Bone Health and Important Micronutrients for Athletes
Have you ever wondered what makes your bones strong and how to ensure long term bone health as an athlete? Today we will go through everything you need to know about bone health. We will cover the micronutrients important for bone health, what promotes bone health and what can be detrimental to bone health.
Bones make up your skeleton system and give your body support and structure as well as protecting vital organs. Life-long bone health is important because it decreases the risk of fractures and osteoporosis. Osteoporosis is a slow and long-acting disease of bone that is marked by low bone mass and deterioration of bones which decreases bone strength and increases the risk of fractures1. To prevent osteoporosis, it is important to focus on bone health in the adolescent years and early adult years. It has been reported that 90% of maximum bone mass is reached by age 20 and the maximum amount of bone mass is usually reached around age 30 (1).
The micronutrients most important for bone health include vitamin D, calcium, and phosphorus. Calcium and phosphorus are important minerals that are used to build bone and vitamin D is an important regulator of bone building and breakdown.
Calcium in the 5th most common element in the human body and 99% of the body’s calcium is in bones and teeth. When calcium levels in the blood get too low a hormone, called parathyroid hormone, is activated which increases the amount of the active form of Vitamin D, calcitriol in the blood. Calcitriol then acts on the kidneys to reabsorb calcium, the intestines to absorb more calcium and bones to release calcium. This returns blood calcium levels back to normal levels at the expense of bone. When calcium levels get too high in the blood, a different hormone, calcitonin, acts on the kidneys to excrete calcium, on the intestines to decrease absorption and promotes bone building activity by incorporating more calcium into bones (2).
Phosphorus is the second most abundant mineral in the body and about 85% of the bodies total phosphorus is found in bones (2). Low phosphorus intakes can lead to decreased bone mass as it is needed to build bone. High intakes can also lead to decreased bone mass because excess phosphorus binds to calcium and carriers it into soft tissues (2). This causes low calcium levels in the blood which stimulates the breakdown of bone to bring blood levels back to normal.
Next, we will run through how much of each of these micronutrients we need daily and good sources of each. For calcium, it is recommended athletes get the RDA (recommended dietary allowance), which is 1000 mg per day for those aged 19 to 50 years (2,3). It is important to note that athletes who frequently exercise in the heat may have higher calcium needs (2). Good sources of calcium include dairy products, kale, almonds, spinach and soy milk or tofu fortified with calcium. Calcium is absorbed best if taken in doses of 500 mg or less (2). This means if you are prescribed higher dose calcium supplements, you will benefit from taking two or more smaller doses.
For vitamin D, the RDA is again the recommended amount for athletes (2). The RDA for those aged 19-50 is 600 IU or 15 mcg per day (3). Needs may be increased for those living in northern states during the winter as the amount of sunlight our skin sees is not enough and sunlight exposure is the primary way we get vitamin D2. Dietary vitamin D can be found fortified into milk, bread, and cereals or naturally in eggs, liver and fish. Vitamin D is often taken in conjunction with calcium because it enhances the absorption of calcium.
For phosphorus, the RDA is 700 mg for adults aged 19-50 years (3). Phosphorus is found in a variety of foods including soft drinks, dairy products, nuts, oatmeal, sardines and asparagus (2). Phosphorus deficiency is rare due to the variety of foods containing phosphorus (2). Usually, overconsumption is the bigger concern since phosphorus is in a lot of foods. Soft drinks are of particular concern because they contain inorganic phosphorus that is more easily absorbed. Research has linked soft drink consumption to increased risk of fractures due to phosphorus binding to calcium and causing bone breakdown (4).
Other factors of bone health include exercise and overall energy balance. Exercise, in general, is considered to have a positive impact on bone health. Weight bearing activity has been shown to have positive impacts by stimulating bone to rebuild stronger (1). Bones need time to rebuild after stress however, so too much impact or weight bearing can lead to fractures without adequate recovery times. For sports that are non-weight bearing, such as cycling and swimming, athletes have been found to have lower bone mass than athletes in other sports. Energy availability also has an impact on bone health. When athletes are unable to replace all the energy they use during large bouts of exercise, they have low energy availability. Low energy availability has been found to be associated with breakdown of bones and poor bone health (1).
Overall, you as an athlete, need to ensure you are getting adequate amounts of calcium and vitamin D while limiting phosphorus intake (esp. soft drinks) to promote healthy bones. You also need to make sure you are eating enough and replacing all the energy that you burn each day. Additionally, weight bearing activities such as strength training can help further promote strong bones.
References
1. Sale C, Elliott-Sale KJ. Nutrition and Athlete Bone Health. Sports Med. 2019;49(Suppl 2):139-151. doi:10.1007/s40279-019-01161-2
2. Karpinski C, Rosenbloom C. Chapter 5: Vitamins, Mineral and Exercise. In: Sports Nutrition: A Handbook for Professionals. Academy of Nutrition and Dietetics; 2017:87-94.
3. “Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Vitamins.” USDA, Food and Nutrition Board, Institute of Medicine, National Academies, www.nal.usda.gov/sites/default/files/fnic_uploads/RDA_AI_vitamins_elements.pdf.
4. Chen L, Liu R, Zhao Y, Shi Z. High Consumption of Soft Drinks Is Associated with an Increased Risk of Fracture: A 7-Year Follow-Up Study. Nutrients. 2020;12(2):530. Published 2020 Feb 19. doi:10.3390/nu12020530
