Vitamin D – actually a hormone – is commonly known as the ‘sunshine vitamin’, because it is synthesized by the liver and kidneys on exposure to sunlight. It also occurs naturally in foods such as salmon and other oily fish. The current recommendation for daily intake is 400 IU (international units) per day, but a number of experts have spoken out for a higher level as research stacks up to support the benefits of higher levels.
However there are concerns that many people are not receiving sufficient vitamin D, and seniors could be especially susceptible to deficiency as the skin generates less as it ages. People with darker skin pigmentation may also generate less.
The Harvard Heart Letter says getting more sunlight helps boost vitamin D levels, but the safety way is to take a daily supplement that provides 800 to 1000 IU per day.
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While many people associate vitamin D with helping make bones stronger (it aids absorption of calcium), it also helps prevent build-up of calcium in the arteries, decreases production of renin, a hormone that elevates blood pressure, in the kidneys, and could help strengthen heart contractions.
Other benefits cited included curbing statin-related muscle pain, and helping protect against infection.
According to the Harvard Heart Letter, at least one-third of Americans are thought to be vitamin D deficient; and 75 per cent of people with cardiovascular disease are deficient.
The letter advises people to ask their physician for a vitamin D test. Levels are determined by measuring the levels of hydroxylvitamin D in the blood – that is the biologically inactive form which the kidneys then convert into the active chemical.
Deficiency is said to be less than 20 nanograms of vitamin 25-hydroxylvitamin D per milliliter of blood (ng/mL); insufficiency is from 20 to 30 ng/mL; and sufficiency is over 30 ng/mL.
The Harvard Heart Letter is intended for the general public, and aims to make health information available and understandable to people who may benefit from it.