Are the Irish victims of a Vitamin D deficiency pandemic?

by Gerry Byrne

(first published 2008, Irish Times Health Supplement)

Every child up to the age of 12 months should receive a daily 5 microgram Vitamin D supplement, the Department of Health has told the HSE following a major departmental policy review.

Alarm bells were rung last year in a Food Safety Authority of Ireland (FSAI) study by nutritional and medical experts which warned most Irish children were receiving less than the recommended daily dose of Vitamin D, especially in winter. The expert report strongly recommended that the Department of Health make Vitamin D supplements a national priority for young children.

The FSAI study in turn was provoked by the discovery of 10 cases of rickets among Irish born children, a finding which one of the report's authors said, "may have been the tip of the iceberg". Rickets is caused by lack of Vitamin D and leads to softening of children's bones and skeletal deformities. It was thought to have been eradicated in Ireland decades ago. Even more cases have come to light since the report was published.

Most Vitamin D is produced by the action of sunshine on the skin but Irish sunshine levels between October and March are insufficient. Skin cancer warnings have also led more people to avoid direct sunlight so even in summer many people do not get enough sun exposure.

Use of a Factor 15 sunscreen can reduce Vitamin D production by 99%, according to a study by Professor Michael Holick of Boston University Medical Center, who has described Vitamin D deficiency as an international "pandemic." However the FSAI is not recommending that young babies be exposed to additional sunshine. Only a handful of foods like oily fish, liver and eggs provide Vitamin D so if these foods are not regularly consumed supplements are essential, said Dr Mary Flynn, chair of the FSAII study group which produced the report.

The FSAI is now to prepare recommendations for Vitamin D levels in other sections of the population, especially women of childbearing ago, and the elderly. Babies born to mothers with Vitamin D deficiencies are most at risk. Some of the recent cases of rickets were in babies born to immigrant mothers with dark skins which can produce as little as one percent the Vitamin D of fair skins. Some were also born to Muslin women who followed strict religious observance of covering up most of the body.

Vitamin D deficiency is a leading cause of osteoporosis or brittle bone disease in the elderly where complications arising from fractures is a major cause of death. Currently international recommended doses of Vitamin D are designed to prevent rickets and osteoporosis. But studies comparing illnesses in sunny areas of the USA with northern states and Canada (which has similar winter sunshine to Ireland) are discovering the rate of many diseases rises the further north one moves leading some researchers to suspect Vitamin D may play a greater role in health than previously recognised.

Not only can the elderly benefit. Research in UCC showed bone mineralisation in girls improved significantly when they were given Vitamin D supplements although Kevin Cashman, Professor of Food and Health at UCC said further work was needed.

Nutritionists and infant health experts have warmly welcomed the Department's new guidance on Vitamin D but some have questioned why it took so long since the report was issued in March 2007.

This recommendation meant a careful balancing act for the FSAI study group and the Department, explained Dr Flynn, who is chief nutritional specialist at the FSAII.

"Mothers' milk is not very rich in Vitamin D while it is added to formula for bottle fed infants but we didn't want to provoke a swing away from breast feeding which is still far more beneficial in almost every respect", she said. Dr Flynn added her group was also anxious to ensure that people didn't simply put young infants in more sun, which could have led to other problems. They also wanted to ensure that the Vitamin D supplement would be in the correct format.

At the time Dr Flynn's report was submitted to the Department, only one approved infant vitamin supplement contained Vitamin D. However, it also contained Vitamin A which can be toxic in excess and is already added to infant formula, so her group was reluctant to promote anything that could lead to over-consumption. Two preparations suited for infants containing only Vitamin D have been approved since Dr Flynn's report was published and these will be recommended.

"You don't idly recommend a population-wide supplement," said Dr Phillip Crowley, deputy medical officer at the Department of Health. "We took some time to reconsider the evidence, take soundings in the nutritional community and consult academics. We believe the recommendation is proportionate and safe."

Further studies of Vitamin D levels in the Irish population are under way at UCC. In one study, funded by the UK Food Standards Agency, Professor Cashman's department is attempting to decide the minimum vitamin D levels needed to prevent bone deterioration, or osteomalacia, in adults.

"The existing threshold only copes with more severe deterioration like rickets and osteoporosis. We are trying to see if we need to raise that threshold to take other diseases into account," Professor Cashman said. A further study is to assess the impact of Vitamin D on the general health of the population.

International studies are finding more and more correlation between high sunshine levels, high Vitamin D levels and a reduced incidence of other serious diseases. According to recent reports by studies by Boston's Professor Holick and other researchers, these include breast, colon, prostate, and several other cancers, Type I diabetes, Chrohn's Disease, multiple sclerosis, hypertension, rheumatoid arthritis, schizophrenia, depression, pre-eclampsia, and even tuberculosis. 

"In every dietary survey we have undertaken in this country the levels of Vitamin D are low, as low as 2 micrograms per day when the international recommendation is 5 micrograms and many experts say even that is too low because of the recommendation to stay out of the sun," said Dr Flynn.

(Update: a major study reported in the New York Times recently consolidates many of the findings described in the above 2008 article, which was written for the Irish Times. See: http://well.blogs.nytimes.com/2014/04/01/low-vitamin-d-levels-linked-to-disease-in-two-big-studies/?action=click&module=Search&region=searchResults&mabReward=&url=http%3A%2F%2Fquery.nytimes.com%2Fsearch%2Fsitesearch%2F%3Faction%3Dclick%26region%3DMasthead%26pgtype%3DHomepage%26module%3DSearchSubmit%26contentCollection%3DHomepage%26t%3Dqry475%23%2FVitamin%2520D3