Nutrients: Can You Have Too Much of a Good Thing?
Last reviewed by Faculty of Harvard Medical School on January 13, 2011
By Robert H. Shmerling, M.D.
You may feel like youre getting advice from all sides: Increase your intake of calcium, iron, vegetables and water; exercise more; take more vitamins; use more sunscreen. Your doctors, your friends and family may reinforce the notion that you are not doing enough to improve your health or reduce risk of illness. In fact, when you also consider all the routine recommendations for medical care a yearly physical examination; getting your eyes checked; seeing your dentist regularly; getting your vaccinations; getting tested for osteoporosis, heart disease, colon cancer, cervical cancer and so on doing the right things may seem like a full-time job. And thats if youre perfectly healthy.
With all the pressure to do more for your health, it may be surprising to learn that in a number of situations, the problem is not too little but too much of a good thing. In a previous column, I discussed how having tests is not always helpful. In today's installment, the issue is how to avoid getting too much of a "healthy" nutrient, whether in the diet or by taking supplements.
Several rather common conditions are marked by too much of something that is usually good for us. These include:
Even too much (or erratic) ingestion of certain fruits and vegetables can cause problems! If you eat broccoli in large quantities or in amounts that vary over time, its vitamin K content can counteract the blood thinning effects of a common blood thinner, warfarin (Coumadin). So, for people taking warfarin, broccoli and other foods that contain significant amount of vitamin K, such as spinach and Brussels sprouts, should probably be avoided or at least closely monitored with blood tests. And for grapefruit juice lovers, an interaction may increase the potency of certain medications such as cyclosporine, atorvastatin and diltiazem. If you take your medicines and the grapefruit juice at the same time each day, tell your doctors about your diet, and have proper monitoring regularly, you dont necessarily have to give up grapefruit juice. (In fact, some people are able to reduce the dose of their medicine by regularly drinking grapefruit juice, but discuss this with your own doctor before pursuing it.)
When there is too much of a good thing such as iron, calcium or water in the body, the initial symptoms may be subtle or nonspecific (meaning they could be due to many different things). In fact, there may be no symptoms at all. However, for most, routine testing usually identifies the problem. Common symptoms and findings related to the conditions mentioned above include:
For people with these symptoms, common blood tests, such as measures of blood counts, kidney and liver function, blood calcium and sodium levels will usually identify the problem. In addition, some physicians (though not all) screen routinely for many of these conditions. For example, some experts recommend screening every adult for hemochromatosis by measuring the amount of iron in the blood. There is no agreement, however, that this screening should be routine.
With all the warnings about increasing ones intake of a variety of nutrients, how can one avoid taking too much? For a start, read nutrition information labels, including the recommended daily allowance; do not increase the dose of supplements above what is recommended by your health care professional, and remember that a little is good, more is better is not always the best approach. See your health care professional if you have symptoms and ask for specific recommendations for vitamins and supplements with focus on your particular health problems or concerns perhaps it would be best if you took no vitamins or supplements at all! Finally, keep an updated list of your medicines and supplements and let your doctor know exactly what you are taking.
Recommendations for people to increase their intake of certain components of their diet or to add supplements may make sense for the average person, but it may not apply to you. Its important to know when enough is enough and when to avoid certain nutrients or supplements that otherwise might be good for you. Know your medical conditions and whether there are specific recommendations not only about what to increase but also what to avoid. There can be too much of a good thing and, depending on your condition, a good thing may not be good for you at all.
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.