Potential impacts of vegetarian diet on nutritional adequacy - Essay Example

? Potential Impacts of Vegetarian Diet on Nutritional Adequacy Word count 650 Introduction Although vegetarian practices appear to vary over a wide spectrum, the term vegetarian, nonetheless, refers to a particular dietary pattern which emphasizes consumption of plant products and avoidance of flesh foods such as meat, poultry, and fish (Haddad and Tanzman, 2003). Those who include milk and other dairy products, and eggs, in addition to plant foods are called lacto-ovo-vegetarians (Barr and Rideout, 2004). Meanwhile, those who include eggs in their diet but avoid consumption of dairy products, meat, poultry, and fish are classified as ovovegetarians (Barr and Rideout, 2004). Lactovegetarians, however, consume milk and dairy products excluding eggs and other animal-derived products (Barr and Rideout, 2004). On the other hand, vegetarians whose diet consists solely of plant foods excluding eggs, milk, dairy, and meat products are called vegans. Demi-vegetarians are those that occasionally eat meat while pesco-vegetarian includes fish and other seafood in their diet (Phillips, 2005). Furthermore, the macrobiotic diet consists primarily of brown rice with some fruits and vegetables while the fruitarian-based diet consists primarily of fresh and dried fruits, nuts, seeds and vegetables (Phillips, 2005). Since vegetarian diet is classified according to the foods being excluded, it is not always possible to ensure that the nutrients derived from the diet are adequate (Sanders and Reddy, 1994; Meirelles et al., 2001; Barr and Rideout, 2004). Nutrient adequacy is often expressed as Recommended Nutrient Intake (RNI), which refers to the level of nutrient intake considered to be sufficient to meet the needs of about 97% of people in a group (Roach and Benyon, 2003). This paper aims to examine the potential impacts of vegetarian diet on nutritional adequacy. Specifically, this paper seeks to assess if the levels of protein, fat, vitamin B12, iron, zinc, and energy obtained from vegetarian diets are sufficient to meet the RNI. Discussion Protein Results of various nutritional studies comparing vegetarian and non-vegetarian nutrient intakes are consistent that protein consumption is generally lower in vegetarians compared to omnivores (Janelle and Barr, 1995; Huang et al., 1999; Huang et al., 2008). Even so, protein intake of vegetarian subjects was noted to be well above the RNI, indicating that protein recommendations for healthy adults, children, and even athletes are met (Sanders and Reddy, 1994; Barr and Rideout, 2004; Dunn-Emke et al., 2005). Even in pregnant women and lactating mothers whose protein requirements increase by 25 g/day compared to nonpregnant, nonlactatating women, plant-based diet is still able to meet the increase in protein demand (Penney and Miller, 2008). This may suggest that in most cases, adequacy of protein consumption from vegetarian diet is not a cause of concern. Plant-based diet can sufficiently supply protein requirements when an assortment of plant foods is consumed to provide all the essential amino acids (ADA, 2009). Fats Total dietary fat intake follows the same pattern as protein intake in vegetarians. In general, consumption of dietary fat was found to be significantly lower in vegetarians compared to non-vegetarians but still falls within the range of the RNI (Janelle and Barr, 1995; Huang et al., 1999). Studies also provided evidence that plant-based diet is also rich in n-6 fatty acids (linoleic acid), which are then converted to arachidonic acid (ADA, 2003; Key et al., 2006). However, it has been reported that vegetarian diets are usually low in n-3 fatty acids such as eicosapentanoic acid (EPA) and docosahexanoic acid (DHA), which are important for proper brain and visual development (Sanders and Reddy, 1992; Dunham and Kollar, 2006). In fact, it was found that cord plasma and cord artery phospholipid levels of pregnant vegetarian women contained significantly less DHA and docosapentanoic acid (n-6 fatty acid) compared to the non-vegetarian controls (Sanders and Reddy, 1992). Low DHA and EPA content of vegetarian diet are greatly felt in pregnant women, lactating mothers, and infants. N-3 fatty acids were found to significantly affect the outcome of pregnancy such as length of gestation and size of infant (Sanders, 1999). Moreover, lactating mothers deprived of n-3 fatty acids were found to produce milk with low DHA and EPA content, much lower if the mother follows a vegan diet (Sanders and Reddy, 1992). Vitamin B12 Another nutritional concern with vegetarian diet is the possible inadequacy of Vitamin B12 (cobalamin) intake, especially in vegan diet (Sanders, and Reddy, 1994; Barr and Rideout, 2004, Phillips, 2005). This concern is logical since plant-based foods normally lack this vitamin, unless fortified (ADA, 2003; Phillips, 2005). In fact, in a study conducted by Herrmann et al. (2001) on the vitamin B12 status of vegetarians, it was found that homocysteine levels of lacto-ovo and lacto-vegetarians were significantly increased in comparison to non-vegetarians. These levels however, were maintained below the pathologic value of 15 umol/L, beyond which vitamin B12 deficiency is diagnosed (Herrmann et al., 2001). Meanwhile, the vegan group exhibited serum homocysteine levels above 15 umol/L. This result is consistent with the findings of Craig (2010) that dietary intake of cobalamin by vegans is not adequate. For pregnant women and lactating mothers, estimated average requirement (EAR) of cobalamin increases to 2.6 mcg/d and 2.8 mcg/d, respectively, thereby increasing the risk of cobalamin deficiency (Penny and Miller, 2008). Moreover, babies born to vegan mothers have a higher risk of developing neural tube defects, cognitive disabilities, and megaloblastic anemia (Keobnik et al., 2004). Iron In plant-based diet, iron only exists in the non-heme form, which is more sensitive to inhibitors such as phytate, calcium, tea, coffee, and cocoa (Hurrell et al., 1999). Enhancers of iron absorption, on the other hand, include vitamin C and organic acids (Hurrell et al., 1999). It has been reported by Hunt (2003), and Ball and Bartlett (1999) that vegetarian diet may contain iron in concentrations approximately similar to that of non-vegetarian diet for all age groups. In fact, previous reports indicated that iron intakes of lacto-ovo vegetarians and vegans are sometimes higher than those exhibited by omnivores (Wilson and Ball, 1999; and Perry et al., 2002). However, iron bioavailability is reported to be lower than those in non-vegetarians but still reaching optimum iron requirements. Hence, a balance in intake between iron absorption enhancers and inhibitor should be maintained so as not to increase the risk of developing iron deficiency. The risk of developing iron deficiency is higher in females, lactating mothers, and pregnant women (Penney and Miller, 2008). This is probably due to blood losses during menstruation and increase in maternal blood volume during pregnancy (Penney and Miller, 2008). Pregnant women are advised to plant foods rich in iron such as soy products, tofu, spinach, prunes, and raisins, among others (ADA, 2003). Intake of inhibitors such as phytates and coffee are discouraged. Zinc Apart from iron, zinc is also negatively affected by the presence of phytates and high dietary fibers (Kannan, 2011). Phytates bind to zinc, reducing its absorption in the intestines (ADA, 2003). This is supported by the findings of different nutritional studies indicating that bioavailability of zinc from vegetarian diet are lower in comparison to omnivore-based diet (Freeland-Graves et al., 1980; Venti and Johnston, 2002). Even so, zinc deficiency is not commonly seen in vegetarians. Although 50% of zinc consumption is usually supplied by meat, vegetarian diet can be planned so that zinc content will reach values similar to that of non-vegetarian diet (Hunt, 2003). Vitamin D Vitamin D, a crucial micronutrient for calcium absorption in the gut to maintain good bone health, is one of those nutrients replete in meat and fish products but is scarce in plant-based foods (Craig, 2010). Although it has been reported by Phillips (2005) that most individuals can synthesize vitamin D through sun exposure, dietary vitamin D from animal meat and fortified food products significantly contributes to its levels in the blood. In fact, in a study conducted by Dwyer et al. (1982), it was observed that lacto-ovo, lacto-vegetarians, and vegan children had vitamin D levels below the RNI. A more alarming finding was that those children following a vegan diet showed mean vitamin D intakes less than of the RNI for children (Dwyer et al., 1982). Low serum vitamin D levels are associated with rickets and decrease in bone mineral density, affecting children, aging people, postmenopausal women, and pregnant mothers (Craig, 2010). An earlier study conducted by Dagnelie et al (1990) observed an increase in the prevalence of rickets in children below 6 years old fed with vegan diet without vitamin D supplementation. It is well recommended to include in the diet vitamin D supplements in the form of tablets or vitamin D fortified plant products such as cereals and soy drink (Phillips, 2005). Energy Total energy derived from vegetarian diet appears to be lower than those derived from non-plant based diet (Huang et al., 1999; Phillips, 2005 Key et al., 2006). This is not surprising since protein and fatty acid intakes are relatively lower in plant-based diet compared to non-vegetarians. Specifically, studies in done in UK comparing lacto-ovo- vegetarians, vegans, fish-eaters and meat-eaters revealed that lacto-ovo- vegetarians and vegans have lower proportion of dietary energy from total fat and saturated fatty acids than fish-eaters and meat eaters (Nathan et al., 1996; Sanders, 1999; Philipps, 2005). However, there is no evidence suggesting that total energy intakes from plant-based diet are compromised. Conclusion Vegetarian diet, in general, offers lower amounts of protein, n-3 long-chain fatty acids, vitamin B12, iron, zinc, vitamin D, and total energy as compared to non-vegetarian diet. Even so, the levels of these nutrients do not necessarily go below the Recommended Nutritional Intake (RNI), except perhaps when vegan diet is followed. Hence, it may be a good strategy to provide nutrient supplements for vegans, especially when the need for these nutrients are increased such as during pregnancy and lactation. Although the risk of developing nutrient deficiencies is higher in vegetarian-based diet, especially if vegan diet is being practiced without any supplements, as compared to non-vegetarian diet, inadequacy of nutrients can be well prevented if the components of the diet will be planned accordingly. Literature Cited American Dietetic Association. 2003. 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