I get questions about carrageenan fairly often so I’m passing on the latest Nutrition Facts video, Is Carrageenan Safe?
Carrageenan is a seaweed that is used as a thickener in many non-dairy milks and other products. It apparently can cause intestinal inflammation in some (or many?) people. Check the very short video out for more information.
I have added another case of vitamin B12 deficiency to Individual Cases of Deficiency of Vitamin B12: Are You Getting It?
Readers have asked me to keep letting them know about these cases, so here it is:
A 62 year old woman in Switzerland, strict vegetarian, was found wandering the streets. Her delirium was determined to be vitamin B12 deficiency. She was treated with 1,000 µg injections weekly and within 4 weeks she had regained a stable mental status and returned to full-time work. (1)
It turns out that she had suffered from B12 deficiency on a number of previous occasions but without the neuropsychiatric symptoms. I hope she will start taking B12 and not rely on being found wandering the streets which might not end so well the next time.
(Thanks, Michael).
References
1. Mavrommati K, Sentissi O. Delirium as a result of vitamin B12 deficiency in a vegetarian female patient. Eur J Clin Nutr. 2013 Jul 17. | link
After posting the article Cadmium Levels in Vegans, Zinc Supplements and Alzheimer’s Disease, Ginny Messina let me know that there is a concern about cadmium contamination of zinc supplements.
I researched the issue and added the following section to VeganHealth.org’s article Cadmium:
In 2001, Krone et al tested six zinc supplements from Seattle area health food stores to see if they contained cadmium (1). According to the authors, “Because the chemical properties of [zinc] and cadmium (Cd) are so similar, these two elements invariably occur together in nature.”
They found that the single zinc supplements had very low levels of cadmium whereas the multi-mineral supplements had enough that taking the RDA of zinc would provide up to 2 µg of cadmium (20% of the daily limit recommended by the US Federal Drug Administration (FDA)). It also happens that three of the supplements with low levels of cadmium were in the form of zinc gluconate whereas none of the multi-mineral preparations were the gluconate form. So, it could be that zinc gluconate is unlikely to have much cadmium or that single zinc supplements are unlikely.
According to their website, the supplement manufacturer Kirkman, from Oregon, does a rigorous job testing their supplements for contamination of cadmium and other impurities (more info). They also have an article on their site, Cadmium: A Serious Heavy Metal and Topic. They ship outside the United States.
References
1. Krone CA, Wyse EJ, Ely JT. Cadmium in zinc-containing mineral supplements. Int J Food Sci Nutr. 2001 Jul;52(4):379-82. | link
A study was released this month that correlated a higher percentage of omega-3 fatty acids in the blood, especially DPA and DHA, with an increased risk for prostate cancer. This made big news and the merits of the study have been debated and people have been asking me if it would make me change my recommendations for taking DHA.
The study by Braskey et al (1) was funded by the National Cancer Institute and was a case-control analysis. It was also an offshoot of the Selenium and Vitamin E Cancer Prevention Trial (SELECT). There were numerous statistically significant findings with the strongest being for DHA. A DHA percentage of >3.62 was associated with a 39% increased risk of prostate cancer when compared to a DHA percentage of < 2.33 (1.39, 1.06-1.82). The finding was stronger for low-grade prostate cancer while insignificant for high-grade.
Interestingly, ALA levels were not associated with an increased risk of prostate cancer and the omega-6 fatty acid, linoleic acid (LA), was slightly associated with a reduced risk.
Additionally, the researchers performed a meta-analysis of 7 similar studies and again found that DHA was associated with an increased risk of prostate cancer (1.16, 1.03-1.31). In the 5 studies that separated low-grade versus high-grade, both low (1.20, 1.04-1.38) and high (1.48, 1.10-1.99) were associated with an increased risk.
As I see it, the strengths of the study are:
– Percentage of fatty acids in the blood is possibly a better indicator of actual intake (or absorption) than a food frequency questionnaire.
– The follow-up was about 8 years, which seems long enough to eliminate the possibility of reverse causation in which DHA levels might be elevated due to the prostate cancer.
The potential weaknesses of the study are:
– Measuring fatty acids as a percentage rather than an absolute amount could be misleading. One person might have a higher percentage of DHA, but a lower total amount of DHA. For example, if you eat a very low-fat diet but with a bit of fish, then your DHA will be high as a percentage, but could possibly be lower, in total, than someone who eats a large amount of fat including fish. In other words, it could be that people with a higher percentage of DHA actually have a lower absolute amount of DHA. I don’t know how likely this is, but it doesn’t seem to be out of the question if many fish-eaters are on low-fat diets. Given some of the findings from other studies I’m about to discuss, this might be plausible.
– The whole project of associating the percentage of various fatty acids with various cancers has been fraught with null, inconsistent, and weak findings. When this is the case, it’s a good indication, in my opinion, that there is nothing really there.
This study was criticized by Dr. Michael Murray in his July 22, 2013 article, Does Fish Oil Really Boost Prostate Cancer? One interesting point he makes is that the omega-3 levels in those with prostate cancer were not very high. Those without cancer had an average DHA level of 2.91% (95% CI: 2.86-2.96) while those with cancer had a level of 3.01% (95% CI: 2.95-3.08). People taking fish oil supplements tend to have amounts quite a bit higher than that.
I will go a step further than Dr. Murray and suggest that the differences between the two groups, while statistically significant, are so minor as to be practically meaningless: a DHA level of 2.91% is pretty much the same as 3.01%. Even when you add EPA + DPA + DHA together, the difference is hardly anything (4.48% for the no cancer group vs. 4.66% for the cancer group).
What about studies measuring intake?
A 2006 meta-analysis of 7 cohort studies found no significant association with the incidence of prostate cancer and intake of EPA or DHA (2). A 2010 meta-analysis of fish consumption and prostate cancer, which included most of the studies from the 2006 meta-analysis plus many more, found no association between fish consumption and prostate cancer incidence, and a reduced risk for prostate consumption mortality (3).
Speaking of fish, there is a question as to whether the association between omega-3 percentage and prostate cancer found in Braskey et al could be explained by mercury contamination of fish. While I found a study indicating that mercury levels in humans are correlated with fish consumption (4), I could not find any examining an association between mercury and prostate cancer. I did find two sources which indicate that if mercury causes prostate cancer, no one seems to know about it yet (5, 6).
So where does this leave us? I have a friend who pointed out that the mere idea that DHA could cause prostate cancer is ridiculous given what an important component of brain tissue DHA is. That’s an interesting perspective, though something good for the brain is not necessarily good for the prostate. I do think his point should increase the burden of proof needed before concluding that DHA causes prostate cancer.
One final point is that vegans who do not supplement with DHA tend to have DHA levels around 1%. As I reported recently, we have an anecdotal report of a 60-year old vegan man who raised his DHA levels from 1.0% to 4.8% using 320 mg of DHA plus 130 mg of EPA per day. My recommendations are for vegetarians 60 and under to supplement with 200-300 mg every other day and for vegans over 60 to supplement with that much every day. If you are someone who is at high risk for prostate cancer, I can see supplementing on the lower side of these recommendations (though I cannot tell any given individual what amount they personally need) to keep your levels below the 3.6% cutoff in Braskey et al.
In summary, I’m skeptical that DHA causes prostate cancer, but if you are at high risk, it might be prudent to stick to the lower end of the daily recommendations until more is known.
References
1. Brasky TM, Darke AK, Song X, Tangen CM, Goodman PJ, Thompson IM, Meyskens FL Jr, Goodman GE, Minasian LM, Parnes HL, Klein EA, Kristal AR. Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial. J Natl Cancer Inst. 2013 Jul 10. [Epub ahead of print] | link
2. MacLean CH, Newberry SJ, Mojica WA, Khanna P, Issa AM, Suttorp MJ, Lim YW, Traina SB, Hilton L, Garland R, Morton SC. Effects of omega-3 fatty acids on cancer risk: a systematic review. JAMA. 2006 Jan 25;295(4):403-15. Review. Erratum in: JAMA. 2006 Apr 26;295(16):1900. | link
3. Szymanski KM, Wheeler DC, Mucci LA. Fish consumption and prostate cancer risk: a review and meta-analysis. Am J Clin Nutr. 2010 Nov;92(5):1223-33. doi: 10.3945/ajcn.2010.29530. Epub 2010 Sep 15. | link
4. Yoshizawa K, Rimm EB, Morris JS, Spate VL, Hsieh CC, Spiegelman D, Stampfer MJ, Willett WC. Mercury and the risk of coronary heart disease in men. N Engl J Med. 2002 Nov 28;347(22):1755-60. (I only read the abstract.) | link
5. Landrigan PJ. Occupational and community exposures to toxic metals: lead, cadmium, mercury and arsenic. West J Med. 1982 Dec;137(6):531-9. | link
6. Järup L. Hazards of heavy metal contamination. Br Med Bull. 2003;68:167-82. | link
Dr. Michael Greger of NutritionFacts.org and the Humane Society of the United States, has a number of new items out.
A fascinating new video explaining how anti-depressives work and the possibility of plants having similar effects:
Fighting the Blues With Greens?
The hour-long presentation of the year in nutrition science:
More Than an Apple a Day: Combating Common Diseases
His most recent DVD:
Latest in Clinical Nutrition: Volume 14
I hope you can check them out!
I just updated the list of symptoms of overt B12 deficiency on the VeganHealth.org page, Overt B12 Deficiency – Nerve Damage and Anemia.
I added one symptom, skin hyperpigmentation which is the darkening of the skin accompanied by even darker spots (1). The study is free to the public and you can see pictures (click here).
Interestingly, the discussion part of the paper points out that B12 deficiency interferes with the production of choline and choline-containing phospholipids. Perhaps this is why, or partially why, some vegans crave eggs (see To Quit or Not to Quit Veganism: Part Two), which are high in choline.
Reference
1. Cherqaoui R, Husain M, Madduri S, Okolie P, Nunlee-Bland G, Williams J. A reversible cause of skin hyperpigmentation and postural hypotension. Case Rep Hematol. 2013;2013:680459. doi: 10.1155/2013/680459. Epub 2013 Jun 11. | link
The new book for women, Vegan For Her, by Ginny Messina, MPH, RD and J.L. Fields is now available. You can order a copy here and check out their website:
Wow – my last real post was on June 27th. But I have not fallen off the face of the earth – rather, it was right around that time that a reader brought my attention to a disconcerting study from 2006 which showed vegans in the Slovak Republic to have significantly higher cadmium levels than other diets groups. This study set me off on quite a journey that led to examining the role of zinc in Alzheimer’s Disease, of all things, and ended up strengthening my suspicions that vegans might benefit from zinc supplementation. In this case, not only because vegans can sometimes have low zinc intakes, but also to help reduce any problem caused by higher cadmium and copper intakes.
I have added this information to VeganHealth.org in an article on Cadmium. The article is too long to reproduce here, so I hope you will click through and give it a read.
I was disappointed that I had not previously heard of the study from the Slovak Republic, but these days I get notifications for any studies on vegetarians or vegans that get added to PubMed, so hopefully none will eascape my notice again.
Ginny Messina has a good article on heart disease and vegan diets:
She’s also going to be in Colorado this weekend and into the following week launching Vegan for Her:
Just added this to Omega-3 Fatty Acid Recommendations for Vegetarians at VeganHealth.org:
A 60 year old, male, long time vegan forwarded his fatty acid lab reports to me. In August 2012 his EPA levels were .3% and DHA was 1.0% (of fatty acids in blood). He had been using “a lot of” canola oil but it apparently wasn’t increasing his EPA and DHA levels. After six months of daily supplementation of 320 mg DHA plus 130 mg of EPA (one capsule of Ovega-3 vegan supplement), his EPA levels went to 1.0% (about average for omnivores) and DHA to 4.8% (towards the higher average range for omnivores). It appears that this regimen was adequate.