by Artin Entezarjou, M.D. and Ph.D. Student
Co-Founder of EBT – Evidence Based Training.
When people ask if vegetarian diets are “good,” the first thing that needs to be considered is “good for what and for who?” Depending on what outcome you look at, you can reach different conclusions as to whether a vegetarian diet is suitable. Apart from muscle gains and performance, there are many other outcomes that can make a diet “good” or “bad.” Many vegans are motivated by ethical reasons, wanting to reduce animal suffering, while others are motivated by improving sustainability and reducing the environmental impact of their diet (47). Indeed, red meat diets release 160-250% more CO2 than a corresponding vegan diet, depending on how much meat is consumed (46). You don’t need to give up meat completely though, as simply cutting back meat consumption to low levels will make your diet environmentally sustainable. Ethically, there is also much to be said, but that is a topic for another article.
Today, we will focus on how the vegetarian diets impact HEALTH. Particularly, what athletes need to consider when on a plant-based diet. We will break down the differences between plant and animal protein, micronutrient considerations, and potential supplements that can be of benefit. The goal is to give concrete advice on food choices, doses, and supplements that can allow a vegetarian or vegan athlete to perform optimally.
Before jumping into this topic, it is a good idea that you understand the limitations of doing studies on diets. Therefore, we recommend you read our Science Guide on the Problem with Diet Research.
Another point that needs to be addressed is that there is no universal “vegetarian diet.” Diets can vary considerably, and a vegetarian diet in Southeast Asia may not at all be the same as a vegetarian diet in the U.S. (20). What they all have in common is that they restrict meat consumption to some degree. In order of most restrictive to least restrictive, variations of the vegetarian diet include:
- Veganism: The strictest vegetarian diet. Excludes ALL animal products from the diet, including food products derived from animals (for example: milk, eggs, and in some cases honey). Some vegans even avoid using animal products made from leather or wool and avoid plants that are not organically grown.
- Lacto Vegetarianism: “Lacto” means “dairy,” and this variation thus includes milk products, but no eggs or meats of any kind (fish, poultry or red meat).
- Lacto-Ovo Vegetarianism: “Ovo” means “egg,” which is why egg products, but no meat, is included in this vegetarian variation.
- Pesco-Vegetarianism: Are similar to lacto-ovo vegetarians, but also eat fish and crustaceans.
- Semi-Vegetarianism or “flexitarianism”: Occasionally consume meat, but try to choose vegetarian options when possible. Some flexitarians exclude red meat completely, but still eat chicken and fish.
Now that we’ve covered the basics, let’s jump into various health outcomes!
VEGETARIAN DIETS & HEALTH
As the debate rages on as to how vegetarian diets impact our health, I found loads of research looking at various health outcomes (26-35). Let’s look into it!
Do Vegetarians Live Longer?
The most obvious health outcome we can look at is death. If a diet is healthier, it should also result in a longer life. If just comparing vegetarians as a group to non-vegetarians in observational studies, vegetarians do indeed live longer, with a 12% lowered risk of dying from any cause compared to non-vegetarians, BUT vegetarians also tend to have a higher education, exercise more, sleep more, smoke less, and drink less alcohol (21). This means that when comparing vegetarians to non-vegetarians, we are also comparing highly educated, physically active, non-smokers to less educated, less active smokers. This issue of so-called confounding factors in observational studies is discussed elsewhere, but it makes it difficult for us to know if vegetarians live longer because of their diet or because of their lifestyle.
In fact, if we use mathematical models to “adjust” for lifestyle differences between vegetarians and non-vegetarians, it turns out that the vegetarian diet doesn’t make us live longer. A 2017 meta-analysis looking at observational data from 130,000 vegetarians and 15,000 vegans, comparing them to a control group of non-vegetarians, reached this conclusion (19). So did another meta-analysis looking at cancer and heart disease among vegetarians (24).
So while the overall lifestyle adopted by vegetarians helps them live longer, the vegetarian diet itself cannot get all the credit for those benefits.
Do Vegetarian Diets Reduce Inflammation?
Inflammation is the new demonic cause of all disease, according to popular media. The truth is, we NEED inflammation to heal wounds and fight disease, but TOO MUCH inflammation over a long time can cause issues. Inflammation is essentially the body’s immune system concentrating its forces in one location. We doctors deal with patients with inflammation daily. There are several ways of measuring inflammation; clinically, we use the biomarker C-reactive protein (CRP) to do this. High CRP indicates that the body has activated inflammatory processes, but says nothing about the CAUSE of the inflammation, which can be due to trauma, infection, or chronic disease.
A meta-analysis looking at the correlation between vegetarian diets and CRP levels found that people who followed a vegetarian diet for more than 2 years had lower CRP levels compared to non-vegetarians, with a small to medium effect size (Hedges’ g= -0.29) (22). Being vegetarian for less than 2 years is NOT associated with lower inflammation levels. The actual impact of having slightly lower CRP levels on health is unclear.
Vegan diets might reduce pain and stiffness in patients with certain diseases where inflammation is high (RCA-score in rheumatoid arthritis), but this effect is seen from other diets too, like the Mediterranean diet, which includes meat (23).
So yes, vegetarian diets do reduce inflammation, but only if you stick to a vegetarian diet for at least 2 years. Once again, this is observational evidence, so the reduced inflammation could simply be a result of the vegetarian lifestyle. Perhaps the rich amounts of fruits, vegetables, fiber, low levels of saturated fat, and low-calorie intake cause the improved symptoms in disease and reduced inflammation.
Vegetarian Diets for Weight Loss?
Since, weight loss occurs relatively quickly, effects can be seen in experimental studies. We’ll look at a meta-analysis of 12 randomized controlled trials (RCTs) with a total of 1,151 subjects, comparing vegetarian diets to a control diet (25). Studies included in the analysis lasted from 9 to 74 weeks, but none lasted more than 18 months, meaning that we can’t use these experimental studies to draw conclusions on the long-term effects of vegetarian diets when it comes to weight and associated diseases like heart disease.
When it comes to weight loss, however, the meta-analysis concluded that people given a vegetarian diet lose more weight by, on average, 2kg (4.4lb) compared to control groups. As with most diets, the lost weight seems to be regained over time to some extent, with studies lasting more than 1 year reporting 1.1kg (2.4lb) additional weight loss in vegetarians compared to controls.
The type of vegetarian diet seems to matter, with vegan diets doing even better with an average weight loss of 2.5kg (5.5lb) more compared to controls, while lacto-ovo vegetarians lost around 1.5kg (3.3lb) more than controls.
Participants in diet studies usually can’t be “blinded,” and in this analysis, participants knew what diet they were getting in 11 of the 13 included studies. In some studies participants were given prepared food, while in others, they were merely told to change their diets. As expected, compliance in the latter groups was in some cases only 51%, meaning that many participants didn’t stick to the diets they were assigned.
Being part of a dieting study will in itself make you more likely to lose weight, and some studies even made sure that participants were in a caloric deficit, obviously resulting in more weight loss (2.2kg more than controls). In reality, we are interested in how a vegetarian diet affects weight WITHOUT counting calories, and average weight loss in studies where people didn’t count calories was 1.7kg (3.7lb) more among vegetarians compared to control diets.
So YES, experimental evidence suggests that vegetarian diets seem to be a good option for people who want to lose weight, and observational studies are in agreement with this finding, making it very likely to be true.
For athletes and bodybuilders looking to cut, however, it is important to keep in mind that this meta-analysis doesn’t give us data on body composition, so we don’t know the TYPE of weight that was lost: Fat? Muscle? Water? Therefore, people who want to preserve muscle during a vegetarian cut should make sure that they are getting enough protein. This and details on other macros and micros is what the next section will deal with.
DIETARY ADVICE TO VEGETARIAN ATHLETES
Athletic Performance in Vegetarians
If, as an athlete, you decide to go vegetarian, impacts on athletic performance are of interest, be it strength, power, or endurance. The question is then if and how a vegetarian diet affects athletic performance. A 2015 review tried to answer this question but could only find 8 experimental studies on the topic. Studies were short term (lasting around 12 weeks) and compared vegetarian diets with non-vegetarian diets for strength or cardio performance. The studies varied greatly in their design and outcome measures, making it hard to draw any general conclusions. Still, none of the studies found a difference between vegetarians and non-vegetarians on athletic performance after around 12 weeks on either diet (36).
There could still be significant effects on a LONG-TERM vegetarian diet, as most people follow these diets for longer than 12 weeks. Since research is limited, the next best thing to do is to look at dietary differences between vegetarian and non-vegetarian diets and SPECULATE which differences might affect athletic performance. The next section will break down the results of a review of the literature with such speculations, and unless we make other references, most claims below come from this review (37).
Keep in mind that there are some ASSUMPTIONS made; thus, these recommendations are likely to change as we get more solid research on the topic. The study looks at potential recommendations to both vegan and vegetarian athletes.
Protein in Vegan & Vegetarian Diets: How Good is it for Building Muscle?
Plant-based protein sources are generally considered less anabolic than protein from animal sources, (15) but how much truth is there to this claim?
Protein Basics: Amino acids, BCAA, and EAA!?
Let’s quickly review the basics. The two most important dietary factors for building muscle are getting enough calories and getting enough protein in your diet (56). As you know, proteins are made of 20 amino acids, 9 of which aren’t made in our bodies, meaning that we need them in our diet (a.k.a. the EAAs). Three of the EAAs are known as branched chain amino acids (BCAAs) and have a particularly important role in protein metabolism. About a third of the protein in your muscles is made of BCAAs (7).
Muscle mass is, in theory, built when muscle protein synthesis (MPS) is greater than muscle protein breakdown. When it comes to stimulating MPS, EAAs as a group do it best, but mostly due to the BCAAs, and particularly the amino acid leucine (6). In your cells, leucine has been shown to activate the main signal for MPS, known as mTORC1 (mammalian target of rapamycin complex 1) (17). Long term, however, there doesn’t seem to be a big difference between BCAAs and EAAs ability to stimulate MPS. (5, 6)
To maximize MPS after a meal, it is estimated that you need around 2-3 g of leucine, or up to 0.05 g/kg bodyweight (2, 3, 4). This is known as the “leucine threshold.” This threshold is important if you want to understand the differences seen between plant and animal protein when it comes to building muscle.
Plants, Leucine, and Muscle Protein Synthesis
Plant-based proteins contain around 6–8% leucine, while animal-based proteins contain about 8–11% leucine (1). At low protein doses (10% of calories), animal protein stimulates MPS better than plant protein. However, at higher doses (30% of calories), there is no difference between the two, since both plant and animal-based protein will then give you enough leucine to reach the leucine threshold and maximize MPS (8). Adding leucine to a plant-based protein diet makes MPS rates similar to animal-based diets (9, 18).
Comparing MPS four hours after eating 0g, 5g, 10g, 20g, and 40g of egg protein after exercise, MPS was maximally stimulated with 20g of egg protein (1.7g leucine). Doubling protein to 40g (3.4g of leucine), made no significant differences. (10, 11).
In older men who don’t exercise, 35g wheat protein (2.5g leucine) had less of an impact on protein synthesis than 35g of casein (3.2g leucine), even though both lead to similar max levels of leucine in the blood (16). Interestingly, in this study, 35g whey protein (4.4g leucine) had less of an impact on MPS than 35g of casein (3.2g leucine)!
The same study equalized leucine levels by comparing 35g whey protein (4.4g leucine) to 60g wheat protein (4.4g leucine). 35g of whey lead to higher leucine levels in the blood, but 60g of wheat protein raised MPS more (!) and raised amino acid levels in the blood for longer (not surprising given that 60g of protein contains more amino acids than 35g).
The studies above show that leucine ALONE is not what stimulates MPS and since both doses were above the leucine threshold, other factors play a role in increasing MPS; other amino acids in the protein and how long amino acid levels are elevated in the blood also matter.
So we can see that as the amount of protein consumed increases, relative leucine content becomes less important. It is important to remember that the findings of the studies above are based on SUPPLEMENTS, which are generally absorbed much more effectively than whole foods. For example, only 45% of whole wheat protein is fully digested, compared to >90% protein digestibility in wheat protein isolate (16).
What About Studies Measuring Muscle Mass and Not MPS?
MPS is a great tool for measuring potential gains in short-term studies. The problem is that it doesn’t always consider muscle protein breakdown, and so, maximizing MPS is not necessarily the same as maximizing muscle mass (hypertrophy). Studies measuring how plant-based diets affect hypertrophy are much rarer since you need a lot of time to be able to detect differences.
In beginner lifters, 17.5g of post-workout milk protein (1.7g leucine) led to greater hypertrophy (type II muscle fiber area) compared with the 17.5g soy protein (1.4g leucine) after 12 weeks lifting (12).
Looking at higher protein doses, a study on 24 more experienced lifters found that 48g of post-workout rice protein (3.8g leucine) led to similar changes in muscle mass as 48g of post-workout whey protein (5.5g leucine) (13).
This is in line with studies measuring MPS: At higher protein doses, it doesn’t seem to matter if you get protein from plant or animal sources; the tough part is simply getting to these doses.
Another study compared 12 weeks of isocaloric leucine supplementation (6g of leucine), given as pure leucine, whey, or soy protein in untrained college males and found no difference in muscle mass between groups. Interestingly though, whey protein was the only supplement that caused significant increases in muscle satellite cells (cells that repair and build muscle) compared to the other groups (the soy protein group almost reached a significant increase in satellite cells, so it could be a matter of too few study participants) (54).
In the elderly, leucine supplementation alone did not improve muscle mass during weight training. It DID however limit weight loss during malnutrition. Protein sources with a mix of amino acids are more effective than leucine alone when it comes to improving muscle mass and performance. So even if leucine is “the most important component,”you still need other amino acids for optimal results (14).
Vegans Need More Protein
We can conclude that plant protein probably needs to be eaten in larger amounts to give the same muscle building signal (MPS) as animal protein. At the same time, it is more difficult to get as high – let alone higher – protein levels from a plant-based diet compared to your average non-vegetarian diet.
Protein from plants is generally absorbed less readily compared to animal-based protein, meaning that less of the plant-based protein you eat actually ends up in your blood. Furthermore, many other essential amino acids are more commonly missing in a plant-based diet. These include lysine (most commonly missing), methionine, isoleucine, threonine, and tryptophan.
Lacto-ovo vegetarians still get a good amount of these amino acids from milk products and eggs, but vegans need to pay more attention and get a daily source of lysine (sources include beans and legumes), leucine (sources include soy beans and lentils), and other BCAAs (leucine, isoleucine, valine -found in seeds, tree nuts, and chickpeas). Vegans don’t need to obsess over getting every amino acid in every meal, but make sure to get all of them in by the end of the day.
Because of the above, we recommend non-athletic vegetarians who eat eggs and dairy eat 1 g/kg/day protein per day (compared to 0.8 g/kg/day for the general population). For non-athletic vegans, we recommend 1.4 g/kg/day. Athletic vegans can aim for 2.0 g/kg/day while bulking and 2.7 g/kg/day while cutting. Protein supplements are therefore a good idea if you want to optimize building muscle on a plant-based diet. There are many vegan-friendly options out there, including pea protein and rice protein supplements.
Other Macros in Vegan & Vegetarian Diets
Generally, vegan diets tend to be lower in calories, protein, and fat while being higher in carbohydrates. The lower calories help explain why vegetarian diets help with weight loss, even when not counting calories (yes, it’s CALORIES and not CARBS that cause weight gain). As long as the vegetarian diet is rich in whole foods (which it usually is), vegetarians will most likely end up consuming fewer calories and therefore gain less weight, or even lose weight, over time.
Fats, Omega-3s, and Testosterone in Vegetarians
Compared to “regular” diets, vegan diets are lower in fat, especially saturated fat but also omega-3 fats (including ALA, EPA, and DHA). At the same time, vegan diets are higher in omega-6 fats.
Low-fat diets have been linked to low testosterone levels (49), and low testosterone levels may impact athletic performance in vegans. Still, studies measuring testosterone levels in vegans don’t find lower levels compared to meat eaters (37).
Omega-3 fats are important for our blood and immunity and body cells, and they help with normal growth and development. They limit inflammation and chronic disease and seem to have a role in preventing heart disease. For athletes, omega-3s improve airway response to exercise (EIB), increase nitric oxide production, and improve heart-rate and blood flow.
Our bodies use omega-3 and omega-6 fatty acids to form hormones known as eicosanoids (include prostaglandins, thromboxanes, and leukotrienes). A balanced ratio of omega-3 to omega-6 is thought to be important for health and performance, and in that case, vegans have an even imbalance in this ratio due to high omega-6 intake and low omega-3 intake.
The reason to avoid too low of fat intakes is that getting less than 20% fat in your diet may result in poorer absorption of the fat soluble vitamins (Vitamins A, D, E, and K) and also poorer intake of the omega-3 and omega-6 fatty acids (45).
Vegans can reach the recommendation of 30% of calories from fat by eating enough oils, avocados, nuts, and seeds. Also, to balance the omega-3 to omega-6 ratio, omega-6 intake can be reduced by limiting sunflower, corn, and safflower oils, while getting more omega-3 from flax seeds, walnuts, and chia seeds (ALA) and microalgae oil (EPA and DHA). Supplements are also available if you aren’t keen on looking for microalgae oil.
Research on optimal omega-3 intake for vegans doesn’t exist as far as we know, but recommendations of 1000-2000 mg of combined EPA and DHA at a ratio of 2:1 have been suggested for athletes (37), meaning 666 mg EPA and 333 mg DHA could be a good target. This would equate to 1 g of microalgae oil, or two capsules of most Omega-3 products.
One reason as to why vegetarian diets lead to less calories being consumed is because they contain high fiber foods with non-digestible carbohydrates and a substance called lignin. Foods like oats, lentils, and beans provide a lot of food volume without the added calories, which make vegetarian meals filling, preventing hunger and overeating.
In some cases, athletes who regularly burn a lot of calories may need a lot of calories to avoid losing muscle over time. In this case, feeling full too soon may be more of a problem than a benefit.
Thus, for athletes requiring more calories, choosing lower fiber foods like rice, pasta, buckwheat, and noodles can make eating higher amounts of carbohydrates and calories easier. These foods can be of particular benefit as a pre-workout snack to boost athletic performance in certain endurance sports.
Micronutrients in Vegan & Vegetarian Diets
Vegan diets are lower in vitamin B12, calcium, and iodine. Calcium, iron, and zinc might also be an issue due to poorer absorption from plant sources. Vegans diets do, however, have the benefit of higher fiber, antioxidants, and phytochemicals (plant-chemicals which, when eaten from plants, have several health benefits).
The next section will go through various vitamins and minerals which may be lacking in a vegetarian diet. Recommendations will be given on potential ways to compensate for these micronutrient deficiencies.
Vitamin B12 or cobalamin is an essential vitamin for our nervous system, DNA, and blood. It is estimated that 50% of vegans are vitamin B12 deficient since the major source of vitamin B12 is from animals and dairy products. Over time, this can lead to lower blood levels (anemia) and even irreversible degeneration of the nervous system. Therefore, it is important for vegetarians, particularly vegans, to ensure adequate intake of vitamin B12.
Good sources of vitamin B12 for vegans include B12 fortified cereals and nutritional yeast. Usually, however, a supplement is needed and vegans are recommended to consume 6 μg of supplemental B12 daily. Absorption of supplemental B12 is poor and may be as low as 2%, and it is therefore important that vegans with suspected symptoms of B12 deficiency (i.e. tiredness or neurological symptoms) consult a doctor to monitor their blood B12 levels and adjust the dose of their supplement accordingly.
Iron is important for your blood to be able to transport oxygen properly, as it forms part of the protein hemoglobin. Low iron intake can therefore cause low hemoglobin levels and limit blood cell production, called iron deficiency anemia. Symptoms include tiredness, irritability, headaches, and reduced exercise performance, meaning low iron levels can negatively impact your workouts. Even WITHOUT anemia, iron deficiency has been shown to increase energy expenditure, reduce endurance, and limit performance improvement after endurance exercise (37). Thus, ALL athletes – vegetarian or not – should ensure adequate iron intake. We can only control how much iron is absorbed from the diet, and we are not able to regulate how much iron is lost.
Iron is measured indirectly in the blood, as simply measuring iron is an unreliable measurement due to the large variation over a day. Before anemia kicks in, doctors can measure the body’s stored iron indirectly through a protein called ferritin. Levels should be 27-365 µg/L for men and 13-148 µg/L for women. Too low of levels can mean that you are running low on iron reserves.
Because of the copious amounts of whole grains and greens in their diets, vegetarians might actually have MORE iron in their DIET compared to non-vegetarians, according to observational studies, though some studies find no differences (50, 51). However, this iron is called non-heme iron and is different from the heme iron found in meat. Non-heme iron is not absorbed as well, meaning that vegetarians might end up with less iron in their blood even though they get a lot of iron from the foods they consume.
Experimental studies lasting up to 12 weeks have NOT found reductions in iron levels on a lacto-ovo vegetarian diet (52). However, the body is very good at storing iron and it can take several months before iron levels become too low. Long term, we only have observational studies, and these suggest that vegetarian males and females (before menopause, at least) have a 12% and 18% increased risk of low iron levels (ferritin), respectively (38). Then again, after statistical adjustments, the study found that only men seem to be at risk. This may be because men generally have more ferritin, making them lose more if they go vegetarian. It is speculated that vegetarians can adapt to become more effective at absorbing iron over time, explaining why lower iron levels may not be a problem.
If you are unsure of whether you have low iron levels or not, it may be worthwhile to get a full check-up by your doctor and begin supplementing. This is especially true for women who have a lot of blood during their period, as bleeding is the most common cause of iron deficiencies in developed countries.
There is some controversy here, though, as some evidence does indicate that higher iron levels are associated with health issues including heart disease, diabetes, and cancer. Supplementing with iron might also affect absorption of other minerals, leading to a lack of other micronutrients.
All in all, vegetarians might be at risk of iron deficiency, especially male vegetarians. However, due to potential risks, I therefore recommend paying attention to iron intake and optimizing it rather than supplementing blindly.
Vegan-friendly iron sources include legumes, grains, nuts, seeds, fortified foods, and green vegetables. You can boost absorption of iron from these foods by soaking, fermenting, or sprouting them. Vitamin C also boosts non-heme iron absorption, so consider combining the iron sources above with broccoli, sweet peppers, tomatoes cauliflower, cabbage, or Brussels sprouts. The easiest way would be to add a glass of lemon or orange juice to your meal. Avoid having coffee, tea, or cocoa in the hours around your iron-rich meals since they contain plant molecules known as polyphenols, which reduce iron absorption. The same goes for milk products, as the calcium in these blocks iron absorption (even though lacto-ovo vegetarians don’t seem to have lower iron levels) (38).
Zinc is important for cell growth, cell repair, DNA, protein metabolism, and testosterone production (37). Like iron, zinc from plant foods is absorbed less effectively. Also like iron, there is controversy as to whether or not the body adapts to absorb more zinc if we get too little from our diets. Vegans especially are advised to eat more zinc compared to the minimal recommendations for the general population.
Good vegetarian sources of zinc include hemp and pumpkin seeds, and other grains, nuts, and beans. Soaking and fermenting such foods further improves how your body absorbs zinc. Supplementation is an option, but avoid consuming zinc supplements in conjunction with other supplements, as they limit absorption of zinc. Thus, multivitamins might not allow for enough zinc absorption.
Calcium is important for maintaining bone structure, nerve signaling, blood clotting, and muscle function. Growing kids and teenagers need higher levels than the general population, but generally calcium intake is an issue for people not consuming milk products. Athletes use more calcium during weight lifting, heavy breathing, and calorie restriction. In some cases, non-vegetarian female athletes, can develop eating disorders, stop having their period, and develop a weaker skeleton (the female athlete triad). This is thought to be due to inadequate calcium intake, which is why these athletes are advised to supplement with calcium.
The recommended level is 1000mg daily and compared to non-vegetarians, vegans consume around 40% less calcium and vegetarians around 8% less. Thus, vegans need to pay special attention, as they limit milk products the most. Vegans have even been shown to have an increased risk of fractures (37), while going vegetarian doesn’t affect fracture risk and barely impacts bone density (39).
For vegans, broccoli, bok choy, and kale are particularly high in calcium. Beans, pulses, and green vegetables may also be good choices, but green vegetables such as spinach and arugula contain oxalate, which limits calcium absorption. Some form of supplemented food may be a good idea, such as calcium-fortified soy or tofu, nut milks, and fruit juices, which are all vegan-friendly. Also, since Vitamin D plays an important role in calcium metabolism, getting enough vitamin D can enhance calcium absorption from food if intakes are low. Unlike vitamin C with iron, you do not need to consume vitamin D at the same time as your calcium sources to improve absorption.
Vitamin D helps control many physiological processes, but mainly helps raise calcium levels by helping the gut absorb calcium from food, helping the kidneys save calcium, and helping free calcium stores from bone when needed. As calcium affects muscle performance, low vitamin D levels negatively affect muscle strength and oxygen consumption, while correcting a deficiency can improve athletic performance and might protect against overuse injury (55). Too low of levels are extremely common, especially in countries with low sunlight levels and during winter, with some studies finding that over 40% of US adults have too low of levels (<20 ng/ml) (40).
Many people, including athletes and non-vegetarians, can potentially benefit from optimizing vitamin D status, but there is still disagreement as to what levels are optimal. More research is needed, but somewhere between 40-70 ng/ml in the blood should be suitable, while levels over 150 ng/ml are toxic and can lead to too high calcium levels (37).
There are actually two versions of vitamin D: vitamin D3 (aka cholecalciferol), found mostly in fish but also produced in the skin when exposed to sunlight, and vitamin D2 (ergocalciferol), found in some vegan-friendly sources like mushrooms, but less effectively absorbed in the gut. Vitamin D2 and D3 are first metabolized in the liver and then activated in the kidneys before being able to regulate calcium levels.
Realistically, most people get limited amounts of vitamin D from food, and Vitamin D3 from sunlight is thus essential. Specific recommendation for how much sunlight exposure is needed depends on the season and your skin type, with winter months and darker individuals requiring longer sunlight exposure to synthesize enough vitamin D. So if you live in an area with limited sunlight, you will need to supplement with vitamin D.
For vegans who want to avoid vitamin D3 supplements from animal products, there are vegan-friendly vitamin D3 supplements from an organism called lichen, which is absorbed much better than vitamin D2. Doses are measured in micrograms (μg) or international units (IU). 1 microgram equals 40 IUs. For sunless populations, 800 IUs (20 μg) per day is the recommended daily dose, with the upper limit being 4000 IU (100 μg).
Some claim that recommended doses should be raised, with studies finding that athletes taking 5000 IU (125 μg per day) together with 50-100 μg of vitamin K1 and K2 recover better and are able to train more frequently (41).
Be careful, however, as it IS possible to overdose on vitamin D with prolonged doses around 10 000 IU (250 μg) or a single dose of 300 000 IU (7500 μg) being dangerously toxic. The limit is even lower if you have liver or kidney problems, so we recommend you stick within the recommended doses of 800-4000 IU/day (20 – 100 μg/day).
If you’ve ever wondered where the word “cretin” comes from, you might be interested in knowing that iodine deficiency during childhood can lead to problems with physical growth and lead to mental retardation, a condition known as cretinism. Apart from this condition, which is extremely rare in developed countries today, iodine is needed to make our thyroid hormones. Thyroid hormones regulate our metabolism, including base metabolic rate (BMR), or how many calories your body burns at rest. Both high and low intakes of iodine can lead to thyroid dysfunction, and depending on their diet type, vegans may be consuming too much or too little iodine (37).
Some, but not all, types of seaweed may have very high levels of iodine, and vegans eating a lot of seaweed might get too much. Fish and dairy products also contain iodine, which is why vegetarians and vegans might also consume too little iodine. Vegans should therefore consider getting enough iodine from potatoes, cranberries, or (the simplest way) iodized salt. Also keep in mind that raw cabbage and cauliflower limit iodine absorption.
Supplements for Vegetarian Athletes
Creatine is a popular supplement but is also made in your body by combining the amino acids arginine, glycine, and methionine. Creatine is stored in muscles. Supplementing with creatine improves short-term high-intensity exercise performance, muscle hypertrophy, and maximal strength, and this effect might be extra beneficial for vegetarians (53). It might also increase blood plasma, improve glycogen storage, reduce oxygen consumption during submaximal exercise, and improve the ventilatory threshold for anaerobic activity (37). Part of the mechanism behind how creatine works is that it allows the cell’s “fuel” molecule ATP to be recycled (42).
As our biggest dietary sources of creatine are from meat, fish, and poultry, it isn’t surprising that vegetarian diets reduce muscle creatine stores. Thus, vegetarians have an extra benefit from supplementing with creatine compared to non-vegetarians. I recommend you do so to enhance performance. To increase muscle levels of creatine (reach “muscle creatine saturation”), it may be helpful to take 20g daily for 3-7 days, followed by 3-5 g daily as maintenance. This is the equivalent of two pounds (around 1kg) of meat, meaning that non-vegetarians will have a difficult time reaching these doses unless they eat copious amounts of meat.
β-alanine is a modified amino acid supplement responsible for the tingling sensation you get from some pre-workouts. It works by increasing muscle and nerve levels of a molecule known as Carnosine. Interestingly, Carnosine in turn works as an antioxidant and a so-called buffer, eliminating waste products of metabolism. It has been shown to reduce tiredness and improve cardio performance and performance of exercise lasting longer than 60 seconds.
Research has shown that vegetarians have lower levels of muscle carnosine. So, like with creatine, vegetarians might have a boosted effect of using β-alanine. Specific studies looking at β-alanine supplementation in vegetarians do not yet exist, so this recommendation is somewhat speculative.
Taurine is another amino acid found in dairy, seafood, and meats and is absent from the vegetarian diet. Vegans have been shown to eat less taurine and have less taurine in their urine (43). It is important for the nervous system, heart, and maintaining blood sugar, and supplementing with taurine has been shown to improve performance and decrease muscle damage in healthy males (44).
If I may speculate, this effect might be enhanced in vegetarians who are already lacking in taurine, though specific research on this topic is needed. Supplementation with 50 mg/kg of body weight is what was used in the referenced study.
β-alanine can theoretically limit taurine uptake into muscles, meaning that it could further cause issues in vegetarians who are already lacking taurine. There is, however, no evidence to support this claim. It may be a good idea, though, to supplement with taurine if you decide to take β-alanine as a vegetarian (37).
THE VEGETARIAN ATHLETE CHECKLIST
We can sum up this article as follows:
- ALL HEALTHY ATHLETES, NO MATTER WHAT DIET need to consider:
- Low micronutrient levels if the diet is repetitive without much variation in food sources – particularly if cutting and limiting calorie intake.
- Getting enough calories depending on your energy needs.
- Getting enough protein (1.6-2.2 g/kg or 0.7-1.0 g/lb bodyweight). Consider a supplement.
- Getting enough carbs for performance benefits (3-10 g/kg or 1.4-4.5 g/lb bodyweight).
- Getting enough fats for vitamin absorption and hormone production (20-40% of calories or 0.5-1.5 g/kg or 0.2-0.7 g/lb bodyweight).
- Supplementing with Vitamin D if living in areas with low sunlight exposure (20-100 μg per day or 800-4000 IU).
- Keep track of calcium intake if cutting. Supplements generally not needed, but recommended supplement dose 500-1000mg daily.
- PESCO-VEGETARIANS need to consider everything above but also risk:
- Low iron, due to lack of red meat. Plant sources include legumes, grains, nuts, seeds, fortified foods, and green vegetables. Supplementation generally not needed unless there is a proven deficiency. Recommended daily dose: 14mg for men, 33mg for women.
- LACTO-OVO VEGETARIANS need to consider everything above but also risk:
- Low Omega-3 due to lack of fish: supplement.
- Low zinc due to poor absorption from plants. Plants sources include beans, nuts, seeds, oats, wheat germ, and nutritional yeast. Supplementation generally not needed. Recommended daily dose for vegans: 16.5mg for men, 12mg for women.
- Lower creatine levels due to lack of meat, fish, or chicken. Consider supplementing with 5g daily after loading.
- Consider Beta-Alanine, and if so, also taurine.
- VEGANS need to consider everything above but also risk:
- Low protein due to poor absorption and poorer amino acid profiles. Get protein from a mix of pulses, grains, legumes, tofu, quinoa, nuts, seeds, and vegetables. High protein vegan foods include pumpkin seeds, red lentils, black beans, almonds, tempeh, rolled oats, and quinoa. Consider a vegan-friendly protein supplement to make things much easier. You need more protein than you would if you were eating dairy or animal products, so aim for 2.0 g/kg while bulking up to 2.7 g/kg while cutting.
- Low fat intake due to many vegan foods being low fat: make sure to eat oils, avocados, nut,s and seeds to reach 0.5–1.5 g fat/kg of bodyweight.
- Low vitamin B12 due to lack of animal products. Use supplements and fortified foods like nutritional yeast or fermented soy. Recommended daily dose for vegans: 2.4 up to 6 μg.
- High iodine if eating lots of seaweed. Limit seaweed consumption.
- Low iodine due to lack of fish and dairy. Eat cranberries, potatoes, prunes, navy beans, or iodized salt. Recommended daily dose: 150 μg.
- Low Omega-3 like vegetarians in general. Vegan-friendly supplements with EA and DHA available from microalgae or seaweed. Also get ALA from flax seeds, walnuts, chia seeds, or hemp seeds. Recommended daily dose: 1000 mg, with 666 mg EPA and 333 mg DHA.
- Low vitamin D like the general population. Vegan-friendly vitamin D3 supplements available from lichen. Recommended daily dose: 800 IU or 20 μg.
- Low calcium like the general population, but also due to poorer absorption. Food sources include calcium set tofu, fortified plant milks and juice, kale, broccoli, sprouts, cauliflower, bok choy. Recommended supplement dose 500-1000 mg daily.
Try Going Flexitarian!
That’s a wrap! Hopefully this article has given you value and taught you what you might need to consider as a vegetarian. If you are having a tough time deciding on whether you should give up meat or not, we believe that the best place to start your vegetarian journey is by going flexitarian (48). Being more open to vegetarian meal options doesn’t mean that your gains are forever lost. Keep track of your protein intake and consider an extra protein shake, and you will be good to go. If anything, you will be doing the planet a favor!
Guest Writer: Artin Entezarjou
I want to thank Greg Nuckols for the opportunity to write for Stronger by Science. Science, health, and fitness are my passions. If you enjoy what I write, I recommend you check out our science-based page, EBT – Evidence Based Training, where we share scientific studies on nutrition and fitness to help you build muscle, burn fat, and perform better. Also make sure to follow us on Instagram and like us on Facebook, where we post most of our content!
Written by Artin Entezarjou, M.D. and PhD Student from Sweden.
Co-Founder of EBT – Evidence Based Training.
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