The most up-to-date information on Vitamin D provides convincing evidence that most people suffer from an inadequate supply which is linked to increased risk of a wide range of common diseases.
The role of Vitamin D in diseases other than rickets can be attributed to the work of 2 brothers Cedric and Frank Garland. In 1974 they attended a lecture which showed that there were major differences in the incidence of cancer across the American states. As a consequence of this both of them decided to dedicate their life’s work to understanding the causes of these diseases. At the outset they noted that the states of New Mexico and Arizona with the highest values for solar radiation (500 gm-cal/cm2) also had colon cancer rates for white males which were relatively low. Between 1959 and 1961 the values were 6.7 and 10.1 per 100?000 population, respectively. By contrast, New York, New Hampshire, and Vermont had the lowest statewide solar radiation values (300 gm-cal/cm2) and experienced colon cancer rates for white males of 17.3, 15.3, and 11.3 per 100?000 populations, respectively, during the same period. As a consequence they decided to conduct a more detailed investigation into the relationship between the colon cancer rates and exposure to sunlight across the USA. The results for white males confirmed that a low incidence of colon cancer is associated with a high exposure to sunlight, which led them to suggest that vitamin D could be the critical factor which helps to prevent the development of the colon cancer(1).
Subsequently it has been established that Vitamin D has many different functions in the body and therefore a deficiency will result in an increased risk of developing a range of different diseases. Traditionally the recommended daily intake has been based on the requirement to prevent the development of the bone disorder rickets but it is now becoming clear that very much higher intakes are needed to reduce the risks of diseases which include heart disease, certain cancers, diabetes and MS.
For a comprehensive account of the Vitamin D story, I can recommend “The Vitamin D Solution” by Michael Holick (2).
The Vitamin D status of an individual is determined by the exposure of the skin to sunshine and/or consuming foods or supplements. In order to meet the actual requirements now considered ideal it is unlikely that this can be achieved by diet alone. The only way to determine whether a person is vitamin D sufficient, deficient, or intoxicated is to measure the circulating concentrations of 25(OH)D This is produced in the liver and is the major circulating form of vitamin D. Its half-life in the circulation is about 2 weeks, and it is a good measure of a person’s Vitamin D status.
Results from the Ludwigshafen Risk and Cardiovascular Health (LURIC) study illustrate the importance of the Vitamin D status with respect to general health and life expectancy(3). Between July 1997 and January 2000, 3316 men and women were recruited in Ludwigshafen in south west Germany who had been referred for coronary angiography. Of these 1801 were found to have Metabolic Syndrome (a cluster of conditions including obesity, diabetes, high blood pressure, raised triglycerides and low HDL Cholesterol). In other words they were high risk for heart disease and related problems. Information was collected and collated on the health and lifestyle. The Vitamin D status was determined by the level in the blood. The participants were followed for almost 8 years, during which time there 462 deaths. The results are shown in Table 1 are absolutely fascinating. First of all, there is a progressive fall in the death rate as the level of Vitamin D in the blood increases. Those in the group with the highest Vitamin D have a death rate which is only one quarter that of those with the lowest level. Although this does not conclusively demonstrate that the Vitamin D is the cause of the improved chances of survival it is certainly consistent with that explanation. Furthermore this result does lend support to other findings (which will dealt with in future Blogs) that ensuring a high level of Vitamin D in the blood is a critical factor in maintaining good health. However some of the other information is also highly relevant. Despite the fact that there are huge differences in the death rates between the different groups the values for total cholesterol in the blood (TC) and for BMI are effectively the same in all groups. This provides confirmation of many other studies which have concluded that TC and BMI are not reliable indicators of heart disease risk. It is evident that the pattern of deaths attributed to cardiovascular causes is essentially to that observed for deaths from all causes.
TABLE 1 SELECTED CHARACTERISTICS, VITAMIN D STATUS AND DEATH RATES IN THE LURIC STUDY
|Vitamin D content in the blood|
|<25 nmol/L||25-50 nmol/L||50-75 nmol/L||>75 nmol/L|
|Total Cholesterol, mmol/L||4.8||4.9||5.0||5.0|
|C reactive protein, mg/L||70.2||37.7||34.8||28.7|
|Above average physical activity, %||12.8||27.8||37.1||52.9|
|Adjusted death rate Model 1(All causes)||1.00||0.56||0.48||0.18|
|Adjusted death rate Model 2(All causes)||1.00||0.62||0.56||0.25|
|Adjusted death rate Model 3(All causes)||1.00||0.63||0.61||0.25|
|Adjusted death rate Model 1(CVD)||1.00||0.55||0.36||0.25|
|Adjusted death rate Model 1(CVD)||1.00||0.60||0.45||0.34|
|Adjusted death rate Model 1(CVD)||1.00||0.61||0.49||0.36|
Note: The crude death rates have to be adjusted to allow for differences in age and the relative proportions of men and women in each group. The reason for the 3 different values is that the assumptions in each model vary slightly.
There is now little doubt that Vitamin D is a much more important nutrient than has been recognised until relatively recently. I will shortly explain what this means to individuals but if you would like further information without delay I recommend you visit the Grassroots website(4).
- C F and F C Garland (2006) International Journal of Epidemiology 35 (2) pp 217-220
- M F Holick (2010) “The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problems” Plume (Penguin) New York
- G N Thomas et al (2012) Diabetes Care 35 (5) pp1158-1164