Harvard expert answers reader questions
Q: Does zinc really work for colds and flu?
A: This question is timely, as cold and flu season will soon be here again.
For many years, there’s been interest in the possibility that zinc, or other supplements, could help prevent or treat colds and flu. A recent analysis reviewed available research and suggested that over-the-counter zinc supplements could be one way to make cold and flu season a bit easier.
Published in November 2021 in BMJ Open, the study looks at zinc for preventing or treating colds and flu-like illness. Researchers reviewed more than 1,300 studies and narrowed the analysis down to 28 well-designed trials, which included more than 5,000 study subjects. Here’s what they found.
For preventing colds and flu
- Zinc therapy was associated with fewer upper respiratory infections compared with placebo. The effect was modest: about one infection was prevented for every 20 people using zinc. The strength of the evidence was considered low.
- A few studies suggest preventive effects were largest for reducing severe symptoms, such as high fever.
- Small studies of intentional exposure to a cold virus found that zinc did not prevent colds.
For treating colds and flu
- Those who took zinc had symptoms go away about two days sooner than those in the placebo group. Of 100 people with upper respiratory infections, an estimated 19 additional people would have completely recovered by day seven with zinc treatment. The strength of the evidence was considered low.
- On day three of the infection, those taking zinc had milder symptoms. Further, there was an 87% lower risk of severe symptoms among those taking zinc. However, the daily average symptom severity was similar between those taking zinc and those taking placebo. The data quality and certainty of these findings were low to moderate.
Before taking zinc, keep these other points in mind:
- Side effects. Zinc-related side effects were mild. These included nausea and mouth or nose irritation.
- Cost. Zinc supplements are generally inexpensive. A daily dose of zinc lozenges for a month may cost less than $2/month.
- Different doses or types. Additional research is needed to determine the best dose and ideal way to take zinc.
- COVID-19. None of the studies in this analysis assessed the impact of zinc on the virus causing COVID-19.
Whether you decide to take zinc or not, keep in mind the following tried and true preventive measures and treatments:
- Get a flu shot
- Wash your hands frequently
- Avoid contact, maintain physical distance, and wear a mask around people who are sick
- Get plenty of sleep
- Choose a healthy diet
Q: There seems to be controversy regarding how much water a person should drink each day. What do you suggest for an older adult?
A: You probably know that it’s important to drink plenty of fluids when the temperatures soar like they have been recently. But staying hydrated is a daily necessity, no matter what the thermometer says.
Many of us aren’t getting enough to drink, especially older adults. Older people don’t sense thirst as much as they did when they were younger. And that could be a problem if they’re on a medication that may cause fluid loss, such as a diuretic.
Water keeps every system in the body functioning properly, such as carrying nutrients and oxygen to the body’s cells, maintaining balance of blood sodium levels, helping to regulate body temperature, and preventing constipation.
Giving your body enough fluids to carry out those tasks means that you’re staying hydrated. If you don’t drink enough water each day, you risk becoming dehydrated.
Warning signs of dehydration include weakness, low blood pressure, dizziness, confusion, or urine that’s dark in color.
So how much water should you drink? Generally healthy people should aim for six to seven cups of water per day. You will need to increase water intake significantly when it’s hot or you’re sweating.
But it’s also possible to take in too much water if you have certain health conditions, such as thyroid disease or kidney, liver or heart problems; or if you’re taking medications that make you retain water, such as non-steroidal anti-inflammatory drugs (NSAIDs), opiate pain medications and some antidepressants.
How much water a day should you drink if you fit into that category? There’s no one-size-fits-all answer. Water intake must be individualized, and you should check with your doctor if you are not sure about the right amount for you.
But even a healthy person’s water needs will vary, especially if you’re losing water through sweat because you’re exercising, or because you’re outside on a hot day.
It’s not just water that keeps you hydrated. All beverages containing water contribute toward your daily needs. And know that you also get fluids from water-rich foods, such as salads and fruit.
To ward off dehydration, drink fluids gradually throughout the day. An easy way to do this is to have a drink at each meal, as well as socially, or with medicine.
Q: I am frequently itchy but don’t see any rash. Why might this be happening?
A: With age, skin loses moisture. A dry skin barrier doesn’t work as well as it used to.
Things that may not have irritated you before may now be absorbed in the skin and cause itching. The skin also develops a somewhat impaired immune response, a reduction in fat and blood flow, and altered sensory perception, making it more prone to itching.
Here are some other reasons for generalized itching:
- Environment. Very hot, dry environments or lots of hot showers can make the skin dry and itchy, as can excessive exposure to sunlight.
- Medication. Itching may be a side effect of some drugs. Even if you’ve been taking a medication that didn’t bother you before, manufacturers can change the inactive ingredients, such as the dye coloring the pill, and that may cause the itch.
- Allergens. Detergents, fabrics, cosmetics, dust and plant pollen can cause itching from irritation. A person can acquire an allergic reaction to anything that comes in contact with the skin, and may not notice a rash.
- Psychological conditions. High stress, anxiety and obsessive-compulsive disorder are common causes of generalized itching. For people with these conditions, symptoms of any kind, including itching, can be amplified.
- Neuropathy. Nerve damage (neuropathy) that causes numbness, tingling, weakness or pain can also cause itching.
- Underlying medical conditions. Itching may be a symptom of liver, kidney or thyroid disease; iron deficiency anemia; or rarely some types of cancer, such as a lymphoma.
Reducing generalized itching starts with changing your lifestyle. Taking too many hot showers? Reduce the number to two to three per week. Make the water warm, not hot, and use bland soap.
If you’re not already moisturizing your skin, it’s time to start. Use an emollient (a mixture of water and oil) every day, especially after getting out of the bath or shower (to lock in moisture).
If your home is hot and dry, consider lowering the temperature and getting a humidifier. Aim for a goal of 40% humidity indoors.
When these measures don’t provide sufficient relief, it’s time to see your doctor. Your doctor will consider your medical history, medications or supplements you’re taking, and your lifestyle. It may be necessary to order blood work to check your blood sugar, red and white blood cell counts, and the function of your thyroid, kidney and liver.
If you do have a rash or other skin changes, it can be difficult to tell whether scratching the itch was the cause rather than some underlying skin problem. Your doctor or a dermatologist might want to take a small sample of skin for examination under the microscope.
Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, visit health.harvard.edu.
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