There is simply no expert that would disagree with the observation that most people do not eat enough vegetables, let alone high-quality organic ones.

So it makes perfect sense that individuals who consume more vegetables are likely to be healthier.

Most Americans also eat far too much low-quality protein and non-vegetable carbohydrates (i.e. grains), which likely accounts for most of the difference seen when comparing vegetarian to non-vegetarian diets.

But that does not justify excluding all animal products for the sake of health.

Previous research1 has demonstrated that people who eat a strictly plant-based diet may suffer from subclinical protein malnutrition, which means you’re also likely not getting enough dietary sulfur.

By eliminating all animal foods you also run the very real risk of a number of other nutrient deficiencies, as some simply cannot be obtained from plant foods.

The featured article by Authority Nutrition2 lists seven such nutrients you need to make sure you’re taking in supplement form should you decide to adopt a strict plant-based diet.

In addition to those seven, I also address the issue of sulfur deficiency, which is one of the lesser-recognized hazards of a diet devoid of animal foods.

Vitamin B12

In terms of health risks from eating a vegetarian or vegan diet, most people think of vitamin B12 deficiency, as vitamin B12 (cobalamin) is present in natural form only in animal sources of food, such as meat, fish, dairy products, and eggs.

Vitamin B12 is known as the energy vitamin, and your body requires it for a number of vital functions. Among them: energy production, blood formation, DNA synthesis, and reproductive health.

Studies3 suggest one in four American adults is deficient in this vitally important nutrient, and nearly two-fifths or more of the population has suboptimal blood levels. Also, the older you get the more likely you are to have a vitamin B12 deficiency.

The two ways you become deficient are through a lack of vitamin B12 in your diet, or through your inability to absorb it from the food you eat. As noted in the featured article,4 signs and symptoms of vitamin B12 deficiency include:

  • Weakness and fatigue
  • Impaired brain function
  • Megaloblastic anemia

Health risks associated with this deficiency include neurological and psychiatric disorders, including Alzheimer’s disease, and an increased risk of heart disease.

If you’re a strict vegan, you have a couple of options. Nori seaweed naturally contains small amounts of bioactive B12, as does tempeh, which is fermented soy. If you don’t eat these foods on a regular basis, you need to take a vitamin B12 supplement.

As noted in the featured article (which includes scientific references):

“Nori seaweed is considered the most suitable source of biologically available vitamin B12 for vegans. Keep in mind that raw or freeze-dried nori may be better than conventionally dried. It seems that some of the vitamin B12 is destroyed in the drying process.

Another plant food often claimed to contain vitamin B12 is spirulina. However, spirulina contains so-called pseudovitamin B12, which is not biologically available. For this reason, it is not suitable as a source of vitamin B12.”

Oral B12 is notoriously ineffective due to the fact it requires intrinsic factor in order to be absorbed. Intrinsic factor is a glycoprotein that mediates gastrointestinal absorption of vitamin B12 in your small intestine. It selectively absorbs only active vitamin B12 from naturally occurring vitamin B12 compounds.

As a result, the effectiveness of eating nori seaweed or taking an oral B12 supplement has been questioned. When it comes to supplementation, you want to look for a sublingual version rather than pill form. But just how bioavailable is nori seaweed?

Animal research published in the British Journal of Nutrition5 sought to clarify the bioavailability of vitamin B12 in nori, and found that it contains five different types of biologically active vitamin B12 compounds (cyano-, hydroxo-, sulfito-, adenosyl-, and methylcobalamin).

Vitamin B12 coenzymes (adenosyl- and methylcobalamin) comprise about 60 percent of the total vitamin B12 content. Results of the experiment showed that the B12 in nori seaweed was in fact bioavailable — at least in rats.

Research6 published last year also concluded that nori seaweed appears to be the most suitable vitamin B12 source available to vegetarians.

While a number of processed foods are enriched with B12, I don’t recommend adding more of these to your diet. Enriched breakfast cereal and bread, for example, have the potential to drive your health in the wrong direction by promoting insulin resistance, even though you might get some B12 from it.


Creatine is an amino acid found in animal foods that is important for muscle energy, proper function of your central nervous system, and brain health.

A trio consisting of creatine, animal-based omega-3 fats, and Coenzyme Q10 are also essential for proper mitochondrial function, and insufficiencies of these may play a role in multiple sclerosis (MS) and other nerve degenerative disorders.

As noted in the featured article:

“Creatine is not essential in the diet, since it can be produced by the liver. However, vegetarians have lower amounts of creatine in their muscles. Placing people on a lacto-ovo vegetarian diet for 26 days causes a significant decrease in muscle creatine.

Because creatine is not found in any plant foods, vegetarians and vegans can only get it from supplements.”


Carnosine is a dipeptide composed of two amino acids: beta-alanine and histidine. It’s a potent antioxidant, the highest concentrations of which are found in your muscles and brain.

If you’re a vegetarian, you will have lower levels of carnosine in your muscles. This is one reason why many strict vegans who do not properly compensate for this and other nutritional deficiencies tend to have trouble building muscle.

Carnosine itself is not very useful as a supplement as it is rapidly broken down into its constituent amino acids by certain enzymes. Your body then reformulates those amino acids back to carnosine in your muscles.

A more efficient alternative is to supplement with its primary precursor, beta-alanine, which appears to be the rate limiting amino acid in the formation of carnosine.

Foods containing beta-alanine, such as meat and fish, are also known to efficiently raise carnosine levels in your muscle, and studies7,8 looking at increasing athletic performance with carnosine have found beta-alanine to be far more effective of the two.

Vitamin D3

Vitamin D is a steroid hormone that you get primarily from sun exposure and certain foods. Vitamin D is involved in the biochemical cellular machinery of all cells and tissues in your body. It also influences your genetic expression, and in recent years, the importance of vitamin D sufficiency for optimal health and chronic disease prevention has become increasingly well recognized.

As revealed in a recent interview with vitamin D researcher Dr. Robert Heaney, while sun exposure is the primary and likely ideal way to get your vitamin D, researchers are also finding that a number of foods contain vitamin D3 (cholecalciferol) in biologically meaningful quantities.

An educated guess is that the average adult living in the central part of the US gets about 1,500-2,000 international units (IUs) of vitamin D3 from food — primarily meats, fatty fish, and egg yolks. Vitamin D2 (ergocalciferol) is found in plants, but the D3 found in animal foods is more potent, and more efficiently raises blood levels of bioactive vitamin D.

However, even if you ate animal foods you would most likely be similar to about 90 percent of the population and also be deficient in vitamin D. It is the rare individual who can achieve optimal vitamin D3 levels without supplementation, especially during the winter.  Supplementation in this instance could also include tanning with an appropriate bed.

Since most of your vitamin D is produced when your skin is exposed to sunlight, shunning animal foods does not equate to a direct threat of vitamin D deficiency. However, if you’re also shunning the sun then it would definitely be wise to consider a vitamin D3 supplement, as deficiency is virtually guaranteed. When supplementing, keep the following considerations in mind:

  1. Use supplemental vitamin D3, not D2. They are not interchangeable, and vitamin D2 may do more harm than good when taken as a supplement
  2. Increase your vitamin K2 concomitant with D3. They work in tandem to slow arterial calcification, and vitamin K2 deficiency is actually what produces the symptoms of vitamin D toxicity, which includes inappropriate calcification that can lead to hardening of your arteries
  3. It’s important to maintain balance between vitamin D, vitamin K2, calcium, and magnesium. Lack of balance between these nutrients is why calcium supplements have become associated with increased risk of heart attack and stroke

Animal-Based Omega-3 DHA

Docosahexaenoic acid (DHA) is an essential omega-3 fat found in marine animals such as fish and krill. It’s important for normal brain function and heart health, and pregnant women who are deficient in DHA also place their children at increased risk for developmental problems.

As noted in the featured article:  “In the body, DHA can also be made from the omega-3 fatty acid ALA, which is found in high amounts in flaxseeds, chia seeds, and walnuts. However, the conversion of ALA to DHA is inefficient. For this reason, vegetarians and vegans are often lower in DHA than meat eaters.”

Most of the health benefits linked to omega-3 fats are linked to the animal-based EPA and DHA, not the plant-based ALA.

That said, plant-based omega-3 fats are NOT inherently harmful and should by no means be avoided. Ideally, you’d get a combination of both. For example, you could combine flax and hemp in your diet with an animal-based omega-3 in the form of krill oil, which has an antioxidant potency that is 48 times greater than fish oil. From an environmental perspective, krill harvesting is also a far more sustainable and eco-friendly choice compared to fish oil.


Iron is found in both plant and animal foods, but the type of iron differs. Heme-iron is found only in meat, primarily red meat. Non-heme iron is found in plants, but this type of iron is more poorly absorbed by your body. Moreover, heme-iron helps with the absorption of non-heme iron from plants, so vegans and strict vegetarians have an elevated risk of anemia, even though they’re getting plant-based iron.

Iron serves many functions in your body, but one of the most important is to bind to the hemoglobin molecule and serve as a carrier of oxygen to your tissues. Without proper oxygenation, your cells quickly start dying. So anemia is not to be taken lightly. If you have iron deficiency anemia, the best source of iron is high-quality red meat, preferably grass-fed and organic. The fact that a vegetarian diet is low in iron may be a phenomenal and good thing if you are an adult male or postmenopausal woman, as both of these groups need far less iron and a significant percentage actually have too much iron. So unless you are a premenopausal woman or child or have iron deficiency from a recent or chronic blood loss, then you likely don’t need to be at all concerned about iron supplementation.

If you do need supplementation, then a strong word of caution is in order. Ferrous sulfate, a form of iron found in many multivitamins, is a relatively toxic inorganic metal that can lead to significant problems. A safe form of supplement is carbonyl iron. To the best of our knowledge, there have been no reported overdoses from carbonyl iron. (However you should still keep any and all iron supplements away from children.)


Taurine is another dietary component that appears to play an important role in brain and heart health. It’s also important for muscle function, bile salt formation, and antioxidant defenses. Together with magnesium, it has a calming effect on your body and mind. Taurine is a byproduct of the sulphurous amino acids cysteine and methionine (technically a sulfonic acid), and is only found in animal foods.

Examples include seafood, red meat, poultry, and dairy products. It’s also available in supplement form. According to the featured article:

It is not essential in the diet since small amounts are produced by the body. However, dietary taurine may play a major role in the maintenance of taurine levels in the body. Levels of taurine are significantly lower in vegans than in meat eaters.”


Which brings us to sulfur.. Sulfur is derived almost exclusively from dietary protein, such as fish and high-quality (organic and/or grass-fed and pastured) beef and poultry. Meat and fish are considered “complete” as they contain all the sulfur-containing amino acids you need to produce new protein. When you abstain from animal protein you significantly increase your risk of sulfur deficiency and related health problems.

Also keep in mind that if you’re a vegetarian who relies on grain-heavy processed foods in lieu of animal protein, you’re likely not getting the sulfur you need because sulfur is lost during the processing.

Sulfur plays a vital role in the structure and biological activity of both proteins and enzymes. If you don’t have sufficient amounts of sulfur in your body, this deficiency can cascade into a number of health problems, as it can affect bones, joints, connective tissues, metabolic processes, and more. According to Dr. Stephanie Seneff, a senior scientist at MIT, areas where sulfur plays an important role include:

  • Your body’s electron transport system, as part of iron/sulfur proteins in mitochondria, the energy factories of your cells
  • Vitamin-B thiamine (B1) and biotin conversion, which in turn are essential for converting carbohydrates into energy
  • Synthesizing important metabolic intermediates, such as glutathione
  • Proper insulin function. The insulin molecule consists of two amino acid chains connected to each other by sulfur bridges, without which the insulin cannot perform its biological activity
  • Detoxification

One 2012 study9 concluded that the low intake of sulfur amino acids by vegetarians and vegans explains the origin of hyperhomocysteinemia (high blood levels of homocysteine, which may lead to blood clots in your arteries — i.e. heart attack and stroke) and the increased vulnerability of vegetarians to cardiovascular diseases. If you don’t eat meat you can get sulfur from coconut oil and olive oil.

Other plant-based sources that contain small amounts of sulfur — provided the food was grown in soil that contains adequate amounts of sulfur — include wheat germ, legumes, garlic, onions, Brussels sprouts, asparagus, and kale. As for supplements, methylsulfonylmethane, commonly known by its acronym MSM, is an option. MSM is an organic form of sulfur and a potent antioxidant, naturally found in many plants.

Your Body Needs Animal-Based Foods

I know that a large number of individuals disagree with this statement but that is my belief after 30 years of practicing nutritional medicine. Interestingly, the average vegetarian is far healthier than the average American, most likely due to them eating far more vegetables and avoiding many processed foods. However, this is not a justification to avoid all animal foods. While I certainly would never argue with anyone for avoiding animal foods for ethical reasons, I would for health reasons.  It is possible to avoid some of the deficiency syndromes that result from choosing to avoid animal foods by following the recommendations above.

Remember, “animal-based foods” are not restricted to just meats. While I do believe that grass-fed and finished organic meats can be quite healthy when they’re cooked properly (avoiding charring is important), I don’t believe that everyone needs to eat meat to stay healthy. You also do not need large amounts of meat. In fact most Americans eat far more than they need for optimal health, which has its own set of health risks.

If you don’t want to eat meat, there are plenty of other animal-based foods you can include in your diet, such as mercury-free fish or seafood, free-range eggs, raw dairy products, and omega-3 fats from krill. Such products, when obtained from humane sources such as organic farms where the animals are free to roam and eat their natural diet, do not need to be avoided for animal-rights or other moral reasons, as the animals are not harmed by providing milk and eggs. Meanwhile, they provide many important nutrients also found in meat.

If you’re convinced a vegan diet is right for you, then at bare minimum consider a program of supplementation to get the nutrients you can’t get from your diet. Bear in mind that the ones included in this article are just some of the ones we’re aware of. Calcium and iodine deficiencies are also common among strict vegans, for example, and there may be other nutrients in animal foods that we’re still ignorant of that you’ll miss out on if you avoid all animal-based foods.

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