Are Vitamins Killing Your Muscle Gains? A Top Antioxidant Could Hurt Recovery.

These vitamins are in 80% of all exercise supplements, and they may hinder our healing.

Should she take a vitamin after that run? Photo by Morgan Sarkissian on Unsplash

Exercise is one of those activities that ought to be simple. Get up, go out, work your muscles. But, as soon as we start thinking about “optimizing” our performance, it gets complex.

What are the best kinds of exercises to do? What sort of training schedule should you adopt? How do you need to adjust your diet? Do you need to take supplements for recovery?

That last question — if supplements are beneficial for exercise — has been hotly debated. Many fitness influencers and coaches will push for supplements, in part because it’s a great revenue stream for them.

But the science is murkier. A new review raises even more doubts about two common vitamins that, on the surface, seem harmless: vitamins C and E.

The pitch: antioxidants to reduce oxidative stress

The pitch for taking vitamins after exercise is simple.

When we exercise, we stress our muscles. Some of the damage from exercise is caused by oxidation, when, in the process of generating energy to power our movements, muscle cells produce oxygen atoms with an extra high-energy electron as a byproduct. These charged oxygen atoms are called free radicals, and they can cause all sorts of damage.

The danger of free radicals is that extra, unpaired electron. Electrons want to be in pairs, so the free radical ends up ripping an electron off of another nearby molecule. This can damage a cell’s machinery. Imagine if someone wandered around a factory, stealing screws wherever they could find one exposed on the factory’s machinery!

To the rescue: antioxidants!

Antioxidants are molecules that are able to donate one of their electrons. If a free radical bumps into an antioxidant, the antioxidant happily gives up its extra electron to neutralize the free radical. It’s a bucket of extra screws sitting out in the factory, so the thief doesn’t take a screw from an important machine.

Two of the most commonly consumed antioxidants? Vitamins C and E.

So the logic is:

1. Exercising causes oxidative damage.
2. Antioxidants reduce the damage from oxidation.
3. Eating antioxidants helps reduce exercise-induced muscle damage, leading to better recovery.

But does this hold up in practice?

Murky data

The use of vitamins C and E in supplements is incredibly widespread; 97% of exercise supplements contain vitamin C, and 78% contain vitamin E.

But in actual trials, the data has been mixed. Some studies have found that high doses of the vitamins does offer some protective effect against muscle damage, and that they can help reduce soreness.

But other studies failed to consistently replicate these results. In soccer players, taking high doses of the vitamins did reduce oxidation — but didn’t yield any improvements in performance or in recovery. In runners, vitamin C and E supplementation actually inhibited their recovery, slowing down some of the healing processes. In elderly men who began strength training, taking high doses of vitamin C and E reduced their muscle gain; the participants who took the vitamins built less muscle than those who were on the placebo.

A 2023 review of published studies proposed that, while vitamins C and E are effective at reducing oxidative stress… that may not actually be a good thing for muscle gains.

As we exercise, our bodies adapt to the new strain put upon them. One aspect of adaptation is ramp up the mechanisms for handling and repairing oxidative damage. When we provide high doses of vitamin C and E as ready-to-use antioxidants, it prevents the body from adapting to produce its own antioxidants and ramp up its repair pathways.

Part of learning to ride a bicycle is learning how to fall, and how to recover from a wobble. Taking high doses of vitamins C and E is like always keeping the training wheels on; it prevents falls, but it won’t help a young rider learn to naturally handle some wobbling on their own.

When are high vitamin C and E doses useful?

From these results, the best conclusion is that high doses of vitamins C and E are not useful in all cases. There needs to be some nuance to when they are effective and when they should be skipped.

In the review article, several use cases for vitamin supplementation are called out:

• When rapid recovery is necessary, like in a tournament or competition setting
• For training for high altitudes
• If there’s a nutrient deficiency
• If someone is exercising primarily for weight loss and not for muscle gain
• During rehabilitation after a serious muscle injury
• If dietary restrictions prevent the consumption of other antioxidants

Except for these cases, however, the authors recommend focusing on aiming for a balanced diet, which includes many different forms of antioxidants, instead of solely loading up on only vitamins C and E.

It’s easy to get pulled into supplement hype when it comes to exercise. We want to make the most of the effort that we put into improving ourselves, and supplements feel like an easy addition. After all, when have vitamins ever been harmful for us?

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Vitamin C is also the most common vitamin additive, as it’s dirt cheap and almost impossible to overdose on; we just pee out the excess (and sometimes lose it through diarrhea). It seems like there’s no harm in tossing back a big dose after exercise…

…except that, by acting as a crutch for absorbing free radicals, it hinders our own oxidation repair systems. Taking vitamin C and E supplements is probably a bad idea if we are training to build muscle and gain overall strength.

If you feel the urge to take something to help recover after exercise, I’d stick with the proven basics: protein powder, water, and creatine.

And you could always follow it up with a salad; spinach is a great source of vitamin C!

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