[2023 update: For a more recent and thorough analysis of the potential impact of cyanide in cyanocobalamin supplements see the VeganHealth.org section, Vitamin B12 and Cyanide.]

The safety of cyanocobalamin has raised concerns due to the fact that cyanide is a component of cyanocobalamin, and the cyanide molecule is removed from cyanocobalamin when used by the body’s cells. Cyanide is also found in many fruits and vegetables and so humans are always ingesting small amounts of cyanide, and like in most fruits and vegetables, the amount of cyanide in cyanocobalamin is considered to be physiologically insignificant.

According to the European Food Safety Authority, “Data of from a Norwegian dietary survey show that the average and high (97.5th percentile) daily intake of [cyanide] among consumers amounts to respectively 95 and 372 micrograms/person or 1.4 and 5.4 micrograms/kg bw/day (7).” The amount of cyanide in a 1,000 microgram cyanocobalamin is 20 micrograms.

Table 1 contains some additional numbers regarding cyanide amounts in cyanocobalamin for comparison purposes.

In summary, the amount of cyanide in 1,000 micrograms of cyanocobalamin is about .6% of the amount that is thought to be the lower level that causes harm.

References

See Side Effects of B12 Supplements.

Thank you, Ginny, for sending some of the research!

While on vacation, my wife, Alex, and I popped into a Denny’s we were staying near and tried the veggie burger which is now vegan (if you hold the cheese). We were so impressed we went back two more times! Topping the burger were fresh mushrooms, spinach, and tomato, and you can get it with a side of broccoli or corn. You might think that broccoli from a chain restaurant would be pretty bad, but it tasted fresh and cooked just right.

A study was released today showing that fiber intake was associated with a reduced risk of developing a colon polyp (.71, .59-.99). The clearest effect was of fiber from vegetables (including legumes) (0.65, .47-.90).

The study measured diet during the Adventist Health Study in 1976 and then followed up during the Adventist Health Study-2 between 2002 and 2005. The Adventist Health Study included a large proportion of vegetarians.

I only have access to the abstract at this time:

Tantamango YM, Knutsen SF, Beeson L, Fraser G, Sabate J. Association between dietary fiber and incident cases of colon polyps: the adventist health study. Gastrointest Cancer Res. 2011 Sep;4(5-6):161-7. (link)

I have been reviewing the research on iron and vegetarians (lacto-ovo and vegan). It appears that the iron status of vegetarian men is fine, but that, roughly, about 10% of vegetarian women have iron deficiency anemia and another 15 to 40% have low iron stores. These rates are not much different than the meat-eating women in the same studies.

From the research I’ve reviewed, vitamin C appears to be the most important factor in absorbing plant iron. I have added a few paragraphs to the Iron page at VeganHealth.org and am reproducing that section here:

“In meat, 65% of iron is bound to the heme molecule (from hemoglobin and myoglobin), which is relatively easily absorbed. The rest of the iron in meat and all iron in plants is non-heme iron. Non-heme iron requires being released from food components by hydrochloric acid and the digestive enzyme pepsin in the stomach. Non-heme iron also needs to be shuttled from the digestive tract into the bloodstream by a protein called transferrin.

“The phytates, found in legumes and grains, and polyphenols (including tannins found in coffee and green and black tea), can inhibit the absorption of plant iron. On the other hand, vitamin C is a strong enough enhancer of plant iron and can overcome the inhibitors in plant foods.

“One study found that various doses of phytate reduced iron absorption by 10 to 50%. But adding 50 mg of vitamin C counteracted the phytate, and adding 150 mg of vitamin C increased iron absorption to almost 30%. Similarly, in the presence of a large dose of tannic acid, 100 mg of vitamin C increased iron absorption from 2 to 8% (13).

“In another study, vegetarian children with iron deficiency anemia and low vitamin C intakes in India were given 100 mg of vitamin C at both lunch and dinner for 60 days. They saw a drastic improvement in their anemia, with most making a full recovery (2).

“Researchers used 500 mg of vitamin C twice daily after meals to increase hemoglobin and serum ferritin in Indian vegetarians. They concluded that vitamin C was more effective at increasing iron status than iron supplements (12).

“Vitamin C is found in citrus fruits, strawberries, green leafy vegetables (broccoli, kale, collards, Swiss chard, Brussels sprouts), bell peppers (yellow, red, and green), and cauliflower.

“Calcium supplements, coffee, and black and green tea inhibit iron absorption if eaten at the same time as iron, so avoid them at meals in which you are trying to increase iron absorption.”

References

2. Seshadri S, Shah A, Bhade S. Haematologic response of anaemic preschool children to ascorbic acid supplementation. Hum Nutr Appl Nutr. 1985 Apr;39(2):151-4. (Link)

12. Sharma DC, Mathur R. Correction of anemia and iron deficiency in vegetarians by administration of ascorbic acid. Indian J Physiol Pharmacol. 1995 Oct;39(4):403-6. PMID: 8582755. (Abstract only)

13. Siegenberg D, Baynes RD, Bothwell TH, Macfarlane BJ, Lamparelli RD, Car NG, MacPhail P, Schmidt U, Tal A, Mayet F. Ascorbic acid prevents the dose dependent inhibitory effects of polyphenols and phytates on nonheme-iron absorption. Am J Clin Nutr. 1991 Feb;53(2):537-41. PMID: 1989423.

Here’s something I’ve been mentioning in my talks lately. A 2000 study measured the percentage of calories as fat in the diet as well as cholesterol levels in a subset of EPIC-Oxford vegan and non-vegan men. Here is what they found:

Vegans ate 30% of their calories as fat compared to 34% for meat-eaters. Not a huge difference and many people would be horrified at such a high fat intake on behalf of the vegans. Yet, their cholesterol levels were well below what is commonly considered the danger zone.

What accounts for this? The vegans’ much lower intake of saturated fat probably explains a lot. But the vegans’ 20% fewer calories also probably accounts for much of their lower cholesterol levels. Addendum 1/27/12: Additionally, higher fiber intake and zero or near-zero cholesterol intake all likely contribute to the vegans’ lower cholesterol levels. Clarification 1/30/12: People who exercise a lot can eat more calories without cholesterol levels increasing as long as they are not eating so much that they gain body fat (thanks, Ginny).

Some people might point out that ideal cholesterol levels are actually less than 150 mg/dl, so 158 mg/dl is too high. While many clinical trials in people with heart disease (and normally on cholesterol-lowering medication) show a benefit to getting levels below 150 mg/dl, I have not seen evidence that this is ideal, or even desirable in people without diagnosed heart disease or normally high cholesterol. Instead, the observational studies I’ve seen measuring cholesterol levels and mortality have not shown a benefit from cholesterol levels less than 160 mg/dl.

I would not completely rule out the idea that studies have not shown reduced mortality in people with cholesterol levels less than 160 mg/dl because they have not included enough people with cholesterol levels that low and who do not have such low levels due to undiagnosed disease. But “not completely ruling out something” is a far cry from saying there is good evidence that it is true.

The reason I think this is particularly important is anecdotal evidence that people on long-term, low-fat diets can find them hard to stick with. I know there are some exceptions – people who find them easy to stick with, but I sense that there are more who find it difficult. When people crave meat, they tend to think they are craving the protein. But meat is also about 50% fat on average and it would not surprise me if such people are often craving fat as much or more than protein. Eating a diet closer to 30% fat might prevent such cravings.

Yes, lots of qualifiers above that I’m not 100% certain of everything I’m saying. But I think there is enough evidence that I should share it with readers rather than just keeping it to myself until “further studies” are done.

Reference

Allen NE, Appleby PN, Davey GK, Key TJ. Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men. Br J Cancer. 2000 Jul;83(1):95-7. Link

The Vegan Culinary Experience (VCE), written by Chef Jason Wyrick, is the first and only vegan culinary magazine in the world. It’s also a free PDF (click on the magazine cover image on the VCE home page to download).

The current issue, Healthy Eats, has an article by yours truly, Thriving on a Vegan Diet. If you’ve followed my writing, there aren’t any surprises here, but it’s a good summary of what you need to know to stay healthy on a vegan diet.

Your Daily Dose of Vegan Outreach has reported that, “In 2009, 2010, and 2011, hundreds of millions fewer land animals were raised and slaughtered for food in the U.S. than at the peak in 2008.”

Looks like our efforts are having an impact!

In 2009, preliminary cross-sectional data on blood pressure rates among various diet groups were reported from Adventist Health Study 2. Just today, a more thorough report was posted at PubMed. The 2012 report only included whites and the results did not appear to be adjusted. But, in any case, vegans had a 63% reduced risk of having high blood pressure, as compared to regular meat-eaters, which was highly statistically significant. Lacto-ovo vegetarians had a 43% reduced rate, which was also statistically significant. More details can be seen in Table 12 of Disease Markers of Vegetarians at VeganHealth.org.

Body mass index was able to account for most of the differences in blood pressure between the diet groups, though other factors probably play a small role, such as higher potassium and lower sodium intakes, and lower insulin levels and blood viscosity.

Reference

Pettersen BJ, Anousheh R, Fan J, Jaceldo-Siegl K, Fraser GE. Vegetarian diets and blood pressure among white subjects: results from the Adventist Health Study-2 (AHS-2). Public Health Nutr. 2012 Jan 10:1-8. [Epub ahead of print] Link

Ginny Messina: Should You Go Vegan to Get Skinny?

A few months ago a study was published on carnitine absorption in the muscles of vegetarians. Here is what I added to VeganHealth.org’s Vegan Weightlifting: What Does the Science Say?, which is where most of my info on carnitine resides (italics added to the new sentences):

“Carnitine levels tend to be lower in people eating lower fat, higher carbohydrate diets. When intake of carnitine is low, less carnitine is excreted. Vegans and lacto-ovo vegetarians have lower blood levels of carnitine. Researchers in one study did not think the lower carnitine levels of vegetarians were unhealthy. It is not known if the lower levels have any bearing on athletic performance. A 2011 study showed vegetarians’ muscles to have a lower ability to absorb carnitine than omnivores. Vegetarians also excreted less carnitine than omnivores, indicating that other tissues or muscles that were not tested were possibly absorbing the carnitine.”

Some added thoughts:

This paper included two studies. In the first study, subjects were given both insulin and carnitine intravenously. The researchers thought the insulin would help enhance carnitine absorption. I would not rule out the possibility that the insulin might have confounded the study in terms of what normally would occur.

In the second study, subjects ate 3 g of carnitine in one dose and had their measurements taken about 24 hours later, only one time. This would give the body very little time to adapt to a larger carnitine intake.

Finally, it is still not clear that vegetarians’ lower levels of muscle carnitine have any physiological significance. I once supplemented with carnitine for a few days and experienced no noticeable health improvement (such as increased energy). But I do know of one person who did very poorly on a vegan diet until he started supplementing with carnitine.

Reference

Stephens FB, Marimuthu K, Cheng Y, Patel N, Constantin D, Simpson EJ, Greenhaff PL. Vegetarians have a reduced skeletal muscle carnitine transport capacity. Am J Clin Nutr. 2011 Sep;94(3):938-44. | Link