Vitamin D deficency can lead to cancer, osteoporosis and bone fractures. Viatmin D, the classical vitamin related to bone health, improves bone strength mainly by increasing intestinal calcium absorption and reabsorption of calcium by the kidney. Several intervention studies demonstrated in humans that vitamin D can improve bone status as measured by bone density. (Int J Vitam Nutr Res. 1999 May;69(3):194-7).
According to the Atlas of Cancer Mortality Rates for the United States (1950-94), 50,000 to 63,000 deaths in America are due to insufficient sunlight and/or vitamin D while only 8,000 are from melanoma.
In the U.K., 19,000 to 25,000 deaths are caused by insufficient sunlight and/or vitamin D while only 2,000 are from melanoma.
Most physicians find it difficult to believe that the absence of something causes disease. Just read the history of beriberi and pellagra and how many decades it took the medical profession to accept that a deficiency of thiamine and niacin, respectively, caused those diseases.
Although dietary sources of vitamin D are important, there is no indication that dietary factors vary geographically throughout the United States in the amount required to explain the large regional variations in cancer mortality rates. (Photochemistry and Photobiology: Vol. 81, No. 6, pp. 1276â€“1286).
Many physicians in the 20â€™s and 30â€™s routinely recommended sun exposure for a wide variety of diseases; many of the same diseases that are now being associated with vitamin D deficiency.
The role that medical advocacy of ultraviolet light exposure played in initially advancing the practice of sunbathing is not commonly appreciated today. Ironically, public health recommendations of the time were often diametrically opposed to those being made at present, since sunlight exposure is currently recognized as the major preventable cause of cancer of the skin. (J Am Acad Dermatol. 2003 Jun;48(6):909-18).
The following is an article written by Fariba Roughead for the USDA, Agricultural Research Service.
Osteoporosis is an insidious disease that silently robs about 25 million Americans of independence and quality of life. Another 34 million Americans are at risk of developing this disease.
The problem is closer to home than we may think. Locally, as a part of the screening processes for our nutrition studies, we exclude about 20% of the female applicants because they do not meet the criteria for normal bone mineral density.
Most of these women have not had a bone scan prior to coming to us, and therefore do not know the status of their bones. If left untreated, osteoporosis can progress painlessly until a bone breaks, typically, in the hip, spine, and wrist.
Of special concern are fractures of the hip and spine. A hip fracture almost always requires hospitalization and major surgery. It can impair a person’s ability to walk unassisted and may cause prolonged or permanent disability or even death.
Spinal or vertebral fractures also have serious consequences, including loss of height, severe back pain, and deformity.
Due to the geographic location, I am concerned that inadequate vitamin D status may play a role in the bone health of North Dakotans because of the long winters.
Exposure to sunlight is an important source of vitamin D. Ultraviolet (UV) rays from sunlight trigger vitamin D synthesis in the skin. Season, latitude, time of day, cloud cover, smog, and suncreens affect UV ray exposure.
In North Dakota, the average amount of sunlight is insufficient to produce significant vitamin D synthesis in the skin from around November through February or so.
Sunscreens with a sun protection factor of 8 or greater will block UV rays that produce vitamin D, but it is still important to routinely use sunscreen whenever sun exposure is longer than 10 to 15 minutes.
Considering all of this, it is especially important for North Dakotans to include good sources of vitamin D in their diet.
Vitamin D is actually a hormone and not a nutrient.
There are very few dietary “natural” sources for this vitamin such as fatty fish, fish oils, and liver. So, fortified foods become the major dietary sources of vitamin D.
In fact prior to the fortification of milk products in the 1930s, rickets (a bone disease seen in children) was a major public health problem in the United States.
One cup of vitamin D fortified milk supplies about one-fourth of the estimated daily need for this vitamin for adults.
Although milk is fortified with vitamin D, dairy products made from milk such as cheese, yogurt, and ice cream are generally not fortified with vitamin D so be sure to read the label.
As we age, the ability of our skin to convert vitamin D to its active form decreases, so older Americans (greater than age 50) are thought to have a higher risk of developing vitamin D deficiency.
With vitamin D, like any other nutrient, one can get too zealous and get too much of a good thing. Vitamin D toxicity does occur and can lead to high blood levels of calcium, heart rhythm abnormalities, as well as calcification of the kidneys.
The good news is you cannot easily get too much vitamin D through the diet (unless you routinely consume large amounts of cod liver oil). You are much more likely to over-do vitamin D supplements. Please consult with your physician to find out about what intakes are suitable for you.
The National Osteoporosis Foundation offers the following 5 steps for better bone health:
Get your daily recommended amounts of calcium and vitamin D
Engage in regular weight-bearing exercise
Avoid smoking and excessive alcohol
Talk to your doctor about bone health
Have a bone density test and take medication when appropriate
Fariba Roughead for the USDA, Agricultural Research Service
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