When asked what his favorite fruit is, Michael Arnstein, my favorite ultra-runner/fruitarian, replied that it was oranges. Why?  Part of the reason, he says, it that he likes high water content fruit, and oranges certainly meet that criteria.  But I wonder if he is aware of some of the health promoting and possible performance enhancing benefits of oranges (or citrus fruits).  

I admit, I haven’t been a big fan of oranges.  I tend to prefer less messy fruits like apples, pears, berries, bananas and grapes.  If I do eat messy fruits, mangoes are more worth the trouble.  But I might have to change my tune after reading some of the research on oranges (or OJ).

Oranges (and OJ) are rich in a class of compounds known as flavonoids.  Flavonoids are widespread in the plant kingdom and have been shown to have anti-oxidant and anti-inflammatory properties.  They also protect LDL from oxidation, and may thus play a role in protecting us from atherosclerosis.   They may also help lower LDL cholesterol and increase HDL by inhibiting endogenous (i.e. our own) production of lipoproteins by the liver.  

Hesperidin, a type of flavonoid found primarily in citrus fruit, has been shown to increase blood flow.  One study, which compared drinking a placebo drink to drinking a juice with added hesperidin to drinking plain orange juice, found that blood flow increased in the hesperidin group but even more in the OJ group, i.e. there were other factors in the OJ in addition to the hesperidin that were beneficial.  The improvements in blood flow were attributed to improvements in endothelial function (a good thing for arterial health).  

One benefit of this improved blood flow was demonstrated in a study which took people with cold sensitivity and put them in a cold room.  Those who drank a citrus drink maintained higher temperatures in their finger tips than those who drank a placebo.  When they plunged their hands into cold water, those drinking the citrus showed a faster rebound in finger tip temperature.  It has been suggested that this might help prevent frost bitten fingers on a cold day of skiing.  But that study has yet to be done.  As someone who has perennially cold hands, this got my interest.

But this study out of Brazil caught my attention.  They took 26 overweight, out of shape women, and put them on an aerobic training program (3x per week) for 90 days.  Half the group drank 500 ml of orange juice a day (in spite of the extra calories they ended up losing some weight) and half the group drank a placebo.  

Both groups improved their endurance by 20% as measured by how fast they could go at their anaerobic threshold.  However, those on the OJ reduced their plasma lactate concentration by 27% compared to the control group who dropped theirs by 17%.  This could represent a significant reduction in perceived muscle fatigue.  As to whether this same effect would occur in trained individuals, however, remains to be seen.  

Also of interest was that those on the OJ also decreased their LDL by 15% and increased their HDL by 18% while those on the placebo experienced no change (in spite of experiencing some weight loss) in their cholesterol levels.  

Hesperidin has also been identified as being a pancreatic lipase (PL) inhibitor.  PL inhibitors present an interesting approach for reducing fat absorption and may thus play a role in fighting obesity.  Orlistat, the only authorized anti-obesity drug in Europe, has been shown to act through inhibition of PL.  There are hundreds of natural compounds in plant foods (hesperidin among them) that have been shown to have PL inhibitory activity (some to even a greater degree than Oristat).  Other PL inhibitors have included certain proteins found in soybeans and wheat bran and wheat germ.  This may be one reason why diets rich in plant foods may be advantageous in preventing weight weight gain compared to those who eat the same number of calories but from animal foods.  

In conclusion, eating a variety of citrus fruits appears to be a good thing.  As per usual the whole fruit is always better than the juiced version, although I do like to add some OJ to my Sunrise Kale smoothie.  Now i can feel good about that.