Calcium Deficiency in Athletes

Introduction

Everyone, regardless of age, should ensure they consume an adequate amount of calcium through their diet. In cases where dietary calcium intake falls short, calcium supplements become essential to meet daily requirements. (Evidence Level A I)

Calcium Supplements

In clinical practice, it is common to combine vitamin D supplements with calcium compounds. The Australian Institute of Sport (AIS) recommends that, in the absence of specific athlete requirements, standard population norms for calcium intake should be followed (see Table 1).

Table 1. Recommended Daily Calcium Intake by AIS

Symptoms of Calcium Deficiency

Common symptoms of calcium deficiency include increased fatigue, dry skin, brittle nails, dental problems, numbness in fingers, and muscle cramps.

Calcium requirements increase with age, especially for children and adolescents. Inadequate calcium intake in this age group can lead to bone health issues, blood clotting problems, and an imbalance between organic and inorganic components of bones by the age of 25–30. In adults, these processes can contribute to osteoporosis.

Osteoporosis in individuals with calcium deficiency can lead to disrupted menstrual cycles and hormonal imbalances in female athletes, negatively affecting calcium metabolism.

Intense physical activities, such as cyclic sports, can result in a rapid loss of calcium through sweat, increasing the secretion of parathyroid hormone to maintain calcium levels in the blood (leading to the removal of calcium from the bone matrix).

Types of Vitamin K

There are three types of vitamin K (Pankaj Р., Mageda М., 2008):

1. K1 (phylloquinone), obtained from plants.
2. K2 (menaquinone), produced by intestinal bacteria.
3. K3 — a synthetic water-soluble form.

The most common form of vitamin K in a standard human diet is K1. K2, found in various fish, meat, dairy products, fermented cheese, etc., has better bioavailability. Both forms play different roles in the body (Dowd P. et al., 1994), but international recommendations primarily focus on K1—90 micrograms per day for women and 120 micrograms per day for men.

Correcting Calcium Deficiency

To maintain adequate calcium levels, calcium carbonate is commonly used, although other forms like calcium citrate, phosphate, and gluconate are also available for clinical use. Calcium carbonate is well-tolerated and efficiently absorbed by the gastrointestinal tract in doses below 500 mg. When using higher daily doses (above 500–600 mg per day), it’s recommended to divide the daily dose into 2–3 portions (common high-dose calcium supplements range from 500–1000 mg per serving).

Combination supplements of calcium with vitamin D, available in the market, can also be highly effective in sports for maintaining calcium levels.

Conditions for Using Calcium Supplements in Sports

Firstly, the use of calcium supplements, especially in combination with vitamin D3, should be regulated and supervised by a sports physician as part of an overall Nutrition and Mineral Program, taking into account other prescribed supplements and medications. Secondly, regular (preferably monthly) biochemical and clinical monitoring of calcium metabolism and vitamin D levels is necessary. Thirdly, calcium supplements alone do not guarantee success without addressing hormonal status, gastrointestinal function, ensuring adequate energy intake, macronutrients, micronutrients, and alignment with the training program. Lastly, athletes with gastrointestinal issues or an imbalanced diet should undergo dietary status correction with the guidance of a dietitian or nutritionist.