nutrition

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It started out as a fun, 50-mile ride with several lengthy climbs. If you're not a cyclist, riding 50 miles probably doesn't sound like much fun. Climbing hills on a bicycle probably sounds like torture.

In some respects, that's exactly what my training ride turned into. On the third serious climb of the afternoon, I began to cramp, my quadriceps pulsating like a Miami night club. As I lay on the side of the road writhing in pain and watching other cyclists pedal by, I wondered what I had done--or not done--to cause these muscle cramps.

Surprisingly, we don't quite know what causes muscle cramps. We have excellent theories. Chief among them: Hot weather, dehydration and loss of electrolytes like sodium, calcium, potassium, chlorine, phosphate and magnesium.

To some extent, these factors work together: Heat leads to dehydration, dehydration brings about the electrolyte imbalance. Conditioning may also play a role, especially since exercise-induced muscle cramps tend to occur during endurance tests--long runs, rides or swims. My cycling condition certainly wasn't up to par for this ride.

Another theory: Muscles misfire because either nerves aren't functioning properly (called altered neuromuscular control) or because they don't fully extend during exercise and lose their ability to bounce back.

Whatever the causes, here's how to reduce the risks of getting cramps and how to treat them if they do occur:

Stay hydrated
When I cycle, I carry several liters of water with me. That sounds like a lot of water, but I sweat a lot. That's one of several variables that go into how much fluid we should drink when we exercise. Temperature, length of workout, even altitude can affect how much you should drink. The American College of Sports Medicine [.PDF] recommends drinking enough before, during and after exercise to prevent water loss greater than 2 percent of your body weight.

But don't over-hydrate. Just as dehydration can cause a dangerous fluid imbalance in your body, so can too much water, which can dilute the concentration of sodium in your body..

Sports drinks are okay, but only during rigorous or lengthy exercise programs. Most sports drinks contain the electrolytes you lose when you sweat. They also have carbohydrates, which can help maintain your energy. But they're overkill for shorter, less intense workouts. For those routines stick with water.

Eat a balanced diet
If you have problems with cramps, focus on foods that are rich in key electrolytes like potassium, sodium and calcium. Most of us already get plenty of sodium in our diet, but if you're ramping up exercise, you might want to add food sources for potassium and calcium. For potassium, eat bananas, raisins, potatoes, and spinach. Dairy products are a good source of calcium, but you can also get it through oily fish, soy products and some dark leafy greens.

Avoid extreme heat
On hot days, cut back the length of exercise, move indoors or shift your workout to the morning or evening when the day is cooler. You can also cramp in extreme cold weather.

Finally, if you do cramp up, stop doing the activity that triggered the cramps. Gently stretch and massage the muscle, holding it in stretched position until the cramp stops. Later, you can apply heat to tight muscles--and cold to sore ones.

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It's become a frustratingly familiar tale: A vitamin or mineral is hailed for its power to ward off disease. Sales of the supplement soar. But then studies suggest that the claims may have been overblown. Eventually, more definitive research--in the form of large, randomized trials--confirms that the supplement is ineffective and possibly even harmful.

Such is the disappointing story of vitamin E, an antioxidant that previous research has suggested may help ward off cancer and heart disease. But several recent studies have cast doubt on the idea. And now two large trials are putting some final nails in the coffin.

One is a massive study, funded by the National Cancer Institute, that involves 35,000 men age 50 and older. Known as SELECT, it was designed to determine whether vitamin E and the mineral selenium, taken either alone or together, prevent prostate cancer. The answer is no, according to an initial review of the data. What's more, those who took vitamin E had a slightly higher risk of prostate cancer, though it's possible the finding was due to chance. As a precaution, researchers recently decided to halt the trial early and advised participants to stop taking their supplements.

Another large randomized trial, involving more than 14,000 male physicians age 50 and older, recently found that subjects who took vitamin E supplements had no fewer heart attacks, strokes, or cardiovascular-related deaths than those who got a placebo.

When vitamin E fails tests such as these, proponents are sometimes quick to blame the research. One common complaint is that studies used synthetic vitamin E rather than the "natural" form. (You can tell which is which by looking at the label; dl-alpha-tocopherol means it's synthetic, while a "d" instead of "dl" indicates it's natural.) Though some vitamin users and sellers believe that natural vitamin E is more effective, there's no compelling evidence to support such assertions.

Other possible explanations are that the dose (400 IUs daily in both studies) wasn't optimal or that the follow-up periods (an average of five years in SELECT and eight in the heart disease trial) were too short.

Perhaps. But the information yielded by health studies is rarely perfect. We have to make decisions based on what's known--not what we hope is true. And multiple studies--involving different doses and different populations, using different forms of vitamin E--have now shown that it does not live up to its earlier billing.

The take-home message is that we need to be careful not to swallow supplement claims prematurely. First, do some homework. Databases provided by the Mayo Clinic and Consumer Reports, which objectively review the scientific evidence for a host of dietary supplements, are two good places to start.

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