At the latitude of Boston during 3 months (around the longest day of the year-- first day of winter) you can get no vitamin D from sunlight. At the latitude of Montreal it is 5 months. The good rule of thumb is when the shadow is the same length of object is when you can barely get vitamin D from sunlight. That is a 45 degree angle.
That was your question.
You can get too much from supplements, but it is rare. You cannot get too much hormone D from sunlight. In the last 3 years 6 MDs wrote 6 books on vitamin D and all say that it is a hormone not a vitamin. The body cannot make a vitamin.
In 2007 Time Magazine chose vitamin D as one of the top 10 medical breakthroughs of the year. In December 2010 the RDA of vitamin D was tripled. Doctor of Public Health, Cedric Garland
, said at a conference to over 100 MDs and scientists that enough vitamin D can virtually eradicate breast cancer. Recently I heard that he is a little depressed since most people are too WHATEVER to understand it (on video with Carole Baggerly and Dr Mercola
But the doctor who invented the stethescope was laughed out for 40 years! So after Dr Garland is dead and buried then breast cancer will be virtually eradicated.
But a little is happening already. Dr Oz has a video explaining how vitamin D prevents breast, colon and uterine cancer
has an article saying that women getting breast cancer have a vitamin D deficiency. Harvard
has a webpage saying that vitamin D prevents breast cancer.Johns Hopkins
has a webpage saying that vitamin D prevents prostate cancer. Christiane Northrup MD
has best selling books on womens health. She has a webpage on the Oprah
Website saying that thousands of lives can be saved by learning that vitamin D can prevent breast cancer
MDs Joel Fuhrman
and Mark Hyman
promote a plant based diet. Both make powerful statements about Vitamin D Preventing Breast Cancer
Dr Hyman wrote Eat Your Medicine: Food as Pharmacology
. He says "What you put at the end of your fork is more powerful medicine than anything you will find at the bottom of a pill bottle
Dr Fuhrman wrote : GOMBBS: Greens, Onions, Mushrooms, Beans, Berries and Seeds
. Both are great articles on plant foods that heal disease. They are not big fans of drugs.