It is not the image classically associated with peak health and fitness. But scientists have found that ginger hair and a pale skin offer an important advantage in the survival game. Redheads, it would seem, boast a secret genetic weapon which enables them to fight off certain debilitating and potentially deadly illnesses more efficiently than blondes or brunettes. A pale complexion permits more sunlight into the skin, where it encourages the productionof vitamin D. This helps to prevent rickets, a disease which progressively weakens bone structures, and the lung disease tuberculosis, which can be fatal. Professor Jonathan Rees, of the University of Edinburgh, speaking at a series of seminars on hair in London yesterday, said the ginger gene may have had a significance throughout history. Did their ginger hair, for instance, assist in the achievements of Napoleon, Cromwell and Columbus? What effect did it have on the exploits of General Custer, Florence Nightingale, Cleopatra, Nell Gwynne and Rob Roy?
In the modern world, is it offering some small advantage to the likes of Nicole Kidman, Chris Evans and Charlie Dimmock. 'Experts in genetics always describe their science as being about the way in which eye and hair colour is passed from parent to child,' said Professor Rees. 'In reality we know little about the inheritance of these characteristics apart from the way red hair is inherited. 'Why did people with red hair survive - was there some advantage to being red? 'Research suggests red hair and pale skin is an advantage in northern Europe because you make vitamin D in your skin, and therefore you are less likely to get rickets if you have pale skin. 'Vitamin D may have played a big role here. 'There's also good data that we need vitamin D to fight against infections like TB. This sort of thing could have a very big evolutionary impact.' The human 'ginger gene', the trait which dictates red hair, is known in scientific terms as the melanocortin-1 receptor. Even as recently as 50 years ago, before improvements in the nation's diet, many people developed rickets, a childhood disorder which causes abnormal bone formation and can lead to bowing of the bones.
This was because they were not getting enough vitamin D, either in the food they ate or through exposure to sunlight. Red hair is mostly found in northwest Europe, although there are far more redheads in Scotland and Ireland than anywhere else. Between seven per cent and ten per cent of Scots have red hair. The downside of pale skin, however, is that it increases the risk of skin cancer in areas with strong prolonged sunlight. Professor Rees was speaking at the Royal Institution in London at an event exploring the science of hair. A recent study in the U.S. suggested that people with red hair are more sensitive to pain than blonds and brunettes. Researchers found that a genetic trait gave them a lower threshold to the pain of injury or surgery. A study of hospital patients at the University of Louisville found that they needed about 20 per cent more anaesthetic than people with other hair colours to achieve the same effect. Redheads May Have Gene Advantage in Cloudy Climates Blondes may have more fun, but new research suggests redheads soak up more sun.
Experts from the ScotlandsDNA project speculate that people with ginger colored hair have a genetic advantage in gloomier climates because they can create more vitamin D in low-light conditions than peers with darker skin or hair. While about 2% of the population has red hair, about 13% of people in Scotland are gingers. Vitamin D is a fat-soluble vitamin. Fat-soluble vitamins are stored in the body's fatty tissue.Vitamin D helps the body absorb calcium. Calcium and phosphate are two minerals that you must have for normal bone formation.In childhood, your body uses these minerals to produce bones. If you do not get enough calcium, or if your body does not absorb enough calcium from your diet, bone production and bone tissues may suffer.Vitamin D deficiency can lead to osteoporosis in adults or rickets in children.The body makes vitamin D when the skin is directly exposed to the sun. That is why it is often called the "sunshine" vitamin. Most people meet at least some of their vitamin D needs this way.
Very few foods naturally contain vitamin D. As a result, many foods are fortified with vitamin D. Fortified means that vitamins have been added to the food.Fatty fish (such as tuna, salmon, and mackerel) are among the best sources of vitamin D. Beef liver, cheese, and egg yolks provide small amounts.Mushrooms provide some vitamin D. Some mushrooms you buy in the store have higher vitamin D content because they have been exposed to ultraviolet light.Most milk in the United States is fortified with 400 IU vitamin D per quart. Most of the time, foods made from milk, such as cheese and ice cream, are not fortified.Vitamin D is added to many breakfast cereals. It is also added to some brands of soy beverages, orange juice, yogurt, and margarine. Check the nutrition fact panel on the food label. SupplementsIt can be very hard to get enough vitamin D from food sources alone. As a result, some people may need to take a vitamin D supplement. Vitamin D found in supplements and fortified foods comes in two different forms:D2 (ergocalciferol)D3 (cholecalciferol) Too much vitamin D can make the intestines absorb too much calcium.
This may cause high levels of calcium in the blood. High blood calcium can lead to: Calcium deposits in soft tissues such as the heart and lungs Damage to the kidneys Kidney stonesNausea, vomiting, constipation, poor appetite, weakness, and weight lossTen to 15 minutes of sunshine three times weekly is enough to produce the body's requirement of vitamin D. The sun needs to shine on the skin of your face, arms, back, or legs (without sunscreen). Because exposure to sunlight is a risk for skin cancer, you should use sunscreen after a few minutes in the sun.People who do not live in sunny places may not make enough vitamin D. Skin that is exposed to sunshine indoors through a window will not produce vitamin D. Cloudy days, shade, and having dark-colored skin also cut down on the amount of vitamin D the skin makes.The best measure of your vitamin D status is to look at blood levels of a form known as 25-hydroxyvitamin D. Blood levels are described either as nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L), where 0.4 ng/mL = 1 nmol/L. Levels below 30 nmol/L (12 ng/mL) are too low for bone or overall health
, and levels above 125 nmol/L (50 ng/mL) are probably too high. Levels of 50 nmol/L or above (20 ng/mL or above) are enough for most people. The Recommended Dietary Allowance (RDA) for vitamins reflects how much of each vitamin most people should get on a daily basis.The RDA for vitamins may be used as goals for each person.How much of each vitamin you need depends on your age and gender. Other factors, such as pregnancy and your health, are also important. Infants (adequate intake of vitamin D)0 to 6 months: 400 IU (10 micrograms (mcg) per day)7 to 12 months: 400 IU (10 mcg/day) Children1 to 3 years: 600 IU (15 mcg/day)4 to 8 years: 600 IU (15 mcg/day) Older children and adults9 to 70 years: 600 IU (15 mcg/day)Adults over 70 years: 800 IU (20 mcg/day)Pregnancy and breast-feeding: 600 IU (15 mcg/day) In general, people over age 50 need higher amounts of vitamin D than younger people. Ask your health care provider which amount is best for you.Vitamin D toxicity almost always occurs from using too many supplements.
The safe upper limit for vitamin D is:1,000 to 1,500 IU/day for infants (25 mcg/day)2,500 to 3,000 IU/day for children 1 to 8 years; ages 1 to 3 63 mcg/day; ages 4 to 8 75 mcg/day4,000 IU/day for children 9 years and older, adults, and pregnant and breast-feeding teens and women (100 mcg/day) One microgram of cholecalciferol (D3) is the same as 40 IU of vitamin D.Cholecalciferol; Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. National Academy Press, Washington, DC, 2011. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; Vitamins and trace elements. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 26.Calcium in diet Updated by: Emily Wax, RD, The Brooklyn Hospital Center, Brooklyn, NY. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.