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Is it necessary to continue taking a vitamin D supplement during the summer months?

Question: Is it necessary to continue taking a vitamin D supplement during the summer months, or will my body synthesize plenty from sun exposure?

Answer: Vitamin D has many protective roles throughout the body including its protection of the skeletal system, and its role in helping to decrease the risk of several autoimmune diseases. In addition, vitamin D deficiency has been linked to increased risk for cancer at different body sites. These are all compelling reasons why it is important to maintain vitamin D sufficiency all year round.

Our skin can become damaged from too much sun exposure, leading to accelerated aging, wrinkling, and skin cancer risk. Unfortunately, the use of sunscreen with an SPF of just 8 reduces our body’s production of vitamin D by 95 %.1,2 The best approach to achieving optimal vitamin D status is a combination of supplements and sensible sun exposure. Make sure to protect all of the areas of the skin that are over-exposed to the sun.  For most people, summertime does not guarantee optimal Vitamin D exposure, without undergoing excessive risk to their skin from age-related sun damage and skin cancer.

One area that sun exposure may  is beneficial is in the regulation of the sleep cycle and treatment of depression, especially seasonal depression. A walk early in the morning, before the sun’s rays are the strongest is the time of day that offers the most benefit on emotions. If you choose to be outside for a prolonged period of time, especially midday, it is wise to protect your skin with a non-chemical sunscreen, hat, clothing etc.

Vitamin D synthesis is also dependent on where you live and at varying times throughout the year there is insufficient UVB sunlight to produce optimal vitamin D levels. Because UVB exposure is related to the angle of the sun’s rays, midday sun is best when it comes to vitamin D synthesis, but worst when it comes to skin cancer risk. In addition, there are groups of people, such as the elderly and darker skinned people who do not efficiently synthesize vitamin D from the sun.

It becomes difficult for most people to manage an amount of sun exposure to achieve optimal vitamin D status while also being sure to not increase their likelihood of skin cancer. Taking a vitamin D supplement is a safe way to take all the guesswork out of it.


1. Tang JY, Fu T, Lau C, et al: Vitamin D in cutaneous carcinogenesis: part I. J Am Acad Dermatol 2012;67:803 e801-812, quiz 815-806. 
2. Matsuoka LY, Ide L, Wortsman J, et al: Sunscreens suppress cutaneous vitamin D3 synthesis. J Clin Endocrinol Metab1987;64:1165-1168.

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