Sunny treatment for diseases: updates on vitamin D deficiency and sufficiency
Sunshine is the major source of vitamin D, an essential vitamin synthesized by skin exposure to sunlight. So how can vitamin D deficiency be a global problem? Below is a review of recent research on the benefits of vitamin D and possible causes of its deficiency.
Vitamin D and Alzheimer’s disease [1]
A small retrospective study (n= 32) found strong links between low serum levels of vitamin D and low performance in cognitive tests in patients with Alzheimer’s disease. Supplementation with vitamin D improved test outcomes. The results suggest that optimal vitamin D levels are important in cognitive function in older adults.
Vitamin D and myopia [2]
Vitamin D deficiency is linked to myopia in the Asia-Pacific region. Results show that 90% of conscription-aged Singaporean males are myopic. This is a dramatic increase compared to the incidence of 20 to 30% about 40 years ago. In Australia on the other hand, the incidence went from 15% to 20-25% within the same time period.
Ethnicity may play a role because of the “genetic susceptibility to environmental risk factors associated with intensive education and urbanisation” among East Asians. However, myopia seems equally prevalent across all ethnic groups (including Malay and Chinese) in Singapore.
Furthermore, the prevalence of myopia was found to be 10 times more among Chinese-Singaporean children than Chinese children based in Sydney. The difference lies in the number of hours of exposure to the sun. The Australian children stayed outdoors 4 times longer than their Singaporean counterparts. Researchers hypothesize that exposure to sunlight encourages the release of dopamine, which in turn inhibit excessive eye growth that leads to myopia. In many Asian countries, sun exposure is actually avoided due to a cultural preference for lighter skin.
Vitamin D and multiple sclerosis [3]
Multiple sclerosis is strongly linked to genetics. However, there are strong geographical patterns in the incidence of multiple sclerosis that cannot be fully explained by genetics alone. It has been observed, for example, that multiple sclerosis is less prevalent in the tropics and subtropics than in higher latitudes. Environmental factors are involved in the epidemiology of this disease and one of these is vitamin D.
Vitamin D3and osteoporosis [4]
Vitamin D plays a major role in the prevention and management of osteoporosis. Vitamin D deficiency has been linked to osteopenia, osteoporosis and osteomalacia. Cholecalciferol or vitamin D3 enhances the absorption of calcium and phosphorous in the intestine.
Vitamin D and pregnancy [5]
Vitamin D during pregnancy can lead to craniotabes or softening of the skulls in newborn infants. This deficiency may persist one month after delivery especially among breastfed babies. This probably the reason behind prescription of vitamin D supplement to breastfed infants in many countries.
Vitamin D synthesis in the skin is influenced by “season, latitude, skin pigmentation, sunscreen use, clothing and aging” [4] as well as lifestyle and cultural preferences [2]. To prevent deficiency, appropriate exposure to sun should be encouraged. A daily supplement of 800 to 1000 IU of vitamin D3 may also help.
Sources:
- Przybelski RJ, Binkleya NC. Is vitamin D important for preserving cognition? A positive correlation of serum 25-hydroxyvitamin D concentration with cognitive function. Arch Biochem Biophys. 2007; 460(2):202-205
- Nowak R. Lifestyle causes myopia, not genes. New Scientist 2004.
- Ascherio A, Munger K. Epidemiology of Multiple Sclerosis: From Risk Factors to Prevention. Seminars in Neurology 2008; 28: 017-028.
- Holick MF. Optimal vitamin D status for the prevention and treatment of osteoporosis. Drugs and Aging, 2007; 24(12): 1017-29.
- Yorifuji J et al. Craniotabes in normal newborns; the earliest sign of subclinical vitamin D deficiency. Journal of Clinical Endocrinology & Metabolism February 12, 2008.
Fast food and CVD: where`s the connection?
Be it burgers, pizza or fries, what is it with fast food diet that makes it a major CVD risk factor? In the recent issue of the Journal of the American College of Cardiology, researchers published the answers [1].
Consumption of high-calorie, low-nutrient food causes a sudden increase in blood glucose and triglyceride levels and results in a state known as postprandial dysmetabolism. These after-meal spikes in sugar and free fatty acids “overwhelm the body’s ability to handle the surge, resulting in a flooding of the Kreb’s cycle and the production of superoxide anions. The postprandial production of these free radicals acutely triggers atherogenic changes, such as increases in LDL oxidation, sympathetic tone, vasoconstriction, and thrombogenicity [2].”
At the end of the scale, traditional Mediterranean or Okinawan diets (consisting of lean protein, fish oil, whole grains, vegetables and low to moderate amounts of alcohol among others) has been shown to be anti-inflammatory and to lower CVD risks [1].
References:
1. O’Keefe JH, Gheewala NM, O’Keefe JO, 2008. Dietary Strategies for Improving Post-Prandial Glucose, Lipids, Inflammation, and Cardiovascular Health. J Am Coll Cardiol, 2008; 51:249-255, doi:10.1016/j.jacc.2007.10.016
2. O`Riordan M. Big Macs and Whoppers: Spikes in after-meal glucose and lipid levels lead to inflammation and CVD. HeartWire 16 Jan 2008.
Baby’s First Solid Food: Later is Not Necessarily Better
More and more mothers are putting off the introduction of first solid food to infants out of fear of food allergies and celiac disease. Two recent reports indicate that this delay is actually unwarranted and can lead to health problems. In a recent review, Guandalini reports that not only early but also “late (7 months or after) first explosure to gluten may favor the onset of celiac disease in predisposed individuals” [1]. Too early and too late gluten introduction can also result “in a significantly higher risk of the appearance of islet cell immunity,” a condition that can lead to type-1 diabetes.
In another study, German researchers did not find any association between the time of solid food introduction, the type of food, and the incidence of eczema in a cohort of 4753 infants. The results of the study indicate that „neither a delayed introduction of solids beyond the fourth month nor a delayed introduction of the most potentially allergenic solids beyond the sixth month of life“ can prevent eczema in infants [2].
Based on recent evidence, introduction of solid foods to babies should occur between 4 and 6 months and only as complementary food to breast milk. Breasfeeding during the introduction of gluten can delay the onset of celiac disease [1].
Sources:
[1] Issues in Complementary Feeding (2007). Nestle Nutr Workshop Ser Pediatr Program 60: 139-155.
[2] Journal of Pediatrics 151:352-358 (October 2007)