When it comes to nutrition, I’d happily agree that it’s certainly important not to become too entrenched in the extreme details constantly. Occasionally though, in our journey to reach physique and performance nirvana it can be easy to overlook other vital nutritional components that could positively affect this expedition.
It is the current consensus that a varied diet with sufficient energy will provide most, if not all, of the nutrients one needs for growth, maturation and to stay in excellent health, even for those who are active (Fogelholm, 2003, Zimmerman, 2003, Volpe, 2007, ADA, 2009).
However, as I’m sure you’ll appreciate, the word “active” is a very loose term.
Time and time again, research shows that even elite athletes may be consuming less than 75% of their requirements for multiple micronutrients (vitamins and minerals) even though they are consuming enough total calories to keep training (Clark et al. 2003, Misner, 2006).
Yet dietary supplementation continues to be consistently reported as a key component of athletes’ and fitness enthusiasts’ training performance. In past reports, up to 84% have reported taking some form of supplement regularly (Ronsen et al. 1999), with micronutrient supplements continuing to increase in use (Heikkinen et al. 2011).
Are trainees that do not supplement missing out on something here? Or is your micronutrient complex simply flushed away?
Perhaps better food choices could make all the difference between being mighty or malnourished.
DELVING INTO THE MINUTIAE
Why supplement at all? Well, the micro-nutrients are often termed the essential nutrients.
Whilst the macronutrients (carbohydrates, fats and protein) can be synthesised or scavenged from the body in times of crisis to meet basic physiological function, the dietary vitamins, minerals and trace elements are organic and inorganic compounds with specific requirements that cannot be met by the body. Thus, vitamins and minerals have a minimal dietary intake or need to be supplemented.
Even though only small amounts of micronutrients are needed (perhaps only micrograms or milligrams per day), these minute marvels of nutrition have extremely diverse chemical functions: hormonal effects, antioxidant function, acting as energy metabolism intermediates or even fortifying the immune system. The list of their roles within the body continues to grow, even today.
Symptoms of deficiency quickly arise in humans when these essential nutrients are lacking. A classic example of this was shown through the work of British naval surgeon and experimenter James Lind of HMS Salisbury in 1746, who first documented the treatment of scurvy, a debilitating disease arising from vitamin C deficiency that results in extreme fatigue, malaise and bleeding gums (Lind, 1753). A nasty disease that was common amongst sea-going voyagers at the time, who may have been on the ocean for months living off preserved food, with little to no fresh fruit or vegetables.
Lind happened upon a remarkably simple treatment for the condition. He wrote the following miraculous account in his works:
“...the most sudden and visible good effects were perceived from the use of oranges and lemons; one of those who had taken them, being at the end of six days fit for duty.”
Some would say Lind’s example would be a rare occurrence in modern society. However, in certain populations, including sportspeople, research has shown a consequential re-emergence of “diseases of the Dark Ages” possibly due in part to modern eating habits, lessened focus on diet and faddish approaches to eating (Mozaffarian & Ludwig, 2010).
As a dedicated reader of Muscle & Fitness, I’m sure you’re no stranger to scouring the nutritional information labels of your foods to top up your dietary know-how. Have you ever wondered where those values come from?
DIETARY REFERENCES: FIT FOR WHOM?
All foods, from both plant and animal sources, contain a mixture of the micronutrients in varying quantities.
Micronutrient recommendations for the general population go back as far as the closing stages of the Second World War in 1943, when the National Research Council (NRC) for the United States produced the first printed version of dietary standards: the Recommended Dietary Allowances (RDAs).
The RDAs were an attempt to provide a benchmark against which diets or food supplies could be assessed to determine their nutritional adequacy...
...it contained a woeful total of ten nutrients (NRC, 1989). Compared to the vast amount of vitamins, minerals and trace elements known to affect health today, that is a very limited scope to say the least!
Over the Atlantic and on home turf, things are not a whole lot better. The last recommended intakes for the various micronutrients were set by the Department of Health in 1991 as Dietary Reference Values (DRVs) (Department of Health, 1991) for the entire UK population.
Seems like sound advice, but is it truly as straightforward as this? Figure 1 illustrates this concept graphically.
Figure 1. Frequency Distribution of Individual Micronutrient Requirements Source. Bender (2002) p.22
As the dietary intake of the micro-nutrient increases, based purely on probability, the likelihood of its meeting the requirements of the majority of the population increases. The mean +/-2 standard deviations (SD) of the average requirement (sometimes referred to as the Lower (threshold) Reference Nutrient Intake and Reference Nutrient Intake) are likely to meet 2.5% and 97.5% of the populations’ needs respectively.
SOUNDS EASY, DOESN’T IT?
Just eat more and you’ll meet your micronutrient needs!
Yet a very clear example of where the current recommendations do not seem to fit the population evidence is vitamin D intake. The DRV presently stands at 600 IUs per day (COMA, 1991) but we’re now starting to recognise that despite this recommendation a large proportion of the population may be deficient, possibly as high as 47% according to recent reports (Davies & Shaw, 2011). For more on the importance of vitamin D supplementation, please see www.muscle-fitness.co.uk/vitamind
Here’s another catch: determining human micronutrient requirements has presented more of a challenge to scientists historically than mapping the human genome; even the basic bioavailability (i.e. how much of the micronutrient is actually absorbed from food or a supplement and then made available to the body for use) compromises most experimental data dramatically.
This is in part due to the regulation of nutrient uptake remaining under rigorous control by the body. It varies according to individual losses or need, drug-nutrient interactions and how much of the nutrient is presented to the gastrointestinal tract in a single load (Yetley, 2007). In this way, to determine just how little of each of these precious nutrients we need, many of the original experiments were (sadly) conducted in animals using depletion studies (Bender, 2002) as to conduct a “gold standard” human experiment would be completely unethical.
Furthermore, the differences in the micronutrient content of foods (mainly due to growing season, variety of the foods, nutrient losses in storage and in food preparation) just throws another problem at this scientific nightmare! Some researchers now argue that these concerns reduce the validity of the original recommendations and as such, new methods should be considered to assess individual nutritional requirements (Blumberg et al. 2010).
So you can probably guess what happens with the “real world data”: when using micronutrient supplementation in athletic individuals all we see is very mixed results in terms of performance benefits (Volpe, 2007).
Overall, this has left many of the resulting micronutrient recommendations very much an estimation (Bender, 2002) but we’re not finished yet...
THE BIG QUESTION
So we finally come to the pièce de résistance. Do active individuals need more micronutrients than their less fitness-orientated counterparts?
There is no denying from a physiological standpoint that regular high intensity exercise has a highly stressful effect on the body and that certain vitamins and minerals are crucial in driving energy metabolism during exercise (Maughan, 1999).
Alongside acute hormonal factors that could affect exercise endurance, muscle power output and bone mineral density, such as insulin, testosterone, cortisol and parathyroid hormone (Halliday et al. 2011) as well as those more related to controlling body composition such as leptin (Casimiro-lopez et al. 2009), these can all be negatively affected by a sub-optimal micronutrient status in sportspeople. Clearly, this could be cause for concern during stressful periods where hormonal stability is likely to be compromised (e.g. dieting to a lower bodyfat level).
Arguments have been made that sufficient micronutrients are needed to drive the endogenous antioxidant properties of the body to mop up free radical damage to cell membrane lipids (Dekkers et al. 1996, Leaf et al. 1997). In the long term, this lack of micronutrients could hinder recovery (Fogelholm, 2003). Even simply perspiring is potentially a way to lose these vital minerals: zinc, magnesium, copper, iron and calcium along with sodium are all documented to be lost in body sweat during exercise (Fogelholm, 2003, Chinevere, McClung & Cheuvront, 2007, Valentine, 2007).
In spite of all this, not all of the statuses of the micronutrients are necessarily challenged by being more active. Your body can store a select few vitamins and minerals (such as vitamin A, iron, calcium and the B vitamins) for the harder times; and these stores are not easily depleted unless following an extremely restricted diet for prolonged periods.
Depending on your current training goals or health needs, there are certain vitamins and minerals to focus on in your diet. These are shown in Figure 2. along with as their role in the body.
Figure 2. Summary of the Roles of Vitamins and Minerals in Sports Performance Adapted from Campbell & Spano (2011) p.92
1. AEROBIC ENDURANCE
Micronutrients: Vitamin B6, vitamin B12, folate, iron, copper and zinc
Sports Involved: Long distance running, cycling, swimming, triathlon
Rationale: If your focus is within sports that have a predominantly aerobic element, these rely heavily on the peak synthesis of erythrocytes (red blood cells). These cells are densely packed with haemoglobin, an iron-rich protein complex that is saturated with oxygen from the lungs for delivery during exercise to muscle tissue, and which subsequently removes carbon dioxide.
Copper is critical in assisting the transport of dietary iron from the intestine to the bloodstream, whilst vitamins B6, B12 and folate are crucial in the initial production of erythrocytes in the bone marrow (Labbe et al. 1999, Bender, 2002). Zinc helps the blood to clot, reducing the risk of infection and bleeding time (Marx & Eldor, 1985).
Foods in Focus: Those who are lovers of red meat can rejoice as this is a supreme source of haem (blood-borne) iron, copper and zinc. Lean (5% or less fat), grass-fed steak or minced beef are superb choices, with darker cuts of poultry (i.e. thigh or leg meat) coming in closely behind. Calf’s liver is possibly the best source of all and a traditional British classic that packs an ironclad punch! For sources of B vitamins and folate, choose fortified wholegrain breakfast cereals, wholegrain breads and freshwater fish (such as trout).
For those athletes choosing to abstain from meat, other superb source of all these minerals are: beans, eggs, dairy products, cruciferous vegetables (e.g. broccoli, kale, spinach) and wholegrain cereals. Try combining those foods with a glass of fresh orange juice: the extra vitamin C improves iron absorption up to fourfold! (Hunt et al. 1990).
2. CENTRAL NERVOUS SYSTEM DRIVE
Micronutrients: Vitamin C and niacin
Sports Involved: Strength and power sports, sprints, Olympic weightlifting, gymnastics, racquet sports
Rationale: The difference between winning or losing in many sports is often seconds. However, in strength and power sports and those requiring a high degree of hand-to-eye coordination (such as racquet sports), a fraction of a second could mean winning or defeat. Superiority in these sports requires a finely tuned central nervous system (CNS) and a healthy set of adrenal glands ready to release adrenaline (shown as epinephrine in Figure 2.), a pivotal neurotransmitter (chemical messenger) that heightens the senses and induces metabolic breakdown of stored energy in the muscle. This allows the athlete to react decisively and forcefully at a moment’s notice (McKardle et al. 2001).
To ensure adrenaline is in constant supply and pumped straight into the bloodstream as needed, vitamin C is the micronutrient of choice. Concentrations of this vitamin are extremely high in the adrenal glands and research has shown a benefit of this vitamin in increasing strength gains in strength athletes (Antonio & Stout, 2002).
Foods in Focus: More research is needed to find the optimal dose of vitamin C for this athlete group but anywhere between 200 mg to 1,000 mg per day seems to be an optimal dosage. Since vitamin C is so easily absorbed and tightly regulated by the body, no benefit has been documented from “megadosing” above 1,000 mg per day, which could lead to health issues such as iron overload, kidney stones and dehydration (Audera, 2001). Fruits are one of your best bet for improving vitamin C intake; some of the richest sources include: kiwi fruits, oranges, lemons, strawberries and papaya.
3. STABLE ENERGY PRODUCTION
Micronutrients: Vitamins B1, B2 and B6, niacin, pantothenic acid, copper, magnesium, zinc and iron
Sports Involved: Football, rugby, hockey, bodybuilding, crossfit, martial arts, boxing
Rationale: Athletes that compete in events or sports lasting longer than a minute start to heavily tax their glycogen (stored glucose), a major source of energy for the muscle cell. The more stable the energy source to a muscle, the longer it can continue to perform before fatiguing. For the athlete whose every last drop of energy counts, this is a definite focus for their attention.
Creating the final “energy currency” for the muscle fibres to contract, adenosine triphosphate (ATP) requires a chain of reactions in which micronutrients act as co-factors along the route. As you can see from Figure 2, the B vitamins, niacin, pantothenic acid, copper, iron and magnesium support the aerobic (in the presence of oxygen) breakdown of the glucose in the muscle cell in a biochemical process known as Kreb’s Cycle. This yields the most ATP (or bang for your buck) but this requires a constant supply of oxygen. Not often does this occur in sport.
When the intensity starts to increase, lactate—a chemical by-product from the anaerobic (no oxygen) breakdown of stored glucose—starts to accumulate. Lactate provides a quick source of energy needed for muscle contraction but as this compound’s concentration alongside hydrogen ions in the muscle cell increases, this reduces the intracellular acid:base balance ratio, lowering the intracellular pH (acidosis). Acidosis induces fatigue and “the burn” from a heavy workout. When the exercise stops, lactate is then very slowly re-utilised in the presence of oxygen to finish the reaction and create more ATP. Zinc is the key micronutrient for this process.
Foods in Focus: Root vegetables (e.g. carrots, parsnips, potatoes) and squash can be great sources of starchy carbohydrates to ensure glycogen levels are fully topped up, as well as providing a good source of zinc, copper and iron that the plant absorbs from the soil it grows in. Almonds, pumpkin and sunflower seeds are also fully loaded with magnesium, a great source of protein and essential fatty acids.
4. IMMUNE FUNCTION AND RECOVERY
Micronutrients: Beta carotene, vitamin E, vitamin C, zinc, copper and manganese
Sports Involved: All
Rationale: If there are two things that sportspeople hate worse than not giving 100% effort, it’s a slow recovery or coming down with acute illness such as influenza. Unfortunately, both are a likelihood in a lifetime’s worth of training. Hard training has a twofold effect on recovery. It creates an “open window” of decreased immune system protection, lasting between 3 to 72 hours (Nieman, 2000) and this creates an opportunity for infection. Secondly, reactive oxygen species (ROS) generated during exercise cause damage to muscle cell membranes, possibly hindering the recovery process further (Fogelholm, 2003). All that hard work and your body just bites back harder.
Micronutrients do have a role to play in this fight, though. Vitamin E, beta carotene (a precursor to vitamin A), vitamin C and the minerals zinc and copper support the natural antioxidant mechanisms of the body by reducing the impact of the ROS; possibly speeding recovery (Dekkers et al. 1996, Leaf et al. 1997); the trace element manganese supports white blood cell production, helping to fight off potential pathogens that could cause sickness (Bender, 2002).
Foods in Focus: Pristine hygiene and monitoring the volume of training can have a significant impact on the frequency of infections for athletes, but there are some foods that can help us stock up our defences when the training does step up a gear. Salad vegetables of an array of colours (such as radishes, spinach, lettuces, peppers, tomatoes) are a rich source of antioxidants, beta carotene, vitamin C and manganese. Throw in some spinach and kale, and you’ve ticked the boxes for copper and iron, too. Vitamin E is a fat-soluble vitamin that you’ll find in plentiful amounts in avocados. So try making up some spicy guacamole and kick that next cold into touch.
BRINGING IT ALL TOGETHER
So now that we’ve determined the right micronutrients to focus our attention on, it seems ironic that, much like the sports we’re interested in, no one micronutrient can be the “star player” and maintain the performance of the athlete alone. The secret lies in a team performance of these compounds within the confines of a well-balanced diet.
A registered dietitian or nutritionist could easily help begin that journey for you by identifying those clinical and food concerns that might be impeding your progress; but for those who are well-versed, here are a few tips.
KEEP ON LOGGING
As I and many other professionals know only too well from the enumerated dietary records received from clients, dietary choices do not always match their goals.
Furthermore, even the best dietary collection method (weighed food intake) is only likely to be a snapshot of an individual’s food intake.
Although three to four days of food diary logging can be reliable (Fyfe, 2009), realistically, at least 36 days of collecting data would be needed to determine the exact quantities of each micronutrient in one’s diet (Bingham, 1987). That’s a significant amount of work, but thankfully technology is saving our minds (and trees!) as various food diary apps are widely available online.
SHARPEN UP THE FOOD SELECTION
A smart trainee knows his weaknesses. Sticking to a limited number of food choices can make preparing your weekly meals easier, but very quickly it can mean your spectrum of micronutrients depletes to almost nothing, creating holes in your diet. Food-based micronutrients are also presented in a different form to the gastrointestinal tract and often better tolerated and absorbed (Thiel, 2000).
For example, just throwing a few legumes (chickpeas, lentils, peas and beans), cruciferous vegetables (broccoli, spinach, kale) and seeds (sunflower, sesame, pumpkin) into that weekly pot of chicken casserole can add a plethora of minerals, such as iron, copper, magnesium and calcium, along with protein, slow digesting carbohydrates, fibre and essential fatty acids.
Break out those past printed or digital issues of Muscle & Fitness for inspiration on weekly meals (luckily we are kind and give you the calories and macronutrient breakdown). Log those results and see where your dietary dilemmas lie.
THE BEST OF THE BEST
So you’ve found something lacking but don’t know where to begin to rectify it? Check out the table below for the very best food sources for each group of micronutrients and start levelling things out.
Fat-Soluble Vitamins (Vitamins A, D, E & K)
- Oily Fish
- Liver
- Dairy Products
- Soya Bean Curd (Tofu)
- Whole Eggs
- Dark Leafy Green Vegetables
- Nuts
- Seeds
Water-Soluble Vitamins (Vitamins B & C, Folate, Niacin & Pantothenic Acid)
- Wholegrain Breakfast Cereal
- Liver
- Wholemeal Bread
- Shellfish
- Yeast Extract
- Cereal Grains (such as Rice)
- All Fresh and Frozen Fruits*
- Fresh and Frozen Vegetables*
Minerals (Iron, Copper, Zinc, Magnesium & Manganese)
- Dried Fruits*
- Liver
- Meat and Fish
- Shellfish
- Legumes
- Nuts and Seeds
- Root and Cruciferous Vegetables
*Tinned fruits and vegetables undergo a heat-treatment process and some micronutrients are destroyed through this (e.g. vitamin C). They can still be a good source of other micronutrients though, so don’t abandon them completely!
FILL IN THE GAPS
There will always be certain circumstances where the “food first” approach doesn’t prevail due to limited food choices or other issues. In this case, some supplementation may be required.
Sadly for those who are feeling the pinch from a financial standpoint, when it comes to vitamin and mineral supplementation the key aspect is the presentation of the micronutrient compound in the supplement. However, these finer preparations do tend to push the cost of the micronutrient supplement up.
Choosing a cheap magnesium oxide preparation, for example, can reduce bioavailability to as low as 4% with the rest lost in the urine (Firoz & Graber, 2001). Limitations in the research aside, if the micronutrient cannot enter your body to do its good work due to being so poorly absorbed then pissing your money away springs to mind. Look for preparations containing the following from a reputable source:
- Organic salts for minerals (aspartate, citrate)
- Complete forms of vitamins (e.g. vitamin D3)
Be willing to invest in your health, readers, or save the money and buy a wider selection of foods.
FINAL THOUGHTS
As we’ve seen, for the dedicated sports-person or hard-training enthusiast, micronutrients are potentially a large loophole for dietary mishaps to fall through. Whilst the research may not always show a clear performance benefit in every circumstance a case can be made for a number of micronutrients, hence the current trend amongst trainees of taking a micronutrient complex “just in case” continues to grow. As we move towards ever more convenient lifestyles, taking a sensible look at your diet and refining those food choices can make a big difference not only on your health and training performance goals, but even on your pocket.
“It’s the little details that are vital. Little things make big things happen.”
- Coach John Wooden (Hall of Fame basketball player and coach, author and inspirational leader) M&F
Rick Miller is an HPC Registered NHS dietitian and works with elite natural bodybuilders on both the training and nutrition aspects of their programmes. Rick holds a BSc with Honours in Human Biology from St Andrews University, a Masters Degree in Sport and Exercise Nutrition from Loughborough University, and, a Postgraduate Diploma in Dietetics from Leeds Metropolitan University. If you have any questions for Rick, please contact him at rmiller@weideruk.com
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