If we take as a reference the WHO report of 2007 related to protein and amino acid requirements in humans, an adult needs 0.66 g of protein per kg of weight per day to maintain the nitrogen balance of the organism, that is, in order to prevent more proteins being destroyed than the ones being synthesized. According to the WHO, an adult with an average weight of 65kg would need at least 42g of protein per day.
The study conducted with the largest sample of vegan population in history aimed at comparing the intake of nutrients of this population with other groups that do consume animal-based foods, determined that the protein intake of the vegan population is 70% above the basic requirements. In fact, it is practically impossible to design a diet (both omnivore, vegetarian, and vegan), that is sufficient in energy and insufficient in proteins.
WHO | Protein and amino acid requirements in human nutrition.
N S Rizzo, K Jaceldo-Siegl, J Sabate, G E Fraser. Nutrient profiles of vegetarian and nonvegetarian dietary patterns. J Acad Nutr Diet 2013 113(12):1610 – 1619.
Proteins are broken down into amino acids, some of which are essential which means that they cannot be synthesized by the organism and must be supplied in its diet. The rest of the animals cannot produce these essential amino acids either, they are synthesized by plants and microorganisms. All plants contain all the essential amino acids, without exception, in varying amounts.
It is a myth that vegetable proteins are incomplete, inferior to animal ones, that they must be combined in the same food so as to increase their nutritional value, or else that they are not digested adequately or are not sufficient to reach the essential amino acid requirements. For decades, these statements extracted at a time from animal experiments, clearly inadequate to draw conclusions in relation to human nutritional needs, have been denied.
Since 2001, the American Heart Association indicates on its website that vegetable proteins provide all the necessary amino acids, without the need to make combinations of “complementary foods” in the same meal. In summary, if you mix lentils with rice, do it because you like it and not because of your concern for the quality of the proteins.
V R Young, P L Pellett. Plant proteins in relation to human protein and amino acid nutrition. Am J Clin Nutr. 1994 May;59(5 Suppl):1203S-1212S.
Vegetarian Diets, American Heart Association
In both vegan and omnivorous diet, the risk of developing osteoporosis depends on whether calcium intake is sufficient. It is true that dairy products are a good source of calcium, but they are also a source of saturated fats, cholesterol, lactose and galactose, casein and other nutrients associated to health problems in human beings. Paradoxically, it is not clear whether a higher intake of dairy products prevents from the risk of suffering from osteoporosis. Some studies have even linked high dairy consumption with an increased risk of hip fractures as a result of a lower bone density.
The best strategy is to focus on vegetable sources of calcium, which also provide fibre, antioxidants and other essential vitamins and minerals: cruciferous vegetables (cabbages of all kinds, broccoli, etc.), legumes (beans, chickpeas, etc.), some fruits such as figs and fortified foods (especially vegetable drinks).
Michaëlsson K, Wolk A, Langenskiöld S, Basu S, Warensjö Lemming E et al. Milk intake and risk of mortality and fractures in women and men: cohort studies. BMJ. 2014 Oct 28;349:g6015.
Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, Kanis JA, Orav E et al. Milk intake and risk of hip fracture in men and women: a meta-analysis of prospective cohort studies. J Bone Miner Res. 2011 Apr;26(4):833-9.
In the same way as with calcium, the risk of iron deficiency anaemia depends directly on the intake of iron in our diet. Epidemiological studies show that iron intake in vegan populations is sufficient, around 17 mg daily, and sometimes even higher than that of omnivores. In addition, the quality of animal based iron (heme iron) has been linked to an increased risk of cardiovascular disease, diabetes and cancer, unlike plant based iron (ferric and ferrous).
Only 1mg of animal iron (heme type) a day increases the risk of cardiovascular disease by 27%.
So as to put you in situation, 100 g of beef tenderloin contains 3mg of heme iron, 100 g of turkey 2.5 mg and 100g of tuna 1.5 mg, quantities that are easily consumed daily in an omnivorous diet.
Legumes, green leafy vegetables (spinach, chard, cabbage) and seeds (sesame, sunflower seeds) are good sources of plant iron and if accompanied by a citrus fruit (juice of half a lemon, orange, kiwi) we increase its absorption.
Farmer B, Larson BT, Fulgoni VL 3rd, Rainville AJ, Liepa GU. A vegetarian dietary pattern as a nutrient-dense approach to weight management: an analysis of the national health and nutrition examination survey 1999-2004. J Am Diet Assoc. 2011 Jun;111(6):819-27.
Bao W, Rong Y, Rong S, Liu L. Dietary iron intake, body iron stores, and the risk of type 2 diabetes: a systematic review and meta-analysis. BMC Med. 2012 Oct 10;10:119.
Fonseca-Nunes A, Jakszyn P, Agudo A. Iron and cancer risk–a systematic review and meta-analysis of the epidemiological evidence. Cancer Epidemiol Biomarkers Prev. 2014 Jan;23(1):12-31.
Yang W, Li B, Dong X, Zhang XQ, Zeng Y et al. Is heme iron intake associated with risk of coronary heart disease? A meta-analysis of prospective studies. Eur J Nutr. 2014;53(2):395-400.
In short, a healthy 100% vegetable diet should contain the following food groups daily:
– Whole grains (brown rice, oat, quinoa, millet, buckwheat, etc.)
– Legumes (checkpeas, lentils, black and white beans, beans, soybean, etc.)
– Green leafy vegetables (lettuce, spinach, Swiss chard, etc.)
– Cruciferous vegetables (broccoli, cabbage, radish, cauliflower, roquette, etc.)
– Other vegetables (tomato, pepper, eggplant, cucumber, zucchini, etc.)
– Fruits (apple, banana, orange, kiwi, etc.)
– Berries (raspberries, blueberries, blackberries, etc.)
– Nuts and oilseeds and seeds (avocado, peanuts, walnuts, almonds, flax seeds, chia seeds, etc.)
One proposal is to divide the daily intake into breakfast, lunch and dinner with some snacks between lunch and dinner with the following characteristics:
Half of the plate should consist of whole grains and the other half of fruit (a mixture of berries and mixed fruit). If we add 2 tablespoons of seeds we will have covered the requirements of essential fatty acids of the day!
Lunch or dinner:
Lunch and dinner have the same composition of food groups. In this case, half of the plate should be composed of whole grains (cereals, legumes or tubers) and the other half of vegetables (green leafy vegetables, cruciferous and other vegetables).
At mid-morning and mid-afternoon we can add small food intakes that help us not to get to the main meals with such hunger. A piece of fruit, nuts, dates, raisins, cherry tomatoes, carrots, etc. are some healthy snack options, both for adults and children.
Finally, do not forget to exercise moderately, choose seasonal fruits and vegetables whenever possible and take your B12 supplement!