Does Protein Source Matter? What New Research Says About Plant vs. Animal Protein
For years, research on plant protein vs animal protein has focused primarily on how much protein to eat and how different protein types may influence disease risk. Recently research has been taking a deeper, more nuanced look at the topic.
Emerging evidence suggests that protein source may influence biological ageing, frailty and long-term health (Xu et al., 2024).
So, what does the latest research actually show?
In short, plant protein vs. animal protein does matter for long-term health. Diets higher in plant protein are consistently associated with healthier ageing, lower inflammation and reduced mortality.
Protein source refers to whether protein comes from plant-based foods (such as beans, lentils and tofu) or animal-based foods (such as meat, fish, eggs and dairy).
Plant protein vs. animal protein: what does the latest research show?
1. From disease risk to biological ageing
Instead of focusing only on lifespan or disease risk, researchers are now looking at biological ageing “clocks”, telomere length and metabolic biomarkers.
Large-scale data (including UK Biobank analyses) indicates that:
- higher plant protein intake is associated with slower biological ageing
- animal protein overall shows more neutral or mixed effects, depending on the source
This marks a major advancement in the field. While lifespan and disease risk remain important, researchers are also examining how well we age – including physical function, metabolic health and overall resilience.
2. Plant protein and better long-term health outcomes
Latest research suggests that plant-forward dietary patterns are consistently associated with better health as we age.
Higher plant protein intake has been linked with lower risk of frailty, healthier ageing, and reduced mortality (Struijk et al., 2022). Replacing animal protein with plant protein may also be associated with improved ageing outcomes over time.
3. Why “plant protein vs animal protein” is too simplistic
Not all protein sources within each category have the same health effects. For example, processed and red meats are consistently linked to poorer health outcomes (Zheng et al., 2019). But fish and some dairy products may have neutral or even beneficial effects.
Also, diet quality plays a critical role. A whole-food, plant-rich diet is associated with positive health outcomes, but an ultra-processed “plant-based” diet is not.
4. Inflammation and metabolic health are now central
Rather than focusing only on disease outcomes, researchers are increasingly examining the underlying processes, including inflammation and metabolic health, that drive long-term health.
Recent research shows that:
- Diets higher in plant protein and fibre are associated with lower levels of inflammation (Jain et al., 2025).
- Diets higher in animal protein (in some populations) are associated with higher inflammation (Papier et al., 2021).
So, it’s not just about protein – it’s about the overall quality and impact of the diet.
Plant foods provide fibre, antioxidants and polyphenols. These compounds support metabolic health, reduced inflammation and overall physiological resilience.
5. Protein needs may change across the lifespan
There is emerging evidence that protein needs and optimal sources may vary across the lifespan. Higher animal protein intake appears beneficial for growth and development in early life, likely due to its amino acid profile and digestibility.
In contrast, observational studies in adults suggest that higher intakes of plant protein are associated with improved cardiometabolic health and longevity. However, these findings should be interpreted cautiously, as they are largely observational and may reflect broader dietary and lifestyle patterns rather than the effects of protein source alone.
6. Iron is an important consideration
Iron is an important consideration in plant-based diets. Iron from plant foods is not absorbed as easily as iron from animal foods (see my guide to vegan iron rich foods to help optimise your intake).
At the same time, very high intake of iron from animal foods may have negative long-term health effects.
In practice, this means plant-based diets can be very healthy – but they require a bit more attention to ensure adequate iron intake.
Key takeaways: does protein source matter?
- Plant protein is consistently linked to better long-term health. Higher intakes are associated with:
- slower biological ageing
- lower frailty risk
- reduced mortality
- Not all animal protein is equal. Plant-based foods provide benefits beyond protein, supporting:
- lower inflammation
- better metabolic health
- improved overall diet quality
- Diet quality matters more than diet type. A whole-food, nutrient-dense diet is key — ultra-processed “plant-based” diets do not offer the same benefits.
- Protein needs may vary across the lifespan (emerging evidence). There are early signals that optimal protein sources may shift with age, but this is not yet a firm recommendation.
- Plant-based diets can be highly nutritious but require attention to key nutrients. See my article on vegan diet deficiencies.
Frequently Asked Questions
Does plant protein support healthy ageing?
Latest research suggests that higher intake of plant protein is associated with healthier ageing, including lower risk of frailty, better metabolic health and reduced mortality. However, these findings are largely observational and should be interpreted in the context of overall diet and lifestyle.
Is plant protein healthier than animal protein?
It is not as simple as “plant vs animal protein”. Plant protein is consistently linked to better long-term health outcomes, but the effects of animal protein vary depending on the source. For example, processed and red meats are associated with poorer health outcomes, while fish and some dairy products may have neutral or beneficial effects.
Is iron a concern on a plant-based diet?
Iron is something to be aware of on a plant-based diet, as it is less easily absorbed than iron from animal foods. However, this can be managed by including iron-rich foods such as lentils, tofu and beans, and pairing them with vitamin C-rich foods to enhance absorption.
Do protein needs change with age?
There is some emerging evidence that protein needs and optimal sources may vary across the lifespan. Animal protein may support growth in early life, while higher plant protein intake is associated with better long-term health in adulthood. However, this area of research is still evolving and not yet definitive.
What are the best sources of protein: plant or animal?
The best sources of protein depend on your overall health goals and dietary pattern. Animal-based proteins such as eggs, dairy and fish provide complete amino acid profiles and are easily absorbed. However, plant-based protein sources such as lentils, beans and tofu offer additional health benefits, including fibre, antioxidants and polyphenols that support metabolic health and reduce inflammation.
Overall, research suggests that a diet that includes more plant-based protein is associated with better long-term health outcomes, while recognising that some high-quality animal protein sources, such as fish and dairy, may also fit within a healthy dietary pattern.
References
Xu X et al. (2024). Association between plant and animal protein and biological aging: findings from the UK Biobank. European Journal of Nutrition. https://doi.org/10.1007/s00394-024-03494-9
Struijk EA et al. (2022). Protein intake and risk of frailty among older women in the Nurses’ Health Study. Journal of Cachexia, Sarcopenia and Muscle. https://doi.org/10.1002/jcsm.12972
Zheng Y et al. (2019). Association of changes in red meat consumption with total and cause specific mortality among US women and men: two prospective cohort studies. BMJ. https://doi.org/10.1136/bmj.l2110
Jain M et al. (2025). Protein source, dietary fibre intake, and inflammation in older adults: A UK Biobank study. Nutrients. https://doi.org/10.3390/nu17091454
Papier K et al. (2021). Higher meat intake is associated with higher inflammatory markers, mostly due to adiposity: Results from UK Biobank. The Journal of Nutrition. https://doi.org/10.1093/jn/nxab314
