Bone health is an essential aspect to the longevity of a gymnast’s career in the sport and has lasting effects years beyond sport. Many high-level gymnasts will have their Vitamin D levels checked as it’s generally known that this vitamin has positive effects on bone health. But, not as well known, vitamin D only facilitates calcium absorption and it’s paramount that adequate amounts of calcium be provided through the diet to maximize bone health. Calcium is an essential mineral in the body, and thus if there are not sufficient amounts from the diet the body will just pull calcium from the bones to keep the blood levels consistent.
This young high-level gymnast (10-20 something years old) is in a critical time period for bone mineralization, and loss of bone mass begins around age 30. Improper nutrition during adolescence will have long-term implications that are minimally reversible (like osteopenia/osteoporosis).
There are three essential factors we must examine for the gymnast to ensure their bone health is protected and optimized: Energy availability, adequate dietary calcium, and adequate vitamin D.
Adequate Energy Availability
You may wonder why we’re starting with a discussion on energy availity instead of talking about calcium or vitamin D in relation to bone health.
Like many aspects of the gymnast’s nutrition and performance, you cannot ignore the glaring issue of underfueling and it’s effects on so many of the body’s systems. I’ve talked about RED-S or the relative energy deficiency in sport at length, see here, here, here, and here.
A gymnast can take all the calcium supplements, all the vitamin D, and do all the weight bearing exercises, but if they are not eating enough to meet their nutrition needs, the bone mineral density will be negatively affected.
Along with adequate energy availability, adequate protein is essential for maximal bone mineralization though this isn’t often as big of an issue as most young athletes tend to meet protein needs over carbohydrate or calorie needs.
The Protective Effect of the Menstrual Cycle
Females who have amenorrhea, or without normal menstrual cycles, will have a significant decrease in reproductive hormones, especially estrogen. Estrogen plays and important role in bone mineralization, and thus normal cycles are part of maintain bone mineral density. It’s often thought that birth control will “protect” the bones for amenorrheic athletes, but this is not true. Studies have shown small detrimental effects on bone density in teenagers on birth control versus non-users.
It’s one thing if a gymnast wants to be on birth control for contraceptive protection OR because she has heavy, painful periods, etc. But, to take hormonal birth control as a “fix” for abnormal or absent menstrual cycles is not a “fix”, especially in the case of inadequate energy availability (with or without disordered eating). Unfortunately, many physicians are not well-versed and may prescribe your gymnast birth control to “protect her bones” when her lack of period is due to inadequate energy availability (hypothalamic amenorrhea) or another hormonal condition like polycystic ovarian syndrome.
Also, certain birth controls like Depo-Provera (depot medroxyprogesterone acetate) can cause 5-7% bone loss from the spine and hip. This is significant and not worth the risk with a high-level gymnast, though this loss can be reversed once the drug is stopped. This injection birth control lasts for 3 months, so care needs to be taken when exploring birth control options and necessity (stay tuned for a post on this soon!).
Why athletes don’t drink milk or get enough calcium
Most young athletes are not meeting their calcium needs, which is 1300 mg per day per the RDA. If you think about it, given the average amount of calcium in a food is about 200-300 mg (dairy products or fortified plant-milks), that’s about 4-5 servings per day.
Does you gymnast have a source of dairy at each main meal?
Does your gymnast have additional dairy at least 1-2 other times during the day?
If not, they’re unlikely to be meeting their needs, especially if they do not consume dairy products (vegan, vegetarian, disordered eating, lactose intolerance, milk protein allergy, or general avoidance).
Some families choose not to drink milk past a certain age out of misguided fears that “milk is inflammatory”, and “humans cannot process cow’s milk” or “milk contains hormones and antibiotics”.
Others just don’t put as much emphasis on milk or other dairy products once the children are out of the early grade-school years (or, it’s “not cool” for your teenager to drink milk anymore).
Is milk inflammatory?
Milk is sometimes thought to be inflammatory due to the saturated fat component, but several studies have shown no evidence that consuming whole fat dairy foods increases inflammatory markers, and if anything has a small anti-inflammatory effect. As with all nutrition research, it’s all about context. A few cups of 1% to whole milk a day and a few servings of low sugar yogurt and cheese is very difference that copious amounts of fried cheese (mozzarella sticks), fast food pizza, super sugary yogurts, and multiple servings of ice cream or other high sugar dairy products. There are some observational studies that show that high intakes of dairy products can cause acne, but again, it’s all about context.
Tolerance to Cow’s Milk- Allergy vs Intolerance
In terms of tolerance to milk, that can be a valid area where an individual may choose not to drink or consume cow’s milk products. Cow’s milk contains three main components that can cause symptoms such as bloating, gas, diarrhea, eczema, or even constipation.
Milk contains two proteins, whey and casein, which are often linked to infant cow’s milk protein intolerance that most grow out of. If not, it can become a milk allergy and thus essentially all dairy products would need to be avoided. Plant-milk alternatives would be appropriate, but keep an eye on added sugar and the minimal protein content. Plant-milk cheeses and yogurts have minimal overall nutrition aside from calories, some carbohydrate, and a little fat—they are not great sources of protein, calcium, vitamin D, etc like their cow’s milk counter-parts.
Milk also contains a carbohydrate, lactose, which some people have an intolerance. Lactose itself does not cause an allergy; the body makes an enzyme called lactase that breaks down the lactose (milk sugar), though the amount of this enzyme decreases with age or in certain ethnicities (Asian, African American see a 75-95% lactose intolerance rate). For some, tolerating lactose is all about the “dose” in order for the carbohydrate to not be what’s called “malabsorbed” and then cause bloating, cramping, diarrhea, etc. Generally, ½ a cup of milk (6g of lactose) can be tolerated in one sitting and thus other dairy sources that are “harder”, i.e. have more lactose removed (yogurt, cheese, sour cream, etc) can be tolerated in slightly larger amounts. If this is the case, a focus on hard cheeses, lower-lactose yogurts (Greek) or even lactose free yogurts and cow’s milk are great choices for the athlete’s diet in order to meet calcium needs.
Vitamin D- Testing, Supplement Compliance, Follow Up
Vitamin D is a fat-soluble vitamin found in fatty fish, eggs, fish liver oils, and fortified products such as milk, cheese, and butter. The RDA for vitamin D is 600 international units (IU) per day, but this has been questioned in terms of adequacy for children and adolescents, and certainly high level athletes. The Endocrine Society suggests that individuals will need at least 1500-2000 IU vitamin D per day to get blood levels above 30 ng/dL.
The specific lab that needs to be checked to monitor vitamin D levels is called 25-hydroxyvitamin D (25(OH)D). If this level is less than 20 ng/dL, that is considered deficiency. Some physicians will order a different lab (often on accident) that looks very similar- 1, 25-dihydroxyvitamin D, but this is used only for monitoring certain conditions or inherited disorders.
For the athlete, it’s recommended that 25-OHD be above 40 ng/dL, and it will likely require at least 1000 IU of Vitamin D3 per day to raise above 30 ng/dL.
An athlete will most likely need a vitamin D supplement, but it’s essential to “test, not guess”. You don’t just want to purchase a random vitamin D supplement and start giving it to your gymnast. It may not be enough, could be too much, etc. It’s safe to say that many individuals will struggle to get adequate vitamin D from the diet, and additional amounts provided through a daily multivitamin or specific vitamin D supplement need to be calculated and monitored.
Vitamin D3 supplements have shown to be more effective than vitamin D2 in some studies, so that would be my recommendation if a supplement is needed. As always, be sure the supplement is third-party verified by an organization like the National Science Foundation or Informed-Choice, especially if the athlete is in the NCAA or has NCAA dreams.
There are several moving parts to ensuring nutritional adequacy for bone health- adequate energy availability, adequate calcium, and adequate vitamin D. As always, if you’re not sure that your gymnast is doing what she can to protect her bone health, let’s chat. If she’s had several injuries, especially stress fractures, stress reactions, or bone breaks, a nutrition check-in is essential. We’ll review her diet, discuss supplements if needed, and as always, I can provide recommendations for appropriate lab testing that the pediatrician or sports medicine physician can order.