I think you have misinterpreted that sentence. It is saying that too little sun exposure is harmful to health in women. See also this study which found the same for men in Norway:
Oslo is about half the UV of SF, so you would need to spend half as much time in the sun for the same benefit. If you are not outside much during the day, its still a risk factor no matter where you live. This would apply to most office workers.
“ Research on a link between vitamin D and cancer is mixed. Some studies have shown a link between low vitamin D levels in the body and a higher risk of getting cancer or dying from cancer. However, it’s not clear if taking vitamin D or having certain vitamin D levels might help prevent cancer. It’s also not clear if vitamin D can help control the growth and spread of cancer. More research is needed to know what role vitamin D does or does not play in helping to prevent or control cancer.”