A scientist reveals why oranges aren’t the cold cure many people think they are

The idea that a daily glass of orange juice can prevent — or even cure a cold is practically folklore at this point. Every winter, plenty of people tweak their diets hoping to “boost” their immune system and load up on vitamins.

But according to nutrition and health professor Susanne Gjedsted Bügel from the University of Copenhagen, science simply doesn’t back up that belief. She calls the idea that vitamin C fights off colds “a pretty persistent myth,” noting that true vitamin C deficiency is actually rare.

If you already eat a balanced diet, adding an extra glass of orange juice won’t make much of a difference. However, there is one vitamin that tends to drop significantly during the winter months — and it’s not vitamin C.

The vitamin you should worry about in winter

Unlike vitamin C, vitamin D is a real concern once the days get shorter. Our main source of vitamin D is sunlight, and during winter the sun’s rays simply aren’t strong enough in many regions to trigger adequate production in the skin. That’s why so many people fall below recommended levels this time of year.

You can get vitamin D from food — especially fatty fish like salmon or mackerel — but diet alone often isn’t enough.

Because of that, Bügel says taking a vitamin D supplement is generally the safer bet in winter. Low vitamin D can show up as fatigue, weakness, or muscle aches, though sometimes it causes no obvious symptoms at all. Long-term deficiency is linked to a higher risk of osteoporosis and bone fractures.

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