DEAR DR. ROACH: I’m 70 years old, and my whole family is prone to edema, varicose veins and deep vein thrombosis due to venous insufficiency. I’ve been wearing support pantyhose for 45 years whenever I get dressed, and I recently increased the compression.

My question is whether it’s OK to wear the support hose all the time, even while I’m sleeping?

• P.H.

ANSWER: The most common reason to develop edema (swelling) in the legs is venous insufficiency, which is caused by the failure of the valve structures in the veins. Without these valves, blood tends to pool in the legs, raising the venous blood pressure and driving fluid out of the blood into the tissues. The legs are affected because gravity pulls the blood and fluid down.

I’m sorry to disagree with your husband, but I agree with the usual recommendation to remove support stockings at bedtime. The reason for support stockings is to try to counteract gravity, and when you’re laying flat in bed, you don’t need to do this anymore.

Research from way back in 1993 showed that oxygen levels in the skin fall when support stockings are worn at night. For most people, this is tolerated well, but people with poor circulation (from blockages in the arteries to the leg, for example) can develop damage to the skin, which can potentially lead to skin ulcers.

Only people who have been recommended for 24-hour compression (such as people with lymphedema) should be wearing them while in bed. Taking them off is more comfortable and allows the skin to recover. Wound care nurses are the experts in managing venous insufficiency.

Finally, regular exercise is good for edema! The muscle action helps bring the fluid back into the circulation. Sitting with your legs down is bad, which is why traveling can be so problematic.

DEAR DR. ROACH: My wife’s become convinced that mixing fruit and vegetables during the same meal is harmful — for instance, eating fruit salad as a side dish or eating a salad that includes avocado and oranges. Is this a valid concern?

• G.O.

ANSWER: There are principals, such as in Ayurvedic tradition, to avoid mixing certain fruits with vegetables due to a concern of fermentation in the stomach. The evidence showing that this is a valid concern isn’t strong. Most people can combine fruits and vegetables without problems, but if they cause stomach upset or bloating, then you shouldn’t do it. But it isn’t dangerous to combine fruits and vegetables.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.