Nuts for Nutrition Part 1: Healthy Eating is More than Just Fruits and Veggies
We've all heard the "eat 5 fruits and veggies a day" and "exercise 30-60 minutes 3-4 times a week" lecture in school. What isn't discussed in school is what it means to have a healthy mental approach to eating, particularly as an athlete.
While I've never experienced an eating disorder, I did undergo disordered eating as a kid (and into my collegiate years), due to misinformation (or lack of information/guidance) and poor body-image confidence. This is a story for another time.
There is a very slow cultural shift towards body inclusivity in both athletics and daily life, but there's still an ingrained image of what an athletic body should look like, or what an ideal body should be. This shouldn't be the driving factor in any nutrition planning and dietary change. Instead, focus on fueling your body's energetic and dietetic needs, and honestly, enjoying your food.
But before we move on, a couple of disclaimers:
1) I hate using the term diet in the terms of sport nutrition, as term is commonly associated with popular nutrition fads and trends that result in diet-crashing and training burnout. However, for the sake of my sanity and for your clarification, I will still use diet to reference one's general eating habits (which is the main definition of diet to begin with).
2) Take my words with a grain of salt. I am not a dietitian, or a doctor, or a research scientist. Just an athlete on the internet invested in learning more about the things that improve overall performance and health, and helping to filter the massive-web of information to make it more understandable and relatable to you as an performer.
Thus, I will have some biases. I'll try my best to take a step back (especially in this first article of the series), provide the sources I used to base my knowledge on, but I may still get information wrong. It happens. I'm only human and learning this as I go in my "free" time. If you do have concerns about your own nutrition plan or health, please consult a dietitian (specifically a sports-dietitian, if possible) or a doctor, as they are more knowledge about this.
Another bias I may have is the type of sports nutrition I consume. (This may not show up here in this article, but it will be prevalent in the next two.) I'm an ambassador (not sponsored) for Honey Stinger and Nuun, so I will mention them more and support them, than other brands.
Lighter isn't always faster
There's a minimum healthy weight range at which an athlete can function normally and perform their best. However, this weight, generally known as "race weight," isn't sustainable for long periods of time, otherwise the system would shut down with illness or injury.
You may see high-caliber athletes, elite amateurs and pros, controlling their weight throughout the year and season. By periodizing body composition throughout the season, you're ensuring that your body has enough energy to train and perform daily activities, as well as be able to recover and build from those training sessions. This approach allows an athlete to sustain heavy training loads, while having a longer career in endurance athletics.
Here's a 9 year case study of an Olympic-level female runner who periodized her body composition, and resulted in better performance and fewer injuries: https://www.ncbi.nlm.nih.gov/pubmed/29140157
Even though the spotlight is on pro runners and other pros regarding the talk about body composition, amateur and collegiate athletes are just as likely, if not more likely, to dig themselves into a hole of low energy availability. This is mostly due to the fact this group of athletes have lives beyond sport: full-time jobs, school, family, and many other obligations. Because of this hectic lifestyle, these athletes tend to forget to take care of their bodies and provide the right amount of fueling.
Poor fueling can also result in higher rates of injuries and illnesses, and decreased training adaptations because the body is trying to survive by breaking down muscle tissue and other energy stores to keep up with high energy demands. Sometimes, this may only manifest itself as fatigue and poor focus in the early stages. As the energy deficit grows, the body can go into a state known as Relative Energy Deficit in Sport (RED-S), formerly the female triad. RED-S can happen in anyone, any gender, any age, and any level, if not more so in amateur athletes who have busy lives, are juggling responsibilities, and less likely to get enough sleep at night. I am very briefly mentioning RED-S here, but here's a list of resources and articles to check out to learn more about RED-S, and I will talk about my experience in another blog or video.
"The IOC consensus statement: beyond the Female Athlete Triad—Relative Energy Deficiency in Sport (RED-S)": https://bjsm.bmj.com/content/48/7/491
"Relative Energy Deficiency in Sport": https://www.brown.edu/campus-life/health/services/promotion/nutrition-eating-concerns-sports-nutrition/relative-energy-deficiency-sport-red-s
"The Risks of Relative Energy Deficiency in Sports": https://www.trainingpeaks.com/blog/the-risks-of-relative-energy-deficiency-in-sports/
So, us common Jills and Joes may not find periodization and micro-managing our body composition sustainable, or even trying to stick to the latest diet fad (more on that later). Heck, our lives are busy and stressful as is trying to fit everything in while still taking care of our bodies. Our best use of our time, energy, and sanity is to focus on fueling our workouts and lives.
Trending or Fad Diets are Not for Everyone
There are big discussions revolving around what's the best diet out there? Keto? Vegan? Fasted? Truth be told, there's no right diet for everyone. Your overall lifestyle, gender, medical history, gut biome/flora, and your genetics are a few of many variables influencing what works best for you. One diet can't be truly generalized to the whole population. The medical and scientific community are still studying many of the processes that influence our metabolism of different nutrients. To add to the confusion, much of nutrition science is sensationalized, occasionally false, and more often not applicable to different populations of people and lifestyles. Now, the last factor isn't the fault of nutrition science itself: we just have to remember that what science tests in a highly controlled setting, may not be effective or applicable in real-life, uncontrolled scenarios.
One of the biggest diet trends in the media today, particularly in the endurance world, is the ketogenic (aka "keto") diet, which a diet consisting of high fat and low/no carbohydrates. The idea behind the keto diet is that you utilize fat as fuel more efficiently, thus resulting in more effective weight loss. In certain populations, this has been shown to work. Key word here being, "certain".
The current research regarding fat oxidation and ketosis in athletes is showing mixed results, with either no improvement of performance or only a small increase in performance. Much of the research that the media has hyped up is referring to very specific populations of people, and doesn't necessarily apply to you. On the other hand, some people have tried this diet and found that it truly does work for them and is sustainable. (2,4,8)
As I'm researching information about what is best for athletes and performance, I've come to realize that despite the guidelines, there's still some debate in the nutritional science community about what is the most ideal, especially (like I mentioned earlier) since a laboratory setting isn't always be realistic.
With all of this flurry of science, misinformation and hyped up media, it is very hard to say what's the best thing for you. I will do my best to give you a starting block for your nutrition plan construction.
Let's Start with the Basics
If you're not sure where to start or you're starting from scratch, there are basic principles that you can follow to help jump start your nutrition plan. These steps may help you discover what does work for you and optimize your performance both on and off the field.
1) Don't count calories (to excess).
While athletes need more energy in general, it's the quality of that increased energy intake that matters, not just the quantity. During workouts, eating sugar fuels your efforts in addition to the glycogen stored in your body's muscles (primary storage for energy utilization), but in your daily nutrition plan, you should be aiming to eat more whole-foods and fewer processed foods. For example: eating a protein bar isn't necessarily going to bring the same energy, nutrition and recovery benefits to your system as say having an egg sandwich.
Another reason why counting calories isn't necessary is because calories on the labels and the calorie-burn count on your watch are inaccurate. Foods can be a little bit more or less more or less than what the label says, or with the case of produce, they can contain more or less nutrients than what your average label says. The calorie-burn tracker uses an algorithm to approximate how much energy you're using,. But, it doesn't know your exact basal metabolic rate, and to measure energy consumption, usually you need equipment to measure the carbon dioxide your exhale and compare it to your oxygen intake. (7)
While the daily recommended caloric consumption on US food labels is 2000 calories, as our basic metabolic needs alone will range from about 1,500 to 2,000 calories depending on your sex, age, body composition, and activity level. Add in hours of training per week, high amount of brain function for work and school (brains consume lots of glucose, about 60% of the body's supply at rest, which is about 120g daily! (1) And that daily caloric requirement goes up even higher. Not to mention, the quality of fuel you put into your body matters, as well.
However (playing devil's advocate here), counting calories could help you give you a sense of the amount of energy you're consuming, despite the inaccurate calorie labels and algorithms. Just remember that these numbers are simply a rough estimate, at best.
2) Eating balanced macronutrients.
Fat doesn't make you fat. Sugar isn't always the enemy, especially in endurance athletics. Like I mentioned before, it's about the quality of macronutrients and the amount you consume that matter: A bag of potato chips isn't the same as a bowl of mashed potatoes with garlic-salted asparagus.
The general recommendation for macronutrient consumption is 40% carbohydrate, 30% protein, and 30% fat, based on your caloric intake. The USA guidelines on food labels for these quantities aren't the exact quantities that athletes need, as the guidelines are based on a 2000 calorie diet. If you have no idea how much of each macronutrient you should consume use the guidelines below:
Carbohydrate: 6-10g/kg/day of body weight
Protein: 1.2-2.2g/kg/day (Higher end recommended for athletes)
Fat: ~30% caloric intake
Female Athlete recommendations (From ROAR by Dr. Stacy Sims)
Carbohydrate: 1.13g to 2.7g/lb/day (more on intense endurance [2-5 hours] days)
Protein: 1.0 to 1.2g/lb/day (more on strength/power days)
Fat: ~30% of caloric intake
*Please note the change in units!
Now, I wanted to clarify something regarding the numbers I have here for female athletes. After spending several days combing through different research articles and resources, there is a discrepancy as to what the recommended protein guidelines are. Currently, the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine all recommend 1.2-2.0 g/kg of protein intake per day. However, there are research studies to recommend higher protein intake for athletes, including endurance athletes, and a few reviews that indicate that we shouldn't be basing our macronutrient ingestion based on caloric needs.
On top of that, with the release of ROAR, a good resource for training and eating for female athletes, there's a push for even greater protein intake for female athletes. So what's the best guideline to follow? It's hard to tell. There's very limited research regarding female-specific nutrition science, and there's lots of anecdotes of what works and what doesn't work. To start, I recommend following the general guidelines. Once you establish your general nutrition plan as part of your lifestyle, then try varying amounts of marcros (without cutting out any macronutrients or food groups without a good medical reason).
But hey...didn't you say trendy diets are not sustainable...in big bold words? Aren't you referring to the "macro" diet here?
Yes, and sort of. Macro diets, and every other diet featured in the media, focus on losing weight through caloric deficit. Here, I'm talking about building performance, which doesn't always equate to weight loss. This is a good place to start building your nutrition guideline. By taking in enough of each type of macronutrient, you're providing your body with the building blocks and energy to sustain your daily life and adapt to your training.
For menstruating, peri- and post-menopausal athletes, it can also become even trickier because of the fluctuating levels of different hormones. Estrogen is a catabolic hormone, meaning it can break down muscle tissue more quickly. So in phases with high estrogen levels, late follicular (days 8-15) and mid-luteal (days 18-26), it's recommended that athletes experiencing these higher levels of estrogen consume more protein to combat the increase muscle breakdown. If you're tech-oriented, I highly encourage for female athletes to check out Fittr Woman and Wild AI to track not only your cycle, but to get reminders and tips of what is recommended for you in each phase of your cycle.
3) Fruits and Veggies are your friends.
Since the release of "Game Changers" on Netflix, more people are coming out and raving about the performance benefits of switching to a vegan-based diet (3). Again, like with most research in nutrition, the science supporting these benefits is iffy, if not highly population-specific. That being said, there are benefits of including more fruits and veggies in your daily diet, and you don't have to go vegan or vegetarian in order to experience those benefits. These benefits include improved immune function, better hormone regulation, and reduced blood pressure. The exact causes of these benefits are still being researched, but it's believed that the vitamins, minerals and other biological active compounds (ex: bacteria), assist our physiology to achieve these benefits.
So, eat your fruits and veggies, and enjoy them!
4) Timing of Meals
Nutrition also has a schedule to follow? Kind of!
When you're running around from home, to school, work, training, etc, one of things that may be forgetting is actually consuming your fuel. As athletes, it's important to that we have enough fuel in our body to recover from the session and keep going throughout our day. Each training session is a form of stress on the body. It requires energy, and in its simplest form, that's carbohydrate. Eating adequate carbs and protein sooner post-workout allows you to replenish muscle glycogen (sugar in a stored form) stores and facilitate muscle repairs sooner.
But would be better is providing the much needed carbohydrate for your body before and during your training. A few people are better at oxidizing fat for endurance sessions or fasting before workouts, but this isn't for everyone. That being said, you'll never know until you try, but remember: work with a endurance sports-nutrition professional and always do your own thorough research! For many athletes, carbs are the most-effective fuel and it's the best starting place when learning what works for your body. I'll dive into workout fueling in #7 below.
Your body also generates some levels of the stress hormone, cortisol, at the end of high intensity workouts. What?? Yup, and it's catabolic (breaks down muscle) in order to undergo a process called gluconeogenesis, which breaks down amino acids from the protein of muscle cells to create glucose (sugar). But for these high-intensity sessions, this may not be enough. When you don't fuel immediately after an intense session, your cortisol levels remain higher for longer to try to increase the blood sugar levels. This can cause grogginess, sleepiness, increased soreness, and poor focus. So, post workout meals and shakes are vital in combatting cortisol's catabolic effect and minimizing the long-term exposure of the hormone. Plus, you'll less likely have cravings for high-carbohydrate, processed foods later in the day. (6)
If that seems to be too overwhelming, try just adding in post-workout fueling. Start with the general 4:1 carbohydrate to protein mixture (ex: chocolate milk!). Dr. Stacy Sims in ROAR recommends female athletes to ingest 25-30g of protein within 30 minutes of completing a hard session. This helps your body to start replenishing those muscle glycogen stores and facilitate muscle recovery with the protein you're providing. It's also recommended to ingest faster metabolizing protein-sources, such as whey, to kick start this recovery process. While it's more ideal if you eat a meal, rather than shake, some people either don't have the time or they're not able to eat a meal immediately after a hard session.
I've personally found way better mental acuity and appetite by implementing the 4:1 technique, and it improved even more so when I added more protein to my post-workout shake.
Drinking 8 glasses of water may not solve all of your hydration problems, nor does drinking until your pee is straw colored, especially as endurance athletes.
It is important to drink water, but over-hydrating with water will dilute the electrolytes (ex: sodium, potassium, magnesium) in your bloodstream. This can be concerning in hot-weather conditions where athletes can enter a state of hyponatremia (too much water, not enough sodium). An athlete will sweat out the salts and only ingest water to replenish the fluids they're losing. This will dilute the bloodstream, and since cells will have a proportionally higher concentration of sodium, the excess water will diffuse into the cells to achieve equilibrium, causing the cells to swell. The point where this becomes dangerous is when neurons (which depend on the sodium and potassium ion concentrations to send signals) swell up with water. (10)
Now, does this mean you should drink less water? Of course not. In your daily life, you can drink water plain, as long as you have enough salt in your diet. If anything, we tend to be dehydrated in our daily lives. An awesome recommendation I've found was to drink a glass of water with every meal you have, and drink to thirst for the rest of the day.
While exercising, you should replenish the fluids and salts that you lose with electrolyte drink mixes. Depending on your sweat rate, gut sensitivity, and gender, the electrolyte and sugar composition of these mixes may or may not work for you.
It is recommended to have hydration in your bottle and food in your pocket, meaning that the sugar content in your bottle shouldn't be fueling your ride. In fact, the sugars in electrolyte mixes are there to aid in the absorption of those electrolytes during exercise. Some mixes have higher sugar concentrations than others. The best sugar to electrolyte ratio may depend on the person's ability to absorb the electrolytes.
An example test protocol: One week with one brand, 2nd week with another, 3rd week with a 3rd brand, etc. Have similar types of sessions and intensities with every week you test. Note any symptoms and feelings you have before, during, and after a session.
6) Fueling your Workouts
We went over daily fueling and hydration, but what about during the session itself? How much should you eat? What should you eat? And when?
Let's start with how much: if you haven't guessed it already, it depends on a number of factors. Some athletes' goals is to lose weight, so they may be following a fasting-plan. However, that is not the focus here. Some people are only able consume 60g of carbohydrates (about 3 gels) per hour. Others are able to and need to consume 120g or more!
With that amount of carbohydrate, it seems like the best options to fuel is with pure sugar, right? I don't know about you, but just downing sugar packets just seems disgusting, and makes my gut churn. The more common sources of fuel are energy chews, gels, energy bars, and bananas. The first two, chews and gels, provide faster acting energy, sugar that can be digested and utilized more quickly. This is great for when you're working very hard and your digestive system isn't able to fully process foods, or when you need a boost of energy. Energy bars and bananas are slower to digest, but provide fuel for a longer period of time. These are best ingested earlier in the training session or during low-intensity sessions. The combination of these fuel sources will help you maintain your energy needs during your session, and you won't be needing an entire pizza to recover.
Plus there are many different types of sugars. The simplest and most well-known form is called glucose (for you chemistry fans out there, the structure is shown below to the left). Other types of sugars build upon this single molecule through covalent bonding with one of the -OH's on the molecule...but I digress. Many of the processed sugars (gels and chews) tend to have glucose, sucrose (aka table sugar), fructose (another simple sugar or monosaccharide), or maltodextrin. Not everyone is able to digest sucrose, fructose, and/or maltodextrin without gastrointestinal (GI) distress. I personally cannot ingest
maltodextrin because it causes severe bloating and pain in my gut when training or racing. Not ideal. So it's important to experiment and try out different types of energy sources, sugars, and combinations to see what works best for your body. Don't let Biker Chad tell you otherwise.
Back in #4, we talked about post-workout fueling to help decrease cortisol levels and to combat the catabolic effects of cortisol. Remember to ingest recovery meal or snack within the recommended time-window after your workout. This will help you get back on your feet and go about the rest of your day.
The USA Doping Agency (USADA) has this awesome breakdown of the recommended carbohydrate intake before, during, and after exercise, plus how to fuel at all-day events and what types of foods: https://www.usada.org/athletes/substances/nutrition/carbohydrates-the-master-fuel/
7) Eat Food, Not Supplements.
Why? The supplement industry is not regulated, therefore what is on the labelled may not be what you're putting into your body. While there are third-party labs that test products for their accuracy, it's generally not worth it. If there was pill that truly delivered the best results without any adverse effects to our health and performance in the short and long term...well, I'd call it magic, and everyone would be taking it. Alas, magic doesn't exist.
You should be getting everything that you really need through your food and diet. Any supplements that you do take are just that: supplementing your diet. However, because of the higher demands for athletes, your genetics, where you live, and so on, you may not be able to get all that you need from just your food.
What are some examples of supplements that could be considered (after talking with your doctor and getting some blood tests done)?
Iron: Especially in endurance and menstruating athletes, and those who live at altitude.
Protein: For vegans, vegetarians, and those with certain conditions that may prevent them from ingesting proteins from certain foods.
Vitamin D: For bone growth, immunity, and overall mood. Even in places with lots of sunshine all year round, your skin may not absorb adequate amounts of vitamin D (and if you're protecting your skin with sunblock or clothing, you'll absorb even less, if any). It bears worth mentioning, but it's now not recommended to take calcium pills, due to increased risk of heart-related conditions from calcium-overdoses. The daily requirement for calcium is (1000-1200mg daily) which you can easily get from foods, such as yogurt, kale and even fortified cereal.
Magnesium: For anything muscle or nerve or immune or glucose related...so everything! It's the 4th most abundant mineral in the body typically. In it's cationic form (positive ion), it binds with adenosine-triphosphate (ATP) to form a complex that's used in many metabolic reactions. In addition, it's involved in neuronal and muscle regulation. Some studies have shown that athletes may need higher levels of magnesium than other populations, due to the increased metabolic rates. (15)
There are maybe one or two more supplements out there that may you benefit from, such as beta-alanine and beet juice, but they're still being researched further, and they may only provide marginal gains for high-caliber athletes (i.e. not worth the time or money for amateur athletes). But you really should do some blood tests before you start taking any supplements, just to be sure that you're not ingesting any additional nutrients that you don't need (and may cause harm, such as iron and calcium).
And last but definitely not least...
8) Follow your nutrition 80-90% of the time.
But, but, but....why not 100?
Because life is meant to be enjoyed, and so is food. There will be times where you want to have pizza and Ben and Jerry's for dinner instead of quinoa and tofu ( don't get me wrong, it's delicious when prepared right). You'll go out with friends, family, or coworkers to a place where the healthiest option of food is a burger. C'est la vie. Enjoy it and don't fret about screwing up a day or two (or even a week). You'll be back to your routine without even realizing it.
Whew...that's a lot of info. A bit overwhelming it seems
Yup! And there's still even more out there in the realm of sports nutrition (that is valid and true). This is just a basic guideline to help you start building a nutrition plan that is effective for your needs and lifestyle. From here, you can start testing and trying out different methods and foods, as long as they're sustainable and beneficial to you.
So, a quick summary of the basics (if there's nothing else you can take away from it)
1) Establish a base nutrition plan based on your needs as an athlete and any other additional lifestyle factors (stress, work, family, school, etc).
- Fuel your workouts!
- Quality is still important
2) Follow this nutrition plan 80-90% of the time for several months.
- Note any changes you feel or observed since establishing your plan.
3) Be patient. Overnight or even over-week changes almost never happen. Observe and see what changes (energy availability, mental acuity, physically, etc). Using an online training diary or a mobile app helps you keep notes of your training sessions, as well as your mood, sleep quality, nutrition intake, and so on.
4) Use food as your primary source of nutrients. Supplements are only there to supplement your lifestyle.
5) Not every diet, sugar type (for workouts), and approach is right for everyone. There are nutrition fundamentals, but there are so many variations in body types, metabolic rates, and digestive systems that nothing is one-size fits all.
6) Enjoy your food! Vivez votre vie!
If you are still struggling or unsure what your dietary requirements are, talk to a dietitian who works with athletes or a sports doctor. They'll be able to go over your needs and requirements one on one, and help you develop a more personal guideline. They may recommend getting some bloodwork done to see what your body is deficient and where you can improve through your diet (maybe with supplementation).
Until next time, Happy Eating and Happy Training!
References: 1. Berg, Jeremy M, et al. “Each Organ Has a Unique Metabolic Profile.” Nih.gov, W H Freeman, 2010, www.ncbi.nlm.nih.gov/books/NBK22436/.
2. Durkalec-Michalski, Krzysztof, et al. “Effect of a Four-Week Ketogenic Diet on Exercise Metabolism in CrossFit-Trained Athletes.” Journal of the International Society of Sports Nutrition, vol. 16, no. 1, 2019, p. 16, www.ncbi.nlm.nih.gov/pubmed/30953522, 10.1186/s12970-019-0284-9.
3. “Going the Distance | Maximizing Endurance on a Plant-Based Diet.” The Game Changers, 22 Aug. 2019, gamechangersmovie.com/benefits/maximizing-performance/going-the-distance/.
4. Hamilton, Andrew. “Athletes: Yes or No to Keto?” Sports Performance Bulletin, 4 June 2018, www.sportsperformancebulletin.com/nutrition-for-endurance-athletes/athletes-yes-or-no-to-keto/. Accessed 30 May 2021.
5. Hassapidou, M. “Carbohydrate Requirements of Elite Athletes.” British Journal of Sports Medicine, vol. 45, no. 2, 20 Jan. 2011, pp. e2–e2, 10.1136/bjsm.2010.081570.23.
6. Hill, E E, et al. “Exercise and Circulating Cortisol Levels: The Intensity Threshold Effect.” Journal of Endocrinological Investigation, vol. 31, no. 7, 2008, pp. 587–91, www.ncbi.nlm.nih.gov/pubmed/18787373, 10.1007/BF03345606.
7. Hiran Patel, and Abhishek Bhardwaj. “Physiology, Respiratory Quotient.” Nih.gov, StatPearls Publishing, 27 Oct. 2018, www.ncbi.nlm.nih.gov/books/NBK531494/.
8. Jeukendrup, Asker. “Ketogenic Diets for Athletes.” Askerjeukendrup, 1 Dec. 2016, www.mysportscience.com/post/2016/12/01/ketogenic-diets-for-athletes. Accessed 30 May 2021.
9. Rodriguez, Nancy R., et al. “Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance.” Journal of the American Dietetic Association, vol. 109, no. 3, Mar. 2009, pp. 509–527, jandonline.org/article/S0002-8223(09)00006-6/fulltext, 10.1016/j.jada.2009.01.005. Accessed 24 Feb. 2019.
10. Rosner, Mitchell H., and Justin Kirven. “Exercise-Associated Hyponatremia.” Clinical Journal of the American Society of Nephrology, vol. 2, no. 1, 29 Nov. 2006, pp. 151–161, cjasn.asnjournals.org/content/2/1/151, 10.2215/cjn.02730806.
11. Sims, Stacy T. Roar : How to Match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life. New York, Ny, Rodale, 2016.
12. Skerrett, Patrick J., and Walter C. Willett. “Essentials of Healthy Eating: A Guide.” Journal of Midwifery & Women’s Health, vol. 55, no. 6, 12 Nov. 2010, pp. 492–501, www.ncbi.nlm.nih.gov/pmc/articles/PMC3471136/, 10.1016/j.jmwh.2010.06.019.
13. Stellingwerff, Trent. “Case Study: Body Composition Periodization in an Olympic-Level Female Middle-Distance Runner over a 9-Year Career.” International Journal of Sport Nutrition and Exercise Metabolism, vol. 28, no. 4, 1 July 2018, pp. 428–433, 10.1123/ijsnem.2017-0312. Accessed 26 Mar. 2020.
14. Wooding, Denise J, et al. “Increased Protein Requirements in Female Athletes after Variable-Intensity Exercise.” Medicine and Science in Sports and Exercise, vol. 49, no. 11, 2017, pp. 2297–2304, www.ncbi.nlm.nih.gov/pubmed/28692631, 10.1249/MSS.0000000000001366. Accessed 15 Nov. 2019.
15. Zhang, Yijia, et al. “Can Magnesium Enhance Exercise Performance?” Nutrients, vol. 9, no. 9, 28 Aug. 2017, p. 946, www.mdpi.com/2072-6643/9/9/946/htm, 10.3390/nu9090946.