Annaleen Koole is a WCRF Academy Fellow and is finalising her PhD at Maastricht University in the Netherlands. Her research focuses on vitamin and supplement use in relation to fatigue and quality of life after a diagnosis of colorectal cancer.
The sunshine vitamin
Vitamin D is often referred to as the sunshine vitamin as sunlight is the main source of vitamin D. When our skin is exposed to ultra-violet B radiation from the sun, our bodies start producing vitamin D. Other ways we can get vitamin D are from our diet and the use of supplements. Foods that contain vitamin D include fatty fish, meat, eggs and fortified products such as margarine. Vitamin D has numerous roles in the body given the fact that many cells have vitamin D receptors. One important function of the vitamin is the promotion of calcium uptake in the gut. In the Netherlands, vitamin D supplementation is therefore recommended for the prevention of osteoporosis for women above the age of 50, and for women and men above the age of 70. Vitamin D has many additional functions in our bodies and has been related to cognition, fatigue and mental health problems such as depression.
Vitamin D and colorectal cancer survivors
Our study aimed to discover whether the vitamin D status of colorectal cancer survivors is associated with health problems that are experienced after treatment has ended. There were two main reasons to investigate this. Firstly, colorectal cancer survivors commonly report a decreased quality of life because of side-effects from cancer and its treatment, such as chemotherapy. A frequently reported problem is fatigue, which is different from normal tiredness and can severely impact the daily life of colorectal cancer survivors. Secondly, colorectal cancer survivors are at risk of having low vitamin D levels. Therapy can cause vitamin D levels to decline, and as colorectal cancer generally develops at a later age, elderly populations are prone to develop vitamin D deficiencies.
The EnCoRe study
We investigated the relationship between vitamin D and the quality of life of colorectal cancer survivors within an ongoing prospective study, the EnCoRe study (Energy for life after ColoRectal cancer). Patients were recruited upon diagnosis with colorectal cancer and followed up over a period of two years. During these two years, patients received regular home visits from our dietitians. We collected blood samples to measure vitamin D, performed body measurements, and carried out multiple questionnaires to assess fatigue and quality of life.
Vitamin D levels over time
We found that almost half (45 per cent) of patients were vitamin D deficient at diagnosis. Vitamin D levels decreased after treatment, particularly in men, but turned out to be higher in all survivors two years post-treatment than at diagnosis, as shown in the figure below. We further observed that 33 per cent of women aged 50–70 years old and 24 per cent of men and women older than 70 used vitamin D supplements at diagnosis.
Relations between vitamin D and fatigue
In longitudinal analyses, higher concentrations of vitamin D were associated with decreased fatigue and better global quality of life in the two years after colorectal cancer treatment. Also, having a vitamin D deficiency was associated with more fatigue and lower global quality of life. Individuals who started using vitamin D supplements during follow-up reported less fatigue and better quality of life.
Higher vitamin D levels seem beneficial for survivors of colorectal cancer. It is therefore important for colorectal cancer survivors to be aware of the guidelines regarding vitamin D supplementation and sun exposure to optimise their vitamin D levels. In addition, individual vitamin D status of colorectal cancer survivors should be monitored by medical professionals.
The EnCoRe study is in part funded by grants from WCRF. This particular study on vitamin D and fatigue was funded by Kankeronderzoekfonds Limburg.