Athletes' Multivitamins: Peace of Mind or Actually Useful? First Understand "Supplement Only When Deficient"

Starting with a Multivitamin I Took for Three Years

A few years ago, I coached a very dedicated amateur cyclist—let’s call him A-Zhe. He rode over 250 km a week, regularly attacked Fengguizui and the Beiyi Highway on weekends, and even tackled Wuling once a year. He was lean, disciplined in his training, but the first thing he said when he came to me was: “Coach, I swallow an imported multivitamin every morning, so why do I still feel tired in the afternoon so often, and why do my legs keep giving out in the latter half of climbs?”

I asked him to bring the vitamin bottle to show me. The label was packed with more than thirty ingredients—vitamins A, C, D, E, B-complex, zinc, magnesium, selenium, coenzyme Q10, and a bunch of plant extracts I could barely pronounce—with dosages ranging from “30% of the daily recommended amount” to “1667%.” He’d been taking them for nearly three years, switching between three brands, each one more expensive than the last, but that vague sense of security that “taking this should be better than not” had never actually been validated by any objective data.

I asked him: “How do you know you need these?” He paused and replied: “Everyone takes them. With this much training volume, you’ve got to supplement something, right?” I’ve heard that sentence too many times. It reflects not knowledge, but anxiety—fear of “not supplementing enough,” fear of losing to people who are more meticulous, fear of shortchanging a body that trains so hard. Manufacturers understand this anxiety well, which is why their ads never sell nutrition—they sell “peace of mind.” And peace of mind is often the most expensive product with the least warranty.

This is exactly the topic I want to discuss with you today. Is a multivitamin (MVM) an insurance policy for athletic performance, or an expensive psychological placebo? My stance is clear, and it’s the core of this article: Vitamins are “supplement when deficient,” not “take it and you’re covered.” That sounds simple, but very few people actually put it into practice.

Let me state the conclusion first, then expand: For a healthy athlete with a generally balanced diet, no specific diseases, and no confirmed deficiencies from blood tests, swallowing a multivitamin every day provides far less real benefit to athletic performance and long-term health than the ads suggest. But that doesn’t mean supplements are useless—the key is whether you’re supplementing “the one thing you’re actually deficient in” or “the thirty things marketing tells you to take.”

Conceptual Foundation: What Vitamins Actually Do in the Body

To decide whether to supplement, you first need to know the role of vitamins. Most vitamins and minerals are “cofactors”—the small screws and bolts the body uses for energy metabolism, oxygen transport, muscle contraction, nerve transmission, and antioxidant defense. They don’t provide calories themselves, but without them, the entire biochemical production line grinds to a halt.

Here’s a key concept many people get wrong: The role of a cofactor is “enough is enough,” not “more is better.”

Think of it this way. Your energy metabolism is like a production line, and B vitamins are the workers on it. If a worker calls in sick (deficiency), production efficiency drops—you feel tired, your legs give out, recovery slows. But if the line is already fully staffed, cramming ten more workers in won’t make the line faster—they’ll just stand around with nothing to do and get flushed out in your urine. That’s why many people’s urine turns bright yellow after taking high-dose B-complex: that’s the vitamins you paid for, your body didn’t need, and flushed straight out.

“Dosage” and “Necessity” Are Two Different Things

There’s a common myth in the athlete community: “I train more than the average person, so my vitamin needs must be much higher too.” That statement is only half right.

The right part: Regular high-intensity training does slightly increase the turnover of certain nutrients—electrolytes lost through sweat (sodium, potassium, magnesium), increased demand for B vitamins when energy metabolism ramps up, and greater need for antioxidant nutrients when oxidative stress rises.

The wrong part: This “increase” is usually automatically covered by the fact that you’re eating more. Someone who trains 2 hours a day typically consumes 500 to 1,000 kcal or more than a sedentary person. The extra rice, vegetables, meat, and fruit you eat already carry more vitamins and minerals with them. Eat more, and you usually supplement more—it’s the body’s elegant self-balancing system.

So the real question isn’t “should athletes take vitamins,” but “does your diet have a genuine gap in any particular nutrient.”

What the Evidence Says: Multivitamins for Healthy Adults

I don’t like speaking from gut feeling, so let’s look at the evidence. Recent large-scale systematic reviews and meta-analyses on multivitamin and mineral supplementation are remarkably consistent:

For healthy adults with generally adequate diets and no known nutrient deficiencies, multivitamins show no clinically meaningful protective effect against cardiovascular disease, cancer, or overall mortality. In other words, buying a multivitamin as “health insurance” doesn’t pay off on paper.

But the same body of literature also clearly shows that multivitamins are justified in specific populations, including: those with malabsorption (e.g., certain intestinal diseases, post-bariatric surgery), chronic alcoholics, pregnant and lactating women, frail elderly individuals, and those with confirmed specific nutrient deficiencies.

Put those two statements together, and you get the backbone of this article: Multivitamins are not a universal health product—they’re a tool for specific gaps. Used in the right place, they’re a lifeline in a snowstorm; used in the wrong place, they’re money spent on expensive urine.

I should also flag a risk that’s often overlooked: fat-soluble vitamins (A, D, E, K) accumulate in the body, and excess can be toxic. Water-soluble ones are mostly excreted, but long-term high doses aren’t entirely without cost either. The mindset that “supplementing won’t hurt” is itself a myth that needs correcting.

What Athletes Are Actually Prone to Lacking: Just a Handful of Items

Instead of worrying about thirty ingredients, focus your energy on the few nutrients that “athletes genuinely often lack, and that genuinely affect performance when deficient.” Based on my practical experience, these are the ones worth the most attention.

One: Iron—The #1 Landmine for Endurance Athletes (Especially Women)

If I had to pick one vitamin or mineral as “the one athletes should check regularly,” I’d choose iron without hesitation.

Iron is involved in hemoglobin synthesis, and hemoglobin is responsible for carrying oxygen from the lungs to the muscles. When iron is insufficient, oxygen-carrying capacity drops—you feel especially breathless on climbs, your heart rate spikes but power won’t go up, recovery slows, and fatigue lingers—which is exactly the problem A-Zhe only discovered after a blood test.

Data shows iron deficiency is quite common among endurance athletes, with female athletes showing significantly higher rates than males and the general population. The literature indicates that iron deficiency affects roughly 15% to 35% of female endurance athletes—far higher than the single-digit rates in male athletes, and also above the general population’s level of around 5%. Interestingly, many athletes have “iron deficiency without anemia”—hemoglobin looks normal, but stored iron (ferritin) has bottomed out, and performance is already suffering.

Why are athletes especially prone to iron deficiency? Causes include: sweat loss, micro-bleeding in the gastrointestinal tract during exercise, hemolysis from repeated foot-strike impact when running, and exercise-induced inflammation that temporarily suppresses iron absorption. Women add the regular loss from menstruation, so their risk is naturally higher.

My advice is straightforward: endurance athletes in regular training—especially women—should include ferritin in their routine health checkups. Those with a history of iron deficiency should consider blood tests twice a year; everyone else at least once a year. This is easy to do in Taiwan—general clinics or health check centers can run it. A complete blood count plus ferritin is inexpensive, yet the informational value is enormous. Remember: Get a blood test before supplementing iron. Excess iron deposits in organs like the liver and causes damage—it is absolutely not something where “more is fine.”

2. Vitamin D: Taiwanese People Can Be Deficient Too — Don’t Assume Plenty of Sunshine Means You’re Safe

Many people assume that because Taiwan gets plenty of sunshine, vitamin D deficiency is impossible. In reality, the opposite is true.

Vitamin D is primarily synthesized by the skin when exposed to ultraviolet B (UVB) radiation, with diet contributing only a small portion. The problem is that modern people — especially office workers, students, and those who train indoors or exercise only in the early morning or evening — actually get very little effective sunlight exposure. Add in sunscreen, long sleeves, face masks, and commutes spent indoors or in cars, and the opportunity for the skin to synthesize vitamin D is drastically reduced.

Community studies in Taiwan have indeed observed a not-insignificant prevalence of deficiency. In one community study in northern Taiwan, the vitamin D deficiency rate among healthy adults was around 20-plus percent, with the rate among women significantly higher than among men. Another long-term voluntary testing study showed that younger adults (ages 18 to 34) had a notably high deficiency rate. This aligns closely with our lifestyle: the more urbanized, the less outdoor activity, and the more thorough the sun protection, the more likely a deficiency becomes.

For athletes, vitamin D matters not only for bone health but also for muscle function, immunity, and the risk of stress fractures. I once coached a client who trained almost exclusively in an indoor cycling studio, barely seeing daylight year-round. One winter, he kept catching colds and his training kept getting interrupted. A blood test revealed clearly low vitamin D. This doesn’t mean vitamin D was the sole cause (sleep and training load also played a role), but after correcting the deficiency and adjusting his routine, he did experience far fewer “training interrupted by illness” cycles that winter. For those who train long-term indoors, exercise in the early morning or at night, or rarely get sun exposure, vitamin D is one of the few nutrients where “it’s reasonable to suspect deficiency and worth testing.” The same principle applies: get a blood test first (serum 25(OH)D level), supplement only if confirmed low, and re-test a few months later to see if levels have normalized. One important reminder: vitamin D is fat-soluble, and long-term high-dose supplementation without guidance can lead to toxicity. So “how much and how long” should be guided by test results, not by self-prescribing high doses.

3. B Vitamins: Needs Increase, But Most People Can Cover Them Through Diet

B vitamins are involved in energy metabolism, and turnover does increase with higher training volumes. But as mentioned earlier, if you’re eating enough calories and a varied diet (whole grains, lean meat, eggs, legumes, dark leafy vegetables), a true B vitamin deficiency is uncommon.

The group that genuinely needs to pay attention to B vitamins — especially B12 — is athletes who are fully vegan or nearly vegan, because B12 comes primarily from animal foods. For this group, B12 supplementation is reasonable and necessary. As for people who eat a mixed diet with regular meals, taking extra high-dose B vitamins mostly just produces expensive yellow urine.

4. Minerals Such as Magnesium, Calcium, and Zinc: Let Dietary Gaps Decide

Magnesium is related to muscle relaxation and nerve transmission, and it’s lost through sweat. People who get cramps often suspect magnesium deficiency — but cramps have complex causes (fatigue, electrolytes, hydration, posture all play a role) and shouldn’t be attributed directly to magnesium deficiency. I’ve had many clients who loaded up on magnesium every time they cramped, only to keep cramping, because the real cause was poor pacing and excessive muscle fatigue in the later stages. Calcium is about bone health; those with low dairy intake or bone health risks should pay attention, especially female athletes who also have inadequate energy intake, menstrual irregularities, or low bone density (collectively part of Relative Energy Deficiency in Sport, or RED-S) — they should actively seek medical evaluation. Zinc is related to immunity and repair, but a normal diet usually provides enough; long-term high-dose zinc supplementation can actually interfere with copper absorption. The principle for all of these is the same: Look at whether your actual diet has a gap; supplement where the gap is, and don’t supplement where there isn’t one.

By now you’ve probably noticed a pattern: every nutrient I keep emphasizing — iron, vitamin D, B12, calcium — shares three traits: “it can be tested, deficiency has clear consequences, and supplementation has clear benefits.” That’s exactly why “supplement only when deficient” is actionable: it’s not an abstract slogan, but a principle where every step has objective evidence. In contrast, the other twenty-plus ingredients in a multivitamin are mostly things where “you don’t even know if you’re deficient, and even if you supplement, you can’t feel a difference.” Spending your effort on the former is far more worthwhile than spending your money on the latter.

At-a-Glance Table: Multivitamins vs. Targeted Supplementation

The table below is a core concept I often use to communicate with clients, helping you quickly decide which path to take.

Aspect	Multivitamin (Broad-Spectrum)	Targeted Single-Nutrient Supplement (Precision)
Logic	“Might be deficient in something, so supplement a bit of everything”	“Confirm what you’re deficient in, then fill that specific gap”
Prerequisite	No testing needed, just take it	Blood test / dietary assessment first to confirm deficiency
Dosage Control	Each nutrient in small amounts; may be insufficient or excessive	Can provide therapeutic doses based on deficiency severity
Toxicity Risk	Watch out when fat-soluble vitamins stack up	Single nutrient is controllable and easier to monitor
Cost-Effectiveness	Most components aren’t used by the body; low benefit	Targets the exact need; high benefit
Suitable For	Transitional period with extremely unbalanced diet and no access to testing	Athletes with confirmed deficiency or high risk
My Verdict	Mostly buying peace of mind	This is the real answer to “supplement only when deficient”

Once you understand this table, you’ll see why I often say: Rather than swallowing a multivitamin with a little bit of everything every day, spend the money on one blood test to find out whether you’re actually deficient and in which nutrient.

Common Nutritional Gaps in Athletic Populations and Testing Recommendations

Here’s another more practical reference table, summarizing “who might be deficient in what, how to check, and how to address it.” Note: the values below are general ranges and directions; actual interpretation should be left to physicians or dietitians.

Population / Situation	Nutrients to Watch	Recommended Testing / Assessment	Management Principles
Female endurance athletes	Iron (ferritin), vitamin D	CBC + ferritin, 1–2 times per year	Supplement only after confirming deficiency; monitor during iron supplementation
Long-term indoor / nighttime trainers	Vitamin D	Serum 25(OH)D	Supplement only if low; re-test after supplementation
Vegan / near-vegan athletes	Vitamin B12, iron, calcium	Dietary assessment + blood test if necessary	B12 usually requires routine supplementation
Mostly eating out, very few vegetables	Multiple vitamins and minerals	Improve dietary structure first	Diet first; MVM can be considered as a transitional measure
Weight loss / long-term caloric deficit	Multiple nutrients (overall insufficiency)	Assess total caloric intake and diet quality	Make eating enough the top priority
Older or frail exercisers	Vitamin D, B12, calcium	Medical evaluation	Individualized, following medical advice

The spirit of this table boils down to one thing: Assess first, then supplement; diet first, then pills.

Common Mistakes and How I Help Clients Correct Them

In my years of coaching, the mistakes I’ve seen regarding supplements generally fall into the categories below. You can use them to check yourself.

Mistake 1: Treating Supplements as a Substitute for Diet

Some clients eat whatever they want, barely touch vegetables, yet diligently take a multivitamin every day, thinking “as long as I get my nutrients, it’s fine.” This puts the cart before the horse.

Natural food provides an entire “nutritional network” — vitamins, minerals, dietary fiber, phytochemicals, protein, and healthy fats all work synergistically. A single pill cannot replicate this network. My first words to such clients are always: “Get your meals right first; pills are the last thing we discuss.” Usually, simply increasing vegetable intake, choosing whole grains for carbohydrates, and eating enough protein resolves a large portion of that “unexplained fatigue.”

Mistake 2: Starting Iron Supplementation Without a Blood Test

This mistake carries risk. Iron deficiency doesn’t automatically mean you should load up on iron, and supplementing doesn’t mean you’re in the clear. Excess iron can accumulate in organs like the liver and cause damage. For some people (such as those with a predisposition to iron overload), iron supplementation can actually be dangerous. Always get a blood test before supplementing iron, and monitor throughout the process. Blood tests are very convenient in Taiwan — don’t skip this step.

Mistake 3: Falling for High Doses and Expensive Imported Products

“1667% of the Daily Value” sounds impressive, but it often simply exceeds what the body can utilize, with the excess being excreted or stored. Price and effectiveness are also not proportional — many expensive imported multivitamins have core ingredients similar to budget options; the extra cost goes to packaging, marketing, and flashy additives with little evidence behind them. Don’t pay for the feeling of “premium.”

Mistake 4: Overdoing Antioxidants Can Backfire

This one is counterintuitive. Exercise creates oxidative stress, so it sounds logical to load up on antioxidants (like high-dose Vitamin C and E). But the oxidative signals after exercise are actually part of your body’s “adaptation to get stronger” process—they’re signals telling the body to repair and improve. Some research suggests that long-term, high-dose antioxidant supplementation may blunt training adaptations. Getting antioxidants in moderate amounts from fruits and vegetables is fine, but relying on long-term high-dose pills isn’t necessarily a good thing.

Mistake 5: Giving Supplements Credit Where It Isn’t Due

Some trainees start taking a product, feel “more energetic,” and assume it’s the product’s doing. But during that same period, they often also sleep earlier, train more consistently, and pay more attention to their bodies psychologically. This mix of placebo effect and lifestyle changes is powerful. This is why I always emphasize objective testing—otherwise, you’ll never be able to tell whether you’re truly supplementing a deficiency or just experiencing a psychological effect.

Actionable Advice for Readers at Different Levels

There’s no one-size-fits-all answer. Based on where you are, here are three tiers of concrete steps.

If You’re a Beginner Just Starting to Exercise

The last thing you need to worry about is a multivitamin. Put your money and attention where the leverage is:

• Eat well, eat enough, eat a variety: include protein at every meal (eggs, beans, fish, meat), choose whole grains for carbs when possible, and have one to two fist-sized portions of vegetables per meal.
• Sleep enough: sleep’s impact on recovery far outweighs any pill.
• Hydrate and basic electrolytes: only needed for prolonged sweating; for regular training, plain water plus a normal diet is sufficient.
• At this stage, unless a doctor recommends it, don’t proactively buy a multivitamin. Making “eat well and sleep well” a habit is worth more than anything else.

If You’re an Advanced Athlete Training Regularly

Your training volume has reached a level where nutrition deserves serious attention. My advice:

• Get a basic health check-up at least once a year, including a complete blood count and ferritin; female endurance athletes may consider twice a year.
• If you train indoors or at night long-term and rarely get sun exposure, add a Vitamin D test.
• If a test shows a deficiency, supplement precisely for that specific item, and re-test after a few months to confirm it’s been corrected.
• For items that aren’t deficient, don’t supplement. Use the money saved to buy better food or get a massage for recovery—that’s a higher return on investment.
• Keep a record of your “test data” and track it over time. Write down your ferritin and Vitamin D values from each blood draw, and compare them with changes in training volume and performance. You’ll gradually build an understanding of your own body. This kind of personalized, long-term data is worth far more than any generic advice. When you can say, “My ferritin dropped to this level last winter, and it took this long to recover after supplementing,” you truly own your nutritional status instead of being led around by advertising.

If You Have Special Conditions (Vegetarian, Chronic Illness, Pregnant/Breastfeeding, Elderly)

This is the group most likely to “actually need supplementation”:

• Vegan: B12 is almost always necessary; iron and calcium also need attention.
• Pregnant/Breastfeeding: This is a group with clear justification for a multivitamin and specific nutrients (like folic acid and iron), but always follow your obstetrician’s instructions.
• Elderly or frail: Vitamin D, B12, and calcium are more commonly deficient, but assessment should be individualized.
• Chronic illness (such as diabetes, hypertension, heart disease, kidney disease, gastrointestinal disorders): In these cases, medical consultation and individualized assessment are absolutely mandatory. Some supplements interact with medications, and certain minerals must be strictly controlled when kidney function is impaired. Proactively show your supplement list to your primary care physician or pharmacist—don’t play doctor yourself.

Practical Tips Local to Taiwan

Here are a few final points close to our daily lives, so this article isn’t just theory.

Nutritional gaps for those who eat out. Eating out in Taiwan is convenient and cheap, but the typical combination of bento boxes, noodles, and bubble tea easily leads to insufficient vegetables, excess refined carbs, and uneven protein distribution. Instead of filling the gaps with pills, start with your ordering habits: swap in an extra plate of blanched vegetables with your bento, add a side of blanched greens and a braised egg at the noodle stand, and choose fruit as a snack. These changes contribute far more to your overall vitamin and mineral intake than a single multivitamin.

Make good use of NHI and testing resources. Getting blood work done in Taiwan is very easy—regular clinics and health check-up centers all offer it, and many company annual check-ups include a complete blood count. Rather than spending money on a year’s supply of expensive vitamins of questionable usefulness, spend the money on one blood draw first to find out whether you’re actually deficient. I consider this the highest-CP-value health investment you can make. One reminder: standard check-up packages don’t necessarily include “ferritin” and “Vitamin D.” If you’re an endurance athlete and particularly care about these two, remember to proactively request them from the medical facility; the small extra cost buys you answers that are actually useful to you, rather than a pile of numbers you don’t understand and that have nothing to do with your gaps. If your results fall in the borderline or abnormal range, don’t jump to conclusions by looking things up online yourself—bring the report to a doctor or dietitian for interpretation. That’s the responsible approach.

Sun exposure and Vitamin D. As mentioned earlier, Taiwanese people can be deficient in D too. In practice, beyond supplementing when necessary, you can also let your limbs get moderate sun exposure outside peak hours, as long as sun protection allows. But if you’re a heavy sunscreen user who rarely goes outside, testing first and then deciding whether to supplement is the more grounded approach.

Don’t be held hostage by marketing language. Phrases like “athlete-grade,” “imported high-concentration,” or “chosen by XX champion” are mostly marketing, not science. Back to the old saying: Supplement only when deficient, test before supplementing, and prioritize diet. Remember these three phrases and you won’t easily be harvested by expensive peace of mind.

How to Read Supplement Ingredient Labels

Since we’re talking about not being held hostage by marketing, here’s a practical “label-reading” method. Next time you pick up a multivitamin, don’t just look at the big adjectives on the front—flip to the ingredient list on the back and examine it calmly from these angles.

First, check the dosages of fat-soluble vitamins (A, D, E, K). These accumulate in the body, so excess is the biggest concern. If one of them is listed at far above the daily recommended amount (for example, Vitamin A at several times the RDA), and your diet already provides enough, stacking them creates risk. Especially if you’re also taking other single-nutrient supplements, you can easily push a fat-soluble vitamin to excess without realizing it.

Second, check whether it contains the items you “know you’re deficient in,” and whether the dosage is sufficient. Take iron deficiency as an example: the iron content in many multivitamins is actually quite low (to avoid gastrointestinal discomfort and overdose concerns), nowhere near enough to correct a true deficiency. This is the core of A-Zhe’s problem: he assumed that “having iron” in a multivitamin meant he was covered, but that dosage was a drop in the bucket for his level of deficiency. To truly correct a deficiency, you often need a targeted single-ingredient supplement at an adequate therapeutic dose, not the tiny amount in a multivitamin.

Third, check whether those fancy additives have evidence behind them. Coenzyme Q10, some plant extract, some berry concentrate—these are often what drive up the price and serve as marketing hooks, but the evidence supporting them for generally healthy athletes is mostly weak. The extra money you pay is likely going right there.

The table below summarizes a simple “should supplement vs. shouldn’t” decision framework to help you avoid wasting money in front of the pharmacy shelf.

Your Situation	Multivitamin	Targeted Supplement	My Recommendation
Balanced diet, no symptoms, never tested	Low benefit	Don’t supplement yet	Focus on diet and sleep first; get blood work if concerned
Blood test confirms low ferritin	Dosage usually insufficient	Targeted iron supplementation (physician-evaluated)	Supplement iron and track it; don’t rely on a multivitamin
Blood test confirms low Vitamin D	Dosage usually insufficient	Targeted Vitamin D supplementation	Re-test after correcting
Vegan	Consider it	B12 recommended as routine	Prioritize B12; iron and calcium as needed
Severely unbalanced diet, hard to fix short-term	Consider during transition	Depends on the gap	Use MVM as a bridge while fixing your diet
Chronic illness, currently on medication	Ask your doctor first	Ask your doctor first	Always defer to medical professional assessment

Timing and Absorption of Supplements: A Few Practical Details

If you’ve been tested and confirmed that you do need to supplement a particular nutrient, whether you supplement it correctly will also affect the results. Here are a few practical details that are frequently asked about.

Pair iron with vitamin C, and avoid tea and coffee. The absorption of non-heme iron (from plant sources) can be affected; pairing it with vitamin C (for example, a glass of orange juice or eating some fruit when taking iron) can help absorption. Meanwhile, compounds in tea and coffee inhibit absorption, so try to avoid strong tea and strong coffee for an hour before and after taking iron. Some people experience gastrointestinal discomfort when supplementing iron; you can discuss dosage forms and how to take it with your doctor.

Take fat-soluble vitamins with meals. Fat-soluble vitamins like vitamins D and E are absorbed better when taken with a meal that contains some fat than on an empty stomach.

Don’t take large doses of calcium and iron at the same time. The two compete with each other for absorption. If you need to supplement both, it’s better to space them out at different times.

Don’t overstate the importance of “timing.” These details are helpful, but they are secondary. What truly determines success or failure remains those three things: whether you are actually deficient, whether the dose is sufficient if you are deficient, and whether your diet is well managed. Timing is a bonus question, not the main course.

Frequently Asked Questions from Athletes (FAQ)

Finally, let me address the questions athletes most often throw at me in a Q&A format.

Q: I don’t feel any discomfort. Do I still need a blood test?
A: Problems like iron deficiency and vitamin D insufficiency often show “no obvious symptoms” in the early stages, or the symptoms are so vague that you just assume it’s training fatigue. For endurance athletes who train regularly (especially women), I still recommend including ferritin in your annual health check. This isn’t to scare you into spending money, but because the informational value of this one test is genuinely high—it may explain the fatigue you’ve never been able to figure out.

Q: Then should I just take a multivitamin and targeted supplements together, as double insurance?
A: I don’t recommend mindlessly stacking them. The biggest risk in doing so is double-counting fat-soluble vitamins and quietly going overboard. If you’re already taking a targeted supplement for a specific nutrient, there’s no need to stack a multivitamin that contains everything on top of it. Either supplement precisely, or use a multivitamin as a transitional option—don’t do both.

Q: I’ve been taking a multivitamin for years. Will anything happen if I suddenly stop?
A: If you already eat a balanced diet and have no confirmed deficiency, stopping usually won’t have any negative effects—because the actual benefit you were getting was limited to begin with. What you should really do is: after stopping, invest the money and attention you save into diet quality, sleep, and one solid blood test.

Q: During race season or high-volume training blocks, do I need to increase my supplements?
A: Increasing the dose of “the nutrient you’re deficient in” makes sense; blindly increasing “everything” does not. During high training volume, I care much more about getting enough total calories, sufficient carbohydrates, proper protein distribution, and adequate hydration and electrolytes—these have a far greater impact on performance and recovery than swallowing one extra multivitamin.

Q: Do these principles apply to children or adolescent athletes?
A: The principles are the same (supplement only if deficient, prioritize diet first), but growing children have different needs than adults, and they should be evaluated by pediatric or nutrition professionals. Parents should not give high-dose supplements on their own. The most common problem in adolescent athletes is actually not vitamin deficiency, but not eating enough overall, or deliberately restricting food for body image reasons—this is far more dangerous. Making sure they eat enough, eat well, and eat a balanced diet must be the top priority.

Conclusion: Spend Money Where It Counts, and Let Data Guide Your Body

Let’s return to A-Zhe from the beginning. He eventually went for a blood test, and his ferritin was indeed low. We didn’t switch to a more expensive multivitamin; instead, under a doctor’s assessment, he took targeted iron supplementation while adjusting his diet (adding iron-rich foods and pairing them with vitamin C to aid absorption). A few months later, his ferritin was retested and had recovered, and the afternoon fatigue and weak legs on climbs that had plagued him for over a year had noticeably improved.

Ironically, he had been taking multivitamins for three years and switched between three brands, and it never solved the problem—because it was casting a wide net, and the one nutrient he was truly deficient in was nowhere near enough in dose. What actually made him better was one blood test, one correct judgment, and targeted replenishment.

This is the core message I want to leave you with: A multivitamin isn’t a bad thing, but it shouldn’t be your default answer. For the vast majority of athletes who eat a roughly balanced diet, it’s closer to “buying peace of mind”; for those who genuinely have a gap, precisely supplementing “that one nutrient” is what works. Stop taking pills based on how you feel—let data tell you what your body actually needs. Take care of your diet, get the tests you should get, and supplement what you’re deficient in—this is the nutritional mindset of a smart athlete. Next time you’re standing in front of the shelf at the drugstore, before your hand reaches for that beautifully packaged multivitamin, ask yourself first: “Do I actually know I’m deficient, or do I just want to buy some peace of mind?” If you can answer that question honestly, you’re already better at taking care of your body than most people.

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This article is for educational purposes and does not replace individual diagnosis and treatment advice from a physician, physical therapist, or nutritionist. If you have a chronic condition, are taking medication, are pregnant or breastfeeding, or are considering starting any supplement, please consult your healthcare professional first and rely on individualized assessment.

References

• Multivitamins in Adult Medical Practice: Evidence, Risks, and Pragmatic Prescribing — https://pmc.ncbi.nlm.nih.gov/articles/PMC12921372/
• High Prevalence of Iron Deficiency Exhibited in Internationally Competitive, Non-Professional Female Endurance Athletes — https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9778947/
• Vitamin D deficiency in northern Taiwan: a community-based cohort study — https://bmcpublichealth.biomedcentral.com/articles/10.1186/s12889-019-6657-9

Related Reading

• Zinc and Immune Support for Athletes: A Complete Guide to Timing, Cold Prevention, and Safety Limits
• The Evidence Pyramid of Sports Supplements: Which Ones Actually Work, Which Are Just Trends, and How to Read the Research
• Should Athletes Take Supplements: A Decision Framework to Stop Wasting Money
• Vitamin C and E: The Antioxidant Dilemma—When the Antioxidants You Supplement Actually Block Your Gains