Walking an hour a day (more vitamin D) decreased chance of breast cancer by 14 percent

http://www.bbc.co.uk/news/health-24381469

73,000 women followed for 17 years

7 hours a week of walking: 14% less breast cancer than those who walked three or fewer hours per week

There was no mention in the article of sunshine and vitamin D reducing Breast Cancer

Probably no need to walk 7 hours a week every week of the year

Best to walk during the summer, at noon, with as much skin exposed to the sun as possible (see tan-thru shirts below)

Suspect that 1 hour of walkin once a week , at noon, during the summer, while wearing a tan-thru shirt would provide the 14% benefit.

That would be about 30 hours a year.

Alternately, could take about 10,000 IU of vitamin D once a week to get a similar benefit (annual cost of the vitamin D: about $10)

If you value your time as worth more than 30 cents per hour ($10/30 hours) then you should take the vitamin supplement

Of course, walking more or taking more vitamin D will reduce the chance of breast cancer

See also VitaminDWiki

• Overview Breast Cancer and Vitamin D

• Breast Cancer probability reduced 12 percent with daily hour of (outdoor) exercise – March 2014 appears to be a different study with a similar conclusion

• Breast Cancer survival 2X more likely if vitamin D sufficient – meta-analysis May 2013

• Breast Cancer chance decreased 16 percent for every extra ng of vitamin D – Jan 2013

• How Vitamin D reduces chance of breast cancer – review May 2012

• Overview Dark Skin and Vitamin D women with dark skins need to walk at least 3X as long to get 14% reduction

• Increase your vitamin D from the sun by wearing a tan-through instead of standard shirt

  • If wear a tan-thru T-shirt would have a choice: 3X less time ( 2.3 hours) or much more benefit from 7 hours (30% reduction instead of 14%)
• Chart of Vitamin D levels vs disease - Grassroots Health June 2013 has the following chart, showing a 80% reduction in Breast Cancer with lots of vitamin D