Supplementation Guide
Evidence Based Micronutrient & Supplementation Guide
Recognise the signs first, confirm them properly, then correct with the right dose, the right form, and the right timing.
Why This Guide Exists
Most coaches know that vitamin D, iron, and B12 deficiencies are common, yet it is far less clear which blood test actually confirms which deficiency, and how reliable that test really is. Blood tests are not always the clean, objective answer they appear to be. Serum magnesium reflects less than one percent of total body magnesium. Serum calcium is tightly regulated by hormones and can look completely normal even when bone stores are badly depleted. Ferritin rises with inflammation and can look falsely reassuring in someone who is actually iron deficient. A normal lab report does not always mean a normal nutrient status.
This guide works from the outside in. It starts with what a coach can actually observe, the signs a client reports or that become apparent over weeks of working together, then moves to which tests genuinely help confirm that nutrient, what their limitations are, and finally, once a deficiency is confirmed by a doctor, how correction is typically dosed, which form absorbs best, and what to switch to if it upsets someone's stomach.
Understanding Functional Ranges
A conventional lab range is built from a broad population average that usually includes a large number of sick, aging, or already unwell people. Its purpose is to catch outright disease, so it tends to be wide. A functional range is narrower, built from research into what genuinely optimal health looks like, and its purpose is to catch a subtle imbalance well before it progresses into disease. A client's result can sit comfortably inside the conventional normal range and still fall outside the narrower functional range, all while the client continues to report real symptoms.
What this means in practice. Do not treat in range and optimal as the same thing, ask where within the range a result falls, not just whether it technically falls inside it. If a client's signs and symptoms clearly match a nutrient covered here but their doctor has reported the relevant test as normal, that gap is worth revisiting rather than dismissing. This does not mean lab results should be ignored, it means they should be read alongside a client's actual signs, symptoms, and risk factors, not in isolation from them.
General Rules For Any Deficiency
These patterns repeat across almost every nutrient in this guide.
| Rule | Why It Matters |
|---|---|
| Do not correct a real deficiency with a multivitamin | A multivitamin is built for general maintenance at low, broad spectrum doses. A confirmed deficiency needs a much higher, targeted dose of that one nutrient. |
| Use an isolated nutrient at a specific dose | Once a deficiency is confirmed, correction should be a standalone supplement dosed at the level a doctor has prescribed, not guessed from a bottle's general label. |
| Prefer the better absorbed form | Different chemical forms of the same nutrient can differ hugely in how much the body actually absorbs and tolerates. |
| Have a backup form ready for digestive issues | Many people quietly stop a supplement because it upsets their stomach and never mention it. Knowing a gentler alternative in advance keeps them on track. |
| Respect nutrient to nutrient competition | Several minerals compete for the same absorption pathways, for example iron, calcium, and zinc. Spacing them apart during the day meaningfully improves absorption of each. |
| Watch for genuine dosing nuances | A handful of nutrients, iron being the clearest example, have specific timing or frequency tricks backed by real physiology rather than habit or tradition. |
Vitamin D
Who Is Commonly At Risk
- Limited sun exposure, indoor jobs or sports, or a low sunlight climate for part of the year
- Darker skin tone, which needs more sun exposure to produce the same amount of vitamin D
- Older adults, obesity, and medications that affect fat absorption
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Major signs | Persistent fatigue not explained by training load; bone pain or unexplained aches, especially lower back, hips, or legs; muscle weakness, particularly in the thighs; frequent infections or slow recovery from minor illness |
| Minor signs | Low mood, particularly in darker months; hair thinning; slow wound healing |
How To Actually Confirm It
Serum 25 hydroxyvitamin D, often written 25(OH)D, is a genuinely reliable, standard marker for this nutrient. On the conventional scale, severe deficiency sits below 25 nmol/L (10 ng/mL), insufficiency around 25 to 50 nmol/L, marginal status 50 to 75 nmol/L, and sufficiency in the 75 to 150 nmol/L (30 to 60 ng/mL) range, with toxicity risk above roughly 375 nmol/L (adapted from Norman, 2011). Many practitioners now aim for a functional range closer to 40 to 60 ng/mL rather than the bare minimum sufficiency cutoff.
Typical Correction Dose, Physician Guided
General health intake commonly ranges from 400 to 4000 IU/day as needed, with blood levels rising roughly 0.6 to 1.0 ng/mL for every additional 100 IU/day taken. One estimate suggests individuals of European ancestry with high sun exposure may need around 1300 IU/day in winter to reach 25(OH)D of at least 75 nmol/L, while individuals of African ancestry with low sun exposure may need 2100 to 3100 IU/day year round (Hall et al., 2009). These are prescription level protocols in many places and should always be confirmed by a doctor based on the client's actual blood level.
Best Bioavailable Form
Vitamin D3, cholecalciferol, is preferred over vitamin D2, ergocalciferol, because it raises and sustains blood levels more effectively. Since vitamin D is fat soluble, taking it with a meal containing some dietary fat meaningfully improves absorption.
If Digestive Issues Occur
True digestive upset from D3 itself is uncommon. If a client reacts poorly to an oil filled softgel, a dry powder capsule or tablet, or a water dispersible micellised D3 drop, is often better tolerated.
Practical Dosing Nuance
Magnesium is required to activate vitamin D in the body, so a client who is also low in magnesium may respond poorly to supplementation until magnesium status is addressed. Observational data links higher magnesium intake to a reduced risk of vitamin D deficiency (Deng et al., 2013), though evidence that magnesium supplementation itself raises vitamin D levels remains inconclusive (Dai et al., 2018). Many practitioners also pair high dose D3 correction with a modest amount of vitamin K2, and there is emerging evidence of a synergistic effect between vitamin D and K for bone and cardiovascular health, including in postmenopausal and osteoporotic populations for maintaining bone mineral density (van Ballegooijen et al., 2017; Bolton Smith et al., 2007; Iwamoto et al., 2000). Vitamin D also carries a significant immune system role, supports calcium absorption for bone health, and has been associated in deficiency with cardiovascular disease, cancer, inflammatory bowel disease, and autoimmune conditions, plus links to reduced depressive symptoms and possible improvements in strength and fat loss (Martens et al., 2020; Hill et al., 2013; Holick, 2007; Vellekkatt and Menon, 2019; Tomlinson et al., 2015; Ortega et al., 2008).
Vitamin A
Who Is Commonly At Risk
- Populations in resource limited regions, where most severe global cases occur
- Fat malabsorption conditions such as celiac disease, Crohn's disease, or pancreatic insufficiency
- Heavy or long term alcohol use, which impairs liver storage and release
- Very restrictive diets with little to no animal food and low colourful fruit and vegetable intake
True severe deficiency is genuinely uncommon in well fed, non endemic populations. Most clients are far more likely to show a borderline or mild insufficiency, usually tied to poor fat intake, a restrictive diet, or an underlying gut absorption issue.
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Mild deficiency | Difficulty seeing in dim light or at dusk, called night blindness; dry eyes; dry, rough skin; somewhat more frequent infections |
| Severe deficiency | Bitot spots, foamy white patches on the white of the eye; corneal dryness progressing to clouding and, in advanced untreated cases, permanent vision loss; poor bone growth in children; a rough, goosebump like skin texture called phrynoderma |
How To Actually Confirm It
This is a nutrient where the eye exam often tells you more than the blood test. Night blindness and Bitot spots are genuinely useful, visible clinical signs. If a blood test is used, a fasting serum retinol below 20 mcg/dL (0.7 micromol/L) suggests deficiency, though this test is far from perfect, one analysis found it correctly identified only about 54 percent of true cases and gave a false positive in about 21 percent of people who were not actually deficient, compared against the more accurate but impractical gold standard of directly measuring liver vitamin A stores. Inflammation or severe malnutrition can make the level look falsely low, since the carrier protein that transports vitamin A drops in those situations independent of true stores. A recent dose can also cause a temporary spike, so testing too soon after supplementation can make a deficiency look more resolved than it really is. Low serum carotene, the plant derived precursor, is a useful supporting clue, particularly when poor fat absorption is suspected.
Typical Correction Dose, Physician Guided
These internationally established medical protocols belong entirely to a doctor and are included so a coach understands what a confirmed, supervised correction looks like.
- Infants 6 to 12 months old: a single dose of 100,000 IU
- Children 12 to 59 months old: 200,000 IU, repeated every four to six months in high risk areas
- Adolescents and adults with confirmed xerophthalmia: three doses of 200,000 IU, the first immediately, the second the next day, and the third at least two weeks later
- Pregnant women, or women of reproductive age, with night blindness: small frequent doses only, no more than 10,000 IU/day or 25,000 IU weekly, continued for at least 12 weeks
For a typical client in a well fed population, a confirmed mild insufficiency is usually corrected far more conservatively, often 10,000 to 25,000 IU/day for a limited, doctor defined period alongside genuine dietary improvement.
Best Bioavailable Form
Preformed vitamin A, retinol or retinyl palmitate, found in animal foods and most supplements, is used directly by the body. Beta carotene, the provitamin A form found in colourful fruit and vegetables, must be converted into retinol, and that conversion is genuinely limited and varies a lot between individuals. For a confirmed deficiency, preformed retinol is the more reliable correction choice.
If Digestive Issues Occur
Vitamin A is fat soluble, so it is both better absorbed and generally better tolerated when taken alongside a meal containing some fat. A dry, powder based capsule or tablet is usually gentler than an oil filled softgel.
Practical Dosing Nuance
Unlike most water soluble vitamins, vitamin A is stored in the liver rather than simply flushed out, so it can build up to genuinely toxic levels with excessive daily supplementation over time. It is also proven to cause birth defects at high doses, so a client who is pregnant or may become pregnant should never receive high dose correction, and correction should never begin within the first 60 days of pregnancy.
Vitamin B12
Who Is Commonly At Risk
- Vegetarians and vegans, since B12 is found almost exclusively in animal foods (Pawlak et al., 2013)
- Older adults, due to reduced stomach acid and intrinsic factor needed for absorption
- Long term metformin users and long term proton pump inhibitor users
- Anyone who has had gastric or intestinal surgery
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Major signs | Persistent fatigue and general weakness; numbness or tingling in the hands and feet; pale or slightly yellow tinged skin; memory difficulty or brain fog, mood changes |
| Minor signs | Sore, red, or smooth feeling tongue; mild balance difficulty |
How To Actually Confirm It
Serum B12 alone is not fully reliable, roughly half of people with a genuine functional deficiency can still show a normal serum result. Methylmalonic acid and homocysteine are more sensitive markers and tend to rise when B12 is truly low at the cellular level even if serum B12 looks acceptable. Where available, active B12, also called holotranscobalamin, is more specific than total serum B12.
Typical Correction Dose, Physician Guided
In cases of poor absorption, such as pernicious anemia, a doctor may instead prescribe intramuscular injections.
Best Bioavailable Form
Methylcobalamin is the active form the body can use directly and is generally preferred, particularly for reduced ability to convert other forms. Hydroxocobalamin is commonly used for injections. Cyanocobalamin is the cheapest and most common supplement form and works well for most people, though some practitioners prefer to avoid it with significant kidney impairment.
If Digestive Issues Occur
A sublingual tablet or oral spray allows some B12 to be absorbed directly through the tissue under the tongue, helpful for clients whose gut absorption is compromised.
Practical Dosing Nuance
At the high doses typically used for correction, roughly one to two percent of an oral dose is absorbed through passive diffusion, independent of intrinsic factor. This is why very high oral doses can still correct a deficiency even in people whose normal, intrinsic factor dependent absorption pathway is impaired.
Folate, Vitamin B9
Who Is Commonly At Risk
- Pregnancy and breastfeeding, when requirements rise significantly
- Regular or heavy alcohol use, which impairs absorption and storage
- Poor intake of leafy greens, legumes, and fortified grains
- Those with MTHFR gene variants, which reduce the ability to convert folic acid into its active form
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Major signs | Fatigue and general weakness; pale skin; irritability |
| Minor signs | Mouth sores or a sore tongue; poor appetite |
How To Actually Confirm It
Serum folate reflects only recent, short term intake and can fluctuate with a single meal. Red blood cell folate is a better indicator of longer term status, since it reflects folate levels over the roughly three month lifespan of a red blood cell.
Typical Correction Dose, Physician Guided
A common correction dose is around 1 mg/day for several weeks, with higher doses used in severe cases, always under medical guidance. Maintenance intake is generally around 400 mcg/day.
Best Bioavailable Form
L methylfolate, the active, already converted form, is preferred for anyone with reduced MTHFR enzyme function, since they cannot efficiently convert standard folic acid into a usable form. Folic acid, the synthetic form, is inexpensive and works well for most of the population.
If Digestive Issues Occur
True digestive upset from folate itself is rare. If a specific product causes discomfort, check the other ingredients or fillers in that formulation and switch brands rather than assuming the folate itself is the cause.
Practical Dosing Nuance
High dose folate supplementation can correct the anemia caused by B12 deficiency while masking it, meaning the blood picture improves while the underlying nerve damage from low B12 continues silently. Always check B12 status alongside any folate correction, particularly in older adults and vegetarians.
Iron
Who Is Commonly At Risk
- Menstruating women, and pregnancy
- Vegetarians and vegans, since plant, or non heme, iron is less well absorbed than animal, or heme, iron
- Endurance athletes, due to foot strike related red blood cell breakdown, sweat losses, and occasional gut blood loss
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Major signs | Persistent fatigue and low exercise tolerance; pale skin, particularly the inner eyelid; shortness of breath with mild exertion; rapid or noticeable heartbeat |
| Minor signs | Brittle nails or spoon shaped nails; hair loss; restless legs, especially at night; craving non food items such as ice, called pica |
How To Actually Confirm It
Ferritin, the storage form of iron, is the primary marker used, but it is also an acute phase reactant, meaning it can rise artificially during infection, inflammation, or intense training, masking a true deficiency underneath. Checking ferritin alongside an inflammation marker, or alongside transferrin saturation, gives a clearer picture. A commonly used target for full repletion is a ferritin of at least 50 ng/mL, with higher targets around 70 to 75 ng/mL sometimes used for specific issues like restless legs or unexplained hair loss.
Typical Correction Dose, Physician Guided
Best Bioavailable Form
Ferrous bisglycinate and ferrous fumarate are generally better absorbed and gentler on the stomach than ferrous sulfate, the older, cheaper, and more commonly poorly tolerated form.
If Digestive Issues Occur
If even a gentler chelated form like bisglycinate causes discomfort, try splitting the total daily dose into two smaller amounts, or reduce the single dose and extend the correction period. A small amount of vitamin C alongside iron can improve absorption, while taking it apart from coffee, tea, calcium, and high fibre meals avoids substances that block absorption. In genuinely severe intolerance, a doctor may consider intravenous iron.
Practical Dosing Nuance
Hepcidin, the body's iron regulating hormone, rises for roughly twenty four hours after a dose of iron and temporarily blocks further absorption. Because of this, taking iron once daily, or even every other day, has been shown to result in better total iron absorption over time than splitting the same total dose across a single day. Every other day dosing is now a commonly recommended strategy, both to improve absorption and to reduce cumulative digestive side effects.
Calcium
Who Is Commonly At Risk
- Low dairy or low calcium diets
- Post menopausal women
- Amenorrheic or under fuelled female athletes
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Major signs | Muscle cramps; numbness or tingling in fingers, toes, or around the mouth; dental problems, including weak or decaying teeth |
| Minor signs | Brittle nails; in severe, longstanding cases, osteoporosis or unexplained fractures |
How To Actually Confirm It
A standard blood calcium test is not a reliable indicator of bone calcium status, because blood calcium is tightly held within a narrow range by parathyroid hormone, calcitonin, and vitamin D, even as bone stores become significantly depleted underneath. A bone density scan, called a DEXA scan, and an X ray in the case of a suspected fracture, are the genuinely useful tools here, alongside a careful clinical history.
Typical Correction Dose, Physician Guided
A common target is 1,000 to 1,200 mg elemental calcium/day, ideally from a combination of diet and supplementation, split into doses of around 500 to 600 mg at a time, since absorption efficiency drops off at higher single doses.
Best Bioavailable Form
Calcium citrate is generally preferred over calcium carbonate, because it does not require stomach acid for absorption, which matters particularly for older adults or anyone on long term acid reducing medication.
If Digestive Issues Occur
If citrate still causes bloating, calcium malate is a reasonable alternative, or the daily total can be split into smaller, more frequent doses spread across the day.
Practical Dosing Nuance
Calcium competes with iron for absorption, so the two should ideally be taken at different times of day, for example iron in the morning and calcium in the evening. Calcium also works best alongside adequate vitamin D and vitamin K2, which help direct it properly toward bone.
Magnesium
Who Is Commonly At Risk
- High stress, poor sleep, high caffeine or alcohol intake
- Athletes, due to increased losses through sweat and urine
- Diabetics, and anyone on long term diuretic medication
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Major signs | Muscle cramps or twitches; persistent fatigue; poor sleep quality; irritability or heightened anxiety |
| Minor signs | Frequent headaches; in severe cases, irregular heartbeat or numbness |
How To Actually Confirm It
This nutrient is genuinely difficult to test accurately. Serum magnesium reflects less than one percent of total body magnesium, and the body tightly regulates it by pulling from large tissue reserves, so a normal serum result can still sit alongside a real underlying deficiency. Red blood cell magnesium offers somewhat better insight but lacks strong clinical validation and is not widely available in many labs. In practice, combining known risk factors, the symptom pattern, and often a cautious trial of supplementation with attention to symptom response is more useful than relying on a single blood number.
Typical Correction Dose, Physician Guided
A common correction range is 300 to 400 mg elemental magnesium/day, occasionally higher for a short period under supervision.
Best Bioavailable Form
Magnesium glycinate or magnesium citrate are far better absorbed than magnesium oxide, which is poorly absorbed and acts mainly as a laxative rather than a genuine correction of magnesium status.
If Digestive Issues Occur
Magnesium citrate itself commonly causes loose stools in some people, since it draws water into the gut. Switching to magnesium glycinate, which is gentler and better tolerated, is usually the simplest fix. Magnesium malate is another reasonable alternative.
Practical Dosing Nuance
Magnesium is best taken apart from high doses of calcium or iron, since they compete for absorption. Many clients also find magnesium glycinate more comfortable taken in the evening, since the glycine component is commonly associated with a calming effect that can support winding down before sleep.
Zinc
Who Is Commonly At Risk
- Vegetarians, and diets high in unprocessed grains and legumes containing phytates that bind zinc
- Athletes with high sweat losses
- Anyone recovering from a significant diarrheal illness
- Ongoing gut conditions such as poorly controlled inflammatory bowel disease or celiac disease
- Long term intravenous nutrition or critical illness on dialysis, though uncommon in general coaching
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Mild deficiency | Poor appetite, and slowed growth in children; weakened immunity, more frequent minor illness; reduced taste or smell; trouble seeing in low light; a mild, scaly skin rash in some cases |
| Severe deficiency | Widespread red, scaly, or blistering skin rash, often around the mouth, the anal area, or on elbows and knees; seriously weakened immunity with frequent, harder to shake infections; ongoing diarrhea; significant hair loss |
How To Actually Confirm It
This is a nutrient where the blood test matters less than people assume. In real clinical practice, doctors often lean more on the overall picture, symptoms, diet history, and a physical exam, than on a single blood number, since no blood marker fully captures true zinc status. Routine testing is usually reserved for specific situations. When done, the sample needs clean skin and zinc free collection equipment, since contamination is a common source of inaccurate results, and a morning sample is preferred. A result below 60 mcg/dL is generally considered low, though some labs use a slightly higher cutoff of 65 to 70 mcg/dL for morning samples.
The result is also easy to misread without context. Inflammation or infection temporarily lowers zinc levels even when true status is fine, so checking a general inflammation marker such as CRP alongside it helps with interpretation. Pregnancy naturally lowers it too, while acute illness or major physical stress can temporarily push levels up, masking a real underlying deficiency. Low blood protein also lowers the measured number, since most zinc in blood is bound to albumin. One of the most practical ways to actually confirm a suspected deficiency is a supervised trial of supplementation, watching for real improvement such as better appetite, better wound healing, or improved taste.
Typical Correction Dose, Physician Guided
A commonly used correction range is roughly 1 to 2 mg elemental zinc per kilogram of body weight per day. Improvement usually takes at least four to six weeks, sometimes longer. People with an ongoing condition that increases zinc losses, such as Crohn's disease, cystic fibrosis, liver disease, or sickle cell disease, may need longer term maintenance dosing.
Best Bioavailable Form
Zinc picolinate or zinc citrate are considerably more bioavailable than zinc oxide, which is poorly absorbed.
If Digestive Issues Occur
Zinc taken on an empty stomach commonly causes nausea, so it should always be taken with food. If discomfort continues even with food, splitting the total dose into two smaller amounts across the day usually resolves it.
Practical Dosing Nuance
There is a real difference between a single large dose and a sustained high daily dose. A high single dose taken without food is the most common cause of short term nausea, gastric discomfort, and vomiting. Sustained daily doses above roughly 50 mg over the long term are linked to a genuine secondary problem, reduced copper absorption, which can weaken immunity and lower HDL cholesterol. If a correction dose needs to stay above about 2 mg per kilogram of body weight per day for an extended period, it is standard practice to add a small amount of copper alongside it and to reassess rather than continuing indefinitely.
Iodine
Who Is Commonly At Risk
- Avoiding iodized salt entirely, or following a very low salt diet
- Very high intake of raw cruciferous vegetables, which contain natural goitrogens that can interfere with iodine uptake
- Pregnancy, when requirements rise significantly
Signs And Symptoms
| Category | What you may notice |
|---|---|
| Major signs | Persistent fatigue; unexplained weight gain; cold intolerance; visible swelling at the front of the neck, called a goiter |
| Minor signs | Dry skin; mild constipation |
How To Actually Confirm It
Urinary iodine concentration is the standard population level marker, though a single individual spot test can vary considerably day to day. Thyroid function tests, particularly TSH and free T4, provide useful supporting information but do not directly measure iodine status. In practice, the clinical picture, dietary history, and a doctor's assessment matter more here than any single individual test.
Typical Correction Dose, Physician Guided
The standard adult intake target is around 150 mcg/day, rising to roughly 220 to 250 mcg/day in pregnancy per standard guidelines. Any correction beyond ensuring adequate dietary intake, such as regular use of iodized salt, should be guided by a doctor, since both too little and too much iodine can affect thyroid function.
Best Bioavailable Form
Potassium iodide is a well established and consistently dosed supplement form. Kelp based iodine sources should be used cautiously, since their iodine content can vary widely and unpredictably between products.
If Digestive Issues Occur
Digestive upset at standard intake levels is uncommon.
Practical Dosing Nuance
This is the one nutrient in this guide where more is genuinely not automatically better. Excess iodine can trigger or worsen autoimmune thyroid conditions in susceptible individuals. Correction should be conservative, food and iodized salt based wherever possible, and any supplementation beyond that should be guided by a doctor, especially if thyroid antibodies are already elevated.
A Word On The Supplement Industry
The supplement industry is lucrative, and quality varies far more than most people assume, so any recommendation deserves the same scrutiny given to a nutrient profile above: is there strong evidence behind it, is it legal for a tested athlete, is it actually useful, and could the same dose be achieved through diet instead.
Most people will genuinely benefit from omega 3 fish oils and vitamin D for general health, though recommendations should still be individualised. Multivitamins and minerals have their place, useful when a diet lacks variety or when someone is eating very low calories, and they may help prevent or correct nutrient deficiencies, though vitamin and mineral supplementation cannot be assumed to fully make up for inadequate dietary intake, since food contains multiple bioactive components that a supplement alone does not replace. Beyond fish oils and vitamin D, most other vitamin and mineral supplementation should only be used when clinically indicated, usually confirmed by blood testing, for example iron for anaemia, vitamin C and zinc lozenges for upper respiratory tract infections (Maggini et al., 2012), or vitamin B12 for vegans and vegetarians (Pawlak et al., 2013). Beyond a small number of genuinely performance enhancing options, there are very few supplements with meaningfully proven ergogenic effects compared with the sheer number available on the market.
Foundations Of Performance Supplementation
The nutrients below sit outside the deficiency correction framework above. They are used proactively, in food adequate individuals, for a measurable performance or health effect rather than to correct a diagnosed shortfall.
Fish Oils, EPA and DHA
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) come mainly from oily fish such as salmon, mackerel, trout, anchovies, fresh tuna, sardines, and herring, plus shellfish and seaweed or algae, with very small amounts from eggs, meat, and dairy from pasture raised animals. About 140 g of cooked salmon supplies roughly 950 mg EPA and 2000 mg DHA. Plant based alpha linolenic acid (ALA), found in avocado, flaxseed, chia, and walnuts, can technically be converted to EPA and DHA, but the conversion is very inefficient, roughly 8 percent to EPA and 0 to 4 percent to DHA in men, and 21 percent to EPA and 9 percent to DHA in women (Burdge and Wootton, 2002; Burdge et al., 2002), meaning a woman would need to eat around 4.2 kg of avocado to match the EPA in 140 g of cooked salmon.
Evidence Of Benefit
- Reduces triglycerides (Eslick et al., 2009)
- Anti inflammatory (Calder, 2010)
- Antiplatelet activity, relevant to stroke and DVT risk (Gao et al., 2013)
- Improvement in depression (Liao et al., 2019)
- May reduce anabolic resistance in elderly adults (Dupont et al., 2019)
- Some antihypertensive, antiarrhythmic, insulin sensitising, and fat loss facilitating evidence (Miller et al., 2014; Metcalf, 2008; Yang et al., 2018; Noreen et al., 2010)
How Much, What, When
- General health: 450 to 1000 mg EPA plus DHA/day, roughly 1 to 2 portions of oily fish per week
- Therapeutic use: 1000 to 4000 mg/day
- Fish oil or algae oil, taken daily, with attention to oxidation and storage
Caffeine
Caffeine is a naturally occurring central nervous system stimulant with peak absorption around 45 minutes, though this is product dependent, with gum absorbed faster than a capsule (Wickham and Spriet, 2018), and a half life of roughly 4 to 6 hours (Busto et al., 1989). Common dietary sources range from about 28 to 44 mg per 150 mL of tea and 40 to 108 mg per 150 mL of coffee, up to around 80 mg per 250 mL energy drink serving and 150 mg per 500 mL of a stronger energy drink.
Evidence Of Benefit
- Reduces reaction time (Santos et al., 2014) and perceived exertion (Backhouse et al., 2011)
- Increases force and strength, muscle fibre excitability (Grgic and Del Coso, 2021; Olorunshola and Achie, 2011)
- Improves muscular endurance and endurance performance, spares muscle glycogen (Grgic and Del Coso, 2021; Southward et al., 2018; Loureiro et al., 2021)
- Increases alertness and decision making, especially when sleep deprived (Kamimori et al., 2015)
- May reduce energy intake, though appetite data is inconclusive (Schubert et al., 2014; Schubert et al., 2017), and may modestly stimulate lipolysis and fat oxidation (Kim et al., 2010; Astrup et al., 1990)
How Much, What, When
- Ergogenic doses range from 2 to 6 mg/kg body weight, for example 3 mg times 70 kg equals 210 mg
- Gum, tablet, or drink to suit the client, tea or coffee less consistent
- Taken 30 to 90 minutes before competition or an important training session
- Considerations: a mild diuretic, can negatively impact sleep, and tolerance or dependence can develop
Creatine Monohydrate
Creatine is a naturally occurring compound stored primarily in muscle but also in the brain and other tissues. Supplementation increases total creatine and phosphocreatine concentrations, which are used to convert ADP back to ATP. It is found naturally in animal muscle including fish, but not at ergogenic dosages, roughly 5 g of creatine is equivalent to more than 1 kg of beef, and the body also produces some of its own.
Evidence Of Benefit
- Biggest ergogenic effect in repeated high intensity efforts with short recovery (Izquierdo et al., 2002)
- Increased isometric strength (Cramer et al., 2007), tolerated training load and quality (Bemben and Lamont, 2005), recovery (Cooke et al., 2009), and training induced adaptations (Olsen et al., 2006)
- Increased muscular endurance, a higher lactate threshold and time to exhaustion (Chwalbinska Moneta, 2003), greater glycogen storage (Nelson et al., 2001)
- Improved working memory and intelligence with as little as 5 g/day, especially during sleep deprivation (Rae et al., 2007; McMorris et al., 2006)
- Significantly increased lean tissue (Burke et al., 2003), with potentially greater benefits in vegetarians and vegans for lean tissue, performance, and memory (Burke et al., 2003; Benton and Donohoe, 2010)
- Non responders do exist (Syrotuik and Bell, 2004)
How Much, What, When
- Loading: 0.3 g/kg/day in 4 equal doses
- Maintenance: 0.03 g/kg/day, for example 0.03 times 80 kg equals 2.4 g
- Creatine monohydrate is the only extensively researched form, be wary of newer variants such as creatine ethyl ester, kre alkalyn, or tricreatine malate
- Ideally taken with food or after training
Beta Alanine
Beta alanine is a component of carnosine, an intracellular buffer of hydrogen ions, typically higher in fast twitch (type II) than slow twitch (type I) muscle fibres. Muscle carnosine was significantly increased by 58.8 percent and 80.1 percent after 4 and 10 weeks of supplementation (Hill et al., 2006). It is available in supplemental powder or tablet form, and the common side effect is paraesthesia, a tingling sensation.
Evidence Of Benefit
- Only helpful in high intensity, anaerobic, high lactate accumulation sports, roughly 60 to 240 seconds of all out effort, or repeated high intensity efforts (Hobson et al., 2012)
- Delays fatigue, attenuating fatigue from exhaustive dynamic contractions versus placebo, supporting greater force production in later stages of fatiguing exercise (Derave, 2007)
How Much, What, When
- Loading: 4 to 10 weeks of 80 mg/kg/day
- Maintenance: 40 mg/kg/day, or single doses of 10 to 20 mg/kg
- Chronic intake matters more than acute intake, daily timing does not appear to matter, though little and often may be preferable
- May be worth avoiding during aerobic base training periods
Sodium Bicarbonate
Sodium bicarbonate acts as an extracellular buffer of hydrogen ions by increasing the blood bicarbonate pool and, in turn, blood pH. It is readily available and inexpensive. The common side effect is gastrointestinal distress, sometimes severe, and consuming carbohydrate alongside it seems to help reduce this (Price and Cripps, 2012; Carr et al., 2011).
Evidence Of Benefit
- Improved 1500 m running performance (Bird et al., 1995)
- Improved 200 m and 400 m swimming performance (Grgic and Mikulic, 2021)
- Improved 30 km cycling with citrate form (Potteiger et al., 1996)
- Improved resistance training performance, more reps (Duncan et al., 2014)
- Improved 2000 m rowing performance (Hobson et al., 2014)
- Improved punch efficacy during boxing (Siegler and Hirscher, 2010)
How Much, What, When
- Ergogenic dose around 300 mg/kg
- Bicarbonate appears more beneficial than lactate, citrate, or chloride forms
- Taken 60 to 90 minutes before competition or important training
- Always test tolerance in training first, added carbohydrate seems to minimise side effects
When To Refer To A Doctor Immediately
Most of what is covered in this guide is appropriate for careful, informed coaching support. The signs below go beyond that and warrant an immediate medical referral rather than a wait and monitor approach.
- Chest pain, a racing or irregular heartbeat, or fainting
- Severe, sudden shortness of breath
- Numbness, tingling, or weakness that is worsening quickly, or affecting one side of the body
- Confusion, significant memory loss, or a sudden change in mental state
- A visibly enlarged neck or difficulty swallowing or breathing
- Any suspected toxicity, for example after accidentally taking a very high dose of a fat soluble vitamin such as A or D
- Any symptom pattern in a pregnant client, since both deficiency and excess of several nutrients here carry real risk to the pregnancy
Quick Reference Table
A fast lookup once a deficiency has already been confirmed, for reviewing form, typical dose, and the one nuance most worth remembering.
| Nutrient | Best Form | Typical Correction | Key Nuance |
|---|---|---|---|
| Vitamin D | D3, cholecalciferol, with a fatty meal | 50,000 IU weekly for 8 to 12 weeks, or 5,000 to 10,000 IU daily, physician guided | Needs magnesium to activate. Pair with K2. |
| Vitamin A | Preformed retinol, with a fatty meal | Severe cases use large WHO doses, milder insufficiency often 10,000 to 25,000 IU/day, physician guided | Never high dose in pregnancy, stored in the liver and can build up to toxic levels. |
| Vitamin B12 | Methylcobalamin, or hydroxocobalamin by injection | 1,000 to 2,000 mcg/day oral, physician guided | High oral doses absorb passively, useful even with poor gut absorption. |
| Folate | L methylfolate, especially with MTHFR variants | Around 1 mg/day, physician guided | Can mask a B12 deficiency, always check B12 alongside it. |
| Iron | Ferrous bisglycinate or ferrous fumarate | 65 to 150 mg elemental/day, physician guided | Every other day dosing often absorbs better, due to hepcidin. |
| Calcium | Calcium citrate | 1,000 to 1,200 mg/day, split into 500 to 600 mg doses | Take apart from iron. Pair with vitamin D and K2. |
| Magnesium | Magnesium glycinate or citrate | 300 to 400 mg elemental/day, physician guided | Citrate can loosen stools, glycinate is gentler. |
| Zinc | Zinc picolinate or citrate | Around 1 to 2 mg/kg body weight/day, physician guided | Long term high doses can impair copper absorption. |
| Iodine | Potassium iodide, or iodized salt | 150 mcg/day, higher in pregnancy, physician guided | More is not better, excess can worsen thyroid conditions. |