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Frequently Asked Questions

 


I have read in several places that consuming milk products might cause ovarian cancer. The women in my ovarian cancer support group endlessly debate if they should be avoiding all dairy products. Can you shed any light on if there is any truth to this possibility and if avoiding milk and other dairy products will help improve the odds for beating my ovarian cancer?

I commend you for seeking more information to help answer this controversial, yet very intriguing, question. It is not possible to give a brief or simple answer to your question. Let me give you some background information first.

Lactose, the main sugar (carbohydrate) molecule in milk, is the primary dietary source of a smaller sugar molecule called galactose. Galactose is produced in the small intestine by the action of the digestive enzyme lactase on lactose. Galactose is readily absorbed and then metabolized primarily in the liver. Galactose itself is not stored in the body. It is either converted to glucose directly in the liver and then further metabolized by the body's cells to release energy and carbon dioxide or rapidly metabolized via the enzyme Galactose-1-phosphatase to be converted to glycogen, the body’s glucose storage substance stored in the liver and muscle. (Cohn RM, Galactose metabolism and its regulation. Metabolism, Vol 22:4:1973)

In 1989, Daniel Cramer, MD and his associates at Harvard University published a
tantalizing clue to a possible origin of ovarian cancer. Not only was ovarian cancer
more common in countries with very high yogurt and lactose consumption, but women with this disease were significantly more likely to have lower activity of an enzyme called GALT, another enzyme that metabolizes galactose. It was a provocative finding because previous animal studies had shown galactose to damage ovarian egg cells, causing ovarian failure, with premature ovarian failure being a precursor to ovarian cancer in these animal models (Cramer DW, Lancet, 1989, Jul 8:2(8654):66-71).

Liu and associates from Cedar Sinai Medical Center, CA have shown
that accumulation of galactose metabolites like galactose-1-phosphate, galactitol, and UDPgal are all important in the development of ovarian toxicity. One proposed mechanism includes interference with ovarian cell apoptosis (programmed cell death). (Reprod Toxicol 2000 Sep-Oct:14(5):377-84).

From these lines of research, it has been suggested that increased exposure to galactose due to consumption of dairy foods or reduced galactose metabolism may be associated with the development of ovarian cancer. To further investigate this association, several recent large epidemiological studies have been conducted and published. I will briefly summarize them and follow with some generalized conclusions.

(1) In the first of these studies (1998), 800 confirmed cases and 800 controls were recruited from three different states in Australia. All the subjects completed dietary questionnaires. Blood samples were also obtained for analysis of the GALT enzyme. The results indicated that ovarian cancer risk was positively associated with increasing consumption of whole milk and other full fat dairy foods, but was not associated with consumption of low fat dairy foods. The risk was inversely related to consumption of skimmed milk. A trend was found for increased risk of ovarian cancer in a subgroup of women with abnormally low GALT levels, however, this observation was not statistically significant. These data suggest that reported associations between milk consumption and ovarian cancer are due to the fat content of milk and not lactose or galactose (Webb et al, Cancer Causes Control 1998 Dec; 9(6): 637-44).

(2) In another study, a total of 558 confirmed cases of ovarian cancer and 607 controls from Hawaii and Los Angeles were interviewed regarding their diet. Consumption of all dairy products and low fat milk (except whole milk) was significantly inversely related to ovarian cancer. Similar inverse relationships were obtained for intakes of lactose and calcium. These results suggest that higher intakes of low fat milk, calcium, or lactose may reduce the risk of ovarian cancer (Goodman et al, Am J Epidemiol 2002 Jul 15; 156(2): 148-57).

(3) In the third study, consumption of dairy products and biochemical genetic assessment of galactose metabolism was carried out in 563 women with newly diagnosed ovarian cancer and 523 control women selected by random digit dialing in eastern Massachusetts.

No significant differences between cases and controls were found for the following:
1. consumption of various types of dairy products,
2. total daily lactose intake
3. Red blood cell (RBC) activity of GALT and galactokinase (another enzyme that processes galactose).

However, cases were more likely to carry the N314D form of the GALT enzyme, which predisposes one to have lower GALT activity. Everyone has two copies of each gene in the body. If the N314D form is found in one or both copies of the gene, then galactose is processed slowly, leading to higher circulating levels. The difference was most evident in women who had diagnoses of endometrioid and clear cell types of ovarian cancer.

The authors concluded that whereas adult consumption of lactose carries no clear risk for the disease, certain genetic or biochemical features of galactose metabolism may influence disease risk for particular types of ovarian cancer (Cramer et al, Cancer Epidemiol Biomarkers Prev 2000 Jan; 9(1): 95-101).

(4) Parameters similar to the previous study were also examined as part of another large case-control study of ovarian cancer conducted in Los Angeles between 1992 and 1998 by Cozen and associates at Norris Cancer Center in California. A total of 1,439 confirmed cases of ovarian cancer and 689 randomly selected healthy female controls were recruited for the study. Interviewer-administered questionnaires included information on reproductive factors, oral contraceptive use, medical history, and diet. Blood samples were also obtained from both controls and cases. The presence of the N314D form of the GALT enzyme and GALT enzyme activity were both determined.

Results indicated that among N314D carriers, galactose consumption was associated with a statistically significant increased risk of borderline, but not invasive ovarian cancer. (This study showed that only 1.6% of the ovarian cancer cases carried this altered gene, an important figure to know when doing a personal risk assessment.)
(Cozen et al, Cancer Causes Control 2002 Mar:13(2):113-20).

In addition, an earlier study also indicates similar results. (Mettlin CJ, Piver MS: A case control study of milk drinking and ovarian cancer risk. Am J of Epidemiology 132(5):871-876,1990. Results: only drinkers of whole milk were at increased risk vs. skim or 2% milk drinkers who were at decreased risk)

(5) Contradicting some these earlier studies, recent data published from the Nurses Health Study showed a 32% higher risk of any type of ovarian cancer and a 69% increased risk of the serous subtype in those women who consumed one or more servings/day of low-fat or skim milk dairy products versus those who consumed 3 or fewer servings monthly. (A prospective study of dietary lactose and ovarian cancer, Fairfield et al, Int J Cancer 2004 June 10;110(2):271-7.)

(6) Another recent large study (>61,000 women followed) also showed a significant association between increased risk of serous ovarian cancer and dairy intake comparing intakes of ≥4 servings/day versus <2 servings/day, with both whole milk and low-fat milk showing this association. (Milk and lactose intakes and ovarian cancer risk in the Swedish Mammography Cohort, Larsson, SC etc, al, Am J Clin Nutr 2004 Nov;80(5):1353-7.)

Generalized conclusions from these studies:

1. Data showing an association between dairy fat intake and ovarian cancer are contradictory, but the two most recent and largest of the population-based studies show no potential protective effect of either whole or skim/low-fat dairy products.

2. The two most recent studies both showed increased risk from dairy food intake to be associated lactose intake and associated primarily with the serous subtype of ovarian cancer.

3. For the small percentage of women with lower levels of GALT enzyme activity, dairy (lactose) consumption may increase their risk of ovarian cancer due to abnormal galactose metabolism. This association was shown for clear cell, endometroid, and borderline ovarian cancer subtype diagnoses.

4. All studies indicated more research is needed to confirm these associations, resolve conflicting data from earlier studies, and understand the biological mechanisms behind the observations that may lead to a potential cause (and prevention) of ovarian cancer.

In summary, here are some reasonable and practical recommendations until more research is completed:

1. If 1. If you have had ovarian cancer, learn the subtype from your doctor or pathology report.

2. Limit or avoid intake of dairy products to only a few times per month if you have had a diagnosis of serous ovarian cancer may be prudent.

3. In addition, while not considered standard practice at this time, discuss with your physician the potential benefit of obtaining a blood test for the GALT enzyme. Alternative names for this test are Galactosemia Screen and Gal-1-PUT test. Normal range is 18.5 to 28.5 U/G Hb (units per gram of hemoglobin).

• If the results are within the normal range, you may feel comfortable consuming low-fat dairy products in amounts of your choice to provide a portion of your calcium requirements (1000 mg/day for pre-menopausal women and 1200 mg/day for post-menopausal women). For example, one 8-ounce glass of milk provides 300 mg of calcium.

• If your results are below normal, there are no current nutritional guidelines to follow. To be prudent, I would suggest limiting dairy products to no more than one low-fat serving per day. This is an area that clearly needs research for appropriate nutritional recommendations.

4. Finally, decrease your risk for recurrence by increasing your vegetable intake (especially those from the broccoli family) as part of a plant-based diet similar to what I have recommended in my book, A Dietitian’s Cancer Story, and on this web site. (Dietary influences on survival after ovarian cancer, Nagel et al, Int J Cancer 2003 Aug 20;106(2):264-9.) I have had recent personal communication with Dr. Dan Cramer who wrote the original article raising this concern about galactose and ovarian cancer (Cramer DW, Lancet, 1989, Jul 8:2(8654):66-71), and he now also largely emphasizes the positive effects of a diet high in anti-oxidants and other phytonutrients rather than strict avoidance of dairy products. (personal communication 4/5/05)

UlUltimately the choice to consume dairy products is yours. However, if you choose to limit or avoid all dairy products, then I strongly recommend that you receive an individualized consultation from the Registered Dietitian (RD) at your cancer center to determine other ways of achieving the important nutrients or dietary components that dairy products provide:

1. Probiotics
2. Calcium
3. Vitamin D
4. Protein
5. Conjugated linoleic acid (CLA)

It is very difficult to make general dietary recommendations for your question because of individual genetic differences and (maybe more importantly) our inability at this point to clearly assess the clinical significance of the GALT enzyme activity assay for any one individual with or at risk for ovarian cancer.

Data are just starting to emerge showing relationships (increased or decreased risk) between intake of specific foods and nutrients and specific cancers. Thus it is clear that any one person needs to have their nutritional needs based on an overall health profile with a risk benefit assessment. By working in partnership with your physician and Registered Dietitian, you will give you receive individualized guidance.

Again, I commend you for trying to make an informed decision about nutritional choices that may increase your odds for long-term recovery. Research to answer these important nutritional questions for cancer survivors is vital and needs to be done. My endowment (funded by proceeds from the sale of my books) at AICR (http://www.aicr.org) is making a small dent in the amount of nutritional research needed by cancer survivors.

If I may make one additional suggestion, please don't lose sight of the big picture by solely focusing on dairy foods. Remember to incorporate other nutrition and lifestyle changes discussed in my book and on my web site into a comprehensive plan to optimize your odds for long-term recovery.

Best wishes to you.

This original answer was researched and developed by Mitali Kapila, MSc, MS, RD. The information posted here was written under the direction of and edited by Diana Dyer, MS, RD, including all updates.


faq posted 11/02, updated 3/05, 5/05

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Ovarian Cancer

Gastric Cancer Will consuming dairy foods increase my risk for ovarian cancer recurring? posted 11/02, updated 4/04, updated 3/05, 5/05
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Gastric Cancer Should I avoid soy foods if I have ovarian cancer? posted 11/04

 


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These questions and answers are intended to be of a general informative nature. Please consult with the Registered Dietitian in your cancer center or your health care provider for nutritional advice that can be individualized to your specific medical condition.


 
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