Women who are vitamin D deficient when they are diagnosed with breast cancer are more likely to have their disease spread and are more likely to die than women who have adequate vitamin D levels, new Canadian research says.

The study found that women who were vitamin D deficient were 94 per cent more likely to have their cancer metastasize (spread) and 73 per cent more likely to die.

The research was led by Dr. Pamela Goodwin, a breast cancer researcher at Mount Sinai Hospital in Toronto. The study analyzed blood samples and disease outcome from more than 500 women diagnosed with breast cancer between 1989 and 1995. Women were followed up for an average of 11 years.

The study found that when they were diagnosed with breast cancer:

  • only 24 per cent of subjects had sufficient levels of vitamin D (defined as more than 72 nanomoles per litre).
  • more then 37 per cent were considered to be vitamin D deficient (defined as less than 50 nanomoles per litre).

The research showed that women who were deficient in vitamin D were more likely to have aggressive forms of breast cancer.

The study also found that 69 per cent of women deficient in vitamin D had their disease metastasize, while 74 per cent were still alive 10 years later.

Yet among those with adequate vitamin D levels, 83 per cent of women did not have their cancer spread and 85 per cent were still alive after  10 years.

Dr. Reinhold Veith of Mount Sinai Hospital, said that vitamin D is a crucial part of normal cell function.

"Vitamin D is a basic that cells need to function properly. If you take that away they don't behave properly and are at greater risk of becoming cancerous."

Previous studies have linked low levels of vitamin D with an increased risk of developing breast cancer. Because breast cancer tumours have vitamin D receptors, the vitamin can slow the growth rate of cancer cells and make them less aggressive, the researchers said.

Time to test your Vitamin D levels?

Goodwin said that it is too early to tell all women with breast cancer to increase their vitamin D intake. However, women may want to have their blood levels of vitamin D measured and, if they are low, supplement to bring them up to the acceptable level of 72 nanomoles per litre.

However, if her findings are confirmed in a second study, the next step will be to test how raising vitamin D levels in breast cancer patients might affect their prognosis.

"I think it would be very worthwhile to see if improving those vitamin D levels will lead to improved breast cancer outcomes," Goodwin said.

"Can we really reduce the risk of recurrence in half by increasing vitamin D levels into the clinically adequate range? That would be very interesting question and a very important question to answer."

People get most of their vitamin D from sunlight. After being exposed to the sun, the skin produces vitamin D, which is then converted to its active form by the kidney. Vitamin D is also easy to get from nutritional supplements.

Daily recommendations for vitamin D intake vary, but the average recommendation is 1,000 international units (IU). Every 1,000 IU of vitamin D translates to a 25 nanomole per litre increase of vitamin D in the blood.

Carole Baggerly is one breast cancer patient who swears by vitamin D. She was diagnosed with breast cancer more than three years ago, and had a mastectomy followed by both radiation and chemotherapy.

The 65-year-old San Diego resident had her vitamin D level measured two years after her diagnosis, and found it to be very low. Her doctors told her she had osteoporosis, which is also linked to low vitamin D levels.

Baggerly started taking 5,000 international units (IU) of vitamin D per day for her bones and to improve her chances of staying cancer-free.

"To be able to reduce this with nothing more than vitamin D, as opposed to having to take some of these very toxic, other drugs, I think is extremely exciting and should be very exciting to every woman," Baggerly said.

She now runs a website, www.grassrootshealth.org, where she extols the virtues of vitamin D.

"It's so easy, it's simple, it's cheap, it's almost risk free, and if people knew about it they would be healthy," Baggerly said.

With a report from CTV's medical correspondent Avis Favaro and senior producer Elizabeth St. Philip.

Abstract:

Vitamin D (Vit D) deficiency is common at breast cancer (BC) diagnosis and is associated with a significantly higher risk of distant recurrence and death in a prospective cohort study of T1-3, N0-1, M0 BC.

Author Block: P. J. Goodwin, M. Ennis, K. I. Pritchard, J. Koo, N. Hood; Samuel Lunenfeld Research Institute, Toronto, ON, Canada; University of Toronto, Toronto, ON, Canada; Sunnybrook Health Sciences Centre, Toronto, ON, Canada; St. Michael's Hospital, Toronto, ON, Canada

Background: Vit D acts through a nuclear transcription factor to regulate many aspects of cellular growth and differentiation. Low levels have been associated with increased BC risk. We examined Vit D levels and prognostic effects in an existing BC cohort.

Methods: 512 consecutive women with newly diagnosed BC were enroled at 3 U of Toronto hospitals between 1989 and 1995. A blood specimen obtained at diagnosis was stored at -80��C. The Block questionnaire was used to measure diet intake. Clinical and pathology data were obtained from medical and pathology records. 25-OH Vit D was measured by radioimmunoassay. Women were followed prospectively to 2006.

Results: Mean age was 50.4��9.7 yrs. 288 women had T1 tumors, 164 T2 and 24 T3/4. 356 tumors were N0. 342 were estrogen receptor (ER) positive. 73 tumors were grade 1, 202 grade 2 and 173 grade 3. 199 women received adjuvant chemotherapy (CXT) and 200 received tamoxifen. 116 women (22.7%) had distant recurrences and 106 (20.7%) died during a median follow-up of 11.6 yrs. Mean 25-OH Vit D was 58.1��23.4 nmol/L. Vit D levels were deficient (<50 nmol/L) in 192 (37.5%), insufficient (50-72 nmol/L) in 197 (38.5%) and adequate (>72 nmol/L) in 123 (24.0%). Low Vit D levels were associated with premenopausal status, high body mass index (BMI), high insulin and high tumor grade (all p��0.03). Low Vit D levels were associated with low dietary intake of retinol, Vitamin E, grains and alcohol (all p<0.02). Vit D was marginally lower when drawn in winter (Oct-Mar) vs summer (Apr-Sept) months (56.7 vs 59.5 nmol/L, p=0.07). Distant disease-free survival (DDFS) was significantly worse in women with deficient (vs adequate) Vit D levels (HR 1.94, 95% CI 1.16-3.24, p=0.02) as was overall survival (OS) (HR 1.73, 95% CI 1.05-2.86, p=0.02). Vit D associations with DDFS were independent of age, BMI, insulin, T and N stage, ER and grade (all HR ��1.55 Q1 vs Q4, all p �� 0.04); they were not significantly modified by ER, adjuvant CXT or tamoxifen. Vit D associations with OS were attenuated by grade and were absent in ER negative BC.

Conclusions: Vit D deficiency is common at BC diagnosis and is associated with poor prognosis.