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Harvard Commentaries
35320
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


What Your Doctor Is Saying What Your Doctor Is Saying
 

The Case for Moderation


September 13, 2012

By Robert H. Shmerling M.D.

Beth Israel Deaconess Medical Center

It's not just your mother who recommends "all things in moderation." Your doctor may suggest this as well.

When it comes to health, I think of the story of Goldilocks and the Three Bears. Many things we do to stay healthy are more beneficial in amounts that are not too much, not too little, but "just right."

Experts don't always agree on or know what the ideal amount is for many healthy behaviors. But for some things, too little is probably a waste of effort while too much may be worse than none at all.

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Vitamins: Just the Right Dose

The word "vitamin" originally referred to substances considered vital for life, such as nutrients that the body cannot make itself (or make enough of). So we rely on foods or supplements to provide them. While vitamin deficiencies can cause disease, vitamin excess can also be harmful.

Take vitamin A, for example. Inadequate vitamin A in the body can cause dryness of the eyes, night blindness and, eventually, total blindness. Other problems associated with vitamin A deficiency include poor immune function, rash and diarrhea.

But too much vitamin A from supplements or eating large amounts of liver may cause too much vitamin A to accumulate in the body's tissues. This is called hypervitaminosis A. Symptoms include headache, fatigue, blurry vision, bone pain and nausea. Pressure can build up in the brain and the liver can be damaged.

So what is just the right dose of vitamin A? It's 900 micrograms daily for men and 700 micrograms daily for women. You can get these amounts by eating a balanced diet. Vitamin A is found in fish, dairy products, and many fruits and vegetables.

Vitamin A is not the only vitamin that can be harmful in excess:

    • Vitamin D - Too much vitamin D (hypervitaminosis D) can cause dangerously high blood calcium. This can lead to kidney stones, kidney failure, weak muscles, bone pain, loss of appetite, vomiting and confusion. Although rare, large amounts of vitamin D can be fatal, especially among people with other medical problems or if combined with excessive calcium intake.
    • Vitamin B3 (niacin) - Excessive niacin may cause a flushing sensation, diarrhea, abdominal pain, vomiting and liver damage.
    • Vitamin B6 - Too much B6 may cause nerve damage.
    • Vitamin C - Overdosing on vitamin C can cause headaches, diarrhea and kidney stones. However, most people who take mega doses of vitamin C simply get rid of it in their urine.

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Exercise: A Happy Medium

It's clear that some exercise is good. Too little, however, and your risk of obesity, diabetes, heart disease and osteoporosis (among other problems) increases. But is more better? To some extent, yes. Past guidelines recommended 30 minutes of moderate intensity exercise 4 or 5 days a week. The current recommendation suggests 45 to 60 minutes of moderate intensity exercise most days of the week.

Still, too much exercise can cause problems. Injuries such as stress fractures or tendon inflammation are common among people who overtrain. Other symptoms of overtraining include menstrual irregularities (in women), unusually severe or prolonged muscle soreness and decreased appetite. Competitive athletes may even notice that their performance suffers when they train too much.

What's the right amount of exercise? No one knows for sure, but I think the current recommendation of 45 to 60 minutes of moderate intensity exercise most days of the week is a reasonable goal.

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Alcohol: A Tricky One

It's not unhealthy to abstain from alcohol. But many studies have linked moderate alcohol intake to a lower incidence of:

  • Heart disease
  • Dementia
  • Diabetes
  • Lung cancer

The type of alcohol may matter. For instance, one study found a lower incidence of lung cancer among smokers who drank red wine, but not those who drank white wine or beer.

Of course, too much alcohol is hazardous. Excessive alcohol intake can lead to:

  • Cirrhosis (severe liver damage)
  • Trauma, including motor vehicle accidents
  • Pancreatitis (inflammation of the pancreas)
  • High blood pressure
  • Heart damage and irregular heart rhythms

So, how much alcohol is too much? Again, no one knows for sure, but a common guideline, which I think is reasonable, is no more than one drink a day for women and two drinks a day for men.

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Sun Exposure: Some Controversy

Too little sun can be bad for your bones. That's because the sun's rays convert an inactive form of vitamin D in the skin to an active form. But the more sun exposure, the higher your skin cancer risk, especially if you've been sunburned frequently.

So, it's important to get just the right amount of sun. How much is ideal? This point is controversial, but I agree with the recommendation that 10 to 15 minutes of sun exposure each day gives you the benefits without undue skin cancer risk. Of course, even short exposure to midday sun in Miami could cause sunburn, especially if you are fair-skinned. So it's important to adjust your sun exposure for the type of skin you have and your location.

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Other Examples

There are many other examples of the importance of moderation in matters of health. Too much of certain types of fish, such as shark, swordfish, tuna and king mackerel, could cause excessive mercury exposure. Yet fatty fish like mackerel, tuna, salmon and shrimp have omega-3 fatty acids that may be beneficial for the heart.

Moderation is also important with respect to the amount of calories fat, protein and carbohydrates in your diet.

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The Bottom Line

Nearly everything that’s good for you is best in moderation. Even the healthiest behaviors, if overdone, can be harmful. So, the next time your doctor recommends something, such as exercise, ask how much is too much or too little. Then try to stick with something in between.

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Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

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