Incidence of Colorectal Cancer in Vegans

March 14th, 2015 by Jack Norris RD
Summary Results from Adventist Health Study-2 show vegans to have a 16% lower risk of colorectal cancer than non-vegetarians, but the finding wasn’t statistically significant. Pesco-vegetarians had the lowest rate of all.

EPIC-Oxford and Adventist Health Study-2 (AHS-2) are the two ongoing studies of diet and disease that contain a large number of vegans. This past week, AHS-2 released a report on colorectal cancer rates among various diet groups (1).

In summarizing the research on diet and colorectal cancer to date, the researchers write:

“Among dietary factors thought to influence risk, the evidence that red meat, especially processed meat, consumption is linked to increased risk and that foods containing dietary fiber are linked to decreased risk has been judged to be convincing. The evidence for a link to decreased risk has been judged as probable for garlic, milk, and calcium. Evidence for other dietary components is considered limited.”

Because of the link with red and processed meat, nutritionists had expected that vegans and vegetarians would have a lower risk for colorectal cancer. To date, EPIC-Oxford has not shown a lower risk for vegetarians (results can be seen in Cancer, Vegetarianism, and Diet).

Better news comes from the latest AHS-2 report. After an average follow-up of 7.3 years, the lacto-ovo vegetarians and vegans had a lower risk of colorectal cancer (18% and 16% respectively), but the findings were not statistically significant. Here are the risk ratios and confidence intervals for each group:

Non-Veg 1.00
Semi-Veg  .92 (.62, 1.37)
Pesco  .57 (.40, .82)
Lacto-ovo  .82 (.65, 1.02)
Vegan  .84 (.59-1.19)

The only group with a statistically significant lower risk was the pesco-vegetarians (who eat no meat other than fish), with a 43% lower risk that was highly statistically significant. Despite this, the difference between the pesco-vegetarians and vegans was not statistically significant, though close (.68, .43-1.08).

When lumping all the groups together (semi-, pesco-, lacto-ovo, and vegan) and comparing to non-vegetarians, the “vegetarians” had a statistically significant, 22% lower risk of colorectal cancer (.78, .64-.95).

Results were adjusted for age, race, gender, education, exercise, smoking, alcohol, family history, peptic ulcers, inflammatory bowel disease, diabetes mellitus, aspirin, statins, prior colonoscopy or flexible sigmoidoscopy, supplemental calcium, supplemental vitamin D, calories, and hormone therapy. Subjects were excluded if they had a prior diagnosis of cancer (except for non-melanoma skin cancer).

Overall, colorectal cancer rates in AHS-2 were lower than the population at large and AHS-2 non-vegetarian eat very little meat (54.5 g/d or just 4.5 servings per week).

Could a higher calcium intake for vegans lower their risk of colorectal cancer? In AHS-2, the vegans had slightly lower calcium intakes (801 mg/day) than the pesco-vegetarians (913 mg/day) and non-vegetarians (882 mg/day). But in EPIC-Oxford, where the results were not as positive for vegetarians, vegans had much lower calcium intakes (583 mg/day compared to 1,005 mg/day for non-vegetarians) (2).

Another difference between the EPIC-Oxford and AHS-2 groups is that the AHS-2 vegans had a substantially greater intake of both dietary fiber and vitamin C.

Does eating fish protect against colorectal cancer? The researchers write, “The existing literature provides some, although inconsistent, support for a possible protective association for fish consumption, particularly for rectal cancer; evidence for omega-3 fatty acid consumption is limited and inconsistent.” In other words, it’s not clear.

In summary, colorectal cancer rates in vegans in AHS-2 are promising, but it might be important for vegans to follow calcium recommendations not only for bone health but also to prevent colorectal cancer.

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References

1. Orlich MJ, Singh PN, Sabaté J, Fan J, Sveen L, Bennett H, Knutsen SF, Beeson WL, Jaceldo-Siegl K, Butler TL, Herring RP, Fraser GE. Vegetarian Dietary Patterns and the Risk of Colorectal Cancers. JAMA Intern Med. 2015 Mar 9. [Epub ahead of print] | link

2. Average calcium intakes for EPIC-Oxford calculated from Nutrient Intakes of Vegetarians and Vegans.

Vegan vs American Heart Association Diet in Obese Children

March 12th, 2015 by Jack Norris RD

This four-week study from the Cleveland Clinic was to study vegan diets in obese children.

Participants on the vegan diet were instructed to avoid all animal products and added fat, and to limit intake of nuts and avocado. They were compared to children on an American Heart Association (AHA) diet which allowed 30% of calories from total fat, 7% of calories from saturated fat, less than 300 mg of cholesterol, and less than 1500 mg of sodium daily.

After four weeks there were a number of small, but statistically significant improvements for children on the vegan diet compared to baseline: body mass index (and body weight), mid-arm circumference, systolic blood pressure, total cholesterol, CRP and MPO (measures of inflammation), and insulin.

Children on the AHA diet had improvements in body weight, mid-arm circumference, waist circumference, and MPO. The statistically significant differences in improvements between the groups were in lower body mass index and CRP for the vegan group and waist circumference for the AHA group.

Parents and children noted that it was difficult finding food on the vegan diet.

Given access to healthy plant foods, a vegan diet could provide a promising way to reduce childhood obesity.

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References

1. Macknin M, Kong T, Weier A, Worley S, Tang AS, Alkhouri N, Golubic M. Plant-Based, No-Added-Fat or American Heart Association Diets: Impact on Cardiovascular Risk in Obese Children with Hypercholesterolemia and Their Parents. J Pediatr. 2015 Feb 5. | link

Links on the Saturated Fat Controversy

March 1st, 2015 by Jack Norris RD

In February, the 2015 Dietary Guidelines Advisory Committee submitted the Scientific Report of the 2015 Dietary Guidelines Advisory Committee which gives recommendations to the U.S. Department of Health and Human Services (HHS) and the U.S. Department of Agriculture (USDA) for the upcoming Dietary Guidelines. The Advisory Report is not the final Dietary Guidelines.

Of note, the Advisory Committee removed the advice to reduce dietary cholesterol and the advice to include lean meat. Ginny Messina, RD wrote a good summary of what this means for animal advocacy in her article, The 2015 Dietary Guidelines: What Will They Mean for Vegans?

On February 20, the New York Times ran an opinion piece, The Government’s Bad Diet Advice, by Nina Teicholz. It’s the typical Weston Price-type, pro-animal-product piece, in the same vein as writings by Nina Planck (no, they are not the same person).

David L. Katz, MD, MPH wrote a fun response to Teicholz’s piece, We’re Fat and Sick and The Broccoli Did It!

And speaking of Dr. Katz, he recently wrote a well thought-out piece on the Paleo diet, Paleo for a Shrinking Planet?

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TVA’s Veg Recidivism Survey

February 19th, 2015 by Jack Norris RD

In December, I blogged about the Humane Research Council’s report on vegetarian recidivism (Vegetarian Recidivism Survey, Dec 15 2014).

Another report has been released on vegetarian recidivism, this time from the Toronto Vegetarian Association. You can download the 10-page report from their post, TVA Conducts First Study of Lapsed Vegetarians in Canada.

Their study surveyed 1,112 people of which 113 were lapsed vegetarians.

Getting enough nutrients was listed at the most common challenge for lapsed vegetarians with 83% listing it as a challenge (as compared to 44% of current vegetarians). Eating out was listed as the second most common challenge, with 75% of lapsed and 65% of current vegetarians considering it a challenge.

It would be interesting to know in what way they believed getting enough nutrients was a challenge–was this theoretical or did they feel bad and suspect they weren’t obtaining enough nutrients?

The report quotes a couple of the lapsed vegetarians regarding nutrition. One person said:

“I grew tired of spending so much time on meal planning to make sure I was getting the proper amount of essential amino acids, etc.”

That makes me wonder what sort of information vegetarians are getting. While vegetarians should include high-lysine foods each day, there are so many–all legumes as well as quinoa and seitan–that it really takes little planning. Hopefully they weren’t carrying around a 1971 copy of Diet for a Small Planet, adding up all the essential amino acids from every meal.

Another respondent said:

“My iron levels were dangerously low and I needed to reintroduce meat sources of iron into my diet; I began having extreme meat cravings near the end of my vegetarianism and I believe that was my body telling me I needed the iron (which I found out later due to blood tests).”

This is disconcerting, but it also reinforces a view that I’ve been cultivating for some time–that cravings for meat might be due to iron deficiency. I would like to see research done on whether this is the case and, more importantly, how easily iron deficiency anemia can be cured while vegan by using the methods I suggest of adding vitamin C to meals and avoiding coffee and tea at meal times (more info).

I have been discussing the possibilities of this sort of research with a medical doctor at a large university and perhaps something will come of it.

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B12 Status of Whole Foods Vegans Consuming Nori and Mushrooms

February 11th, 2015 by Jack Norris RD
Summary A German study suggests that whole foods vegans who do not supplement with vitamin B12 have subpar vitamin B12 status and that nori and dried mushrooms do not improve B12 status.

In a 2014 study from Germany (1), a group of 10 whole foods vegans, who did not take supplements, were found to have methylmalonic acid (MMA) levels of almost 400 nmol/l. MMA is the most specific way to measure vitamin B12 status, with healthy levels being 270 nmol/l or less.

A second group of vegans who supplemented – it’s not clear with how much but it seems to have been at least 2 doses of 1,000 µg/week of B12 on average – had MMA levels of just above 200 nmol/l.

The whole foods-only vegans were given a minimum of 12 g/week of nori and 15 g/week of sun dried mushrooms, which the researchers calculated to contain an average of 3.1 µg/day of vitamin B12; the RDA is 2.4 µg. Their MMA levels were measured every 2 months for 8 months and they did not dip much below 350 nmol/l.

The vegans who took supplements were given more B12 than normal (though it’s not clear how much), and their MMA levels steadily decreased to about 150 nmol/l at 6 months, but then back up to 200 nmol/l at 8 months.

This research indicates that at the amounts given, nori and sun dried mushrooms do not improve vitamin B12 status.

I have updated the VeganHealth.org article B12 in Plant Foods with this information.

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References

1. Schwarz J, Dschietzig T, Schwarz J, Dura A, Nelle E, Watanabe F, Wintgens KF, Reich M, Armbruster FP. The influence of a whole food vegan diet with Nori algae and wild mushrooms on selected blood parameters. Clin Lab. 2014;60(12):2039-50. | link

Can Supplements be Trusted?

February 8th, 2015 by Jack Norris RD

On February 3rd, the New York Times released an article, New York Attorney General Targets Supplements at Major Retailers, in which they found that four of five herbal supplements did not contain the herb they purported to. The supplements came from four national retailers: GNC’s Herbal Plus, Target’s Up & Up, Walgreens’ Finest Nutrition, and Walmart’s Spring Valley. Even most of the garlic supplements didn’t contain garlic – a component that would seem rather unchallenging to obtain.

A reader asked me to weigh in on whether this has any ramifications for the supplements vegans are recommended.

In my recent Interview with Talk to a Doc, I talked about how vegans do not necessarily need to take supplement pills since there are other ways to obtain recommended nutrients. That said, it’s often easier and more convenient, and some might argue even more American to just take a pill!

So what does this NY Attorney General report mean for those of us taking supplements? In most cases, the controversy over what’s in supplements is about herbal supplements that are supposed to have medicinal effects rather than for vitamins and minerals. Even so, I’d be hesitant to rely on the exposed companies even for vitamins and minerals.

You can trust that supplements with the U.S. Pharmacopeia’s USP Verified symbol have what the label indicates. But getting the USP Verified symbol is expensive and so most smaller companies don’t go through the process.

While I can’t know for sure, I have no reason to doubt the supplement brands I generally take (Whole Foods, Trader Joe’s) or the supplements popular in the vegan community such as VegLife, Deva, Vitashine, or Opti3.

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Dr. Greger: New DVD and More on Paleo

February 6th, 2015 by Jack Norris RD

Michael Greger, MD has released the Latest in Clinical Nutrition Volume 23 which has a strong focus on the Mediterranean Diet. From his website:

The Mediterranean Diet is an “in” topic nowadays, in both the medical literature and the lay media. More than 450 papers were published in the medical literature during just the last year alone, more than one a day. As a recent commentary noted “Uncritical laudatory coverage is the common parlance. Specifics are hard to come by: what is it? what is its history? why is it good? Merits are rarely detailed; possible downsides are never mentioned.” I answer these questions and more in a 6-part video series.

You can order the full DVD from his website (click here), or you can watch them in short videos as they are released starting with another interesting one about the Paleo diet, The Problem With the Paleo Diet Argument.

Interview with Talk to a Doc

January 23rd, 2015 by Jack Norris RD

I recently did a 30-minute interview with Katya Trent of Wellness with Katya: Talk To A Doc.

We mainly discussed whether vegans need to take supplements.

Towards the end of the interview, I said that vegans can get all the nutrients they need without taking supplements. I should have clarified that this is based on three assumptions:

1. You’re getting vitamin B12 through fortified foods.

2. You’re getting enough sunlight to make adequate vitamin D or that you’re eating UV-treated mushrooms with large amounts of vitamin D.

3. You’re getting enough short chain omega-3 fatty acids from plant foods and that your body is converting enough to the long chain DHA. The jury is still out on whether vegans, especially older vegans, need a direct source of DHA (more info).

If you listen, I hope you enjoy it!

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Dr. Greger on Paleo

December 22nd, 2014 by Jack Norris RD

Dr. Greger has a video to share with your paleo friends, Paleo Diets May Negate Benefits of Exercise. He tackles the myth that plant foods raise insulin levels more than meat.

The video above is part of Latest in Clinical Nutrition: Volume 22 available for download or DVD (all proceeds go to charity). In Volume 22, Dr. G also takes on the idea that has been making the rounds for a while, that saturated fat does not contribute to heart disease.

Vegetarian Recidivism Survey

December 15th, 2014 by Jack Norris RD

The underlying motivation for my nutrition work is to prevent vegetarian/vegan recidivism. I have focused on nutrition and put myself out there as someone who will help people who are having health issues with becoming vegetarian/vegan. Because of this, I regularly hear from people who are struggling and it can sometimes seem like a lot of people, but I know my view is likely skewed and I have always wanted to know just how many people quit due to health difficulties.

On December 2, the Humane Research Council (HRC) released a report, How Many Former Vegetarians Are There? which sheds some light on this question. I helped out a bit in designing some of the nutrition-related questions and have been anxiously anticipating the results. I would like to thank HRC and all the people who funded this important research.

A quick overview of the report is that it was a cross-sectional survey of 11,000 people in the USA aged 17 and older. They found that 2% are currently vegetarian/vegan, 10% are ex-vegetarian/vegan, and 84% of people who go vegetarian/vegan quit.

The researchers used a high bar for determining who was vegetarian/vegan and ex-vegetarian/vegan – the participants had to answer a food list questionnaire indicating that they were vegetarian/vegan and then also say that they considered themselves “vegetarian” or “vegan”. I have not seen such a high bar used in any previous research.

Their report covers many of the difficulties former vegetarians/vegans had on the diet, but I’m only going to focus on the health aspects in this post. I have more to say about the rest in my post Humane Research Council Survey on Vegetarian Recidivism on Vegan Outreach’s blog.

The HRC blog post linked above does not include much information about health issues, but their complete report (which you can access by signing up for a free account on their site) has more. Below are excerpts followed by my comments.

“Former vegetarians/vegans were asked if they began to experience any of the following when they were eating a vegetarian/vegan diet: depression/anxiety, digestive problems, food allergies, low cholesterol, an eating disorder, thyroid problems, protein deficiency, B12 deficiency, calcium deficiency, iron deficiency, iodine deficiency, vitamin A deficiency, vitamin D deficiency, zinc deficiency. The findings show that 71% of former vegetarians/vegans experienced none of the above. It is quite noteworthy that such a small proportion of individuals experienced ill health.”

HRC sounds pleased that only 29% experienced ill health – but that’s almost one-third of people who tried the diet. I was actually hoping to find out that, say, only 1% of former vegetarians experienced poor health because it would allow me to retire from my nutrition work that, while being a labor of love, is indeed a labor, and takes away from my other efforts. At almost 1 out of 3 people, I’m not so sure it’s time to cross the finish line and declare victory.

“All of the conditions [listed above] were experienced by some participants, though only rarely. In each case, less than 10% of lapsed vegetarians/vegans experienced one of these issues, except iron deficiency (experienced by 11%).”

Fatigue is the most common complaint I hear. I have not found any one explanation for most cases of fatigue though vitamin D deficiency and iron deficiency in female endurance runners are common.

The fact that B12 deficiency was not a big complaint is not surprising given that overt vitamin B12 deficiency symptoms normally take years to develop whereas most of the former vegetarians/vegans were only on the diet for a few months, and any lacto-ovo-vegetarians would be getting B12 from dairy and eggs.

“Respondents who indicated they began to experience at least one of the conditions were asked if it improved after they started eating meat. 82% of these respondents indicated that some or all of the conditions improved when they reintroduced meat. The most typical timeframes for improvement were: within 2–6 days (20%), within 1–3 weeks (33%), and within 1–3 months (22%).”

Interesting. For some people who come to me with severe problems that we cannot seem to solve, I have often wondered if I should suggest they try going back to eating animal products, reset their health (if it does in fact reset), and then try becoming vegetarian/vegan again more slowly.

HRC emphasized the rates at which vegetarians/vegans had gotten their vitamin B12 levels checked. I would find this somewhat irrelevant other than as a marker for knowing that vitamin B12 is important for vegans. I generally discourage vegans from getting their B12 levels checked as a way to prevent B12 deficiency in most cases because of the unreliability for people who regularly eat seaweed (including sushi) and the fact that no matter what your B12 levels turn out to be, all vegans should be getting a regular, reliable source of B12 (see Should I Get My B12 Status Tested?).

In their section on Taste, they found that about one-third of former vegetarians/vegans craved meat compared to about 8% of current. It’s a mistake to consider “cravings” and “taste” to be equivalent. You can’t simply add the taste of meat to a low-fat, low-protein vegetable and expect that to take away someone’s meat cravings. Meat cravings are about the nutrients, most notably fat and protein. Craving the “taste” of meat is a Pavlovian response for craving those nutrients. (Note: I don’t know if this has been scientifically tested in a rigorous way.)

There were two positive findings from the HRC report:

More than one-third of former vegetarians/vegans said they are interested in resuming the diet, and vegans were less likely to abandon the diet (at rate of 70% compared to 86% for vegetarians).

The rest of my comments on this survey are regarding what it means for advocacy. If interested, please see Humane Research Council Survey on Vegetarian Recidivism.

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