• Men can only meet 80% of their winter vitamin D requirement from summer sunlight stores
• A healthy adult man uses between 3,000 and 5,000 international units (iu) of vitamin D3 a day

So concluded Robert Heaney and colleagues at Creighton University in Omaha and at Boston University (US) after they had monitored the blood serum vitamin D levels of 67 men living in Omaha across two winters.

They also administered different levels of vitamin D supplements and monitored the effect these had on the men’s blood serum D3 levels.

Ed.- Omaha in Nebraska (US) is 41.2 degrees latitude North of the equator. Birmingham in the Midlands (UK) is 52° 30' North, so receives weaker sunshine overall.

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