I.e. if you eat enough grains, pulses, fruits and vegetables, but not processed foods like tofu, seitan, mock meats, etc.
It is very easy to get adaquate protein from whole plant based products. Below is an excerpt from an article in scientific literature.
... Protein needs are the nutritional issue for which there is probably the least reason for concern. The fact is that all essential and nonessential amino acids can be supplied by plant sources alone, assuming that a reasonable variety of foods is consumed and that calorie intake is adequate to meet energy needs. Assuming that these two criteria are met, it would actually be difficult to plan a protein-deficient diet. There is also no need for a conscious combining of foods within a given meal to form a "complete" protein, as the outmoded complementary protein theory suggested was necessary.
Tofu and other processed products are not required for a vegetarian to meet protein needs. Now, fructarians and raw vegans may have more difficulty due to restricting many foods that vegans typically eat, such as beans, potatoes, rice and grain. They can still get protein from nuts and other sources, but may have to plan their diet more carefully.
If you are really worried about protein, eat a variety of different types of foods throughout the week, seeds, nuts, rice, beans, root vegetables (such as potatoes), leafy vegetables, etc. It's really easy to get all your essential amino acids without thinking about it as long as you are not eating the same single ingredient at every meal. No need to mix food types in the same meal though, variety is only required at longer time scales.
Yes, you can get sufficient protein from whole plant foods.
If you are an average weight male (84 kg) you'll want to aim for at least 67 grams (268 kcal) of protein per day (based on 0.80 g protein/kg body weight). Assuming you're consuming 2000 kcal per day, your goal is to get at least 13.5% of your food energy from protein.
Different food categories provide different amounts of protein. I'll calculate the average amount of food energy provided by protein across a basket of examples in each category.
- Fruits: 4.5% energy from protein (apple, banana, orange, mango, grapefruit)
- Grains: 10.2% energy from protein (rice, buckwheat, barley, oats)
- Vegetables: 12% energy from protein (onion, potato, kale, broccoli)
- Pulses: 21.0% energy from protein (chickpeas, lentils, black beans, navy beans)
Remember, based on our assumptions we want to get 13.5% of food energy from protein. We can't meet that target by eating only fruits, grains, and vegetables, but it's easy once we add in some pulses. Pulses are also a high source of the amino acid called lysine which makes them a great addition to our diet. We want to eat a bit of fruit, but if we eat too much it will get harder to meet our protein requirement.
It's a good idea to eat 3 servings of legumes/beans each day, especially when aiming to get all protein from whole plant foods.
If avoiding processed proteins, avoid oil and sugar too
There's one more category I haven't mentioned yet that is particularly challenging.
- Refined oils and sugars: 0% energy from protein (olive oil, candy, margarine)
Unlike the whole vegetable foods listed above, refined oils and sugars don't contribute any useful protein to the diet. Incorporating any of these foods makes it much more challenging to meet the protein requirement from whole foods alone. If the diet includes too much refined oils and sugars, then the protein requirement needs to be met in other ways such as with meat substitutes or protein powder or refined proteins like tofu and seitan.
All of the numbers I provided in this post were calculated using Cronometer, a web-based tool for adding up nutrient values of various whole and packaged foods.