I opted out of my nutrition symposium to surprise my family back home and have a better visit; the three days at home during Christmas were kind of spoiled by a stomach virus. So glad I decided to come home, it’s nice to spend time with my family and dog, especially before my school life gets busier. Oh, and if you haven’t already, I strongly recommend seeing Les Mis; such a great movie!
Overall, vegetarians have a tendency towards lower BMIs, better health, longer lifespans and reduced rates of chronic diseases, but is it the vegetarian diet itself that’s providing these positive outcomes? It’s still unclear if benefits are derived from; lack of meat, increased fruits and vegetables, or other components of the vegetarian diet. While there is some very clear health benefits derived from plant based diets, there are also risks in terms of adequate nutrients when following an unplanned vegetarian diet. This blog post will explore many aspects of the vegetarian diet, hope you enjoy!
What exactly does a vegetarian diet entail to? Vegetarian diets are traditionally defined as the absence of meat but there are many variations including lacto-vegetarians (includes dairy), lacto-ovo-vegetarians (includes eggs and dairy), pesco-vegetarian (includes fish) and vegan (no animal products). These diets are characterised by a high intake of fruits, vegetables, soy, nuts, legumes, etc. which independently provide many health benefits.
A pooled analysis of several cohort studies involving about 76000 individuals over about a decade reported that vegetarians had a 24% reduction in death from heart disease when compared to regular meat eaters. Further, people who were only eating meat occasionally had a 20% reduction compared to regular meat eaters in the development of heart disease. Current research indicates the reduction of meat will result in a reduced risk for heart disease. Much of this stems from the differences in BMI’s, cholesterol (reduction in both total and LDL cholesterol) and blood pressure between vegetarians and omnivores. Vegetarians, especially vegans, have significantly lower body weights than the general population; on average, the BMI of vegetarians are 1-2kg/m2 less than omnivores (gender and age matched). In the Adventist Health study, they found that BMI increased as meat consumption increased.
Research is limited on the relation between vegetarianism and cancer and diabetes but overall, epidemiological data suggests that cancer and diabetes rates are both lower in vegetarians. Furthermore, clinical vegetarian dietary interventions have shown significant reductions in fasting blood sugar, although these results may be due to the weight loss of the intervention groups.
So what makes plant based diets so effective against fighting and preventing chronic diseases? The answer to this question is multifactorial and complex and includes (but isn’t limited to) the following…
Vegetarian diets are characterised by an increased consumption of both fruit and vegetables which contain many healthy compounds including fibre, phytochemicals, antioxidants and vitamins that may offer protection from chronic diseases. Fruit and vegetable consumption consistently reduces risks for heart disease and other chronic diseases. Nuts, which are consumed in greater frequencies on average in vegetarians, are good sources of sterols (as well as antioxidants and minerals) and consistently show a reduced risk for heart disease. A meta-analysis showed that people who consumed nuts four or more times weekly had a 37% reduced risk of death from heart disease.
In several epidemiological studies, consumption of red and processed meat resulted in an increased risk for heart disease, diabetes and certain cancers. Processed meat consumption was associated with a 42% increase in heart disease risk for each 50g/day increase in consumption. For more on this topic, see my blog post on processed meat.
While carefully planned vegetarian diets can provide enough nutrients, nutrient deficiencies can occur when diets are not carefully planned (like any other diet). The nutrients most likely to be deficient are iron, vitamin D, vitamin B12 and omega-3s.
Intakes of iron should be higher in vegetarians since plant sourced, non-heme, iron is less bioavailable. The bioavailability of non-heme iron can be enhanced by an increased intake of vitamin C.
Vitamin B12 is almost only found in animal based products, deficiencies can result in pernicious anemia and megaloblastic anemia. Vitamin B12 deficiencies are often hard to determine, especially in vegetarians, because folic acid (in plants) will mask a B12 deficiency. Frequently B12 will have to be achieved through fortification (in many yeasts, soy and cereals) or supplementation.
Dietary vitamin D typically comes from oily fish, fortified margarines and cereals; vitamin D can be a concern, especially in northern latitudes with less sunlight exposure or during the winter. Many vegan products are fortified with vitamin D, but a supplement may be required in some cases,
particularly in the winter.
Omega-3s are essential for good health (see blog post on omega-3s), but in vegetarian diets, omega-3s are often much lower (particularly marine omega-3s EPA and DHA) and higher in omega-6s. Plant derived ALA omega-3s, which is a common part of a vegetarian diet, need to be converted in our bodies after consumption to EPA and then DHA. The rate of that conversion is extremely low and therefore ALA omega-3s may not be sufficient. Vegan DHA supplements, which are derived from algae, would be a good idea for vegetarians.
And some concluding thoughts; a plant based diet can be a powerful tool in disease prevention, when done right, and an environmentally friendly way of life. Whether you’re vegetarian or not, hopefully this post has shed light on the many aspects of a plant based diet!
Hope you all have a great start to the week!
Fraser GE (1999) Associations between diet and cancer, ischemic heart disease, and all cause mortality in non- Hispanic white California Seventh-day Adventists. Am J Clin Nutr 70, Suppl. 3, 532S–538S.
Jenkins DJ, Kendall CW, Marchie A et al. (2003) Type 2 diabetes and the vegetarian diet. Am J Clin Nutr 78, 3 Suppl., 610S–616S.
Kelly JH Jr, Sabate´ J (2006) Nuts and coronary heart disease: an epidemiological perspective. Br J Nutr 96, Suppl. 2, S61–S67.
McEvoy C, Temple N, Woodside J. (2012) Vegetarian diets, low-meat diets and health: a review. Public Health Nutri., 15:12.