We've had a properly lovely summer by British standards — plenty of sunshine, warm evenings and hopefully enough time outdoors to enjoy it.
But now that September is here, it's worth thinking about vitamin D.
Vitamin D is unusual because our bodies can make it from sunlight. Unfortunately, the sun in the UK isn't strong enough to produce significant amounts of vitamin D through our skin during the winter months. From around October until early spring, most of us need to rely on our diet and supplements instead.
So September is a good time to start thinking about your winter vitamin D intake, rather than waiting until the middle of winter when your levels may already have fallen.
Vitamin D is important for maintaining healthy bones and muscles, and low levels have been associated with:
The NHS recommends that adults consider taking 400 IU (10 micrograms) of vitamin D daily during autumn and winter. This is essentially a maintenance dose intended to help prevent deficiency in the general population.
But 400 IU isn't necessarily enough if your vitamin D levels are already low.
Some people are more likely to have low vitamin D throughout the year, including those who:
If you're in one of these groups, you may need more than the standard maintenance dose.
If you've previously been diagnosed with vitamin D deficiency, considerably higher doses may be recommended to restore your levels. Doses up to 4,000 IU a day are considered the upper safe daily intake for adults, although treatment of significant deficiency can involve higher doses for a limited period under medical supervision.
You'll often see vitamin D supplements combined with vitamin K2 and calcium, particularly in products aimed at supporting bone health.
Vitamin D helps the body absorb calcium, while vitamin K is involved in normal bone metabolism. Calcium is, of course, one of the main building blocks of bone.
You don't necessarily need to take all three, but they are commonly combined in good quality bone-health supplements.
If you're generally healthy and don't have any particular risk factors, 400-800 IU (10 micrograms) of vitamin D daily from October through March is a sensible place to start.
If you're at higher risk of deficiency, have previously had low vitamin D, or have symptoms that could be related to deficiency, it's worth discussing whether you need a higher dose — and whether testing your vitamin D level would be useful.
At C3, we stock a vitamin D3 supplement containing 4,000 IU of vitamin D3 with vitamin K2 for people who want a higher-dose option.
The important thing is to know what you're taking and why.
September is a good time to start thinking about it — before winter starts taking its toll.
