听
How did people in the Arctic in the distant past deal with no sun in winter and weak sun the rest of the year? Did food provide vitamin D?
Advertisement
Roger Williams, Lucerne, Switzerland
According to the US National Institutes of Health, 100 grams of salmon or trout provides enough daily vitamin D for adults of most ages. This wouldn鈥檛 have been hard for a hunter-gatherer to find in Arctic Scandinavia, North America or Russia.
Guy Cox, School of medical sciences, University of Sydney, Australia
The major dietary source of vitamin D is oily fish, which was, and is, a staple food in northern latitudes (just try to separate a Swede from pickled herrings). So vitamin D deficiency wasn鈥檛 a problem. In English slums, rickets caused by vitamin D deficiency was a major problem in the 19th and early 20th century. During and after the second world war, the UK government issued cod liver oil to all children. Because of this, rickets didn鈥檛 really exist at the time. But the oil tasted awful.
鈥淩aw meat comes to the rescue: seal brain, uncooked caribou liver and muktuk, made from whale skin and blubber鈥�
Mike Follows, Sutton Coldfield, West Midlands, UK
Most people get the bulk of the vitamin D they need from the action of sunlight on their skin. Ultraviolet light turns cholesterol in the skin into vitamin D.
However, many indigenous Arctic people have a dark complexion that acts as a natural sunscreen and makes getting vitamin D this way more difficult. While it is widely believed that they derive the vitamin D they need from their diet, which includes oily fish, , yet their skeletons show no signs of rickets.
Vitamin D is biologically inert and is converted into its active form by a chemical reaction in the liver and kidneys. Even though a single exposure of UVB produces less vitamin D in darker-skinned people than in those with lighter skin, it appears that the former have adapted to be better at converting vitamin D into its active form. , yet they show fewer signs of the health impacts that would usually result from this.
David Muir, Edinburgh, UK
The traditional diet of Arctic coastal indigenous people, like the Inuit, is high in protein and fat from marine mammals and fish. Berries, roots and seaweed can supply carbohydrate, but so does fresh meat in the form of glycogen when the meat is eaten raw.
Vital vitamins and minerals are present in Inuit diets. More than adequate amounts of vitamins A and D are found in the livers and oils of cold-water fish and mammals, so the synthesis of vitamin D in the skin through exposure to the sun isn鈥檛 vital.
As the richest natural sources of vitamin C are fruits and vegetables, you would think that getting enough of this might pose a problem for Arctic indigenous communities. Once again, the consumption of raw meat comes to the rescue: vitamin C is present in uncooked caribou liver, seal brain and muktuk, a traditional food of frozen whale skin and blubber. If these were cooked, the vitamin C would be destroyed.
To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
快猫短视频 retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
You can also submit answers by post to: The Last Word, 快猫短视频, 25 Bedford Street, London WC2E 9ES.