Fish and Risk of Non Hodgkins Lymphoma, Multiple Myeloma, and Leukemia

Fish and Risk of Non Hodgkins Lymphoma, Multiple Myeloma, and Leukemia

Review of Cancer Epidemiol Biomarkers Prev 2004;13(4):532-537.

A study published in the journal Cancer Epidemiology Biomarkers & Prevention looked at how certain dietary factors may affect the risk of non-Hodgkin's lymphoma, leukemia, and multiple myeloma. The findings of this study indicate that eating fish regularly may reduce risk of these three types of cancer. This article review discusses the findings of this study. We provide PRACTICAL information on what these findings mean. Most importantly, we provide ideas for using this information in a dietary plan to reduce risk of non-Hodgkin's lymphoma, leukemia, and multiple myeloma. Factors such as age and gender cannot be changed, but diet and nutrition can. This type of information will allow people who are at risk of these cancers to take concrete and practical steps to decrease their risk.

Note: Numbers appearing at the end of sentences indicate research references. References are listed at the end of each article.

Background

Non-Hodgkin's lymphoma, leukemia, and multiple myeloma all are cancers that occur in the blood or lymph system. The medical term for these cancers is lymphohematopoeitic. Only a very small portion blood and lymph system cancers are due to known risk factors, such as exposure to certain chemicals and radiation (1-11). This means that many unknown factors must account for the remainder of blood and lymph cancers. This is why it is important that researchers continue to study these diseases. Some studies have suggested that there may be a connection between what we eat, being overweight and risk of blood and lymph cancers (12-18). A recent study published in the journal Cancer Epidemiology Biomarkers & Prevention looked at the relationship between eating fish regularly and risk of blood and lymph system cancers (19). It is hoped that this type of research will identify diet and nutrition factors that may increase or decrease risk of these diseases. Factors such as age, ethnicity and genetics cannot be changed, but diet and nutrition can. This type of information will allow people who are at risk of Non-Hodgkin's lymphoma, leukemia, and multiple myeloma to take concrete and practical steps that may lower their risk of these diseases.

What The Researchers Studied

For this study (19), researchers asked 2,624 people who had been diagnosed with blood or lymph system cancer within the previous three to five months and 4,202 people without cancer about their diet. Of the 2,624 people with cancer, 919 had leukemia, 287 had multiple myeloma and 1,418 had non-Hodgkin's lymphoma. Information on other lifestyle and health related factors, including smoking, education level, type of work (occupation) each person had done over their lifetime, height, weight, age, and gender was collected and accounted for in the study. Researchers used all of this information to examine whether regularly eating fish was related to having blood or lymph system cancer. Some useful results came out of this study.

What The Study Found

First, researchers found that people without cancer ate less total fat, less total calories and were less overweight than the people who had been diagnosed with leukemia, multiple myeloma, or non-Hodgkin's lymphoma.

Second, researchers found that for all blood and lymph system cancers combined, people who ate four or more servings of fresh fish per week had 19% lower risk of cancer when compared to people who ate less than one-half serving of fish per week. In other words, eating fresh fish four or more times per week appeared to reduce the likelihood of being diagnosed with blood or lymph system cancer.

Third, researchers found that people who ate a larger percent of their total calories from fish had lower likelihood of being diagnosed with a blood of lymph system cancer. This was true for all cancers combined and for each type of cancer individually. In other words, when comparing people eating the least amount of their total calories from fish with people eating moderate and high amounts of their total calories from fish, researchers found that the more calories from fish eaten, the lower the risk of cancer.

Fourth, researchers found that people who got a larger percent of their total fat intake from fish had lower likelihood of being diagnosed with a blood of lymph system cancer. This was true for all cancers combined and for each type of cancer individually. In other words, when comparing people eating the least percentage of their fat calories from fish fat with people eating moderate and high percentages of their fat calories from fish fat, researchers found that the more fat from fish eaten, the lower the risk of cancer.

What do these results mean?

If the people in this study are similar to most people, the results of this research suggest that maintaining a healthy body weight (avoiding obesity) and eating more fish and more of your total calories and total fat from fish may reduce the risk of blood and lymph system cancers.

This study does have a several weak points. This type of study cannot prove cause and effect; it only tells us that there is an association between certain dietary factors and risk of blood and lymph cancers. It is important to remember that an association is not causation (cause and effect). As well, this study asked people about their diet after they were diagnosed with cancer. This can create problems with the research because sometimes people remember their diet differently if they already have a disease. This is called recall bias and it can be a problem with this type of research.

On a positive note, these findings do agree with some other research studies that tell us that what we eat and whether or not we are overweight may be related to risk of blood and lymph system cancers (16,17,20-22). Additionally, this research agrees with thousands of studies that tell us that vegetables, fruit, whole grains and fiber reduce risk of many types of cancer (23).

In summary, even though this research study (19) does have some weaknesses, it fits well with what we know about diet, eating fish and risk of cancer, including blood and lymph cancers.

How can I change my diet to reduce my risk of non-Hodgkin's lymphoma, leukemia and multiple myeloma?

General Goals

This research tells us that for good health, and possibly reducing risk of blood and lymph cancers, it is important to maintain a healthy weight and eat fish regularly in the diet.

More positively, thousands of studies tell us over and over that maintaining a healthy weight and regularly eating fish can reduce risk of heart disease as well, the number one killer in the United States (24-34). So remember, regardless of the weaknesses of the research reviewed here (19), it does support a diet change that can be important for better health in many aspects! Not only may this change reduce risk of blood and lymph cancers, but also it may improve health overall.

Maintain A Healthy Weight  

• The first thing to remember is that weight loss is not easy. Don't be hard on yourself if you've struggled with maintaining a healthy weight. This is a health concern for many people. If you've tried to lose weight in the past and have not succeeded, don't give up! Just because you haven't met your weight loss goals in the past does not mean you won't be able to succeed this time!
• Consult with a Registered Dietitian (RD) or receive support from a weight loss organization such as Weight Watchers©. Either of these approaches will work to help you develop a sensible and successful weight loss plan. 
• Be sure you think about weight loss and healthy eating as a lifestyle rather than a temporary diet. This is important! For long-term weight loss success, you must change your eating and exercise habits permanently.
• For basic tips and ideas on getting started with healthy weight loss see the Prevent Weight Gain patient education material in the Customized Patient Education section. 

Eat More Fish

• Eating at least 2 servings of fresh fish each week is a reasonable goal. A serving of fish is 3 to 4 ounces, or about the size of the palm of your hand.
• Stick with fresh fish that is not breaded and fried. Try our recipe below for delicious fish without all of the extra calories and unhealthy fat that comes along with frying.
• The only downside to eating fish is that some types of fish contain higher levels of environmental contaminants such as mercury or lead. However, many types of fish are healthy and safe to eat.
• For information on the healthiest types of fish to eat, both for you and for the environment, check out the The Audubon Guide to Seafood, the EPA National Listing of Fish and Wildlife Advisories and the Sea Turtle Restoration Project Mercury Calculator.
• As well, you can check your state environmental agency for information about the safety of eating local fish.

Finally, try our recipe for Baked Alaskan Salmon to get more fish into your diet.

NOTE: If you are in cancer treatment, these diet changes may not be right for you.

References  

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Publish Date: 04/2004