Vegetarian and Vegan Diets: Nutritional Disasters Part 3

Vegetarian Diet | The Paleo Diet

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Vegetarian Diets: Other Nutritional Shortcomings

You don’t have to look any further than the ADA’s Position Statement28 or the USDA’s recommendations on vegetarian diets142 to discover additional nutrient shortcomings caused by plant based diets. The ADA matter of factly mentions that “…key nutrients for vegetarians include protein, n-3 fatty acids, iron, zinc, iodine, calcium, and vitamins D and B12..28 The USDA notes that “…vegetarians may need to focus on…iron, calcium, zinc, and vitamin B12.142 These subtle admissions of potential nutrient deficiency problems associated with vegetarian diets represent the tip of a nutritional nightmare. Just as was the case with vegetarian diets and vitamin B12 deficiency, there is little credible scientific evidence to show that people eating a lifelong plant based diet (without taking supplements or eating fortified foods) can achieve adequate dietary intakes of omega 3 fatty acids (EPA and DHA), iron, zinc, iodine, calcium, and vitamin D. To this list you can also add vitamin B6 and taurine, an amino acid.

Mineral Deficiencies and Vegetarian Diets

One of the major complications with the assessment of dietary nutrient adequacy in vegetarian diets, or for that matter, any diet has to do with whether or not the vitamins and minerals measured in certain foods actually get absorbed into our bodies. The bioavailability of vitamins and minerals in foods is just as important in how they impact our health as is the simple content of these nutrients in a food. By now you know that phytate is not a good thing because it prevents absorption of essential minerals. Whole grains and legumes are rich sources of phytate. Accordingly, our bodies have great difficulty extracting certain minerals from these foods because they are tightly bound to phytate. Phytate in whole grains impairs calcium absorption and may adversely affect bone health. Further, phytate also binds zinc, thereby interfering with its assimilation and incorporation into our cells. To this list you can add iron and magnesium. Because vegetarian diets are virtually impossible to follow without including lots of whole grains, beans, soy and legumes, they are inherently high in phytate. This is why it is difficult or impossible for vegetarians and vegans to maintain adequate body stores of calcium, zinc and iron.

Zinc Deficiencies in Vegetarian Diets

From the discussion above, you know that zinc is crucial for normal male reproductive function, but it is also required for good health and disease resistance in virtually every cell in our bodies, whether you are a man, woman or child.20, 41 Marginal zinc status impairs our immune system, slows wound healing, adversely affects glucose and insulin metabolism, and damages our body’s built in antioxidant system.16, 55 Without adequate dietary zinc we experience more upper respiratory illnesses that last longer. Zinc lozenges can slow or prevent common cold symptoms, and zinc oxide creams applied topically can speed healing. If you have ever experienced painful cracked heels or nose bleeds that just wouldn’t stop, try rubbing zinc oxide ointments on these wounds – you will be amazed at how rapidly zinc can heal these stubborn sores. How we got into this problem (marginal zinc status or deficiencies) in the first place originates directly from our diets. Anybody eating excessive whole grains and/or legumes and not eating meat, fish or animal products on a regular basis45, 59, 62 puts themselves at risk for all illnesses and health problems associated with borderline or deficient zinc intakes.

Iron Deficiencies in Vegetarian Diets

Your body stores of iron run hand in hand with zinc. The same types of diets that produce zinc deficiencies also create iron deficiencies. High phytate vegetarian diets based upon whole grains, beans, soy and other legumes invariably cause iron deficiencies5, 135 which are the most common nutrient deficit worldwide. In the U.S. 9% of all women between 12 and 49 years are iron deficient, while 4% of 3 to 5 year old children have insufficient stores of this crucial mineral.25 If you are pregnant, low iron status increases your risk of dying during childbirth, and frequently causes low birth weights and preterm deliveries. Even more disturbing is the potential for iron deficiencies to prevent normal mental development in our children and young adults.39, 90, 96 As a parent, I would never wish upon my child or for that matter anyone else’s, a diet causing nutritional deficiencies known to impair brain development and normal mental function. But this is just the case if you eat a vegetarian diet and impose it upon your children. Plant based diets not only increase the risk of impaired cognitive function in your children, but will hamper your own mental functioning. Numerous experimental studies show that inadequate iron stores in adults can slow or impair tasks requiring concentration and mental clarity.73

One of the most important outcomes of diets that cause iron deficiencies is that they make us fatigued and tired. If you are an athlete or have a demanding job requiring physical exertion, low iron stores will invariably reduce your performance. A recent (2009) experiment involving 219 female soldiers during military training showed that iron supplements improved blood iron stores, increased performance for a 2 mile run and enhanced mood.92 Similarly a study by Dr. Hinton and colleagues demonstrated that iron supplements in iron deficient male and female athletes improved endurance performance and efficiency.56 Whether you are an athlete, a laborer or even an office worker, your best nutritional strategy to improve iron stores, add vigor to your life and improve performance is to eliminate whole grains and legumes from your diet by adopting The Paleo Diet.

The burden of proof that vegetarian diets will not produce multiple vitamin and mineral deficiencies lies upon the governmental (USDA) and dietary organizations (ADA) that recommend these diets to us all and tell us that they are safe.28, 142 You might expect that the experimental evidence surrounding vegetarian diet recommendations would be convincing and overpowering. Nothing could be further from the truth, particularly when it comes to iron deficiencies and vegetarian diets.

As always the devil is in the details when it comes to getting correct answers to nutritional questions. Scientists who believe that vegetarian diets don’t adversely affect our iron stores often cite scientific papers showing no difference between blood iron concentrations in vegetarians and meat eaters. What they don’t tell us is how iron measurements were performed in the experiments they quote to support their viewpoint. This information is absolutely essential in knowing if iron deficiencies exist or not. Any study examining blood levels of iron in vegetarians using either measurements of hemoglobin (an iron carrying substance in red blood cells) or hematocrit (the concentration of red blood cells) are unreliable indicators of long term iron status. A much better marker is an iron carrying molecule called ferritin.75 Virtually all epidemiological (population) studies of vegans or ovo/lacto vegetarians show them to be either deficient or borderline iron deficient when blood ferritin levels are measured. Given this nearly unanimous finding from epidemiological studies, you might think that either the USDA or the ADA would become concerned and re-examine their endorsement of vegetarian diets. Unfortunately, we still live with governmental and institutional dietary recommendations that may do considerable harm to our health.

The most convincing type of experiments to reveal whether or not vegetarian diets may cause our iron stores to nosedive are called dietary interventions. Why not put a large group of non-vegetarians on a plant based diet for an extended period and see what happens to their blood iron levels? Wow what a great idea – unfortunately no such study has ever been conducted. The closest we have come to this experiment is a short term study (8 weeks) by Dr. Janet Hunt and co-workers at the Grand Forks Human Nutrition Research Center in North Dakota.63 The results of this experiment were anything but conclusive as the researchers made a fundamental blunder in the design of their experiment – they forgot to include a control group. Without a control group, it is impossible to interpret the outcome of this or any experiment.

Nevertheless, when women were placed on lacto/ovo vegetarian diets, their intestinal iron absorption was reduced by 70%; however, inexplicably, blood ferritin levels (a marker of their long-term iron status) did not decline for the group as a whole. It should be noted that nearly half of the subjects did experience drops in blood ferritin concentrations. Because the authors of this study failed to include a control group, then extraneous variables likely swayed the experiment’s outcome. You recall from earlier in this essay that vegetarian diets caused 7 out of 9 women to stop ovulating. With the cessation of menstrual periods, monthly blood loses also cease which in turn prevents monthly iron losses because blood is a rich source of iron. Hence, in any study evaluating blood iron stores in women, it is absolutely essential to know if their normal menstrual cycles were altered. Unfortunately, Dr. Hunt did not provide us with this information, thereby making the correct interpretation of her experiment difficult or impossible.

In order to once and for all know whether or not vegetarian diets cause iron deficiencies, we would need to perform Dr. Hunt’s experiment again, for at least a year with more subjects, a control group and monitor changes in menstrual periods. You would think that this kind of very basic experimental evidence would have already been in place before any governmental or institutional organization told us that vegetarian diets were safe and didn’t cause nutritional deficiencies. Unfortunately, these precautionary steps have never been taken, and millions of Americans who adhere to vegetarian diets with the mistaken belief that they will benefit health-wise will actually suffer.

Iodine Deficiencies in Vegetarian Diets

A number of studies have reported that vegetarian and vegan diets increase the risk for iodine deficiency.40, 77, 102, 153 One study from Europe demonstrated that 80% of vegans and 25% of ovo/lacto vegetarians suffered from iodine deficiency.77 Additionally, a dietary intervention by Dr. Remer and colleagues in 1999 confirmed this epidemiological evidence.102 After only five days on ovo/lacto vegetarian diets, iodine status and function became impaired in healthy adults.102 The primary reason why vegetarian diets cause iodine deficiencies is that plant foods (except for seaweed) are generally poor sources of iodine compared to meat, eggs, poultry and fish. Gross deficiencies of iodine cause our thyroid glands to swell producing a condition known as goiter, and in pregnant women result in severe birth defects called cretinism.141 Because salt is fortified with iodine, most people in the U.S. and Europe rarely develop gross iodine deficiencies.40, 140, 141 However moderate to mild iodine deficiencies appear in westernized countries, particularly among vegetarians and vegans.77, 102 Moderate iodine deficiency impairs normal growth in children and adversely affects mental development.140, 141, 152 A large meta analysis revealed that moderate childhood iodine deficiency lowered I.Q. by 12-13.5 points.153 Paleo Diets are not just good medicine for adults, but they also ensure normal physical and mental development in our children because of their high iodine content.

One of the problems with plant based diets is that they may put into play a vicious cycle that makes iodine deficiencies worse. When the thyroid glands iodine stores become depleted, as often happens with vegetarian diets, then certain antinutrients found in plant foods can gain a foot hold and further aggravate iodine shortages. Soy beans and soy products are frequently a mainstay in vegetarian diets and may promote inflammation.66 Unfortunately soy contains certain antinutrients (isoflavones) that impair iodine metabolism in the thyroid gland,43, 95 but only when our body stores of iodine are already depleted. Other plant foods (millet, cassava root, lima beans, sweet potatoes, and cruciferous vegetables [broccoli, cauliflower, turnips, kale, cabbage]) also contain a variety of antinutrients which hinder normal iodine metabolism. So, plant based diets put us at risk for developing iodine deficiencies in the first place, and when this happens our bodies become vulnerable to plant antinutrients that worsen the pre-existing deficiency. The important point here is that antinutritional compounds have virtually zero effect upon our thyroid gland when our body stores of iodine are normal and fully replete. Because meats, fish, eggs and poultry are rich sources of iodine, you will never have to worry about this nutrient when you eat Paleo style.

Vitamin D and Vitamin B6 Deficiencies in Vegetarian Diets

In my paper, Cereal Grains: Humanity’s Double Edged Sword, I have pointed out how excessive consumption of whole grains adversely affects vitamin D status in our bodies.148 Hence it goes without saying that vitamin D deficiencies run rampant in vegetarians worldwide because it is nearly impossible to become a full-fledged vegetarian without eating lots of grains. In the largest study of vegetarians ever undertaken (The Epic-Oxford Study), Dr. Crowe and fellow researchers reported that blood concentrations of vitamin D were highest in meat eaters and lowest in vegans and vegetarians.29 Nearly 8% of the vegans maintained clinical deficiencies of vitamin D. Vitamin D is not really a vitamin at all, but rather a crucial hormone that impacts virtually every cell in our bodies.

By now, you are starting to get a pretty good picture of what a nutritional nightmare vegetarian diets really are. When we let the data speak for itself, the number of nutrient deficiencies and adverse health effects associated with plant based diets are appalling and far outweigh any supposed health effects of this unnatural way of eating. One of the biggest kept secrets about vegan or vegetarian diets is that they frequently cause vitamin B6 deficiencies. If you recall, neither the ADA,28 nor the USDA142 has given us any warning that meatless diets increase our risk for vitamin B6 deficiencies.

On paper, it would appear that vegetarian diets generally meet daily recommended intakes for vitamin B6. This assumption comes primarily from population surveys examining the foods that vegans and vegetarians normally eat. In contrast, when blood samples are analyzed from people relying upon plant based diets, they unexpectedly reveal that long term vegetarians and vegans frequently are deficient vitamin B6. A recent study of 93 German vegans by Dr. Waldman and colleagues showed that 58% of these men and women suffered from vitamin B6 deficiencies despite seemingly adequate intakes of this essential nutrient.131 It turns out that the type of vitamin B-6 (pyridoxine glucoside) found in plant foods is poorly absorbed.47, 103 The presence of pyridoxine glucoside in plant foods along with fiber has been reported to reduce the bioavailability of vitamin B6 so that only 20 to 25% is absorbed and completely utilized.47 In contrast, vitamin B6 found in animal foods is easily assimilated, and an estimated 75 to 100% fully makes its way into our bloodstreams.47

Compelling evidence that vegetarian diets relying upon the plant form of vitamin B6 adversely affect our body’s overall vitamin B6 stores comes from Dr. Leklem’s laboratory at Oregon State University.47 Nine women were put on diets either high or low in the plant form of vitamin B6 (pyridoxine glucoside). After only 18 days, the high pyridoxine glucoside diets consistently lowered blood concentrations and other indices of vitamin B6 status. Deficiencies in this vitamin elevate blood homocysteine concentrations and increase our risk for cardiovascular disease similar to shortages of folate and vitamin B12. Further, vitamin B6 is an important factor in normal immune system functioning149 and shortfalls of this crucial nutrient have been identified in depression150 and colorectal cancer.151

Omega 3 Fatty Acid Deficiencies in Vegetarian Diets

A few years ago I was involved in a series of experiments here at Colorado State University in which we were interested in determining how high and low salt diets affected exercise-induced asthma. Our working hypothesis was that high salt diets would make measures of lung function worse, and low salt diets would improve things. One of our concerns with this experiment was to somehow make sure our subjects had fully complied with either the high or low salt diets. Completely removing salt from your diet is not an easy thing to do, and if some of our subjects had decided to sneak in a piece of pizza or some Doritos, it would mess up the experiment’s outcome. Fortunately, there was an easy way to figure out if our subjects had been compliant with the prescribed diets. All we had to do was to spot check their urine, because measurement of urinary salt levels is an accurate gauge of dietary salt consumption. High urinary salt levels universally reflect high salt consumption, whereas low urinary salt concentrations indicate low salt consumption. Short of major disease, there is virtually no other way high amounts of salt in the urine don’t indicate high amounts of salt in the diet.

In a similar manner, there are equivalent telltale indicators of omega 3 fatty acids in our bloodstreams that tell us beyond a shadow of a doubt whether or not we have regularly consumed fish, seafood or other good sources these healthful fats. The three main types of omega 3 fatty acids we need to concern ourselves with are EPA, DHA and ALA. EPA and DHA are called long chain omega 3 fatty acids and are only found in high amounts in fish, seafood, certain meats, and other foods of animal origin. Plant foods contain no EPA or DHA. On the other hand, ALA is called a short chain fatty acid and is found in both plant and animal foods. Both EPA and DHA in our red blood cells are markers of these important fatty acids in our diet. Without good dietary sources of EPA and DHA such as are found in fish, seafood and certain meats, our blood levels of EPA and DHA will decline. Just like salt in our urine was an indicator for dietary salt, EPA and DHA concentrations in our red blood cells are markers for our dietary intake of these long chain omega 3 fatty acids. It is virtually impossible to achieve high blood levels of EPA and DHA without regularly consuming fish, seafood and certain meats and organ meats (particularly grass produced meats and organ meats).

One of the major nutritional shortcomings in vegans is that they obtain absolutely no EPA or DHA from their diets.108, 110, 111 Consequently, they are totally dependent upon plant based ALA, supplements or fortified foods to obtain these healthful long chain omega 3 fatty acids. Without supplements or fortified foods, all vegans will become deficient in EPA and DHA because plant based ALA is inefficiently converted into these long chain fatty acids in our bodies. The liver converts less than 5% of ALA into EPA and less than 1% of ALA into DHA.15, 97 Virtually every epidemiological study that has ever been published shows that vegans, who do not supplement or consume long chain omega 3 fortified foods, to be deficient in both EPA and DHA76, 88, 108, 110, 111 Lacto/ovo vegetarians don’t fare much better because milk and egg based vegetarian diets simply do not supply sufficient DHA or EPA to maintain normal blood concentrations.88, 111

There is little doubt that vegan or vegetarian diets cause reductions in blood concentrations of DHA and EPA, which in turn represent a potent risk factor for many chronic diseases. Perhaps the single most important dietary recommendation to improve your health and prevent illness is to increase your dietary intake of EPA and DHA. Thousands of scientific papers covering an assortment of diseases clearly show the health benefits of these fatty acids. In randomized clinical trials in patients with pre-existing heart disease, omega-3 fatty acid supplements significantly reduced cardiovascular events (deaths, non-fatal heart attacks, and non-fatal strokes).19, 48, 138 Omega-3 fatty acids lessen the risk for heart disease through a number of means including a reduction in heart beat irregularities called arrhythmias, a decrease in blood clots, and reduced inflammation which is now known to be an chief factor causing atherosclerosis or artery clogging.

In addition to lowering the risk for heart disease, regular consumption of fish or supplemental omega-3 fatty acids may be useful in averting, treating, or improving a wide range of diseases and disorders, including virtually all inflammatory diseases (any disease ending with “itis”): rheumatoid arthritis,99 inflammatory bowel disorders (Crohn’s disease, ulcerative colitis), periodontal disease (gingivitis). Also mental disorders (autism, depression),3, 84 postpartum depression, bi-polar disorder, borderline personality disorder, impaired cognitive development in infants and children) may respond favorably to these beneficial fatty acids. Further, acne, asthma, exercise induced asthma, many types of cancers,120 macular degeneration, pre-term birth, psoriasis, insulin resistance, type 2 diabetes, cancer cachexia, intermittent claudication, skin damage from sunlight, IgA nephropathy, lupus erythematosus, type 1 diabetes, multiple sclerosis, and migraine headaches also improve with omega 3 fatty acids.

Taurine deficiencies in Vegetarian Diets

Although the number of nutrients which are frequently lacking in vegetarian and vegan diets may seem endless to you, we are now at the end of the list. Taurine is an amino acid (actually a sulfonic acid because it lacks a carboxyl group) in our bloodstreams that has multiple functions in every cell of our body. Unfortunately, this nutrient is not present in any plant food and is found in low concentrations in milk (6 mg per cup).80 In contrast, all flesh foods are excellent sources of taurine.80 For example, ¼ pound of dark meat from chicken provides 200mg of taurine. Shellfish are even richer still with over 800mg per quarter pound. The daily taurine intake in non-vegetarians is about 150mg, whereas lacto/ovo vegetarians take in about 17mg per day, and vegans get none. Although our livers can manufacture taurine from precursor molecules, our capacity to do so is limited – so much so that this amino acid is regularly fortified in infant formulas. As you might expect, studies of vegans show that their blood taurine levels are lower than meat eaters.81, 100 How depleted blood concentrations of taurine affect our overall health, is not entirely understood. Nevertheless, shortages of this amino acid and omega 3 fatty acids (EPA and DHA) may cause certain elements (platelets) in our blood to clot more rapidly which in turn increase our risk for cardiovascular disease.85, 91 Despite their meat free diets, vegetarians almost always exhibit abnormal platelets that excessively adhere to one another. In one dietary intervention, Dr. Mezzano and colleagues demonstrated that after eight weeks of EPA and DHA supplementation normal platelet function was restored in a group of 18 lacto/ovo vegetarians.85 Obviously, compromised taurine status will never become a problem in Paleo Diets, because meat, fish, poultry and animal products are consumed at nearly every meal.

In summary, if you have adopted, or are considering adopting a plant based diet for reasons of improving your health, make sure you reread this chapter and look up all of the references I have provided you. The evidence that vegetarian and vegan diets almost always cause a multitude of nutritional deficiencies is overwhelming and conclusive. Over the course of a lifetime, vegetarian diets will not reduce your risk of chronic disease and will not allow you to live longer. Rather, this abnormal way of eating will predispose you to a host of health problems and illnesses. Vegetarianism is an unnatural way of eating that has no evolutionary precedence in our species. No hunter-gatherer society ever consumed a meatless diet, nor should you. The ADA has labeled The Paleo Diet a fad diet because it eliminates “two entire food groups” (grains and dairy). Yet hypocritically, they exempt vegan diets from this characterization despite also eliminating two food groups (dairy, meats and fish). If The Paleo Diet is a fad diet, then it is the world’s oldest.


Loren Cordain, Ph.D., Professor Emeritus


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About Loren Cordain, PhD, Professor Emeritus

Loren Cordain, PhD, Professor EmeritusDr. Loren Cordain is Professor Emeritus of the Department of Health and Exercise Science at Colorado State University in Fort Collins, Colorado. His research emphasis over the past 20 years has focused upon the evolutionary and anthropological basis for diet, health and well being in modern humans. Dr. Cordain’s scientific publications have examined the nutritional characteristics of worldwide hunter-gatherer diets as well as the nutrient composition of wild plant and animal foods consumed by foraging humans. He is the world’s leading expert on Paleolithic diets and has lectured extensively on the Paleolithic nutrition worldwide. Dr. Cordain is the author of six popular bestselling books including The Real Paleo Diet Cookbook, The Paleo Diet, The Paleo Answer, and The Paleo Diet Cookbook, summarizing his research findings.

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“11” Comments

  1. Also, you can get vegan long chain omega 3’s through algae oil capsules or echium seed oil capsules. These are vegan sources without the mercury worries. It’s nice to educate people, but always be truthful and fair to both sides.

  2. Vitamin D should be obtained through exposure to sunlight. As you mentioned, it’s really a hormone, and unless you get enough sun or eat products fortified with vitamin D you will probably be deficient regardless of your diet. Cod liver oil is a good source of vitamin A and D, but again it is a supplement. I’ve been a meat eater my entire life and especially have enjoyed many steaks, yet I was always chronically deficient when tested before supplementing or taking cod liver oil. I stay out of the sun because I burn easily, so that’s the main reason.

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  6. I disagree completely. Regardless – even if what you say is correct ( I am highly dubious as my health has improved significantly on a gluten free vegan diet) I ethically cannot eat another living creature and would accept a few minor health issues. Plant based it the way to go! Read the Thrive Diet by Brendan Brazier for plant based raw foods that do help improve overall health!

    • Dear cturner,

      I agree and disagree with your comment.
      Why I agree:
      – For some people, being vegetarian is the way to go for better health
      – For the planet, I shudder to think what would happen to this earth in terms of sustainability if everyone decides to eat more meat and animal products given that animal agriculture is one of the largest emitters of CO2.
      Why I disagree:
      – As a former vegetarian, I disagree that everyone benefits from a vegetarian diet. Actually I also disagree that everyone benefits from a Paleo diet too. I am medically trained and also a scientific researcher and I was absolutely well educated about how to do a vegetarian diet well and how to ensure adequate nutrients. I became a vegetarian (after years of eating very little meat anyway) after a period of great personal stress. It felt like the right decision for my health and for the planet (I am also an environmental activist). Unbeknown to me, the adrenal fatigue I was suffering from was not helped by the vegetarian diet. I felt worse and worse despite I exercised regularly, meditated etc etc. I also suffered from unexplained infertility (I only started to conceive after I went on diet). A month ago, I started feeling absolutely rotten…the vitamin B12 supplementation was giving me awful acne breakouts, that I started doing more research into my diet. I found out that different people may have a different requirement for meat or vegetables..that unfortunately my type required meat for optimum functioning. It was difficult to begin eating animals again, but for my health, I had to try and I started with sardines. Within days my body felt much better and my acne began to clear. So my advice to the world: find out what your body needs…and be a responsible consumer. Be thankful for what you eat (like all native tribes who consume animals responsibly), and know that our very own existence here on earth causes harm (even plants are intelligent). There is a delicate balance on this earth, and no one size fits all. Some may thrive on a vegetarian diet, and others on animal protein. It’s in your genetics and you can only thanks or blame your ancestors for it.

      • “It’s in your genetics and you can only thanks or blame your ancestors for it”

        Oh, it is? Is this why our stomach bacteria manufactures TMAO when it comes into contact with animal flesh? Seems like nature messed up big time.

        No, we are not designed to eat meat, unless getting heart disease from TMAO is your idea of evolution.

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