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Fish Oil and Prostate Cancer

A recent report in the Journal of the National Cancer institute concluded that men with a high blood concentration of fatty acids (omega-3) had an increased prostate cancer risk. The conclusion is concerning since it appears to contradict the assumption that fish oil and fatty fish consumption improve the overall health of men.

Moreover, the authors had previously found that high concentrations of trans-fatty acids (yes, the ones now restricted in food processing because of a clear association with heart disease) were associated with a decreased risk of aggressive prostate cancer. Trans-fatty acids are found in margarine and frying oils. Omega-6 fatty acids were associated with a lower risk of total prostate cancer.

Other studies have shown numerous health benefits of omega-3 fatty acid. One study showed a two- to three-fold greater risk for prostate cancer in men who ate no fish compared with those who consumed large amounts of fish in their diet. Other studies have also shown a decreased risk of prostate cancer and of metastatic prostate cancer in men who eat fish more than three times a week.

There are a number of problems with the recent study associating omega-3 fatty acid concentration with prostate cancer. We don’t know the source of the fatty acids in the study patients; there was no information on dietary habits or supplements taken. We don’t know anything about the subject’s risk factors for prostate cancer such as ethnicity, PSA levels, age and weight. Additionally, the study was based on a single blood test, not an analysis of concentrations over time.

Of interest, Japanese men consume the most omega-3 fatty acids from their diet in the world and yet are experiencing a declining risk for death due to prostate cancer. Additionally, many studies have demonstrated the cardiovascular benefits of omega-3 fatty acids.

Until more information is available to the contrary, in my opinion, it is prudent for patients with cardiovascular disease to consume oil fish several times a week and use fish oil if a dietary source is unavailable or unappealing.

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Are Extra Vitamins a Good Idea?

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The standard authorities state that for most healthy adults consuming a well-balanced diet, multivitamins (which usually contain 50%-150% of the recommended adult daily requirement of the standard vitamins) are not needed. However, some evidence suggests that taking a daily multivitamin causes a small decrease in cancer risk.

All authorities agree that there are important areas where extra vitamins are needed:

It is very important for women who might become pregnant to take a supplemental dose of 400 mcg of folic acid daily. The extra folic acid insures against inadequate reserves and prevents neural tube defects in the newborn such as spinal bifida.

A multivitamin is important for individuals with malabsorption (such as celiac disease, gluten-sensitivity), a vegan diet, alcoholism and certain other chronic conditions.

For other adults folic acid supplementation is unnecessary and perhaps unwise. An increased level of folic acid can mask vitamin B12 deficiency, a very serious deficiency problem, and may stimulate the growth of some cancers.

In order to prevent osteoporosis and decrease the risk of falls (a curious, but substantiated association) adults need a minimum of 800 units of vitamin D daily, taken either through dietary sources or as a supplement. Unlike all other vitamins, vitamin D can be produced by humans internally. In this case sunlight is needed, and exposure is often insufficient.

Dietary sources of vitamin D include milk, yogurt and soy milk—all of which are usually fortified with vitamin D. Salmon, sardines, tuna and cheese are other good sources of vitamin D.

Since vitamin D levels are often low in adults and since vitamin D deficiency causes bone problems and has been possibly linked to other diseases, taking 600-800 units daily, particularly in older adults, seems prudent.

Vitamin A levels are usually normal in the industrialized world and supplementation is not needed and, indeed, may be harmful. Excessive doses in pregnant women can cause abnormalities in the newborn. Additionally, in all adults excessive doses can cause osteoporosis as well as possibly increasing the risk of cancer and cardiovascular disease.

Likewise, vitamin E levels are usually adequate and high dose vitamin E (more than 400 units daily) supplementation is unwarranted since excessive vitamin E levels are associated with increased all-cause mortality.

Vitamin C supplementation is safe, but has no proven benefit.

Older persons should consider taking a B12 supplement since levels of this very important vitamin can drop with age. Liver, fish, beef, cheese and eggs are dietary sources of vitamin B12. A vegan diet eliminates many dietary sources, making supplementation necessary.

Types of Fatigue

Over 100 years ago William Osler, the father of internal medicine, divided fatigue into three types. The first is the lassitude and malaise associated with systemic illness such as tuberculosis, cancer, rheumatoid arthritis, etc. The second is the weakness associated with muscle and nerve disorders resulting from ordinary exertion. The last is a painful weariness – the cause of which often eludes investigation.

These categories provide a useful framework in attempting to diagnose the cause of an individual’s fatigue. Duration further categorizes the symptom. Most patients with prolonged, unexplained fatigue have the third type of fatigue described by Osler, a painful weariness.

Fatigue that is less than one-month in duration is often due to a passing virus, stress, or other causes that are difficult to define. The relatively brief nature of the problem eliminates the need for an intense medical investigation, and, unless the problem becomes recurrent, it can be dismissed as one of life’s minor problems.

Persistent, significant fatigue, however, is not a minor problem. Even a loss of 10% of a person’s vigor removes enthusiasm and joy from the day’s tasks. Fatigue pulls down the mood and makes everything an effort. Approximately 15% of the general population suffers from chronic fatigue, unrelieved by rest, lacking an adequate medical explanation.

Approximately 25% of patients visiting a medical doctor complain of fatigue. Less than half will be explained by a medical illness.

Fatigue caused by medical conditions has certain characteristics. A serious medical problem will occasionally present itself as unexplained fatigue before other symptoms become apparent but, inevitably, other symptoms will appear. For instance, a person with pancreatic cancer may first notice fatigue before the appearance of abdominal pain and the other symptoms of cancer occur. Therefore, the longer fatigue persists without other symptoms, the less likely a serious medical condition will serve as the eventual explanation.

Fatigue caused by a medical problem has other characteristics as well. Usually patients with typical, diagnosable, medical problems note that their energy is highest in the morning and slowly winds down over the course of the day as if the store of vigor slowly depletes. A nap may recharge the person.

Fatigue that remains unexplained usually has different characteristics. Many times, a person has a bimodal curve of energy, worse in the morning, improving with the day, fading in the afternoon, and, finally, getting a second wind at night. A nap can actually worsen things. Additionally, sleeping a long time can produce an overslept sensation.

Patients with less serious medical problems can, in certain circumstances, have fatigue with the absence of other symptoms, as is the case with hypothyroidism. Patients with low thyroid may notice tiredness before the other symptoms appear. These include dry skin, constipation, cold intolerance, etc. Likewise, a patient with anemia can feel tired before noticing other symptoms such as pale skin or obvious blood loss.

Causes of fatigue are often easy to figure out. Usually a visit to the doctor and a standard panel of blood tests provides a definite answer. If, after a thorough exam and appropriate blood tests, no answer is apparent, it is unlikely that a medical explanation will be found.