Commentary

Sunlight “D”ilemma: risk of skin cancer or bone disease and muscle weakness

Vitamin D deficiency among adult people with epilepsy (PWE) is scarcely studied, despite its essential role in bone health and maintaining homeostasis. Several studies have studied the relationship between factors related to epilepsy and vitamin D metabolism. We aim to investigate this in our multi-ethnic society.

This was a single-center cross-sectional study. We recruited 159 participants diagnosed with epilepsy on antiseizure medications (ASMs). We included those aged 18 years and above, excluding patients with long-term medical conditions that would affect vitamin D metabolism. Sociodemographic data and details of epilepsy were collated. Venous sampling was performed to analyze the levels of albumin-corrected calcium, phosphate, alkaline phosphatase, and 25-hydroxyvitamin D3 [25(OH)D]. Serum 25(OH)D level is defined as deficient (<20 ng/ml), insufficient (20–29 ng/ml), and sufficient (≥30 ng/ml).

The study reported that 73 (45.9%) participants had vitamin D deficiency, 38 (23.9%) had vitamin D insufficiency, and 48 (30.2%) patients had sufficient vitamin D levels. The predictors identified were PWE aged 18 to 44 years old (p = 0.001), female gender (OR 3.396, p = 0.002), and ethnicity (p < 0.001), specifically Malay and Chinese. However, no significant association was identified between types of ASMs, serum calcium, or the prevalence of vitamin D deficiency.

Vitamin D deficiency among PWE is prevalent in our local population, suggesting that regular screening should be considered for those at risk. Early identification would allow intervention to reduce the risk of future complications.

Vitamin D is the sunshine vitamin. During exposure to sunlight, 7-dehydrocholesterol in the skin absorbs ultraviolet B (UVB) radiation converting it to previtamin D3. Previtamin D3 being thermodynamically unstable isomerizes within a few hours to form vitamin D3. Prolonged exposure to UVB leads to transformation into tachysterol or lumisterol, which can be further metabolized to biologically active hydroxyforms. A multitude of factors affect its synthesis including skin pigmentation, time of day, season, latitude, altitude, and sunscreen use. The body has a large capacity to produce vitamin D₃, and sensible sun exposure can be effective in helping to maintain blood levels of 25-hydroxyvitamin D. Exposure to sunlight also provides other health-related benefits that are independent of vitamin D production. These include activation of central neuroendocrine mediators including activation of hypothalamus-pituitary-adrenal axis (HPA) or its elements and production of nitric oxide. The latter would lead to a reduction of blood pressure. The goal of this chapter is to provide a broad overview on the role of sunlight in providing vitamin D and other health benefits including action of pro-vitamin D3 derivatives or vitamin D-independent effects.

In this study, we investigated the circulating levels of 25-hydroxyvitamin D (25[OH]D) in Brazilian women with breast cancer in samples collected at diagnosis, and correlated these with clinicopathological parameters relevant to disease prognosis.

This study involved 147 women diagnosed with infiltrative ductal carcinoma whose peripheral blood samples were collected, to have 25(OH)D levels measured in plasma.

Our findings indicated that circulating 25(OH)D levels at diagnosis were insufficient in patients with breast cancer. Further, 25(OH)D reduced plasmatic levels at diagnosis correlated significantly with poor prognosis parameters, including axillar positivity, chemoresistance and metastasis. Patients bearing triple-negative tumors also presented reduced 25(OH)D in plasma when compared to those who carried Luminal tumors. Our data suggest relevant correlations when 25(OH)D is reduced in plasma at diagnosis, such as advanced disease with axillar positivity, chemoresistance with advanced disease, early age at diagnosis with high histological grade and dead with axilla positivity. Conclusions: Altogether, our findings reinforce that 25(OH)D reduction can be a plausible marker of disease prognosis in breast cancer.

This chapter provides an up-to-date summary of key facts and concepts regarding sunscreens. Sunscreen products are regulated by the US Food and Drug Administration. Labels may only indicate ‘broad-spectrum’ for products that demonstrate an in vitro critical wavelength of 370 nm or greater. Sunscreens may contain chemical absorbers or physical blockers. The most important ingredients are discussed further in the chapter. Sunscreen application technique alters sun protection factor (SPF) and therefore ultraviolet radiation protection. There are several forms of sunscreen products in the market, most commonly lotions and creams, but also gels, sprays, and sticks. The most common adverse reaction to sunscreens is irritation; true allergies are rare. Sunscreens should be applied liberally and reapplied every 2 hours. The ‘teaspoon rule’ may help in applying an adequate amount of sunscreen.

Vitamin D deficiency is common among dialysis patients and may impact blood concentrations of calcium, phosphorus, intact parathyroid hormone (iPTH), and alkaline phosphatase (ALP). Seasonal variation of serum 25-hydroxyvitamin D [25(OH)D] concentrations has been well established for the general population; however, less is known about circannual variation in 25(OH)D as well as other parameters of mineral and bone disorder among dialysis patients.

Based on 57,500 serum 25(OH)D measurements collected over two years from January 2009 to December 2010 among 25,025 dialysis patients, we evaluated the circannual variations in serum concentrations of 25(OH)D, calcium, phosphorus, iPTH, and ALP by a linear regression model with a cosinor function for the time period (month). We adjusted for potential confounders including case-mix variables, and ultraviolet index.

Serum 25(OH)D concentrations showed significant circannual variation and mean serum 25(OH)D was 3.2 ng/mL higher in summer than in winter. Furthermore, 25(OH)D concentration increased steadily by 1.3 ng/mL per year. While serum calcium concentrations showed statistically significant but clinically negligible seasonal variation (0.02 mg/dL in peak-trough difference), serum phosphorus did not follow such a pattern. Serum iPTH concentrations also showed a modest seasonal variation with 9% higher values in winter than in summer. Concordantly, ALP concentrations in the winter were 2% higher than in the summer time. Seasonal variation of 25(OH)D was greater in male (vs. female), African-American (vs. non-African-American), and younger (vs. older) dialysis patients.

Serum 25(OH)D and iPTH concentrations show seasonal variation among dialysis patients while the variation in other parameters of mineral and bone disorder was clinically irrelevant, if any. Serum 25(OH)D also showed a gradual increase over time. Clinicians and researchers should be aware of these changes when interpreting laboratory results in dialysis patients.

The purpose of the chapter is to view vitamin D in the context of sport nutrition and its vital role in enhancing athletic performance. The chapter focuses on the present understanding of the physiological functions of vitamin D in bone health, musculoskeletal system, and immunity, in addition to the potential impact on athletic performance. Based on the available evidence, retaining the serum 25-hydroxy vitamin D (25(OH)D) concentration above the optimal level (up to 100 nmol/L) increases musculoskeletal function, reduces fracture recovery period from exercise, improves both force as well as power production, and enhances production of testosterone, all of which influence the athletic performance. On the other hand, deficiency of vitamin D can cause numerous health problems, such as increased incidence of bone injuries, stress fracture, prolonged skeletal muscle pain, and respiratory tract illness. In spite of these, large populations of athletes are vitamin D deficient. Regular intake of dietary vitamin D sources alone is not enough to preserve sufficient level of vitamin D. Adequate level of sun exposure and regular supplements of vitamin D or a mixture of dietary intake and sun exposure along with vitamin D supplements are necessary to attain adequate levels vitamin D. Recommendation of vitamin D to each athletes should be individualized based on their serum 25(OH)D level, clinical symptoms, season, and diet. However, intoxication of vitamin D from over consumption of the supplements is unusual. Normally, athletes with insufficient vitamin D status need daily vitamin D supplementation with a minimum of 1500–2000 IU.