Author Archives: Paul Jaminet - Page 35

Omega-3 Fats and Cancer

Posted by on July 14, 2013 77 comments

On Wednesday a new paper reported that higher levels of long-chain omega-3 fats (EPA, DPA, and DHA) in blood are associated with a 43% increased risk of prostate cancer and a 71% increased risk of aggressive prostate cancer. [1] This built on earlier work by the same group. [2] In a press release, the authors stated:

“We’ve shown once again that use of nutritional supplements may be harmful,” said Alan Kristal, Dr.P.H., the paper’s senior author …

“[W]e have confirmed that marine omega-3 fatty acids play a role in prostate cancer occurrence,” said corresponding author Theodore Brasky, Ph.D.

They sound confident! Is there anything to it, and should it affect our dietary advice?

Mechanisms Linking Omega-3 Fats to Cancer

In our book and on this blog, we’ve already discussed two mechanisms linking excessive omega-3 intake to cancer risk.

First, there is the issue of lipid peroxidation. Of all fatty acids, long-chain omega-3 fats are the most readily peroxidized:

PUFA relative peroxidizability

Peroxidation of PUFA generates highly toxic compounds, such as aldehydes, which mutate DNA and turn proteins into advanced lipoxidation end products (ALEs). [3, 4] These lipid peroxidation products have been implicated as causal factors in cancer. [5]

Second, oxidation products of DHA promote angiogenesis – the creation of new blood vessels to feed tumors. These products make cancers grow rapidly. I’ve blogged about this (DHA and Angiogenesis: The Bottom Line, May 4, 2011; Omega-3s, Angiogenesis and Cancer: Part II, April 29, 2011; Omega-3 Fats, Angiogenesis, and Cancer: Part I, April 26, 2011).

So there are known mechanisms by which the long omega-3s in fish oil may promote cancer.

The Brasky et al Papers

The new study by Brasky et al measured omega-3 fat levels in plasma phospholipids. Thus, it doesn’t measure any omega-3s in cells, only omega-3s in serum particles like LDL, HDL, and VLDL; and even in those particles it excludes omega-3 fats found in triglycerides.

This is a very different biomarker than the Omega-3 Index of William Harris, which looks at the omega-3 phospholipids in red blood cell membranes. [6] This biomarker might behave quite differently than the Omega-3 Index.

The study measured plasma phospholipid omega-3s in a group of people, then followed them for 6 years or so to see who developed cancer. Here are the group averages [1]:

Brasky 2013 Table 2

Statistically the most reliable data is in the no cancer vs total cancer comparison. There we find that subjects who went on to develop prostate cancer averaged 3% more DHA and 4% more EPA+DPA+DHA in plasma phospholipids than those who didn’t develop cancer.

Does This Variation Reflect Dietary Intake?

Chris Kresser kindly sent a link to an analysis of the study published at LecturePad by William Harris: “Omega-3 Fatty Acids and Risk for Prostate Cancer.” Harris tells us how to translate the plasma numbers to the corresponding Omega-3 Index numbers:

Based on experiments in our lab, the lowest quartile would correspond to an HS-Omega-3 Index of <3.16% and the highest to an Index of >4.77%).

Even the top quartile of the Brasky et al subjects had quite low omega-3 levels:

In Framingham, the mean Omega-3 Index of participants who were not taking fish oil supplements was 5.2% and for those taking supplements, it was 7.5% [7]. Both of these numbers are considerably higher than the values reported by Braskey et al., even in their highest quartile.

The trial asked its participants not to take supplements, and it looks like they drew a study population whose fish intake was much lower than that of Framingham, Massachusetts, residents.

If dietary omega-3 intake was low in all subjects and varied only slightly among participants, how do we know that this biomarker is related in any way to dietary intake? There could be other factors – genetics, oxidative environment, omega-6 fat intake, antioxidant intake, changes in the proportions of VLDL, LDL, and HDL, to name a few – that affect this biomarker.

Does High Dietary Intake Lead to More Cancer?

If high dietary intake of omega-3s caused more cancer, we would expect cultures that consume lots of fish oil to have higher prostate cancer rates. But epidemiological studies have found that high omega-3 intakes seem to be associated with low cancer rates. For instance, the Japanese eat eight times more omega-3 fatty acids than Americans and their blood levels are twice as high, yet the prostate cancer rates are only one-sixth the American rate.

Of course, there are many confounders in epidemiological studies. Harris helpfully provides a summary of clinical trials in which fish oil was provided as part of the study and cancer outcomes measured:

Harris reply to Brasky 2013

Although none of these studies produced a statistically significant link between omega-3 intake and cancer, incidence of cancer diagnosis or death was increased in every one of the clinical trials except the GISSI-Heart Failure study and perhaps the Origin study. A meta-analysis might find a small cancer promoting effect of omega-3s.

UPDATE: Vladimir Heiskanen points me to an interesting paper in which the effect of dietary fatty acids on cancer metastasis was examined. Colon carcinoma cells were injected into the portal vein (which leads from intestine to liver) of rats and 3 weeks later rats were sacrificed and their livers were examined for metastases. The rats were on three diets — low-fat, high omega-6 (safflower oil), high omega-3 (fish oil). The results:

At 3 weeks after tumor transplantation, the fish oil diet and the safflower oil diet had induced, respectively, 10- and 4-fold more metastases (number) and over 1000- and 500-fold more metastases (size) than were found in the livers of rats on the low-fat diet. [7]

I wish they’d used a saturated fat or monounsaturated fat diet, rather than a low-fat diet, as the control, as this would have clarified that polyunsaturates specifically promote metastasis; in the study the rats’ food was mixed with fish oil or safflower oil, greatly increasing the fat fraction and decreasing the carbohydrate, protein, and micronutrient fractions, so the control diet deviates in many respects from the high-PUFA diets. However, the results are consistent with the idea that fish oil is more cancer-promoting than the less peroxidizable safflower oil, perhaps because of the unique pro-angiogenic effects of DHA products.

Conclusion

There might be biological contexts in which omega-3 fats promote cancer.

This doesn’t mean we should refrain from eating omega-3 fats. Cardiovascular disease causes more deaths than cancer, and omega-3 fats are protective against CVD.

However, I think these studies support the PHD advice:

  • Eat enough oily marine fish to achieve omega-6 and omega-3 balance;
  • Minimize omega-6 intake so that omega-6 and omega-3 balance is achieved at the lowest possible intake of polyunsaturated fats.

All nutrients can be eaten in excess, and omega-3 fats surely fall into this category. The right amount of oily fish is probably about one to two meals per week.

References

[1] Brasky TM et al. Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial. J Natl Cancer Inst. 2013 Jul 10. [Epub ahead of print] http://pmid.us/23843441.

[2] Brasky TM et al. Serum phospholipid fatty acids and prostate cancer risk: results from the prostate cancer prevention trial. Am J Epidemiol. 2011 Jun 15;173(12):1429-39. http://pmid.us/21518693.

[3] Hulbert AJ et al. Life and death: metabolic rate, membrane composition, and life span of animals. Physiological Reviews 2007 Oct;87(4):1175–213, http://pmid.us/17928583.

[4] Hulbert AJ. Metabolism and longevity: is there a role for membrane fatty acids? Integretive and Comparative Biology 2010 Nov;50(5):808–17, http://pmid.us/21558243.

[5] Nair U, Bartsch H, Nair J. Lipid peroxidation-induced DNA damage in cancer-prone inflammatory diseases: a review of published adduct types and levels in humans. Free Radic Biol Med. 2007 Oct 15;43(8):1109-20. http://pmid.us/17854706.

[6] Harris WS, Von Schacky C. The Omega-3 Index: a new risk factor for death from coronary heart disease? Prev Med. 2004 Jul;39(1):212-20. http://pmid.us/15208005.

[7] Griffini P et al. Dietary omega-3 polyunsaturated fatty acids promote colon carcinoma metastasis in rat liver. Cancer Res. 1998 Aug 1;58(15):3312-9. http://pmid.us/9699661.

Review and Interview at PaleoDiet++

Posted by on July 10, 2013 24 comments

I’m still catching up after our vacation, but here is something that may be as interesting as a post: Dee of PaleoDiet++ did an email interview of me, and had some unusual questions I haven’t been asked before. The interview (and Dee’s review of our book) is here.

Pictures from Korea

Posted by on July 2, 2013 17 comments

We’re in the midst of our Korean vacation, and I’d like to share a few pictures.

Our Talk at Reebok Crossfit Sentinel

Crossfit has come to Korea in an impressive way. Crossfit Sentinel has opened four gyms in the Seoul area and their facility in Seoul’s City Center, where we spoke, has a golf facility and a café that sells PHD-like food.

On Saturday I gave two talks, one on diet and one on lifestyle. Our photographer (Shou-Ching) neglected to take photos during the talks, but here we are afterward with the leaders of Crossfit Sentinel:

Korea trip 2

Tombs

Our first priority, once our talk was out of the way, was a trip to Shou-Ching’s hometown, Yeongwol, to pay respects to her father. In traditional Korean Buddhism, graves are marked by a mound of earth, and our first step was to weed the plants on and around the grave:

Korea trip 3a

Buddhism assumes communication between our world and the spirit world, and descendants support their ancestors’ spirits with gift offerings, such as food. Here we paid our respects to Shou-Ching’s father with prayer and an offering of bananas, oranges, and chicken:

Korea trip 3b

We also sprinkled a bottle of wine around the grave to provide him with something to drink, and made a gift of gold and silver, transmuted by fire from gold and silver paper:

Korea trip 3c

Shou-Ching’s father was extremely sociable, the center of Yeongwol’s Chinese community, owner of Yeongwol’s most popular restaurant, the creator of the town’s Chinese school, and everyone’s first recourse in times of trouble. With food, wine, and money for gifts and gambling, he may be equally popular among the spirits.

Yeongwol would be a minor backwater in the Korean countryside were it not for a notorious event in Korean history. King Munjong of the Joseon dynasty died in 1452 when his son was 12 years old. The son, King Danjong, ascended to the throne, but regents ruled in his place. The regency was overthrown a year later in a coup led by Danjong’s uncle. After a counter-coup attempting to restore Danjong to the throne failed, he was exiled to Yeongwol. After a second failed restoration attempt when Danjong was 17, he was forced to commit suicide. Two hundred sixty-eight supporters of Danjong were executed. After the suicide, Danjong’s body was left to decay in the river, and a royal edict threatened anyone who rescued the body with three generations of persecution. However, a local man recovered the body and buried it in a secret grave, which was eventually found a few centuries later.

Over the course of subsequent centuries, Danjong and his followers were posthumously accorded greater and greater honors, in an attempt to appease their spirits; the man who recovered his body was given the status of a royal minister. Danjong began to be honored in art:

Korea trip 3e

His grave was moved to a suitable site for a king, on a high ridge overlooking Yeongwol:

Korea trip 3d

Today the tomb complex is a UNESCO world heritage site, you have to pay admission to visit, and the tomb is roped off. But in Shou-Ching’s youth, it was untended, and the village children would race up the hill to ride on the stone stallions, tigers, and sheep that surround the grave. If the sculptures look worn, it is not only because of the weather!

Temples

Buddhist temples are found in remote mountain sites throughout Korea. They are places of retreat and meditation; it was central to their purpose that they were not, in the days before roads and automobiles, easy to visit. City-dwellers would have to make an arduous journey to reach them, and might spend a week in prayer and meditation repenting misdeeds and repairing their spiritual affairs.

A common feature of temples is a source of spring or mountain water, channeled into a drinking fountain.  At Geummongam in Yeongwol, my nieces and I had a contest to see who could stand the longest in a pool of cold spring water downstream from the fountain:

Korea trip 4a

At Baekdamsa in Inje, here is a typical prayer room. Three Buddhas and a large number of figurine monks are mounted on the back wall.

Korea trip 4b

Meditative prayer will typically be led by a monk who chants sutras and strikes a mok-tak to keep rhythm. In the temples we visited, a chanting monk would wear a microphone and loudspeakers around the temple would broadcast the rhythmic chanting.

Baekdamsa also had a wishing pond with water lilies. Tossing a coin into the central reservoir would grant a prayer:

Korea trip 4c

Around the river that runs in front of the temple, visitors had built rock cairns:

Korea trip 4d

Food

We had a delicious meal at a traditional Korean restaurant devoted to an uncommon “safe starch,” acorn starch. Acorn starch is usually served as a sort of jelly, called Dotorimuk, but it can also be used to make noodles or other foods.

At this meal, almost every food (apart from the cured duck – the reddish ham-like food on the left of the large plate – and the vegetables) used acorns:

Korea trip 5a

On Sunday we went to a restaurant made popular by a TV special, which offered a wide range of vegetable dishes made with medicinal plants traditionally used in Chinese medicine, along with pork belly and rice:

Korea trip 5b

Lynh wanted us to blog about eating live octopus, so we had to go to a sashimi restaurant. At Gisamun-ri south of Yangyang, we had this feast.  First, the appetizers:

Korea trip 5c

Here I’m eating a barnacle:

Korea trip 5d

Then the sashimi. Puffer fish:

Korea trip 5e

Two other varieties of fish:

Korea trip 5f

Live squid, tunicate or sea squirt, abalone, and sea cucumber:

Korea trip 5g

Sea urchins (which taste like a seafood pudding):

Korea trip 5h

There is a risk to eating sashimi: many wild fish and shellfish carry parasites. This was brought home to us the next day. After our sashimi dinner, we stopped in Yangyang to buy some fresh seafood – scallops, clams, and octopus. The next day we extracted Anisakis worms from all three foods:

Korea trip 5i

Other Sights

Nearly all free land in Korea that has not been built upon and is flat enough to support agriculture hosts cultivated crops. Here is a rice field in front of a restaurant:

Korea trip 6a

Typically the farmers also operate restaurants or shops. This woman is a buckwheat farmer who operates a stall in the market at Yeongwol selling buckwheat, cabbage, and scallion pancakes:

Korea trip 6b

Here I am with Shou-Ching’s mom at the beach in Yangyang, sporting a seaweed necktie:

Korea trip 6c

Finally, some landscape photos. Korea is over 70% mountainous and resembles West Virginia or the White Mountains of New Hampshire, but the landscape is geologically younger and more rugged. Here are three photos from scenic Seoroksan National Park:

Korea trip 6d

Korea trip 6e

Korea trip 6f

Conclusion

Koreans probably eat one of the globe’s most healthful diets. They eat a tremendous variety of vegetables – probably rivaling the hundreds of species eaten by Paleolithic hunter-gatherers.  However, I noticed that Korean food has become appreciably sweeter and more processed since my last visit 11 years ago; the kimchi is now much less tasty than before, and inferior to our homemade kimchi; bread has made major inroads replacing rice and rice cakes; and the number of overweight Koreans has significantly increased.

Here is a slide from my Seoul talk, based on data from Gapminder. Korea and other east Asian countries have led the world in life expectancy:

Korea trip 7

If Koreans continue to shift their foods toward processed and sugary western foods, I doubt this superior longevity will continue. Korea, I believe, needs the Perfect Health Diet.

In Korea? Please Come to Our Seoul Event!

Posted by on June 23, 2013 3 comments

I’ve been so busy with the Perfect Health Retreat that I’ve been remiss in failing to promote our upcoming Seoul event.

This Saturday, June 29, Paul and Shou-Ching will be speaking at Reebok Crossfit Sentinel in Seoul. We will talk about diet at 1 pm, lifestyle at 3 pm, and do a book signing and Q&A inbetween. Over the two talks, we’ll provide a complete view of what drives good health.

Promotional flyers with all the details are here. If you are in Korea, please consider attending!