After a long, grey British winter, a spell of proper hot weather is very welcome here in the UK. We’re outside more, the sun finally has some real strength again (and importantly is finally at the right angle again. Check out my article on this here), and our bodies are able to produce vitamin D through the skin.
From early April until the end of September, most people in the UK can make vitamin D through sunlight on the skin. But there is one detail that is often missed. Whether your vitamin D comes from the sun, food or a supplement, your body still has to convert it into its active form. That process depends heavily on magnesium.
Without sufficient magnesium, vitamin D cannot be properly activated in the body. That means even people who supplement regularly, or who show adequate vitamin D levels on blood tests, may not be receiving its full benefits.
Without sufficient magnesium, vitamin D cannot be properly activated in the body.
How vitamin D works
Often referred to as the “sunshine vitamin,” vitamin D is more accurately described as a pro-hormone.
It is produced in the skin through sunlight exposure or taken in through food and supplements. Once in the body, it undergoes two conversion steps. The liver first turns it into 25-hydroxyvitamin D, and the kidneys then convert it into its active form, 1,25-dihydroxyvitamin D.
These conversion steps rely on enzymes that require magnesium. Without it, vitamin D remains largely inactive. Research published in The Journal of the American Osteopathic Association has shown that magnesium deficiency can impair this process. As a result, vitamin D may be present in the bloodstream but unable to regulate calcium, support bone strength or contribute effectively to immune function.
Why magnesium is crucial
Magnesium also helps regulate calcium in the body. Vitamin D increases calcium absorption, but without enough magnesium, that calcium can end up in soft tissues rather than bones, which may raise the risk of kidney stones or vascular issues. Research shows that improving magnesium intake can support vitamin D activity and bone health without needing very high doses of vitamin D. In other words, the two nutrients work together, and supplementing one without the other may limit its effectiveness.
Are we getting enough magnesium?
Many modern diets are not especially magnesium-rich. Stress, alcohol and high caffeine intake can also increase the body’s demand for magnesium, which means it is not always easy to get enough from food alone.
Good food sources include leafy greens, pumpkin seeds, almonds, cashews, dark chocolate, beans, lentils and whole grains. But the problem is consistency. A handful of spinach here and there is not the same as a consistently magnesium-rich diet.
Some people will get there through diet. Many will not.
Choosing the right magnesium
Not all magnesium supplements are worth taking. Some, like magnesium oxide or citrate, are poorly absorbed. They may claim a higher elemental level but if your body can't absorb it effectively, it's mostly pointless. Chelated forms, such as TRAACS magnesium bisglycinate, are generally better absorbed because the mineral is bound to (not just mixed) amino acids. This helps it reach the cells where it's needed and is usually gentler on the stomach. The added benefit of the glycine is a calming effect, supporting sleep and stress management.
Making it work for you
I certainly hear of this and you may have experienced it yourself: taking vitamin D all winter without noticing any improvement in energy or immunity. Adding magnesium, around 240mg a day from supplements or magnesium-rich foods such as leafy greens, nuts and seeds, can make a significant difference. Over a few weeks, it can help activate vitamin D while also supporting muscle function, energy metabolism and the nervous system.
Maximising your summer vitamin D
If you are spending more time outside now the weather has improved, it's a good opportunity to support your natural vitamin D levels.
But don't forget the cofactor.
Magnesium is one of the key minerals that helps your body activate and use vitamin D. Without enough of it, you may not get the full benefit from the vitamin D you make in the sun or take as a supplement.
So yes, enjoy the sunshine sensibly. Get outdoors. Let your body do what it is designed to do.
Just remember that vitamin D and any vitamin, mineral or indeed part of the human body, does not work in isolation. Magnesium is a big part of the process.
Wondering if you might be deficient in Magnesium? Have a read of this article which highlights some of the common signs and symptoms.
