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Note: a condensed and edited version of the material below was posted on the
Fresh Network blog on 12 Feb 2010, at the URL:
Here we provide:
[Main article]
A 100%
vegan diet – done intelligently – can work well for many people, but that does
not mean it is optimal for everyone. A vegan diet can be unhealthy, e.g., diets
based on junk foods or soy meat analogues. Those attempting strict vegan diets
are advised to pay attention to their nutrition.
Nutritional issues
Vitamin B-12. A vegan diet needs a reliable
source of vitamin B-12. Plant foods can contain some vitamin B-12, which is
absorbed from soil and water (Mozafar 1994). However,
the amount varies with the B-12 content of the soil (some soil has no B-12), so
plant foods alone are not a reliable source (
Essential fatty acids (EFA).
It can be difficult to get adequate amounts of EFAs on low-fat vegan
diets. There are two primary types of EFA:
omega-3 (n-3) and omega-6 (n-6). Vegan diets are usually very low in n-3
(
Both
The
conversion to EPA, DHA depends on many factors, including the n-6/n-3 ratio in
the diet. Because the conversion is inefficient, some researchers recommend
double the AI for
Genetics may
be a factor (for some individuals) in the conversion to EPA, DHA. Individuals
descended from populations that consumed significant quantities of fish (fresh
and/or salt-water) over a long/evolutionary period of time might not produce
adequate levels of the enzymes required for conversion (Davis, personal
communication; also see Simopolous 1999). This may be relevant to, for example, some
people from:
That low
fat vegan diets may fail to provide adequate EFA intakes is demonstrated in Doug
Graham’s The 80/10/10 Diet book; on p.
118 he gives a sample day’s menu that fails to meet a man’s AI for ALA, barely
meets a woman’s AI for ALA, and provides only a small percentage (8.2-11%) of
the AI for LA (Graham 2008). If we follow the recommendation to double the AI
for
Other supplementation may be appropriate
for optimal health:
Vegetarian advocacy: rhetoric vs.
reality
Model diets cited by vegetarian advocates
are non-vegetarian and based on cooked starches. The traditional diet of
In a
similar vein, on pg. 69 of his book, Doug Graham repeats information from John
Robbins, showing similar high-carb, cooked-starch-based,
non-vegetarian diets as models. The diets are labeled as from Abkhasia, Vilcabamba, and Hunza; these are allegedly long-lived cultures but that
claim is highly suspect (Tu 1999). Note
that extensions of this model diet data to 100% raw, 100% vegan, and/or
fruit-based diets constitute extrapolations beyond the range of the data.
Beware of misleading comparisons in nutritional
research. Vegetarian
advocates often cite research studies when promoting the diet. However, just as
there are many different vegan diets, so too there are many different
omnivorous diets. Results of research on people following the SWD - the standard
Western diet - are often interpreted as a proxy for all omnivorous diets. This is misleading and inaccurate; it is
well-known that the SWD is unhealthy and too high in calories, fat, sugar, and
salt. An omnivorous diet with a low level of animal products can be based
primarily on unprocessed or minimally processed foods and be a healthy diet
(the model diets above are examples).
Results
from biomedical research studies on self-identified vegetarians also can be
misleading. Individuals who eat limited amounts of meat – only fish or non-red
meat – often self-identity as vegetarians (Barr et. al., 2002; Haddad and Tanzman, 2003). This means that a study that compares the
SWD to self-identified vegetarians is actually comparing a high-meat group to a
lower-meat group!
Can you see
the contradiction and irony here: based on studies that used the SWD, some vegetarian
advocates condemn all omnivorous
diets (an obvious logical fallacy), while at the same time presenting the
healthy omnivorous diets of
Vegan naturalism: realistic or idealistic?
Raw vegan
diets are often promoted as the “most natural” diet. Such claims are based on a
view of nature that is naive, idealistic, and inaccurate. Some sample beliefs
about nature include:
·
Humans don’t need
tools to acquire or consume their natural diet.
·
Nature gives you
perfect foods that are ready to eat.
·
These natural
foods are easy to acquire, and abundant.
·
A diet based on these
foods will grant perfect health and prevent/cure disease.
Consider the roots of the natural
hygiene movement: some health reformers in the 1800’s were ministers who mixed
religious teachings with dietary teachings (e.g., Sylvester Graham), and
traditional Christianity was dominant at the time. Given this background, one
must ask: could the anthropocentric, benevolent view of nature described above be
derived from (or influenced by) the Garden of Eden story from the Bible? Is the
raw vegan/natural hygiene “scientific” view of nature really a recycled
religious view?
A more realistic view is to observe
that the range of our natural diet is defined by evolution, which for humans
includes tool use and the effects of language and culture, all of which are
strong evolutionary selective pressures. The natural human diet is a hybrid
between a non-vegetarian hunter-gatherer diet and the plant-based agricultural
diets that have dominated since the Neolithic revolution. Where each individual
falls in that range will vary according to genetics and other factors.
An important reminder: we live in an unnatural world, and hunter-gatherer or
Neolithic subsistence farmer lifestyles are not feasible nowadays. The fact
that some of your genes were inherited from hunter-gatherers does not justify a
diet based on modern feedlot meats. We are alive here and now; the relevant
question is: what sustainable diet(s) can
work well for us? A false, Edenic view of nature
is not helpful in answering this important question.
Maximizing the probability of
success on vegan diets
Strict vegans need to make intelligent
food choices to
avoid problems: eat mostly unprocessed foods, take a B-12 supplement, pay
attention to your EFA intake (supplementation may be appropriate), consider
other supplementation if relevant, and base your diet on the widest range of
vegan foods possible: vegetables including greens, roots & tubers; fruits, nuts, seeds, seaweed,
sprouted (or conservatively cooked): grains, legumes.
Finally, if
100% raw vegan does not work, options available include supplementation, increasing
consumption of cooked foods, and/or including non-vegan foods in your diet. Remember
that your diet should serve you, and not the other way around.
Note: References are listed at the end, including a link to free full text of
the EFA article by Davis & Kris-Etherton (2003). Vegans
who want evidence-based information on EFAs are strongly
encouraged to read that article.
Thomas E.
(Tom)
26 Jan 2010
Edited reply to/comment on pro-vegan article on Fresh
Network blog
Note: I won’t post the pro-vegan article or its comments; it is
available via the Fresh Network blog article URL at the top of this page. Consequently,
that makes posting my reply to the pro-vegan article more difficult, as there
is no context for it. To enable posting here, I have chosen to edit my reply to
remove references to the other author. What remains is posted here as it is
directly related to the main article topic.
Use of supplements. Dr. Michael Klaper
recommends that vegans use supplements: vitamin B-12, DHA, multivitamins (Klaper 2008A,B,C). In a separate
interview, Dr. Klaper repeated the suggestions to
supplement, and made the interesting remark: "...we see most people do
quite well on vegan diets. But, there are some folks who will lose muscle mass,
experience lower energy levels and not feel at their best eating a vegan
diet." (Klaper as quoted in Horton, 2009). Any
claim that Klaper says that (unsupplemented)
vegan diets are nutritionally complete, is clearly incorrect.
The original China Study is an ecological study; such
studies may generate hypotheses but they prove nothing. The China Study report
lists only 6 statistically significant correlations between meat-eating and
disease mortality. Further, 4 of those correlations are negative, which
indicates that the mortality rate for that disease decreased as meat consumption increased. The direct evidence of the
study is hardly the condemnation of meat consumption that vegan advocates may
claim it to be (
Re: the “humans are frugivores” claim made by some vegan advocates. It is hard to understand why
this claim is so important to some vegans, when one considers that nonhuman primate
frugivores are generally non-vegetarian. That is,
even if humans are frugivores, it does not mean that
we are natural vegetarians, e.g., chimpanzees and bonobos
are frugivores and they are non-vegetarian. (Hunting
by chimpanzees is common and well-documented; less well known is that bonobos also hunt animals for food.)
The idea
that humans cannot eat animal foods because we lack claws and fangs is invalid
because tool use made those adaptations unnecessary. Humans have used tools
since our inception as a species; the natural hygiene teaching that humans are ”naked apes without tools” is a fantasy.
The “humans
are frugivores” claim falls apart under cursory
examination. Let’s assume that humans are obligate frugivores
adapted to high-fruit vegan diets. That would imply:
·
A highly specialized diet means we are adapted only to a narrow ecological niche, and
we should not have succeeded outside the tropics.
·
Over the course of evolution, human tribes that adopted
fruit-based diets should have out-reproduced the tribes who ate animal foods,
i.e., fruit-based diets should be the norm.
·
Long-term success should be the norm on high-fruit diets;
instead we see a high failure rate.
·
In order to pick the fruit that is supposed to be the basis
of our diet, humans should be quadrupedal (like
chimps) and have the special adaptations
for tree climbing that many non-human primates have.
With so many obvious fallacies in the “humans are obligate frugivores” claim, why does anyone promote such
misinformation?
Re: claims that humans have a
single, narrow “species-specific” diet. The reality is that our species-specific dietary range is
defined by evolution. Humans are generalists who not only have survived, but
thrived and colonized the entire planet (land area, excluding
Re: importance of vegan morals. Evolution is an amoral force,
driven by species survival in the face of selective pressures. Vegan moral preferences
are irrelevant in evolution. Similarly, natural hygiene myths about humans
living on fruit diets in an Edenic paradise are also
irrelevant.
In closing,
let’s return to the important question posed in my article: what sustainable diet(s) can work well for
us? If you thrive on them, then raw, vegan, or vegetarian diets may be part
of your answer to this question. However, consider that diet gurus who promote
idealistic and “perfect” diets (for their own financial gain) don’t necessarily
have your interests at heart, and be open to the possibility that you may need
to supplement and/or modify your diet to thrive, long term.
Supplement and replies to comments
on Fresh Network blog posting:
Blog comment on EFAs.
One
commenter questioned the paragraph:
Genetics may be a factor (for some individuals)
in the conversion to EPA, DHA. Individuals descended from populations that
consumed significant quantities of fish (fresh and/or salt-water) over a
long/evolutionary period of time might not produce adequate levels of the
enzymes required for conversion (Davis, personal communication; also see Simopolous 1999). This may
be relevant to, for example, some people from:
The
commenter pointed out that one of my citations is from an archeological
journal, but does not explain why that is objectionable. I can only guess that
the person is questioning how long it would take for fish consumption to impact
(in a hereditary way) EFA metabolism.
The
archeological journal citation is Adán et al. (2009);
the article in question is titled “Fish as diet resource in
“It has
long been recognised that fish were a valuable
resource which was exploited from early prehistoric times (Clarke 1948)...The
population of Ireland was especially reliant on fish because the limited fauna resident
on the island provided little opportunity for hunting (van Wijngaarden–Bakker 1983: 39;Mitchell 1990: 75;Woodman et al. 1997).
This dependence on fishing is evident from the marked concentration of
Mesolithic material recovered from lakeside, riverine
and coastal settings (Woodman 2003: 8-10). Moreover fish formed a significant
percentage of the faunal remains from both coastal and inland sites of the
period (Waddell 1998: 13; Woodman et al. 1999: 142).”
In
retrospect, it might have been better to cite Clark (1948), which starts with a
discussion of fishing in
Clark JGD,
1948. The Development of Fishing in Prehistoric
The
commenter also challenged Simopolous (1999), based
only on reading the abstract. The reference here is to Tables 3 & 4, pp.
563S-564S of Simopolous (1999), which serve as
pointers to the underlying factor: the well-known fact that fatty acids are
involved in gene expression (gene-nutrient interactions). “It
has been shown that fatty acids rapidly and directly alter the transcription of
specific genes (49)” (Simopolous 1999, p. 561S).
Nutritional
regulation of gene expression can “produce changes that define phenotypic
expression” (Cousins 2006, p. 615). Nutrient-gene interaction can serve as a
kind of feedback control mechanism that directly impacts genetics and evolution
(Hargrove & Berdanier 1993).
The
interaction between gene expression and evolution is currently an area of
active research. My paragraph on the topic was carefully worded, e.g., “over a
long/evolutionary period,” because I am not aware of any studies that examine
the length of time required (i.e., number of generations) for the downregulation of the enzymes to create DHA, EPA that is
induced by fish consumption, to have an impact in a human population.
One study
on the interrelationship between evolution and gene expression compared DNA and
RNA arrays for humans, chimpanzees, orangutans, and rhesus macaques.
Statistical analysis of the arrays showed rapid evolution of human
transcription factors (recall that fatty acids are involved in transcription).
The study notes: “These observations suggest that genes with expression levels
under directional selection [i.e., transcription] in humans are somewhat more
likely to show accelerated amino acid evolution.” (Gilad
et al. 2006, p. 244; also see Nielsen 2006). However, this does not tell
us how long it would take for fish consumption to have an impact on hereditary
ability to synthesize EPA, DHA.
A personal note to the commenter who falsely
accused me of not wanting readers to check the references: the fact is that I
want you to check the references that I cite, whenever it interests you. But
please note that, with very few exceptions – which I usually specify in the
relevant reference list – I work from full text and not from abstracts only. I
encourage you to follow the same practice: obtain and read full text; don’t
rely on abstracts only.
And please,
for your own benefit, start demanding that the raw/veg
diet gurus back up any important claims with references and citations to the
scientific literature. If the gurus actually supply
citations, then be sure to check those too when they are of interest.
Any time
that a diet guru makes exaggerated or nonsensical claims,
challenge him or her to provide support for those claims. Example: if your diet
guru claims that there are “thousands of studies” to support his/her claims,
then why can’t he/she quickly and easily supply you with, say, 50 citations in
support of the claim? Another example: a diet guru who talks of “hundreds of
thousands” or “countless” nutrients; ask him/her to point you to the large
databases that contain lists and documentation for these (mysterious)
nutrients.
Blog comment on the
My reply
paragraph on the China Study was very carefully worded: “The original China Study” was specified
because the material I was replying to was ambiguous. There are two books that
could be identified as “The China Study,” and when no citation is given I
cannot tell which book is the subject.
The original
Junshi C, Campbell TC, Junyao
L, Peto R, 1990. Diet, Life-style, and Mortality in
A later followup book by Campbell, The China Study, was published in 2005. My comments refer to the 1990 book because it is the more
credible of the two references.
Supplement on choline.
Choline
is a complex nutrient. Humans can synthesize it but we should not rely on
self-synthesis: “The presence of a pathway for endogenous synthesis [of choline] does not make it a dispensable nutrient for most
animals or humans” (Zeisel & Niculescu
2006, p. 525). Betaine is a metabolite of choline, so consuming foods that contain betaine may reduce choline
requirements. Choline can also be degraded (to betaine) by gut bacteria, and this
process can reduce net absorption of choline (Zeisel & Niculescu 2006).
Choline
is extremely important for brain development, especially the hippocampus, the
part of the brain involved in memory. This makes it very important for pregnant
or lactating women:
“Pregnancy
and lactation are periods when maternal reserves of choline
are depleted. At the same time, the availability of choline
for normal development of brain is critical…Lack of choline
in a mother’s diet during pregnancy and lactation may have life-long effects on
their child.” (Zeisel 2004, p.
621S).
Supplement on EFAs.
AI controversy.
As stated above, the
·
LA: AI = 4.44 grams with UL (upper limit) 6.67 grams
·
·
(DHA
+ EPA) total AI = 0.65
grams, with DHA at least 0.22 grams, EPA at least 0.22 grams.
The AIs
suggested above are different from those of the
The
Role of body fat reserves. "Relatively large reserves of
LA in body fat, as are found in vegans or in the diet of omnivores in Western
societies, would tend to slow down the formation of long-chain n-3 fatty acids
from ALA" (Simopolous 1999, p. 563S). This factor
may be particularly relevant during a switchover to a low fat diet.
Ratios: n-6/n-3. Vegan diets are criticized for unfavorable
n-6/n-3 fatty acid ratios. The criticism is valid but also applies to many other
diets. Sample n-6/n-3 ratios, from Simopolous (2004):
·
Paleolithic
period = 0.79
·
Current
·
Current
·
Current
·
Current
·
Current
[Side
remark: note the large difference between rural and urban
Ratio implied by AIs?
The ratio
of the AIs suggested by Simopolous et al. (1999B) is
2:1, and the ratio:
(UL for LA)/(AI for ALA)
is 3:1,
so overall these recommendations fall in the 2:1 – 4:1 range suggested above.
Looking at the recommended worst case ratio (UL for LA)/(AI
for
6.67 + 2.22
= 8.89 grams
8.89 grams
* (9 calories/gram) = 80.01 calories = 4% of calories in 2000 calories/day
diet.
The low
value here - 4% of calories - provides some leeway in meeting the AIs on a
low-fat diet, e.g., 10% fat by calories.
The
Let’s play
with the numbers. How much
17/4 = 4.25
17 grams LA
+ 4.25 grams
21.25 grams
* (9 calories/gram) = 191.25 calories = 9.6% of calories in 2000 calories/day
diet.
Thus
meeting the Institute of Medicine AIs with a 4:1
ratio on a 10% fat diet is clearly problematic, but would be easier on diets
that are 15+% fat by calories. Recall that the base of diets used to establish
the
The
questions that remain to be answered here include:
·
Which
set of AIs is better?
·
If
low fat vegans adopt the Simopolous et al. (1999B)
recommended AIs, will they also adopt the AIs for preformed EPA & DHA?
(That would require supplementation.)
·
What
should the AIs for EPA, DHA be?
References:
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