughout. Babies and children up to 4 years old are recommended to take supplements, and those on a vegan diet are also at risk of low levels.

What strength of vitamin D should I take?

Vitamin D supplements are available at the pharmacy or health food stores, and they usually come in a version called vitamin D3 or cholecalciferol. You can buy this on its own, combined with other vitamins such as calcium, or as a multivitamin.

Vitamin D comes in tablets, capsules, gummies, sprays, or oral liquids. You can take it daily or at a higher dose weekly. It comes in a variety of strengths, depending on your personal needs:

  • 10 mcg (or 400 IU) for children over 4 years old
  • 20-25 mcg (800-1000 IU) for women during pregnancy
  • 25 mcg (1000 IU) for general year-round maintenance
  • 50-100 mcg (2000-4000 IU) preparations for those at high risk of severe deficiencies, such as the elderly, those with darker skin, vegans or those with dietary restrictions, and those who may be housebound or have little opportunity to get good sunlight during spring and summer

Vitamin D is often combined with calcium, which works together to properly absorb it and maintain healthy, strong bones and teeth. Combined with vitamin K, it can help maintain healthy circulation as it mops up excess calcium in the bloodstream, preventing it from forming plaques to block arteries, which can lead to a heart attack or stroke.

Vitamin D is a fat-soluble vitamin that maximizes absorption with healthy fats such as avocados, nuts, seeds, eggs, or a dressing made with olive oil. Vitamin D is stored in your body’s fatty tissues for a while.

Should I get a test before starting supplements?

If you are in a high-risk group or for anyone living in the northern US states in winter, you may want to speak to your doctor. They may want to check your levels in a blood test to determine the correct dose of vitamin D.

You should check with your doctor before taking supplements if you are on certain medications, such as digoxin or water tablets (diuretics), if you have liver or kidney disease, or if you are receiving treatment for osteoporosis or another bone condition.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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