caffeine, coffee also contains a number of alkaloids and phenolic compounds
including cafestol and kahweol. Kahweol is known for its beneficial effects on
bone and cafestol is said to inhibit the progress of Parkinson's disease.
Although there is no recorded study on the association of caffeine with the
circulating levels of vitamin D in the body, there is evidence that caffeine negatively influences calcium
balance by reducing calcium re-absorption by kidneys and reducing
intestinal calcium absorption efficiency. An earlier study has also showed that
caffeine intake of more than 18 ounces of brewed coffee (or more than 300 mg
per day of caffeine) can accelerate bone loss from the spine in elderly
postmenopausal women. In children, the recommended daily caffeine intake is
limited to 2.5 mg / kg of body weight.
Similarly, data regarding tea consumption and vitamin
D levels is limited, though it has been reported that excessive consumption of
brewed tea can lead to skeletal fluorosis and increased bone mineral density.
In order to
determine the association between the frequency of coffee and tea consumption
and circulating vitamin D and calcium levels in Saudi adolescents, Abdulaziz
Al-Othman and his colleagues from the King Saud University, Riyadh, randomly
selected 330 Saudi boys (155) and girls (175) aged 11 to 14 years.
were divided into three groups based on 30 ml cup of coffee and tea
Group I - those
who drank 0 to 4 cups of tea or coffee per week,
Group II - those
who consumed 5 to 8 cups of tea or coffee per week, and
Group III -
those who consumed 8 to 12 cups of tea or coffee per week.
Frequency of coffee and tea consumption was recorded.
Routine analysis of fasting glucose, lipid levels, calcium, albumin and
phosphorous were done. 25-hydroxyvitamin D levels were measured using
enzyme-linked immunosorbent assays.
The results showed that vitamin D levels were highest
in the Group III irrespective of the age, gender, BMI, physical activity and
sun exposure of the subjects indicating an association between coffee and tea
drinking and circulating vitamin D levels in the body.
The study, thus,
found that serum vitamin D level increases as coffee and tea consumption
One of the
factors contributing to higher vitamin D levels in heavy coffee drinkers, is
the weight reducing effect of coffee. The study found that BMI mean value was
significantly decreased in heavy drinkers when compared to low and moderate
drinkers. This is because coffee
consumption decreases fat tissue by increasing thermogenesis, that is,
production of heat in the body, and thereby promoting weight loss in
Again heavy coffee drinking stimulates the
sympathoadrenal system, consisting of sympathetic nervous system and
adrenal glands, which increases break down of fats leading to reduction in
obesity and type-2 diabetes. However, this may not be among the healthy ways to
lose weight and should not be advised in general.
however had two limitations. Comprehensive data on outdoor physical activity
and diet, the two most important factors that affect vitamin D levels in the
body, was lacking. And, the type of coffee and tea used were also not taken
into consideration. Excessive tea and coffee intake have been associated with
other adverse effects like increased gastric acidity. These factors should be
kept in mind before deciding to take or advising others to start drinking
excessive tea or coffee.
Reference: Al-Othman, A. et. al. Tea and coffee consumption in
relation to vitamin D and calcium levels in Saudi adolescents. Nutrition
Journal 2012, 11:56 doi:10.1186/1475-2891-11-56