Michael Arnstein, an elite ultra-runner, got me turned on to eating more fruit. He is a fruitarian which means he eats mostly fruits and vegetables, and lots of them---6,000 calories per day. He swears it helps his performance and recovery. He does crazy stuff like run a 100-mile race on weekend and then race a marathon the next (and do well). He typically runs 150+ miles per week, and since he changed his diet, he no longer gets sick or injured and his running times continue to improve.

A triathlete I was coaching heard about this and decided to give this way of eating a try. Almost immediately she started seeing PRs in her running and swimming times (this after coming off of two months of very little training).

In some ways this way of eating makes intuitive sense, as fruits and vegetables are the most nutrient dense foods on the planet, i.e. they pack a lot of nutrients for your calorie buck. If you are eating 6,000 calories and getting a boat load of nutrients along with those calories, well this can only be a good thing. These foods are also high in water (which helps with staying hydrated) and fruits, in particular, are high in carbohydrates which athletes need in abundance.

Now I don’t fully embrace (or even advocate) for a full-on fruitarian diet, but I think we would all benefit from eating more fruits and vegetables and that these foods should make up the bulk of one’s diet. Here’s why.

Oxidative stress has been implicated as playing a central role in many of the disease that we suffer from. The aging process has also been blamed on oxidative stress. As one paper put it, “inflammation and oxidative stress are the villains of aging.” Foods can and do play a role in either promoting or neutralizing oxidative stress.

But what causes oxidative stress? Breathing air for one thing and more so if we breath polluted air. So, if breathing oxygen can do it, what about when we are breathing lots of air, as in during exercise?

Herein lies the dilemma, could exercise that is so good for us be inducing greater levels of oxidative stress?

As one paper put it, “Some authors have looked on the exercise-induced increase in free radical production [oxidative stress] as a paradox: an apparently healthy act leading to detrimental effects through damage to various molecules and tissues.” 

The good news is that exercise training has been shown to enhance our own internal antioxidant defenses. Two defenses that increase with exercise are superoxide dismutase and glutathione peroxidase. Both of these are found in the mitochondria (where oxidative metabolism occurs). This is a good thing as many antioxidants from our food can’t penetrate into the mitochondria where they are needed (although they can protect the rest of the cell, like the DNA).

So how can diet help? Go to the next post to find out.