Does the combination of Vitamin D and calcium not really provide protection?

According to various estimates, falls are the lot of about a third of the elderly population every year. Usually, these are people aged 65 and over, and in this age group, they are the main cause leading to fatal and non-fatal injuries. Repeated falls in old age have been linked in follow-up studies to an increased risk of mortality even years later. For example, in a follow-up study that lasted nine years, it was found that two or more falls were linked to an increase of about 60 percent in mortality. In contrast, a single fall was not found to be clearly linked to an increase in risk. However, it is possible that the connection does not stem from the fall itself alone, but from processes such as functional decline, activity limitation, loss of independence, or moving to a nursing facility. On the other hand, frailty is considered in itself a significant risk factor for falls, mortality, hospitalizations, and disability. Therefore, repeated falls may also be a sign of a poor health condition that already existed before the event itself, although this is an assessment that has not yet received full research validation. The article was originally published on the Davidson Institute of Science Education website.

Bone health organizations note that about half of women and a fifth of men are expected to experience a fracture during their lifetime caused by "low trauma" — for example, a fall from standing height. In many cases, the fracture occurs following an injury that in a person with a healthy bone should not have ended in a fracture. Therefore, reducing the risk of fractures has become a central goal in public health, through a combination of preventing falls, maintaining bone health, and treating risk factors that can be changed. Against the background of the medical effort to reduce these risks, a systematic review with a meta-analysis published in the medical journal BMJ seeks to examine closely the administration of Vitamin D and calcium, and discovers that the effectiveness of the supplements in preventing fractures is in doubt for many.

What do calcium and Vitamin D do in the body?

Calcium is a central raw material in the bone structure, while the active form of Vitamin D — which actually acts as a hormone — helps regulate the calcium balance in the body, mainly by increasing its absorption in the intestine, alongside its effect on the kidneys and bones. Both components have been considered for years as possible means for improving bone health. When Vitamin D levels are low, calcium absorption may be impaired and leave less calcium available for the normal process of bone building. This biological logic received reinforcement from observational studies in which higher calcium intake was linked in some populations to higher bone density — especially among women with low levels of Vitamin D. At the same time, low levels of Vitamin D were linked to a higher risk of fractures. In this sense, bone diseases are not just a problem of a "broken bone", but sometimes also an expression of a disorder in the hormonal system and metabolic processes, and therefore their treatment often involves also endocrinologists, and not just orthopedists.

The supplements that catch on?

The biological logic and observational findings led many medical bodies to recommend over the years the use of Vitamin D and calcium supplements: a review of 34 medical guidelines found that about 70 percent of them recommended or suggested the use of Vitamin D for preventing fractures or for maintaining bone health. However, the recommendations were not uniform, and in most cases were not intended for the entire population but for certain groups — for example, for people with a Vitamin D deficiency, for elderly people at high risk, or for patients on osteoporosis medication. The perception that Vitamin D and calcium protect against fractures was established not only in the medical system but also in the general public. Surveys from different countries found that information about Vitamin D and bone health reaches people also through the media, social networks, family members, and friends. However, in various studies, medical professionals remained the main and most reliable source of information, and information received from doctors was often linked to greater reliability.

Myth busters

To resolve the gap between the biological logic, the prevailing recommendations, and the inconsistent findings that arose in previous studies, researchers conducted a new systematic review with a meta-analysis. The review included 69 randomized studies with the participation of almost 154 thousand participants. In the studies, calcium supplements, Vitamin D, or a combination of the two were compared to a dummy treatment (placebo) or no treatment, with the goal of checking if they reduce the risk of fractures and falls among the elderly. The median age of the participants was about 71 years, and the median follow-up duration stood at about two years. Most of the participants lived in the community, and about three-quarters of the studies did not focus on populations at particularly high risk. Therefore, the findings reflect mainly the effect of routine use of supplements among the elderly, and not necessarily in people with a Vitamin D deficiency or significant bone diseases.

The findings showed that Vitamin D alone did not reduce the risk of fractures. In 36 studies that included 92,415 participants, the rate of fractures stood at about 6.5 percent, both in the supplement group and in the control group. Calcium alone also did not provide a clear advantage. Only the combination of Vitamin D and calcium was linked to a small decrease in the rate of fractures — from 11.3 to 10.3 percent. That is, about one fracture less for every hundred patients. Despite the statistical significance of the result, it did not reach the threshold that the researchers defined in advance as having clinical significance — a decrease of at least two percent. Also regarding falls, no clear advantage was found for any of the interventions tested.

In an additional analysis, where each time another study was removed from the review, it turned out that a single study influenced significantly the overall results. The study was conducted on women aged about 84 who lived in institutions, with low Vitamin D levels and calcium intake and a particularly high risk of fractures. After its removal, the decrease observed in fractures of all types, in hip fractures, and in non-vertebral fractures weakened and even lost statistical significance. Also, the subgroup analyses did not show that the relative effect of the supplements is greater in populations at high risk. However, the researchers noted that it is possible that the absolute benefit in these people will be greater, because their baseline risk is high to begin with, although the evidence on the subject is still limited.

Not for everyone

The researchers note that the absolute effects calculated in the review were based mainly on populations at low risk, and therefore it is possible that they underestimate the degree of possible benefit in people at high risk — especially when it comes to the combination of Vitamin D and calcium. However, this is a hypothesis based on the baseline risk level of the participants and not on direct proof that a certain group derives greater benefit from the supplements. Here too, the existing evidence is still not enough to determine an unequivocal conclusion.

It is important to note that the review was not intended to check if the supplements improve bone density, but if they succeed in reducing the results that are truly important from the patients' perspective. Therefore, the researchers defined in advance the rate of fractures of all types as the central measure for checking the effectiveness of the supplements. In addition, hip fractures, vertebral fractures, non-vertebral fractures, falls, and the total number of falls were also examined. That is, the researchers did not ask if Vitamin D and calcium change a biological measure like bone density, but if this change is translated into fewer fractures and fewer falls in practice. This is an important distinction, because the supplement may affect bone metabolism and yet still not lead to a significant decrease in fractures in the general population.

Bottom line, there is no dispute that Vitamin D and calcium are essential for bone health. However, their biological importance does not guarantee that they will prevent fractures or falls. The review found that Vitamin D or calcium alone had almost no effect on the results, and even the combination between them provided at most a small benefit. Therefore, the findings do not support the routine taking of supplements by the general population for the purpose of preventing fractures and falls. However, the conclusions are not necessarily true for people with a diagnosed Vitamin D deficiency, bone diseases, particularly low calcium intake, or osteoporosis medication. In these cases, the decision on treatment should be made personally, in accordance with a doctor's recommendation.