I received an article sent to me by Dato Dr Ong Eng
Leong, PhD asking me for an answer, has eating meat become unfairly demonised
as bad for your health? That’s the question a global, multidisciplinary team of
researchers has been studying and the results are in - eating meat still offers
important benefits for overall human health and life expectancy.
This nutrition and health claim Dr Ong sent to me for an
answer is here:
Dato Dr Ong asked:
“Dear Dr JB Lim, can this be true? That Meat of small and
large animals provided optimal nutrition to our ancestors who developed
genetic, physiological, and morphological adaptations to eating meat products
and we have inherited those adaptations” - Emeritus Professor, Maciej Henneberg
This question was both a surprise and a challenge to me.
Like most people, we expect a vegetarian diet to be more
health-protective than a diet from derived from animal sources, such as beef,
poultry, eggs, mutton, fish and seafoods.
Most of us would believe a plant-based diet is rich in
antioxidants and phytochemicals, vitamin C, minerals generally absent in meat
and animal products.
However, we cannot ignore scientific evidence with clear
data presented to us, no matter what our thoughts.
I thought this over, and I decide to present my own analysis
here in blue:
................................................
The study did not tell us the nature, types, make-up, and
composition of the vegetarian diet. This is extremely important in deciding
whether they are life supporting and health protective. Meat, eggs and poultry
are high in proteins, not just high in content, but in biological values.
Before we go further, let me briefly explain the role of
proteins in human nutrition.
Proteins are made up of amino acids. They are the basic
building blocks of proteins, the compounds that synthesize hormones and
neurotransmitters in our bodies. Amino acids help our bodies to grow, repair
body tissue, maintain immunity and produce hormones that maintain body
functions.
There are 20 (or 21) amino acids that make up tens of
hundreds into thousands of different types of proteins, all of which are
required for growth and development by the human body. They all support life
and body functions. They produce immunoglobulins among other hormones and
enzymes, and they are disease protective, besides perhaps longevity as well.
These amino acids are:
Alanine, arginine, asparagine, aspartic acid, cysteine,
glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine,
methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine,
valine, and selenocysteine (same as cysteine).
Out of these 20 amino acids only nine of them are classified
as essential amino acids, namely: phenylalanine, valine, tryptophan,
threonine, isoleucine, methionine, histidine, leucine, and lysine.
The term “essential amino acids” means these amino acids
cannot be synthesized by the body, and they must be obtained from food sources.
“Essential” does not mean only these 9 are essential, and the rest are not
essential. All the amino acids are required to make a protein complete
and wholesome, and most of them are found in meat. Vegetables lack essential
amino-acids, especially lysine, a sulphur containing amino-acids which is very
rich in beef and meat products.
Unfortunately, lysine cannot be synthesized by the body, and
neither cereal grain, nuts and seeds have them. But legumes have them. Hence,
when we say the limiting amino acids in cereal grain such as rice is lysine, we
mean lysine is lacking in rice and this limits the biological value of rice as
a complete protein which must be obtained from meat, and legumes.
Hence a meat diet is better than a vegetarian diet if a
vegetarian or a vegan solely depends on one type of vegetable. But if a
vegetarian / vegan mixes his diet with various types of vegetables, cereal
grains, nuts, seeds, and legumes its nutritive (protein) quality is as good as
meat. In this way there would be no difference in the status of health and
longevity between a meat-eater and a vegetarian / vegan who has a mixed
plant-based diet.
A legume refers to any plant from the Fabaceae family that
includes its leaves, stems, and pods. A pulse is the edible seed from a
legume plant. Pulses include beans, lentils, and peas. For example, a pea pod
is a legume, but the pea inside the pod is the pulse.
In short, if the limiting amino acid in a vegetable diet is
lysine and threonine, it must be complemented in a diet rich in legumes,
pulses, nuts, and seed. Similarly, if a vegetable diet where the limiting amino
acid is methionine this can be made wholesome when mixed with grains, nuts, and
seeds.
By combining vegetarian protein sources, we can ensure that
we are getting all the 9 essential amino acids that would make the protein with
high biological values. Protein complementation does not have to be done at the
same meal. If beans are for lunch and then if a person had some raw almonds for
a snack later, that would have added methionine into it across the day.
A mixed vegetarian diet can provide all the vitamins,
minerals, and amino acids the body needs. Deficiency in methionine and
cysteine results in atrophy of the thymus, spleen, and lymph nodes in mice
and prevents recovery from protein-energy malnutrition.
Sulphur-containing amino-acids are methionine, cysteine, and
phenylalanine. Methionine, cysteine, homocysteine, and taurine are the 4
common sulphur-containing amino acids, but only the first 2 are incorporated
into proteins.
Grains, such as wheat, rice, oats, cornmeal, barley, and
corn, are low in essential amino acid lysine in comparison to other essential
amino acids. Legumes, such as beans, lentils, and peas, are also low in
lysine.
Lysine is a vital amino acid in human and animal
feeding, and it is present in high quantities in beef, poultry, and dairy
products, although it is found in small amounts in plant proteins. Lysine
does not contain sulphur.
Some African countries, especially in poor rural areas, rely
on cassava, maize and corn as their staple diet. Such a staple diet seriously
lacks tryptophan, which is also the precursor to niacin synthesis, a deficiency
of which causes pellagra we shall discuss shortly.
But by combining vegetarian protein sources, we can ensure
that we are getting all the 9 essential amino acids. That would make the
protein with high biological values. Protein complementation does not have to
be done at the same meal. If beans are for lunch and then we had some raw
almonds for a snack later, that would have added methionine into it across the
day.
A mixed vegetarian diet can provide all the vitamins,
minerals, and amino acids the body needs. Deficiency in methionine and
cysteine results in atrophy of the thymus, spleen, and lymph nodes in mice
and prevents recovery from protein-energy malnutrition.
Maize for instance lacks tryptophan which can be converted
into niacin (vitamin B3). A diet consisting mainly or purely on maize resulting
in children suffering from both kwashiorkor and pellagra. Babies fed solely on
maize and no milk results in high infant mortality and shortening their lives
greatly.
Vegetarians and vegans in more affluent countries who
complement their diet with legumes and pulses they can afford, give their diet
high nutritive quality. Such a diet is in par or even better than those who are
mainly meat eaters.
Similarly, in poor rural communities in India they may
depend mainly on rice, carbohydrates, surgery foods or wheat such as chapati
flatbread, paratha sweet pastry, etc as some studies showed. Such a diet as a
staple is nutritionally inadequate and can shorten life expectancy greatly
compared to meat eaters, whereas a rich traditional Indian diet consumed by the
more affluent Indian city dwellers may have a variety of whole grains, legumes,
fruits, and vegetables, each contributing significantly to health benefits.
Generally, a vegetable diet is deficient in cyanocobalamin or vitamin B12. A
deficiency of vitamin B12 can cause macrocytic anaemia, often presented as
fatigue and pallor.
Pernicious anaemia is a relatively rare disorder due to
dietary vitamin B12 (cobalamin) malabsorption, resulting in megaloblastic
anaemia.
A meat-based diet is better than a vegetarian diet if the
vegetarian or vegan solely depends on one type of vegetable. But if a
vegetarian mixes his diet with various types of vegetables, cereal grains,
nuts, seeds, and legumes it is as good as eating meat. I would expect
there would be no difference between a meat-eater and a vegetarian / vegan who
has a mixed plant-based diet in life expectancy.
Consider a cow. A cow eats mainly grass. But its body's
biological efficiency can convert the the
grass proteins into first class beef though not very efficient. To a human, we cannot eat grass, but even
if we have the cellulase to break down the cellulose in grass, we still are
unable to get the amino acids into proteins.
We shall talk more on this later.
In another study "Total Meat Intake is Associated with
Life Expectancy: A Cross-Sectional Data Analysis of 175 Contemporary
Populations”.
by Wenpeng You, Renata Henneberg, Arthur
Saniotis, Yanfei Ge, and Maciej
Henneberg given here:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8881926/ it
showed the same
Part of the above papers says:
“Meat has advantages over food of plant origin in containing
complete protein with all essential amino acids, is rich in vitamins, in
particular vitamin B12, and all essential minerals. It has a
significant role not only for maintenance of health, development and proper
growth but also has played an important evolutionary role in ancestral
hominins for approximately 2.6 million years.
Benefits of meat eating include better physical growth and
development, optimal breastfeeding of neonates, and offspring growth.
Human adaptation to meat eating and mechanisms to digest and metabolise
meat have been supported by studies in human dietary evolution. This may
also be reflected in the importance of meat eating for human’s whole life
span. Culturally, meat production and eating have also been integrated
into human societies.
Before agriculture was introduced (circa 11–9000 years
ago), human ancestors could not grow, harvest, and store the majority of
plant-based products as the staple food. Plant foods are mostly accessible only
in particular seasons of the year. Contrariwise, animals, including large game,
small animal, fish, and some insects, could constantly provide humans with meat
as the staple food.
Although modern agriculture diversifies our diet components
and offers us many food choices, meat is still one of the significant food
components worldwide. Modern nutritional science has revealed that meat
provides complete nutrition. Modern food technology is capable of producing
artificially all meat components, so that in special situations complete meat
contents can be introduced into a diet without including actual muscle tissue
of animals. This, however, does not argue against the benefits of eating meat.
On the contrary, it supports that meat contents are necessary for good human
nutrition. Availability of artificially produced meat may provide a solution
for people who are ethically opposed to killing animals”.
The authors
examined the association between meat intake and life expectancy at a
population level based on ecological data published by the United Nations
agencies. The method they used in the study was based on population-specific
data obtained from 175 countries/territories. Scatter plots, bivariate, partial
correlation and linear regression models were used with SPSS 25 to explore and
compare the correlations between newborn life expectancy, life expectancy at 5
years of life and intakes of meat, and carbohydrate crops, respectively. The
established risk factors to life expectancy – caloric intake, urbanization,
obesity, and education levels – were included as the potential confounders.
The results of
their study worldwide, based on bivariate correlation analyses revealed that
meat intake is positively correlated with life expectancies. This relationship
remained significant when influences of caloric intake, urbanization, obesity,
education, and carbohydrate crops were statistically controlled. Stepwise
linear regression selected meat intake, not carbohydrate crops, as one of the
significant predictors of life expectancy. In contrast, carbohydrate crops
showed weak and negative correlation with life expectancy.
They concluded
that if meat intake is not incorporated into nutrition science for predicting
human life expectancy, results could prove inaccurate.
However, the
authors made no mention of the vegetarian diet in quantity or quality in their
study group except ‘worldwide’. Neither was there any mention of specic
countries involved in the study. If they have made a worldwide study, I expect
they would have included India that has the second largest population in the
world, most of them are poor communities living in rural India subsisting on
poor vegetarian diets especially among the Hindus. So, are in the African
countries which are second most populous in the continent after Asia.
Had the study identified poor rural communities such as in
India and Africa or even Yemen where they live on poor quality plant-based diet
lacking not just in proteins and calories, but also in most of the vitamins and
minerals, we can expect such populations suffer from marasmus and kwashiorkor
in children along with most of the other deficiency diseases like night
blindness, clinically or sub clinically xerophthalmia, other spectrum of ocular
manifestations of vitamin A deficiency, Bitot spots to the potentially blinding
stages of corneal xerosis, ulceration and necrosis (keratomalacia), beriberi
from thiamine deficiency, pellagra, rickets, all the way down to multiple
deficiency disorders with consequences of much shorter life spans as compared
to meat consumers or in population that thrives on a good mixture of
vegetarian diet we can expect in more affluent vegetarian cultures.
But unfortunately, this was not shown in the studies except
gross comparison between a vegetarian diet and those from meat, fish and animal
products. Such a study renders the conclusion highly
questionable.
The current
population of Africa is 1,472,537,717 as of Tuesday, November 7,
2023, based on the latest United Nations estimates. So are many poor highly
populated countries where undernutrition are rampant that includes Nigeria with
a population of 223,804,632, Ethiopia with a population of 125,527,050, Egypt
with 112,716,598 people and also in Yemen a very poor country where
undernutrition with protein-energy malnutrition is still very rampant as it was
in the 1960’s. These countries cannot afford a rich meat-based diet, but
poor-quality cereal grains that may have grossly affected their health and
subsequent lifespan.
When we think of protein rich foods, we probably visualise
meat, eggs, beans and the like. However, animals that eat almost exclusively
grass, such as cows and horses, have no problem getting enough protein in their
diet. Unlike humans, herbivores are capable of digesting plant cells and
getting to the nutrients locked inside, like protein.
Humans cannot eat
grass of course unlike cows, sheep, goats, moose, camels, deer,
giraffes, and buffalos. We are unlike herbivore ruminants that have a
four-chambered stomach. They harbour millions of cellulolytic microbes such as
Fibrobacter succinogenes, Ruminococcus flavefaciens, and Ruminococcus
albus in their rumens that can break down cellulose into sugars and realizing
proteins and other nutrients trapped in the grass or leaves.
But how much protein are there in grass and leaves we are
unable to digest?
Plants belonging to the Fabaceae family such
as clover, peas and legumes have impressively high protein contents. Most
plants have a mean leaf protein content of 4 to 6% w/v. Fabaceae plants such as
clover, peas and legumes tend to have nearly double that value at 8 to 10% v/w,
depending on the protein estimation method employed.
Moringa leaves are a step ahead due to their
exceptionally high protein content of 8% for fresh leaves, and 30% for
dehydrated leaves. The quantity of protein in grass that cows eat to convert
them into meat varies typically from 16-28%, depending on the sward type,
growth stage, fertiliser regime and time of the year. Occasionally, protein
levels in grass dip as low as 11-12%.
Typically, grass
has 33 calories per 100 grams (roughly 4 calories per ounce) and 3.3 grams of
carbohydrates, 2.2 grams of protein and a whopping 4.6 grams of
fiber.
In this link below:
https://ourworldindata.org/grapher/feed-required-to-produce-one-kilogram-of-meat-or-dairy-product
We see cows are the least efficient in converting grass or
other feeds and fodder proteins into meat (beef). It requires 25 kg of feed to
get one kg of beef. This is only 4 % efficient. The quantity of protein in
grass that cows eat to convert them into meat varies typically
from 16-28%, depending on the sward type, growth stage, fertiliser regime
and time of the year. Occasionally, protein levels in grass dip as low as
11-12%.
The conversion efficiency is followed by mutton or lamb that
requires 15 kg feeds or fodder (6.7 %) to get their meat, then pork at 6.4 kg
(15.6 %), poultry 3.3 kg (30 %), eggs at 2.3 kg (43.5 %), and whole milk that
requires only 0.7 kg of feeds (143 %) which of course is mainly water.
However, we can extract these proteins and use them for
human nutrition for poor countries suffering from protein malnutrition. Plants
belonging to the Fabaceae family such as clover, peas and legumes
have high protein content. Most plants have a mean leaf protein content of 4 to
6% w/v. Fabaceae plants have nearly double that value at 8 to 10% v/w. Moringa
leaves are a step ahead due to their exceptionally high protein content of
8% for fresh leaves, and 30% for dehydrated leaves.
In 1957 NW Pirie,
working at the Rothamsted Experimental Station
in England managed to
extract protein from leaves using specially-designed machinery. He showed leaf
proteins have high nutritive values and can be added into animal feeds or
incorporated into the diets for humans.
Although it is possible to extract leaf proteins on a
commercial scale for human consumption as shown by Dr NW Pirie at the Rothamsted
Experimental Station in the UK, would a mass of tasteless proteins from leaves
be acceptable to most human taste? Food choice, food acceptance and food taboos
are one of the most difficult hurdles nutritionists face.
But I think in order to prolong our lifespan longer it is
for us to restrict food intake, especially caloric intake.
As early as the 1910s it was found that restricting food
intake prolongs lifespan. It was not until the early 1930s (around 1935)
that Clive Maine McCay, a professor of animal husbandry at Cornell
University, started his study of this topic and promoted it as a productive
research program in the multidisciplinary science of gerontology. Initially,
McCay observed that when rats were put on a very low-calorie diet, he and his
colleagues showed that their lifespan was extended from three to four years
which is a 33 % increase.
Subsequently over the years numerous experiments on other
animals have consistently shown the same result.
A paper on human nutrition published below looks at the
effects of “Calorie Restriction and Aging in Humans”.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9042193/
This may
seriously affect the authors of the study conclusion despite very elegant
statistical analysis done showing positive and negative correlation with
good correlation coefficient, a statistical measure of the
strength of a linear relationship between two variables.
However, they gave no figure on the odds ratio (OR)
which is a measure of association between a (dietary) exposure and a
(lifespan) outcome.
In the study the authors mentioned before agriculture was
introduced (circa 11–9000 years ago), human ancestors could not grow, harvest,
and store most plant-based products as the staple food.
My view is, the hunter-gatherer culture is a type of
subsistence lifestyle that relies on hunting and fishing animals and foraging
for wild vegetation and other nutrients like honey, for food. Until
approximately 12,000 years ago, all humans practiced
hunting-gathering. In such a human evolutionary socio-economic scenario, I
would expect our ancestors already were omnivorous by nature 12,000 years ago.
Agrarian civilization and early agriculture already began
8,000 years ago with domestication of cattle 6,000 years ago and the
domestication of horses 6,000 years ago, and iron tools used 3,000
years ago. There is no evidence that humans ever subsist entirely on
plant-based or animal foods. We have not much clue how long ancient humans live
except those given in Genesis in the Bible. The early patriarchs often lived to
be nearly 1,000 years old and even had children when they were several hundred
years old!
For instance, Methuselah lived for 969 years, Jared 962
years old, Noah was 950 years old, Adam, 930 years, Seth 912 years, Kenan 910
years, Enos 905 years, Mahalalel 895 years, Lamech 777 years, and Enoch was 365
years old before he died. We have no clue what they ate for longevity.
The oldest person in the Bible, Methuselah was Noah’s grandfather and his
father walked so closely with God that God took him. Methuselah died the same
year as the flood, living to 969 years of age.
Whatever our answers, since the 1930s Clive Maine McCay, a
professor of animal husbandry at Cornell University has shown that caloric
restriction in rats greatly prolongs their lifespans. So did other
scientists from fields such as biochemistry, pathology, immunology, genetics,
neuroscience, and nutrition have studied the relation of dietary caloric intake
to longevity and aging. Their results are consistently the same whether
fed on a vegetable or on a meat diet. It was the caloric restriction that
matters.
Finally, in a good and reliable scientific study normally,
we would pay a lot of attention to the study design, methodology of sample
collection, materials, and methods as the first as the most important criteria.
If there are biases and flaws in the sampling, material and methods used, then
no matter how elegant, impressive, and sophisticated our data analysis were,
the entire study, its conclusion is unreliable and inconclusive.
In summary, I do not think it matters if we are vegetarians
or vegans whose diet is solely plant-based or if we are meat eaters that can
extend our life span. Neither does it matter if the proteins of an entirely
vegetarian or vegan diet is of high or poor quality compared to meat, nor would
it matter if we extract the protein from plants, leaves and vegetables to make
it like what ruminant cattle naturally eat, after which we consume their meat of high protein quality that would increase our longevity.
I believe finally it would be restricting eating
especially restricting caloric intake that would not just prolong our human
life span, but it will prevent all the scourges of ill health and morbidities
of modern society caused by our dietary and other lifestyles that bring about
chronic and degenerative diseases like abdominal obesity, high blood pressure,
impaired fasting glucose, high triglyceride levels, low HDL cholesterol levels,
gout, cardiovascular events among other metabolic syndromes, and probably
cancers as well.
This is my opinion.
Thank you for your question, Dato Dr Ong Eng Leong.
(A 3,783 worded answer in 8 pages)
Lim ju boo BSc MD Postgrad Dip Nutrition, MSc, PhD (Med),
FRSPH, FRSM
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