Vitamin D is vital for strong bones and a healthy immune system. The Arthritis Foundation offers the following suggestions for boosting one’s vitamin D levels: get direct sunlight without sunscreen for just 10 to 15 minutes every other day; eat 3 ounces of a fish rich in vitamin D, such as salmon or Atlantic mackerel, two to four times a week; take a cod liver oil supplement; and eat vitamin D-fortified foods. Arthritis Foundation, October 2018