Year 11 | 10 December 2019 | firstname.lastname@example.org
Meat eaters are known for having a significantly higher combination of cardiovascular risk factors than vegetarians. Lower-risk vegans, however, may not be immune
People who follow a vegan lifestyle, strict vegetarians who try to eat no meat or animal products of any kind, may increase their risk of developing blood clots and atherosclerosis or “hardening of the arteries,” which are conditions that can lead to heart attacks and stroke. That’s the conclusion of a review of dozens of articles published on the biochemistry of vegetarianism during the past 30 years.
Vegan diets tend to be lacking several key nutrients, including iron, zinc, vitamin B12, and omega-3 fatty acids.
While a balanced vegetarian diet can provide enough protein, this isn't always the case when it comes to fat and fatty acids. As a result, vegans tend to have elevated blood levels of homocysteine and decreased levels of HDL, the "good" form of cholesterol. Both are risk factors for heart disease.
In general, compared with an omnivorous diet, vegetarian diets are rich in fiber, magnesium, Fe3+, folic acid, vitamins C and E, n-6 polyunsaturated fatty acid (PUFA), phytochemicals, and antioxidants but low in total fat, saturated fatty acid (SFA), cholesterol, sodium, zinc, Fe2+, vitamins A, B12, and D, and especially n-3 PUFA (Table 2). Low intake of total fat, SFA, and sodium and increased intake of fiber, phytochemicals, and antioxidants in vegetarians is associated with decreased blood pressure and body mass index (BMI). These factors are known to reduce the risk of cardiovascular disease (CVD). However, there is concern over whether vegetarians, and particularly vegans, have an adequate intake of several important nutrients, particularly Fe, Zn, vitamin B12, and n-3 PUFA.
Iron, zinc, and vitamin B12 are currently the micronutrients of greatest concern when considering the nutritional value of vegetarian diets.
Iron is an essential trace element for blood formation. Most iron in the human body is found in hemoglobin and myoglobin or occurs as part of enzymes in the energy-yielding pathway. Iron deficiency is the most common mineral nutritional deficiency globally, although vegetarians are not more likely to be iron-deficient than omnivores.
Studies reported that vegetarians have iron intakes that are significantly higher than or similar to those of omnivores in different populations. However, vegetarians have a significantly lower serum ferritin concentration than omnivores.
Zn is an essential trace mineral that is a constituent of more than 50 different enzymes involved in most metabolic pathways and is important for protein metabolism, cell growth and repair, and immune function.
Zinc is found in a wide range of foods, including protein foods and plant foods such as legumes, whole grains, nuts, and seeds. Zn from animal sources is more bioavailable than Zn from plant foods. Because there is low zinc bioavailability in vegetarian diets, vegetarians have lower status compared with omnivores.
Vitamin B12 is essential for new cell synthesis, blood formation, maintenance of the nervous system, etc. Of the vitamins, B12 is the only one containing a mineral (cobalt); it also known as the red vitamin. Seafood, animal meats, eggs, and liver are good sources for vitamin B12. Vitamin B12 is not found in plant foods. Vegetarians have a lower vitamin B12 status compared with omnivores.
Vitamin D is rare in vegetarian diets; however, it does not seem that ovo-lactovegetarians or vegans are more likely to be deficient than omnivores because human beings can synthesize it. The body’s cholesterol can be converted into vitamin D by ultraviolet irradiation from the sun.
There is no difference in carbohydrate sources between vegetarian and omnivorous diets. Despite the protein sources being different between the two groups, dietary protein cannot be incorporated into human tissues. When we eat proteins from plant or animal sources, the body must first alter them by breaking them down via denaturation and hydrolysis into amino acids; only then can it rearrange them into specific human body proteins. A balanced vegetarian diet could provide sufficient protein to meet physiological needs. However, this is not the case when it comes to fat and fatty acids.
The predominant PUFA in the Western diet is linoleic acid (18:2n-6), which is commonly found in vegetable seed oils. This is the parent fatty acid of the n-6 series PUFA, which can be converted in vivo to C20 and C22 n-6 long chain (LC) PUFA. α-Linolenic acid (18:3n-3) is less abundant than 18:2n-6; however, it is also present in vegetable oils and is the precursor of C20 and C22 n-3 LC PUFA. Omnivores can obtain their C20 and C22 n-3 LC PUFA either from dietary 18:3n-3 or directly from the consumption of fish, eggs, or animal products. Ovo-lactovegetarians can gain a limited amount of C20 and C22 n-3 LC PUFA from milk, dairy products, and eggs. In contrast, vegans must rely totally on endogenous synthesis from 18:3n-3 by desaturation and elongation.
On the basis of the present data, it is suggested that vegetarians, especially vegans, could benefit from increased dietary intake of n-3 PUFA and vitamin B12 and thus improve the balance ratio of n-3 to n-6 PUFA and vitamin B12 status, which may reduce any thrombotic tendency that might increase their generally low risk of cardiovascular disease.
Good sources of omega-3s include salmon and other oily fish, walnuts and certain other nuts. Good sources of vitamin B12 include seafood, eggs, and fortified milk. Dietary supplements also can supply these nutrients.
Duo Li; Chemistry behind Vegetarianism; J. Agric. Food Chem., 2011, 59 (3), pp 777–784
by Ernesto Vania
07 february 2011, Food & Fun > Health