By HPN intern Amy Lynn
Teenage years are the period of life with the fastest rate of body growth. This is also the period of sexual maturation, which is accompanied by significant physiological changes. As a result, nutritional requirements of teenagers tend to be significantly different from those of adults (1). Due to accelerated growth, the teenage body yearns for elevated nutrition, although it’s the last thought a teen wishes to engage in. Unfortunately, today, we are seeing higher nutritional deficiencies in teens due to an over active, hyper driven society. Several health conditions such as loss of height, osteoporosis, and even delayed sexual maturation may present themselves in these delicate growing years (2). In addition, the increasing decision to undertake vegan or vegetarian based diets are increasing amongst teens, which then gives nutritional deficiencies another level of disconcertment, especially within the athletic group.
Physically active teenagers expel a lot of energy during training, which in turn, requires huge levels of replacement energy. Often teens can push hard to incorporate desired goals, leading to possible outcomes of long and exhausting training sessions (2). This means their caloric intake should be adjusted according to the intensity of their training. If a sporty teen is also a vegan, and is not getting the proper nutritional intake, the results of training might be rather different from his or her expectations.
Being a vegan at this age puts additional demands on the anatomy if not incorporating macro and micro nutrients found in an animal based diet. Vegans do not consume any animal products including fish, dairy or eggs, therefore alternative nutritional resources need to be incorporated. This type of eating alters the number of nutrition sources available to them and may result in insufficiencies of several nutrients if not properly guided. Such nutrients may include proteins, microelements (iron, calcium and zinc), vitamins (D and B12) and essential fatty acids that are found predominantly in animal products. However, these additional challenges can be addressed with a well-planned diet (3-5). Due to the lower energy density of the vegan diet, one of the major concerns for vegan athletes is the inadequate intake of calories. Insufficient caloric intake may lead to excessive metabolism of proteins and amino acids in the body, eventually resulting in slowing down of metabolic processes. This may lead to reduced sport performance and weight loss (4).
Many of the protein sources vegans consume contain proteins lacking in some of the essential amino acids (6,7). Amino acids are building blocks of the proteins produced by our body and whereas the cells of our body can synthesize most of them, there are eight amino acids (called essential amino acids) that our body cannot produce (8). These amino acids must come from an outside source. The proteins of meat contain all essential amino acids, whereas vegetable proteins lack in some which classifies it as an incomplete amino acid source. Although, different plant sources lack different amino acids, consuming a variety of different protein-containing vegan foods can supplement the diet with all essential amino acids necessary to obtain the complete essential amino acids the body needs to function at its best (8).
Athletes with high level of physical activity, or those involved in endurance sports, do benefit from higher intake of proteins (5). The specific requirements depend on the type and typical duration of the training session and can be calculated by taking into account other individual parameters such as age, gender, weight and height (8).
Both vegetarian and vegan diets are low in omega-3 fatty acids (EPA and DHA). Among other things such as optimal brain function, these acids are important for the control of exercise induced inflammation (8). EPA and DHA are present in walnuts, soy, hemp and flaxseeds and should be consumed regularly to keep the levels of these important fatty acids balanced. If this is a challenge, then speaking to your trusted health practitioner will help you find a suitable supplement.
Iron stores in the body tend to be lower in vegetarians compared to omnivores. Iron from plant origin is non-heme iron, the form which is not easily absorbed by the human body, however when non-heme iron is included with vitamin C, it increases the absorbancy (9). Young vegan athletes must include sufficient amounts of iron rich foods with Vitamin C such as dark leafy greens, legumes and rice, falafel and lemon, raisins, and broccoli. It is recommended that vegetarians consume twice more iron than non-vegetarians (10). Athletes need to increase the iron intake even further. Experimental data show that replenishing the iron level in iron-deficient young athletes results in the increase of maximal aerobic performance capacity (11). Girls are particularly vulnerable to the shortage of iron and can develop iron-deficient anemia (6).
Calcium is particularly important during teenage years, as the body grows fast and requires lots of calcium to build the bones. However, due to exclusion of dairy products, the intake of calcium is often rather low in vegans. Consumption of caffeine and energy drinks by vegan athletes represent an additional challenge due to the high intake of sodium which increases the excretion of calcium (12). Leafy green vegetables such as collard and Chinese cabbage along with turnip and broccoli are good sources of this microelement. It is of paramount importance to get adequate calcium intake at this age. According to New Zealand Ministry of health, teens need to consume at least 1,300mg per day (17). If it cannot be achieved through the diet alone, calcium supplementation could be considered.
Vitamin D works together with calcium to make the bones stronger, and therefore its deficiency can be detrimental for both body growth of teenagers and their athletic performance. Like in the case with calcium, due to exclusion of dairy products, vegans may have low intake of this vitamin. Studies show a deficiency in vitamin D may lead to reduced body mass, depressed moods and a 30% higher risk of bone fractures especially among vegans as opposed to omnivores (12). Vitamin D can be obtained from tofu, mushrooms or plant derived supplements. Also, the production of vitamin D within the body is stimulated from sun exposure. Twenty minutes a day in the sun can be beneficial.
The other important dietary components that might be in a short supply in vegan diet include vitamin B12 and zinc. Vegans are at particularly high risk of vitamin B12 depletion which may lead to macrocytic anaemia and result in decreased energy to reach athletic goals.6 The deficiency of vitamin B12 can be addressed by vitamin supplementation or consumption of vitamin B12 containing foods such as nori and algae (13).
Zinc is vital for body’s development and growth and athletic training is associated with increased zinc loss in sweat and urine (14). Zinc containing plant sources of food available for vegans include tofu, whole grains, nuts and legumes, but they may be insufficient. In such cases, taking additional mineral supplements should be considered.
Creatine is one of the molecules required for muscle movement. As the most common source of this amino acid is meat, vegans can have rather low levels of creatine in the body (6). This may affect their strength and performance therefore a creatine supplementation could be included in the diet. Although research studies consider oral creatine supplementation safe in small doses, its long-term consequences are not well studied (15).
In conclusion, combining active sport participation with a vegan diet can be a serious challenge in teenagers. However, there are no reasons to believe their athletic performance and general health can be affected if the proper attention is paid to their diet. The points of particular concern at this age include the adequate supply of essential amino acids, calcium, vitamin D, and iron (particularly in female young athletes). Also, a proper monitoring of intensity and duration of training sessions should be done, as over training can often occur within the young athletic community. For more information and guidance, please contact a nutritionist.