Preventing osteoporosis means reducing the possibility of fractures. For this reason, bones should be strengthened over the years following an appropriate lifestyle. Dietary calcium intake is important to assist bone growth and maintain bone health. However, is the intake of supplements of this mineral and vitamin D equally important? Can supplementing diet with these micronutrients help prevent osteoporosis fractures? We discuss the topic with Professor Bianca Marasini, Senior Consultant in Rheumatology and Clinical Immunology at Humanitas.
Diet and bones
Calcium and vitamin D are two key micronutrients for bone health, and a diet with sufficient intake of both helps to strengthen our bones. The bones store calcium, which is present in various products, such as milk and its derivatives, as well as in green leafy vegetables or almonds although in smaller quantities.
The body needs vitamin D for calcium absorption. Vitamin D is found in a few foods (such as eggs, and liver), but its main source is the sun (the vitamin D is also referred to as “the vitamin of the sun”). The sun promotes, with a relatively complex mechanism, the synthesis of vitamin D from the skin. However, sun creams prevent much of the synthesis, which also depends on the presence of adipose tissue and pigmentation of the skin. Moreover, in the elderly, where we know that osteoporosis is particularly frequent, vitamin D synthesis is reduced. Thus, a deficiency in vitamin D is very frequent among the elderly. A vitamin D deficiency is reported in about 80% of the population.
Supplements as “pills”?
With diet as well as exercise, it is possible to contain the risk of osteoporosis, a condition characterized by the very significant reduction of bone mass that makes bones fragile and therefore exposed to the risk of fractures. In addition to diet, should supplements of these two micronutrients be taken continuously in order to keep bones strong with age?
A recent article published in the Journal of the American Medicine Association has reopened the debate of not associating the intake of calcium and vitamin D supplements with a reduction in the risk of fracture from osteoporosis in the elderly. As its authors recall, previous studies had provided conflicting conclusions on this association.
A research team from Tianjin Hospital (China) conducted a meta-analysis of thirty-three studies that compared the intake of supplements with placebo and the number of fractures. The data related to 51,145 adults over 50 years of age. The conclusion of this, like other studies, has called into question that calcium and/or vitamin D supplementation reduces the risk of fracture: “Studies have not convincingly demonstrated that calcium and vitamin D supplementation taken as pills reduces the risk of fracture. However, since most of the population is deficient in vitamin D, and vitamin D is found only in traces in certain foods and since sun exposure without sun protection is absolutely to be avoided, vitamin D supplementation is often necessary,” says Professor Marasini.
But how much vitamin D is needed? “It depends on the plasma levels of the individual person, bearing in mind that optimal levels are between 30 and 60ng. Therefore, the advice is to dose vitamin D levels in the blood and supplement, when necessary, with a personalized dosage,” continues the expert.
For calcium, the discourse is different because calcium is found in food; thus, it is far preferable to take calcium through diet. However, it is important to remember that, while the range of vitamin D levels in the blood is very wide and it is really difficult to reach toxic levels, the range of calcium in the blood is very narrow, and low levels (hypocalcaemia), as well as high levels (hypercalcaemia) can create serious problems”.
However, since vitamin D promotes the absorption of calcium in the intestine, it is good practice to avoid an excess of vitamin D, which is seldom toxic in itself, but it can lead to dangerous hypercalcaemia. Therefore, the doctor will remember to periodically check both vitamin D and calcium levels.
So in what cases could supplements be indicated? “Taking supplements is necessary if vitamin D or calcium levels in the blood are low. As mentioned above, a deficiency in D is very frequent and consequently the need to resort to vitamin D supplements, usually taken orally and more rarely by intramuscular administration”, replies the professor.
It is less common to find low levels of calcium, as the most common foods provide a sufficient amount of calcium. However, attention should be paid to the drugs taken for osteoporosis, especially those used through a venous pathway, because they can lead to significant hypocalcaemia; in these cases, supplementation with calcium is mandatory. In conclusion, vitamin D and/or calcium supplementation is only necessary when plasma levels are not sufficient to keep a bone healthy; therefore, it should be dosed individually, based on physical characteristics (such as diet, degree of sun exposure, obesity) and any ongoing medications”.