In our first article, Stop Protein Obsession, we explored why most people already get enough protein and why chasing more isn’t always better for health. As promised, in this follow-up we’ll take a closer look at protein ‘quality’—what completeness really means, and how animal and plant proteins compare when it comes to meeting our nutritional needs and supporting long-term health.
Animal vs. Plant Proteins: Rethinking ‘Complete’ and ‘Incomplete
You’ve probably heard the buzz: animal proteins are “complete” and “high quality,” while plant proteins are “incomplete” and somehow less impressive. But is this really the full story? Let’s break it down in a way that’s easy to digest, exploring what these terms actually mean and whether “high-quality” proteins are always the healthiest choice.
🔍 Biological Value and Efficiency
Animal proteins generally have a higher biological value, meaning they’re used more efficiently by the body. This is because their amino acid profiles closely match those required by humans—a reflection of our shared animal biology.
But here’s the key question: Does efficiency equal superiority?
⚠️ The Hidden Trade-Offs
Efficient protein utilization isn’t always beneficial. So-called “high-quality” proteins can just as effectively fuel undesirable growth, including cancer cells and atherogenic (plaque-forming) tissue. By contrast, plant proteins—whose amino acid profiles differ slightly from ours—are less efficient at driving such harmful growth.
The downside of this efficiency is evident with high-biological-value proteins like casein and egg albumin. These not only accelerate cell growth but also increase production of growth factors such as IGF-1 (insulin-like growth factor-1), which has been linked to elevated cancer1. In humans, this heightened activity is associated with earlier puberty2 and a greater likelihood of developing certain cancers.
How does your body know the difference between plant-protein and animal-protein? Isn’t Protein, Protein? No, unlike animal protein, plant protein is generally low in branched-chain amino acids. Per research , decreased consumption of branched-chain amino acids improves metabolic health3. Replacement of 3% energy from various animal protein sources with plant protein was associated with 10% decreased overall mortality in both sexes. Evidence4 from prospective cohort studies to date suggests that total protein intake is positively associated with all-cause mortality, mainly driven by a harmful association of animal protein with CVD (Cardiovascular Disease) mortality. Plant protein intake is inversely associated with all-cause and CVD mortality.
From5: Dietary protein intake and all-cause and cause-specific mortality: results from the Rotterdam Study and a meta-analysis of prospective cohort studies
🌾 The Truth About “Incomplete” Plant Proteins
Despite being labeled “incomplete,” plant proteins do contain all essential amino acids.
Proteins are made of 22 amino acids. The body can synthesize 13 of them, while 9—called essential amino acids—must come from food. Of these, only three are worth close attention: lysine, tryptophan, and methionine.
- Legumes (beans, lentils): High in lysine, lower in tryptophan and methionine
- Grains (rice, quinoa, oats): Lower in lysine, higher in tryptophan and methionine
When eaten together—like the classic rajma-rice or dal-rice—they form a complete protein, nutritionally on par with meat or eggs, but without the harmful baggage. However, it’s not required to be eaten together to get complete protein as our body maintains pools of free amino acids that can be used to do all the complementing for us.
🔄 Amino Acid Recycling
As pointed above, here’s something often overlooked: the body stores and recycles amino acids. That means you don’t need to balance proteins in every single meal. As long as your diet includes a variety of plant foods and enough calories to maintain body weight, you’ll get all the protein you need. Our body is perfectly capable of mixing and matching amino acids from different foods to create exactly what it needs. This means those eating plant-based diets don’t have to worry about amino acid imbalances—the variety in everyday plant foods is more than enough.
✅ Rethinking “Quality”
Although plant proteins don’t perfectly match the human amino acid profile, they are fully capable of supporting human health. Their so-called “lower quality” doesn’t translate into deficiency or weakness.
In fact, the long-celebrated “high quality” of animal proteins may come at a cost—accelerated growth that can fuel chronic disease.
What truly matters is not chasing so-called “high-quality” protein but choosing proteins that support long-term health—and plants do exactly that.
🌟 The Bottom Line
The “complete” vs. “incomplete” protein debate is outdated. Plant proteins are more than capable of meeting your needs while offering health perks that animal proteins often lack. It’s not about chasing “high-quality” proteins—it’s about choosing foods that support your long-term health. So, next time you hear someone dissing plant proteins, you’ll know the real deal. Ready to give lentils or quinoa a starring role on your plate? Your body (and the planet) will thank you!
Stay tuned: Carbohydrates—demonized, misunderstood, and due for a reality check.
- https://www.ceu.ox.ac.uk/news/study-of-almost-400-000-confirms-that-higher-blood-levels-of-igf-1-are-a-risk-factor-for-several-types-of-cancer ↩︎
- https://pmc.ncbi.nlm.nih.gov/articles/PMC7902462/ ↩︎
- https://pubmed.ncbi.nlm.nih.gov/27346343/ ↩︎
- https://link.springer.com/article/10.1007/s10654-020-00607-6 ↩︎
- https://link.springer.com/article/10.1007/s10654-020-00607-6/figures/2 ↩︎
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