Friday, 28 April 2017

Preventing cancer

Vitamin D

Vitamin D refers to a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calciumironmagnesiumphosphate, and zinc. In humans, the most important compounds in this group are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol).

Vitamin D status is defined by the circulating concentration of 25-hydroxyvitamin D.
low serum levels of 25-hydroxyvitamin D concentrations is linked to health outcomes such as hip fracture, heart attack, cancer, and death. 

Higher levels of vitamin D are associated with a reduction in cancer risk of more than a 65%, according to a study published online April 6 in PLOS ONE.
The finding comes from a pooled analysis of results from a randomized trial and a prospective cohort study, and the higher levels of vitamin D are serum levels of 25-hydroxyvitamin D (25[OH]D) above 40 ng/mL.
"Higher serum 25-hydroxyvitamin D concentrations have been associated with a lower risk of many different cancers, for example breast, colon, and lung, across a range of concentrations," said researcher Cedric Garland, DrPH, from the University of California, San Diego, School of Medicine and the Moores Cancer Center.
"We have been studying this since the 1980s, when my brother, Frank Garland, who is now deceased, and I observed that cancer was mainly due to a deficiency of vitamin D, the same way that scurvy was due to a deficiency of vitamin C," Dr Garland told medscape.
Most people get at least some of the vitamin D they need through sunlight exposure. Dietary sources include a few foods that naturally contain vitamin D, such as fatty fish, fish liver oil, and eggs. However, most dietary vitamin D comes from foods fortified with vitamin D, such as milk, juices, and breakfast cereals. Vitamin D can also be obtained through dietary supplements.
The Institute of Medicine (IOM) of the National Academies has developed the following recommended daily intakes of vitamin D, assuming minimal sun exposure (1,2):
  • For those between 1 and 70 years of age, including women who are pregnant or lactating, the recommended dietary allowance (RDA) is 15 micrograms (μg) per day. Because 1 μg is equal to 40 International Units (IU), this RDA can also be expressed as 600 IU per day.
  • For those 71 years or older, the RDA is 20 μg per day (800 IU per day).
  • For infants, the IOM could not determine an RDA due to a lack of data. However, the IOM set an Adequate Intake level of 10 μg per day (400 IU per day), which should provide sufficient vitamin D.
Although the average dietary intakes of vitamin D in the United States are below guideline levels, data from the National Health and Nutrition Examination Survey revealed that more than 80 percent of Americans had adequate vitamin D levels in their blood (2).
Even though most people are unlikely to have high vitamin D intakes, it is important to remember that excessive intake of any nutrient, including vitamin D, can cause toxiceffects. Too much vitamin D can be harmful because it increases calcium levels, which can lead to calcinosis (the deposit of calcium salts in soft tissues, such as the kidneys, heart, or lungs) and hypercalcemia (high blood levels of calcium). The safe upper intake level of vitamin D for adults and children older than 8 years of age is 100 μg per day (4000 IU per day). Toxicity from too much vitamin D is more likely to occur from high intakes of dietary supplements than from high intakes of foods that contain vitamin D. Excessive sun exposure does not cause vitamin D toxicity. However, the IOM states that people should not try to increase vitamin D production by increasing their exposure to sunlight because this will also increase their risk of skin cancer.