Special Considerations for Athletes
By Joel Fuhrman, M.D. www.drfuhrman.com
Potential Shortcomings Of A Vegan Diet Should Not Be Overlooked!
There are several concerns about micronutrient adequacy of a vegan diet; some are justified and others are not. Vitamin B12, for example, is essential for proper nervous system function, homocysteine metabolism, and DNA synthesis. Vitamin B12 is synthesized only by microorganisms, and, therefore, is far more abundant in animal foods than in plant foods. Supplementation of a minimum of 6 mcg vitamin B12 per day is essential for vegans, but this is common knowledge today, and it is rare to find a vegan who does not know that this is necessary.
Since iodized salt is the chief source of iodine in the American diet, it is important for vegan athletes (and all nutritarians) to supplement with iodine in a multi-vitamin or consume a small amount of kelp or other seaweeds on a regular basis. Zinc requirements are estimated to be 50 percent higher in vegans than in omnivores 14 because absorption efficiency may be quite low from plant foods. A 2009 study of vegetarians found a high prevalence of zinc deficiency.15 For those who refuse supplementation, or those who wish to increase their food based zinc intake, pumpkin seeds and hemp seeds are rich in zinc.
For athletes on a vegan diet, special attention also should be paid to obtain adequate omega-3s, iron, and vitamin D, as these nutrients have benefits specific to athletes. Vegan athletes also may consider supplementing with the amino acid taurine (discussed later).
Nuts, seeds, and greens provide sufficient calcium for athletes. Low oxalate vegetables such as bok choy and kale have higher levels of calcium bioavailability than milk (approximately 50 percent vs. 30 percent). 16 Nuts and seeds are also rich in several minerals, including calcium. Seeds are invaluable in the diet of an athlete— vegan or non-vegan—because they are protein- and mineral-rich. Seeds can contribute to fulfilling the increased caloric and protein needs of athletes while simultaneously delivering many useful micronutrients.
The great availability of calcium in vegetables, nuts, and seeds renders calcium deficiency an invalid concern for vegan athletes. The U.S. RDI for calcium is 1000 mg, whereas the World Health Organization recommends a lower calcium intake— 400-500 mg. These needs can easily be met on a vegan nutritarian diet.
Green vegetables and seeds can protect against exercise-induced iron losses. The concern for iron deficiency in vegans is based on the reduced bioavailability of iron from plant foods; vegan diets often contain more iron than omnivorous diets. Plant foods contain non-heme iron, which is generally not as absorbable (10 percent) as the heme iron contained in animal foods (18 percent). Absorption of each type of iron increases when body iron stores are low, but non-heme iron is more responsive to iron stores. This means that when iron stores are low, non-heme iron actually has greater absorption efficiency than heme iron. This efficiency, however, also depends on absorption enhancers and inhibitors present in foods. Plant foods contain inhibitors of iron absorption such as phytate (found in legumes and grains), but also contain absorption-enhancing substances such as vitamin C and carotenes. Although some studies have cited decreased iron stores in vegetarians and vegans, none have demonstrated increased rates of iron deficiency anemia or decreased hemoglobin concentrations.
Athletes may be at risk for iron deficiency due to iron losses associated with physical training. A recent study of female professional athletes reported a general high prevalence of iron depletion and anemia in these athletes.
Vegan athletes should include iron rich plant foods in their diets, but iron supplementation is not usually required except in cases of iron insufficiency marked by a very low ferritin or anemia, or in women with heavy monthly bleeding in which supplementation can be beneficial. High body iron stores may be a risk factor for cardiovascular disease and cancer , and also are associated with reduced cardiovascular fitness.
Leafy greens are an often overlooked but rich source of iron. In the typical American diet, greens are eaten in small serving sizes that do not supply adequate iron, but athletes who consume large portions of greens in vegetable-based meals, smoothies, and shakes receive the benefit of extra protein and iron from those greens. Based on the table above, it is clear that iron is readily available in a nutritarian vegan diet. But a vegan diet using grain products and protein powders as major calorie sources without the inclusion of iron-rich plant foods could contribute to suboptimal athletic performance.
Omega-3 fatty acids
There is overwhelming evidence that the essential omega-3 fatty acids eicosapentaenoic acid (EPA) and DHA contribute to brain and heart health, and additional beneficial effects of these fatty acids continue to be revealed. Alpha-linolenic acid (ALA), an omega-3 fat that can be elongated to produce EPA and DHA, is present in flaxseed, chia seeds, hemp seeds, walnuts, and leafy greens.
Most individuals can maintain adequate levels of omega-3 fats by careful attention to regular consumption of plant sources of ALA. However,there is evidence that many individuals do not self-produce adequate or ideal levels of DHA and EPA even when proper attention is placed on obtaining sufficient ALA-rich foods. For example, genetic differences account for varying degrees of activation of the enzyme delta-6 desaturase, which elongates the ALA, EPA, and DHA. I have evaluated the blood tests of hundreds of vegans, and I have seen lower than ideal levels of DHA and EPA in a substantial percentage of them. This is consistent with research that has documented long chain omega-3 deficiencies in vegans. A reasonable way to ensure sufficiency is to take an algae-based DHA supplement, which, of course, is vegan.
Omega-3 supplementation may be especially beneficial to vegan athletes. A recent study suggested that omega-3 supplementation attenuates exercise-induced inflammation and oxidative stress. 25 Wrestlers given omega-3 supplements (1000 mg/day) for 12 weeks experienced enhanced lung function during training. 26
Since ALA is readily converted to EPA, and DHA can undergo retro-conversion to EPA 27, you can ensure an adequate supply of omega-3 fatty acids by taking an algae-based DHA supplement and eating ALA-rich foods such as flaxseed or hemp seeds.
Widespread vitamin D deficiency has been reported in the general population. This vitamin may be especially important for athletes because of its functional role in skeletal muscle. In the early part of the 20th century, athletes and trainers believed that UVB radiation had effects on athletic performance. In light of current data, these observations could have been vitamin D dependent. Vitamin D receptors are present in almost all cells of the body, including muscle cells. Vitamin D’s primary function is the regulation of calcium transport and metabolism. Since calcium transport is an integral part of muscle contraction and relaxation, vitamin D is extremely important for proper muscle function. This could have implications for both performance and injury prevention. 28 Vitamin D supplements of 2000 IU usually assure adequacy, and the proper level of supplementation can be confirmed with a blood test.
In 1973, my sister and I were the number one ranked pairs figure skaters in the U. S.(The team that was first in the national championships earlier in the year had just retired.) While training, I suffered a severe heel injury that did not heal adequately for years, essentially ending my dream of Olympic participation. In retrospect, with what I know today, I suspect that vitamin D deficiency may have prevented adequate and timely healing from the initial bone injury. I lived my whole life indoors and did not know to supplement with adequate vitamin D.
Taurine is a supplement that may offer a performance benefit to athletes. Taurine is an amino acid that is concentrated in skeletal muscle tissue. Urinary excretion of taurine correlates with markers of muscle damage. 29 Taurine pre-supplementation has been shown to increase athletic performance in human and animal studies. Animal studies also have reported benefits to insulin sensitivity and muscle glycogen storage. 30 Taurine benefits non-vegan athletes, but its use is even more appropriate for vegans because taurine is the amino acid that is most commonly low when measured in those eating a vegan diet.31
Branched Chain Amino Acids
Branched chain amino acids (BCAA) supplements (containing the amino acids isoleucine, leucine, and valine in approximate 1:2:1 ratio) have been studied for their effects on performance, muscle protein synthesis, and recovery. Oxidation of leucine is significantly upregulated during endurance exercise, reflecting the need for increased protein intake by athletes. A review of the literature concluded that BCAA supplements do not significantly affect performance; however, they did attenuate exercise-induced muscle damage and promoted muscle protein synthesis. 32 Plant proteins such as sesame seeds, sunflower seeds, tofu, and pumpkin seeds are rich sources of BCAA and offer these beneficial effects.
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