Dear Doctor: I love swimming and doing water exercises in the pool. The problem is that I tend to get painful cramps in my legs and feet. Is there anything I can do to avoid them? Does my age (I'm 69) have anything to do with this?

Dear Reader: Muscle cramps in the legs -- the calf and thigh, as well as the feet -- are a fact of life for some of us who exercise. And while there are many theories as to why they occur (many of them presented quite forcefully as fact), the truth is, we don't really know the cause. It does appear that cramps, or muscle spasms, can become more common as we age. That's particularly true of leg cramps that occur at night, during sleep. For others, as you have discovered, they can intrude into the activities of daily life.

What's happening is that, due to a nerve malfunction, the muscle fibers suddenly contract and don't release. Unless you've ever lived through a muscle spasm (sometimes it's called a charley horse), you can't understand just how helpless you feel and how painful it is. And while the spasm itself typically ends relatively quickly, that area of the muscle may feel tender for a day or so.

If you decide to check in with your family doctor regarding the onset of these muscle spasms, he or she will most likely begin with a physical examination of the area involved. Your doctor will also collect the information needed to rule out any underlying disease or condition that could be the cause of the spasms. This includes diabetes, kidney disease, heavy drinking or alcoholism, and peripheral artery disease. The latter, which Dr. Ashley covered in a recent column, is a condition in which certain arteries, including those in the legs, become narrow. Pregnant women are also prone to muscle cramps, particularly in the final months before delivery.

Other factors in persistent leg cramps can include a pinched nerve, flat feet, muscle fatigue from overuse and an imbalance of essential minerals such as calcium and magnesium. Muscle cramps can also be a side effect of certain medications, such as diuretics and statins.

We see two potential factors associated with muscle spasms in your situation. One is muscle overuse, and the other is cold temperature. Do the cramps occur in the later stages of your workouts? If so, try taking a break before you reach that danger zone. Hop out of the pool, get something to drink, warm up your legs with a quick walk. Do some stretches and massage the muscles before getting back into the pool.

Another area of agreement around muscle spasms is the importance of potassium, calcium and magnesium in neural health. Dark leafy greens are a good source of magnesium. Potassium-rich foods include sweet potatoes, bananas, broccoli, halibut, cantaloupe and orange juice.

When a cramp does occur, gently massage the affected area and gradually stretch the muscle. It's possible for a cramp to last up to a minute or more, so be patient. And if the cramps are severe enough to interfere with daily life, please do get in touch with your doctor.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My family tries to limit dairy products; it just doesn't make sense to me that, marketing aside, humans should need milk from another species. But now I read that non-cow milk may be linked to shorter kids. Why would that be?

Dear Reader: Your question is a logical one. The milk from breastfeeding is necessary for infant growth across all mammalian species, and humans are the only species of mammal that not only raises their young using the milk of another animal, but also consumes this milk in later life. So while it doesn't make biological sense to drink cow milk, eat cheese, or have creams and yogurt well beyond the time of breastfeeding, does it have a positive or negative effect on our bodies? And, if cow milk has an effect, what are the effects of cow milk substitutes like soy milk, almond milk and goat milk?

A 2017 article in the American Journal of Clinical Nutrition, which received widespread news coverage, attempted to answer these questions. The authors asked 5,034 Canadian parents of children ages 2 to 6 about their children's daily consumption of cow milk and non-cow milk products. Based on the parents' answers, 4,632 children were identified as cow milk drinkers, and 643 were identified as non-cow milk drinkers. (Note that some non-cow milk drinkers also drank cow milk.) There were no appreciable differences between the two groups of children, except for height.

Each daily cup of non-cow milk was linked to a height difference of 0.4 centimeter. That is, children who drank three cups of non-cow milk a day were 1.2 centimeters (approximately 1/2 inch) shorter than children who drank no non-cow milk. Similarly, children who drank three cups of cow milk a day were 1.5 centimeters taller than those who drank 3 cups of non-cow milk.

Here's a possible explanation: The cow milk proteins, casein and whey, have been linked to an increase in size. Also, cow milk contains insulin-like growth factor-1 (IGF-1), which leads to the formation of more bone and cartilage and thus greater height. IGF-1 is also found in goat milk. Note that this study lumped goat milk with soy, almond and other non-mammalian milk, so goat milk may not actually have the height correlation seen with these non-animal milks.

Another possible explanation is that plant-based milks do not contain as much protein and fat as mammalian milk. Thus, children who drink these types of milks don't get the calories or protein needed for greater growth.

Lastly, children who have food allergies are less likely to drink cow milk. Because food allergies have been associated with decreased height and weight, the allergies themselves may be a factor.

In summary, there could be myriad reasons why children who drink cow milk are taller than those who drink plant-based milks, but the fact remains that this seems to be the case. If you're worried that avoiding dairy products will interfere with your child's height, but you're opposed to dairy products for personal or health reasons, I'd recommend you ensure that your child consumes plenty of protein in other ways -- and that your pediatrician keeps a close eye on your child's development.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: When a medication says "take with food," what exactly does that mean? If you take it with a few crackers, does that count? I have a medication I take before going to bed, when I don't feel like eating anything big!

Dear Reader: When it comes to medications, how and when you take them can play a significant role on how effective they are. It also affects how they interact with your body. The direction to "take with food" means that you should not ingest that particular medication on an empty stomach.

There are multiple reasons for this. One is that the components of some medications can cause stomach upset, such as nausea or vomiting, if they are not taken along with food. Additionally, the presence of food can help to buffer the stomach and prevent potential irritation. Over the long term, medications like aspirin and other NSAIDs, corticosteroids like prednisone, as well as some oral contraceptives can cause inflammation or even ulcers when taken on an empty stomach.

The other thing that the presence of food does is to initiate digestion. When you eat, gastric acid is released into the stomach, which helps break down food -- and any medication -- into smaller components. For some medications, the bile and stomach acid produced during digestion boost the rate at which they break down and are absorbed. Conversely, other medications would be absorbed too quickly if taken on an empty stomach. The presence of food helps slow that process.

As to what "with food" actually means, it's not necessarily a full meal. If you happen to be timing your medication to breakfast, lunch and dinner, that's fine. But a few crackers at bedtime, as you said, can be adequate. Ditto for a piece of fruit or a glass of milk. It's probably a good idea to ask your pharmacist why your medication should be accompanied by food. That way, if it's to prevent inflammation or indigestion, you can monitor your response and increase or change the kind of food you're eating to maintain maximum comfort.

But -- and it's a very important one -- not all foods are created equal when it comes to medications. Grapefruit juice and some other fruit juices can change how drugs behave. They can increase the absorption rate of some drugs, including some statins. They can also change how the body metabolizes certain drugs, including antihistamines, birth control pills and blood pressure medications, among others. That means you can wind up with blood levels of a medication that are lower or higher than are optimal. Be sure to read the medication label. If you're uncertain what foods are OK, check with your pharmacist.

What about medications that require an empty stomach?

For these, take them either no less than one hour before a meal, or at least two hours after a meal. And if you're taking them after a meal, that means your medication will do its best work if you don't eat again for another two hours.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)