Vitamins and antioxidants are often linked to health, yet their impact on performance isn't always straightforward. This article explores how supplements influence athletes' training when there aren't any deficiencies, and why more doesn't always equate to better outcomes. When the body undergoes training, a certain amount of stress is necessary for development—something that high doses of antioxidants can counteract. Research indicates that regular consumption of certain supplements can actually hinder adaptations and, over time, impair performance. However, there are exceptions and specific circumstances where targeted actions might be appropriate. Overall, the evidence suggests that the foundation should be a varied diet, not dietary supplements.

Vitamins are often linked to health and well-being. However, as we've come to understand, health and performance don't always align. A bowl of arugula salad with avocado and a drizzle of olive oil may be great for health, but if you're competing for several hours, it's not our top travel snack suggestion.

Let's walk through some of the most common vitamins and antioxidants, examining their effects (both positive and negative) on your performance. The effects discussed apply to supplementation in athletes without deficiencies. If you have a measured deficiency, your performance will likely improve by returning your levels to normal.

Additionally, the rule is – More is not always better, and in many cases, it can actually be worse.

First, let's ensure we're on the same page. There are 13 vitamins: A, D, E, K (fat-soluble and stored in the body) and vitamin C along with the eight different B vitamins (water-soluble and not stored in the body). In everyday language, we often group minerals and antioxidants together under the term "vitamins," but in this text, we'll try to differentiate them where relevant.

For a historical overview of the discovery of vitamins, we recommend the article – VITAMIN B.S.

During intense physical activity, oxygen consumption increases, leading to the creation of more free radicals that can damage working cells. Some damage is necessary: it signals the cells (and ultimately the muscle) to repair and become stronger for the next session. The body manages these oxidative damages on its own, partly with antioxidants that inhibit the formation and harmful effects of free radicals.

The intake of certain vitamins/antioxidants as supplements has been shown to inhibit the body's natural adaptations to training and over time result in:

1. decreased performance,
2. unchanged cholesterol levels in the blood,
3. unchanged insulin sensitivity,
4. unchanged blood pressure.

In short: Vitamin C and E are a big no-no when it comes to training — at least as a chronic supplement. As early as 2011, it was shown that antioxidants like Vitamin E and alpha-lipoic acid inhibited the formation of new mitochondria in mice on training programs (2011). In 2014, the same hypothesis was tested on humans: 54 participants underwent 11 weeks of endurance training (primarily running), and the creation of new mitochondria was inhibited in those who received supplements of C and E — something that did not occur in the control group.

The formation of new mitochondria is a key adaptation in endurance training. More mitochondria generally mean a better ability to use oxygen and produce energy. There is weak evidence that Vitamin E can be beneficial with acute intake during high-altitude training but negative at sea level. The risk-benefit tilts towards the negative, so we advise against the long-term use of Vitamin E as a supplement.

Resveratrol is well studied and should be avoided around training sessions. In a 2013 study, 27 males trained for eight weeks with or without Resveratrol. The result: those who didn't take the supplement increased their oxygen uptake by 45% more than those who took Resveratrol. This antioxidant thus appears to significantly inhibit training adaptations.

In a study from 2014, the capillarization (the formation of new blood vessels) during training with or without Resveratrol was examined. Half of the participants received 250 mg of Resveratrol per day, while the other half received a placebo. The placebo group increased their capillary-to-muscle fiber ratio by about 20%. Those taking Resveratrol showed no new capillary formation.

“In conclusion, these data show that exercise training has a strong angiogenic effect, whereas resveratrol supplementation may limit basal and training-induced angiogenesis.”

Aside from the alcohol in wine, there could be other negative aspects of drinking a couple of glasses the day before a competition. The levels of Resveratrol in wine vary and can reach up to about 10–12 mg/L. However, studies use around 250 mg/day — equivalent to approximately 20 liters of wine — so you don't need to stress over a single glass.

The point is that supplements can provide high concentrations of these substances, which can hinder your training adaptations.

The issue with antioxidants related to training is that they can suppress the body's natural ability to manage oxidative stress. You become less adaptive to training naturally if you're constantly "assisting" your body externally. Therefore, researchers note:

"Based on studies of vitamin E and NAC, acute intake of antioxidants is likely beneficial. However, chronic intakes of most antioxidants have a detrimental effect on performance."

In short: acute intake can offer benefits through more effective recovery, but chronic intake leads to dependency on aids in the long run and hinders adaptation. It seems rather negative than positive with continuous antioxidant supplements for athletic performance.

"There are no convincing effects of supplementation in well-trained athletes. Risk/benefit analysis reveals evidence for an unknown risk of supranutritional intakes, a supposed impairment of adaptive effects, and a still unknown long-term risk."

This overview is partially based on a review from July 2015 that included 71 studies focusing on performance. Overall, antioxidants are not recommended as supplements from a performance perspective, but there are some variants that may be positive when consumed acutely (around training/competition, not daily over time):

1. Nitrate (beetroot juice) – See previous article on dosing.
2. Quercetin (apple, onion, capers) – intake of about 1g/day in connection with competition can have a small effect.
3. Vitamin E during high-altitude training — only during high-altitude training. We advise against intake at sea level.

Besides these immediate options, we recommend avoiding large consumption of antioxidant supplements during the season. Trust your body's own adaptation mechanisms.

Coenzyme Q10 is in a tricky middle ground. The research isn't comprehensive for athletes; much of it originates from healthcare, where patients on dialysis, for example, might see some improvements (see study). Animal studies show potential effects (rats), but in humans, no effect at all has been noted with an intake of about 100 mg Coenzyme Q10 daily for 2-4 weeks. A study from 2007 examined the impact on liver mitochondria and cell membrane damage during increased oxygen consumption but found no significant effects.

Overall, we're dismissing Coenzyme Q10, but it remains a potentially promising candidate for performance enhancement. That said, it's too uncertain at present and with 90% certainty, purchasing it is mostly money down the drain.

What could be beneficial to take extra of around training?

First and foremost: with a varied diet rich in vegetables, fruits, root vegetables, berries, nuts, eggs, and dairy products, you're likely already getting a good intake of vitamins and antioxidants. However, certain substances may be more beneficial than harmful when associated with training.

“Use of vitamin and mineral supplements does not improve measures of performance in people consuming adequate diets”

Iron is one of the elements we most often associate with endurance performance. It's not uncommon for endurance athletes, especially women, to have low iron levels. Research indicates that targeted nutritional interventions are needed to minimize the risk of iron deficiency in long-distance athletes, such as marathon runners.

The focus should be on an adequate diet so that supplements do not become a daily necessity year after year—there is an upper limit where high iron levels become negative and even dangerous. For women, supplements of 100 mg iron/day may be recommended during the training season according to this study. A larger meta-analysis (2014) showed, among other things, that women could lower their heart rate by about 4 beats during submaximal work and reduce oxygen cost at higher intensities. We therefore recommend extra focus on iron for women during intense training periods and competition seasons—especially if you avoid iron-rich foods.

We usually group B vitamins together as a B complex. Even though each B vitamin has unique roles, they're often consumed collectively. A slight deficiency typically doesn't noticeably affect performance. However, a pronounced deficiency, as in B12 or folate, can negatively impact performance (review 2004). B vitamins are primarily found in animal products: beef, pork (especially offal), shellfish, fish, eggs, and dairy products. Vegetarians and vegans should carefully plan their diet or consider supplements.

If you want to read more, this article is recommended with more references.

So, there might be a slight advantage to supplementing with B vitamins if you skimp on the veggies!

Vitamin D is essential in Nordic latitudes. It's often recommended to take around 2000 IU per day, but ideally, take it away from training times (for instance, in the morning or evening with meals). Read our previous article on Vitamin D.

Two primary risk groups in Sweden are vegetarians/vegans and athletes experiencing an energy deficit during intense training (such as weight loss). Those who avoid animal products typically have a good understanding of their dietary needs, and those who train frequently are usually mindful of their nutrition. However, weight loss may involve more salad and lean protein sources, which can sometimes make it challenging to obtain sufficient nutrients.

If you're looking to check specific foods and their contents, the National Food Agency's database is an excellent resource. For instance, type in "Vitamin B12," and you'll get a list of foods ranked from most to least.

SLV Nutrition Search