As a preface, it is important to point out that there is no evidence to support the claims made by your source. In fact, a large body of scientific literature suggests that the maximum amount of protein we can utilise is about 2.0 g/kg/day (0.9 g/lb/d), with approximately 1.5-1.6 g/kg/d (~0.7 g/lb/d) being optimum for most strength, power, and endurance athletes. This matter is discussed in greater length here.
Most people who follow such high protein diets do indeed use supplementation, since it is by far the easiest way to meet their protein goals. However, it is entirely possible to attain that same protein through whole- rather than refined foods. Being ovo-vegetarian (or ‘eggetarian’) presents further challenges, too, but those challenges are not insurmountable. The principle problem is that plant protein is always accompanied by significant quantities of starch, fibre, and water, and that means that it is necessary to eat a larger volume of food. This can be a problem for those who do not have a large appetite. Furthermore, plants tend to have significantly lower proportions of one or more essential amino acids, and we must therefore eat a broad variety of different classes of plant, such that the amino acids that are scarce in one are abundant in the other, and vice versa. This is normally not a problem for anyone who eats a diversity of foods, but again, it can present a challenge to fussy eaters.
The key, therefore, is to identify which plant-based foods have higher protein contents, and to eat a broad variety of those foods. It is optimum to combine foods that complement each other in a single meal—a practice known as protein complementation—but not necessary. Provided that our overall consumption includes appreciable amounts of each essential amino acid, the benefits are similar. Of course, as an ovo-vegetarian, plant-based meals may be combined with eggs, or supplemented with ovalbumin.
From the source above, the classes of food that should be combined are as follows:
Class Scarce amino acids Complement
Legumes Methionine Grains, nuts/seeds
Grains Lysine, threonine Legumes
Nuts/seeds Lysine Legumes
Vegetables Methionine Grains, nuts/seeds
Corn/maize Tryptophan, lysine Legumes
Some plant foods such as soy, quinoa, and amaranth contain appreciable quantities of all of the essential amino acids, and are therefore described as having higher protein quality. However, it is important to point out that provided the amino acids are present in combination, the quality of plant protein is identical to that of meat.
If a broad variety of protein-rich plant-based foods are consumed, total protein consumption can be calculated in exactly the same manner as normal, summing the individual protein contents of each component food.
Some common protein-dense plant-based foods are listed below.
Food Approximate protein/100 g
Peanuts, raw 25.8 g
Wheat germ 23.1 g
Tofu, firm 15.8
Bread, multigrain 13.4 g
Shredded wheat 11.4 g
Lentils, brown 9.0 g
Chickpeas 8.9 g
Quinoa 4.4 g
Amaranth 3.8 g
Sweet corn 3.3 g
Rice, white long-grain 2.7 g
Broccoli 2.4 g
These data are sourced from SELFNutritionData. It should be noted that data vary greatly between different sources, reflecting varieties, seasonal variation, and different testing protocol.
Eating a variety of different foods, spacing your meals, and if necessary complementing your plant sources with eggs and/or ovalbumin, high-quality protein intake of above 100 grams is entirely achievable. But as stated at the beginning of this post, it is unnecessary for all but the most extreme (endurance) athletes.
I hope that helps.