How much sleep do we need? Experts believe that seven to nine hours is about right. The goal is to wake up feeling refreshed and to stay awake and alert throughout the day without relying on stimulants or other pick-me-ups.

While more research is needed to understand the relationship between chronic sleep loss and health, it’s safe to say that sleep is too important to shortchange. So if you haven't considered sleep as part of your healthy lifestyle goals, here are six reasons to consider doing so.

1. Learning and memory

Sleep helps the brain commit new information to memory by way of a process called memory consolidation. One study showed that those who slept before a cognitive task did better. In others, subjects discovered more insightful or creative ways to problem-solve after a night’s sleep.

2. Metabolism and weight

Chronic sleep deprivation may cause weight gain by altering metabolic functions, such as processing and storing carbohydrates, and by stimulating the release of excess cortisol, a stress hormone. Loss of sleep also reduces levels of leptin, a hormone that suppresses appetite, and increases levels of ghrelin (pronounced GRELL-in), an appetite-stimulating hormone — a combination that can encourage eating.

3. Safety

Sleep debt contributes to a greater tendency to fall asleep during the daytime. These lapses may cause falls and mistakes such as medical errors, air traffic mishaps, and road accidents.

4. Mood/quality of life

Sleep loss, whether long- or short-term, may result in symptoms — irritability, impatience, inability to concentrate, and moodiness — that suggest psychological problems such as anxiety and depression. Too little sleep can leave you so tired that you don’t want to do the things you enjoy. Poor sleep also affects the ability to work effectively.

5. Cardiovascular health

We don’t know much yet about the effect of chronic partial sleep loss on cardiovascular health. But serious sleep disorders such as insomnia and sleep apnea have been linked to hypertension, increased stress hormone levels, cardiac arrhythmias, and increased inflammation (which has been implicated in heart attacks).

6. Immunity/cancer prevention

Though all the mechanisms aren’t clear, scientists have found that sleep deprivation alters immune function, including the activity of the body’s killer cells. For example, sleep loss around the time of a flu vaccine has been shown to reduce the production of flu-fighting antibodies. Keeping up with sleep may also help fight cancer. Harvard researchers have shown that women who work at night are at increased risk for breast and colon cancer. The connection may be through melatonin, a hormone that helps put us to sleep; light at night cuts melatonin production.

Getting your Zs

So if you think you aren't getting enough rest at night, follow these tips to get better sleep:

• Get regular exercise, but not within three hours of bedtime.
• Don’t use alcohol as a sleep aid.
• Avoid caffeine after noon.
• Establish times for going to bed and getting up.
• Keep your bedroom temperature cool.

For more information on sleep, order our special health report Improving Sleep: A Guide to a Good Night’s Rest www.health.harvard.edu/IS.

Q: I get headaches after drinking red wine. Why? I’m 56 years old and in excellent health.

A: Getting a headache after drinking red wine seems to be common, but no single explanation has been found. Several theories have been proposed, but none has much evidence behind it.

One theory holds that the culprit is histamine, a compound found in grape skins. Red wine contains more histamine than white wine because it’s made from the whole grape (including the skin), not just the juice. Some people have a shortage of an enzyme that breaks down histamine in the small intestine. Alcohol also inhibits this enzyme, so the combination may boost histamine levels in the blood, which can dilate blood vessels and cause a headache.

Tannins, another grape-skin constituent, could also be at fault. Tannins are plant chemicals that impart flavor to red wines and contain antioxidants. But they also spur the release of the neurotransmitter serotonin, which at high levels can cause headaches in some people. Other plant chemicals (polyphenols) may be involved.

Some experts think that sulfites, a preservative in wine, are to blame. But sulfite sensitivity usually causes breathing problems rather than headaches. Moreover, many white wines and other foods also contain sulfites.

These potential culprits vary from wine to wine, so if you don’t want to give up red wine altogether, you might try different brands or varieties to see how they affect you. When you try a new red wine, start with less than half a drink. If it’s going to give you a headache, it’ll do so within 15 minutes.

Any alcoholic beverage can dilate blood vessels in the brain and cause a headache. Avoid drinking wine, beer, or liquor on an empty stomach or when you’re dehydrated. Try to drink a glass of water between glasses of wine. And limit your wine intake. No more than one glass per day is most healthful for women, and men should aim for two at most. But if you have two at a sitting, they should be separated by at least an hour.

Celeste Robb-Nicholson, M.D. is the Editor in Chief of Harvard Women’s Health Watch www.health.harvard.edu/women