Dr. Stacey Kenfield, Associate Professor in the Departments of Urology and Epidemiology & Biostatistics at UCSF, was a recent guest on PCF’s monthly webinar series hosted by CEO Dr. Charles Ryan. She discussed her research on Prostate 8, a collection of lifestyle changes that have been shown to reduce a patient’s risk of prostate cancer recurrence or death from prostate cancer.
Here we answer some of the most common questions posed during the webinar—covering eggs, dairy, sugar, and supplements—and provide additional details.
I have read and been told that eggs are bad for existing prostate cancer. There seems to be some science behind this finding, but eggs have been a major part of protein for me.
Eggs have come up as being associated with increased risk of lethal prostate cancer in a cohort of men who did not have prostate cancer. A direct link has not been firmly established (for men with prostate cancer) and there is no strong evidence at this point to suggest the need to completely exclude all food sources of choline from the diet. Choline is a required nutrient, and until we know why, it is recommended to limit whole eggs (including yolks) to an average of 2 per week or less. Almost all of the choline in eggs is contained in the yolk, not in the white. You can reduce choline by using egg whites without the yolks.
What types of dairy products should be avoided, and which are OK to eat?
Since Prostate 8 was published, more findings have come to light on dairy. Consuming whole milk after prostate cancer diagnosis is linked to increased risk of prostate cancer progression and death from prostate cancer. However, for prostate cancer, dairy products do not need to be avoided entirely. Low-fat and non-fat dairy are not consistently associated with bad prostate cancer outcomes.
How much sugar is OK to eat? What about artificial sweeteners?
Sugar and artificial sweeteners fall under the ‘not recommended or limit’ category. We know that diets high in added sugar promote weight gain, type 2 diabetes and heart disease. The links between sugar, sugar-sweetened beverages, and highly-processed food and cancer are closely tied to how the foods promote weight gain.
Regarding artificial sweeteners, they can help to reduce added sugar intake, though they are not necessarily a better choice. Regular, frequent use of artificial sweeteners may change food tastes with a preference for sweet foods. It may prevent someone from associating sweetness with caloric intake. We say that it’s fine to enjoy a sweet treat from time to time, but the goal is to avoid sugar-sweetened beverages, reduce added sugar, and not replace them with artificial sweeteners.
Can you elaborate on why vitamin and mineral supplements should be avoided?
Current data suggest that supplements do not help you prevent cancer or prevent cancer growth. In fact, some studies have shown an increased risk of prostate cancer in people on clinical trials who took high doses of Vitamin E or selenium. In an observational study of men with prostate cancer, men taking 140 micrograms per day of selenium were more than two-and-a-half times more likely to die of prostate cancer. There is not much data on effects of other high-dose supplements, but to err on the side of caution (because we do not see any benefit), it is recommended to avoid supplements UNLESS your doctor has recommended them.
What about taking a multivitamin?
Long-term, regular use of multivitamins have been shown to have neither benefit nor harm related to prostate cancer. There is no increased (or decreased) risk of developing prostate cancer or of death from prostate cancer. Investigators from the Physicians’ Health Study II Randomized Controlled Trial comparing a daily multivitamin or placebo reported that daily multivitamin use was associated with a reduction in total cancer among the men with a baseline history of cancer.
What about calcium or Vitamin D, especially for people at risk of osteoporosis?
There are certain caveats around the recommendation against supplements, and people should discuss their specific situation with their doctor. For example, many men and women have low Vitamin D levels. Ask your doctor about measuring your Vitamin D level and work with them to see if you need to supplement to get to an adequate level. Some people are deficient in certain nutrients due to cancer treatment or problems digesting certain types of foods and may need supplementation. Regarding bone health, calcium, vitamin D, and exercise are essential. This is especially true for patients taking hormone therapy as part of their treatment of prostate cancer. If you are not getting 1000-1200 mg/day of calcium, you may need a supplement. However, adequate calcium can often be obtained from food sources such as leafy greens (especially collard greens, bok choy, and kale), canned fish with soft bones, beans, tofu, almonds, and fortified products such as soy milk.
UCSF’s Department of Urology Resources for Healthy Living.
Global Action Plan (GAP-4) trial of exercise in patients with metastatic prostate cancer
PCF’s wellness guide, The Science of Living Well, Beyond Cancer