Full sun has no benefit in the winter for most of the US.
"Human skin or [3 alpha-3H]7-dehydrocholesterol exposed to sunlight on cloudless days in Boston (42.2 degrees N) from November through February produced
no previtamin D3. In Edmonton (52 degrees N) this ineffective winter period extended from
October through March. Further south (34 degrees N and 18 degrees N), sunlight effectively photoconverted 7-dehydrocholesterol to previtamin D3 in the middle of winter. These results quantify the dramatic influence of changes in solar UVB radiation on cutaneous vitamin D3 synthesis and indicate the latitudinal increase in the length of the "vitamin D winter" during which dietary supplementation of the vitamin may be advisable."
Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin The solution is of course supplementation. A starting point is about 5,000 IU per day of Vitamin D3. To evaluate your need, take a Vitamin D blood test .(available at:
Vitamin D, 25-Hydroxy Blood Test Note that the cost has recently increased from $35 to $47 thanks to Bidenflation (and demand). Likewise, the cost for a bottle of 60 5,000 IU capsules of D3 has gone from about $6 to about $14.
The argument from nature ("don't need no stinkin supplement") only applies if you have the same lifestyle as early man (running around naked all day under an equatorial African sun). The Hadza and Masai tribes live that way, maintaining a blood level of around 45 ng/ml. Most Americans are at 15 or so. Studies have shown a correlation between low blood levels of Vitamin D and susceptibility to the flu, Covid and other viruses. Studies have also shown a correlation between low Vitamin D levels and susceptibility to blood clots. So Vitamin seems to also protect against one of the side effects of the vaccine (although not necessarily against the "high beam" side effect :)).
Masai tribes live that way, maintaining a blood level of around 45 ng/ml. Most Americans are at 15 or so The wife & I are at about 60 for the last several years. 4000-5000 units a day
About 8 years ago my wife at 59 or 60 shattered her wrist in a freak fall. Surgery and plate inserted. The surgeon said it was completely healed at 4 weeks. He said he had never seen anyone of any age have that injury heal so fast.....our family doctor had found she had a D deficiency a couple of years before that and put her and me on a serious program of D supplementation. The surgeon was suitably impressed with the results.