As we age, our muscle mass decreases, and we are at increased risk to develop sarcopenia and other muscle-related diseases. It can also become a bit harder for us to absorb and synthesize proteins from our diet, or we simply stop eating enough nutrients. What's the obvious solution? Well, adding more proteins to our diets sounds like the obvious choice.
However, some research shows that we might not need to increase our protein levels at all. It would rather be better to eat as less protein as possible, or at least eat only animal-derived proteins! Even notable health and longevity researchers, like Peter Attia, Michael Gregor, and Victor Longo can't seem to agree on a clear answer.
So what's the real truth, do we need to eat protein as we age or not? Keep reading this article and find out.
What are proteins and why do we need them?
Before we jump into the vast sea of information on how we should eat as we age, let's start with some basics. By understanding the basic biology behind proteins, and their roles in our bodies, we'll be able to understand why we might or might not need them.
Proteins, along with fats and carbohydrates, are the basic building blocks of food we consume. But that's not all. Proteins are also the basic building blocks of our cells, tissues, and organs (along with fats, sugars, minerals etc). They play a critical role in nearly every biological and molecular process, and are often called the building blocks of life.
Here are some biological functions of proteins (1):
- Critical for muscle function and movement,
- Providing strength and support to cells and tissues,
- Transporting molecules throughout the body,
- Maintaining the balance of fluids in the body,
- Communicating between cells and tissues,
- Blood clotting,
- Immune defense,
- Synthesis of DNA and energy molecules,
- Some proteins function as hormones, which act as chemical messengers.
What are amino acids?
Proteins are complex, and often large, organic molecules that are composed of chains of amino acids. The smallest proteins can have only a couple of amino acids, and the biggest proteins have up to millions of amino acids. There are 20 different amino acids, and their arrangement determines a protein's structure and function. How proteins are arranged and made is encoded by our DNA.
Our bodies can produce some amino acids (non-essential amino acids), but some we have to get from food (essential amino acids) (2). Now you understand why it's crucial that we eat proteins, at least at minimum levels. Without proteins, there is no life.
Recommended daily protein intake
For an adult with average body weight and level of activity, the recommended daily dose of protein is 0.8 grams of protein per kilogram of body weight. This amounts to about 10% calories of your diet, or up to 60 grams of protein per day (depending on your weight, of course) (3).
This will significantly change if:
- your level of activity is high,
- you're a child or a teen,
- you're pregnant or breastfeeding,
- you're above the age of 65.
There is really no recommended maximum protein intake per day, as it depends on a variety of factors. However, a general maximum can be taken as approximately 2 grams of protein per kilogram of body weight per day, as this can be very demanding on the kidneys.
Do we need to eat proteins as we age?
In short, yes. Multiple scientific studies done on human subjects show that we need to eat proteins as we age, but the question is how much protein do we need?
In practical terms, the recommended amounts of protein a person above 65 should eat would be 1.2 to 1.5 grams of protein per kilogram of body weight (3, 4, 5). This amount of protein should prevent muscle loss and the development of sarcopenia, which are so common in older individuals. These claims are also supported by many physicians and scientists, like dr. Peter Attia and dr. Victor Longo.
However, there are also studies which show that eating more than the recommended daily amount of protein in adult age (0.8 grams per kg of body weight) can be harmful and not offer additional health benefits. American physician and nutritionist, dr. Michael Greger is a huge advocate of not increasing the amount of protein in our diets as we age, for several reasons:
- increased cause of mortality and cancer development,
- increased stress on kidneys,
- increased risk of heart diseases and diabetes when eating more animal proteins.
So who is right? Let's have a look on the existing scientific studies.
Is eating more protein in older age actually bad for you?
Let's explore dr. Greger's claims one by one.
Eating animal proteins increases mortality in old age
The first of dr. Greger's concerns is that eating more protein in old age increases mortality and the risk of developing cancer, heart and kidney diseases, and diabetes. The claim mostly comes from a 2014. study published in Cell Metabolism, that showed how eating animal protein increases the levels of the insulin-growth factor 1 (IGF1) (6). This factor is connected to tissue growth, muscle repair, and cancer (as it pushes cells to grow more).
The middle-aged test subjects who ate animal protein had a 75% increased risk of overall mortality and a 400% increased risk of cancer mortality (6), all connected to the levels of IGF1 in their blood. However, this connection was lost in individuals older than 65. They had lower IGF1 levels in general, because as we age, we lose that growth factor, and our muscles can't repair themselves as they could before. This is why it's generally considered that older individuals should keep eating protein.
Eating more protein in old age stresses kidneys
In people with pre-existing kidney conditions, eating more protein can completely stress the kidneys out and reduce their function. Eating animal proteins is also more harmful in this context, because it increases metabolic acidosis more in comparison to plant proteins (7).
However, for healthy individuals, even if they are old(er), there is no harm in increasing the daily protein intake to 1.5 grams per kg of body weight. Older people do have a slower metabolism and should have regular health check ups to make sure all their organs are functioning correctly, but if they're healthy, there is no harm in eating a bit more protein.
Eating plant proteins reduces the risk of heart diseases and diabetes
This part of dr. Greger's claim is deeply rooted in existing scientific evidence. Multiple studies have shown that if you replace animal proteins with plant-derived proteins, you will have a reduced risk of mortality and heart disease (8). You will also increase your fiber intake and reduce the fat intake if you eat more plant-based foods.
The so-called Blue Zone studies, that study the longest living populations on Earth, have found that eating plant-based proteins and diets rich in legumes significantly reduces the risk of chronic diseases (9).
Yes, you should eat more plant-based protein in general, but should you do it as you age? We saw until now that the risk of not eating enough protein in older age is the highest risk you could take. The plant-based protein claim from dr. Greger is also the only one that has been scientifically proven for older people as well. His claim that you should eat the same amount of protein when you're a young adult and when you're over 65 probably doesn't hold true, given the vast amount of research that says otherwise.
But how realistic is that you will get your increased amount of protein in older age just by eating plant-based proteins, that is supposedly so much better for you? Let's discuss.
The protein source debate - animal or plant proteins in old age?
We mentioned the research on plant-based proteins and how much better they are for you in terms of longevity and reducing the development of chronic diseases. You also eat less fat and more fiber when you eat more plant-based foods, which is healthy for you.
However, plant-based proteins are notoriously less bioavailable than animal-based proteins. What does that mean?
Well, in simple terms, animal proteins are the most similar to our own proteins, as we are also animals. When we eat animal proteins, we can recognize and metabolize them much easier than plant-based proteins, which are quite different. That means you will need to eat more plant-based proteins to get the necessary amounts, especially when you're older. Animals proteins also have a higher amount of the amino acid leucine, which aids in muscle synthesis. so important in older age.
Furthermore, it can be a bit trickier to manage your protein intake by eating only plant-based protein. It can and probably will be more expensive than eating animal proteins, and you may to eat much bigger portions. This can be tricky for the elderly, who generally prefer to eat less frequently and in smaller portions. Higher fiber intake also may not agree with their slowed-down metabolism. A lot of the claims around plant vs. animal protein don't account for these important social aspects.
How to manage your diet as you age?
However, if you persist and manage your diet carefully, you can easily take in more protein only through plant-based foods. If you cannot, there's always protein supplements, like whey. The combination of these can reduce the risk of sarcopenia, and also reduce the risk of chronic diseases and mortality that animal-based proteins bring.
Therefore, there is no proper or correct answer to this question. What you eat will highly depend on your health, social preferences, culture, the will to change your diet, and financial abilities (10). The balance between eating more protein, but also increasing plant-based protein, is probably the way to go.
Conclusion
When talking about protein intake in different stages of life, the scientific evidence supports the claim that as an older person, you should eat more protein that when you were younger. Science also supports the claim that you should eat more plant proteins if you want to reduce your mortality and the risk of developing chronic diseases.
However, it's not always so easy to completely change your diet, especially if you're elderly. If you eat only plant-based foods, it might be harder to meet your increased protein needs. There is the added financial stress, metabolic changes and social difficulties that scientists often forget to mention.
For a holistic approach, it might be best for you to combine the higher protein intake with an emphasis on plant-based sources. Even a mix of plant and lean animal proteins could strike a balance between the two perspectives. In that way, you won't eat a lot of fat, and you will still manage to increase your intake of proteins and healthy fiber. Also, don't forget to exercise as well!
Literature sources:
- LaPelusa A, Kaushik R. Physiology, Proteins. [Updated 2022 Nov 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555990/
- Church DD, Hirsch KR, Park S, Kim IY, Gwin JA, Pasiakos SM, Wolfe RR, Ferrando AA. Essential Amino Acids and Protein Synthesis: Insights into Maximizing the Muscle and Whole-Body Response to Feeding. Nutrients. 2020 Dec 2;12(12):3717. doi: 10.3390/nu12123717.
- Deutz NE, Bauer JM, Barazzoni R, et al. Protein intake and exercise for optimal muscle function with aging: recommendations from the ESPEN Expert Group. Clin Nutr. 2014;33(6):929-936. https://doi.org/10.1016/j.clnu.2014.04.007
- Putra C, Konow N, Gage M, York CG, Mangano KM. Protein Source and Muscle Health in Older Adults: A Literature Review. Nutrients. 2021;13(3):743. Published 2021 Feb 26. https://doi.org/10.3390/nu13030743
- Rogeri PS, Zanella R Jr, Martins GL, Garcia MDA, Leite G, Lugaresi R, Gasparini SO, Sperandio GA, Ferreira LHB, Souza-Junior TP, Lancha AH Jr. Strategies to Prevent Sarcopenia in the Aging Process: Role of Protein Intake and Exercise. Nutrients. 2021 Dec 23;14(1):52. doi: 10.3390/nu14010052.
- Levine ME, Suarez JA, Brandhorst S, Balasubramanian P, Cheng CW, Madia F, Fontana L, Mirisola MG, Guevara-Aguirre J, Wan J, Passarino G, Kennedy BK, Wei M, Cohen P, Crimmins EM, Longo VD. Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population. Cell Metab. 2014 Mar 4;19(3):407-17. doi: 10.1016/j.cmet.2014.02.006.
- Zarantonello D, Brunori G. The Role of Plant-Based Diets in Preventing and Mitigating Chronic Kidney Disease: More Light than Shadows. J Clin Med. 2023 Sep 22;12(19):6137. doi: 10.3390/jcm12196137.
- Budhathoki S, Sawada N, Iwasaki M, Yamaji T, Goto A, Kotemori A, Ishihara J, Takachi R, Charvat H, Mizoue T, Iso H, Tsugane S; Japan Public Health Center–based Prospective Study Group. Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality in a Japanese Cohort. JAMA Intern Med. 2019 Nov 1;179(11):1509-1518. doi: 10.1001/jamainternmed.2019.2806. Erratum in: JAMA Intern Med. 2019 Oct 1;179(10):1448. doi: 10.1001/jamainternmed.2019.4883.
- Buettner D, Skemp S. Blue Zones: Lessons From the World's Longest Lived. Am J Lifestyle Med. 2016 Jul 7;10(5):318-321. doi: 10.1177/1559827616637066.
- Xiao X, Zou PR, Hu F, Zhu W, Wei ZJ. Updates on Plant-Based Protein Products as an Alternative to Animal Protein: Technology, Properties, and Their Health Benefits. Molecules. 2023 May 11;28(10):4016. doi: 10.3390/molecules28104016.
