How Much Protein Do We Really Need? A Plant-Based Look at Longevity

My food and health journey is a rollercoaster. I tend to eat plant-based, with the odd piece of fish or some kefir as the exception. But plant-based does not automatically mean healthy. I am very good at finding unhealthy vegan food, and I eat a lot of white bread.

I tend to read up on health topics when I need inspiration, usually when my weight crosses one of my magic lines. Reminders from my family and my wife are often what set it off. That is where I am right now: my weight has gone up, and I am motivated to eat healthier again.

This time I wanted to understand protein. On social media everyone seems to be talking about protein intake, and I had recently started adding a scoop of clean, simple protein powder to my day, just to be safe. One camp says we all need much more protein, especially without meat. Another, including doctors like Michael Greger of NutritionFacts.org, warns against loading up on it, even from plants.

So I looked at what PubMed has on protein and long-term health. This post is my short recap.

Quick Answer: Most healthy adults need less protein than the official guideline, which is set high on purpose to cover almost everyone. Protein from plants such as beans, lentils, soy and nuts is linked to a longer life. In midlife, very high protein intake is a possible concern for longevity, while after 65 needs go up. A varied whole-food plant-based diet, fully vegan or close to it, can cover this without protein powder.

Most of us need less than we think

The official recommendation for adults is 0.8 grams of protein per kilogram of body weight per day. What I did not know is how that number is made.

A meta-analysis of nitrogen balance studies, the classic way of measuring how much protein the body actually uses, combined data from 235 healthy adults. The average requirement came out at 0.65 g/kg per day. The recommendation of about 0.8 g/kg is deliberately set higher, so that it covers 97.5% of people. So for most of us, the guideline already includes a generous safety margin.

For a 60 kg woman, that means an average need of about 39 grams a day and a guideline of about 48 grams. For a 75 kg man, about 49 and 60 grams. Those are modest amounts, easily reached with ordinary food.

Where the protein comes from matters

The largest review I found pooled 31 long-term studies with more than 715,000 people, followed for up to 32 years. People who ate more plant protein had a lower risk of dying from any cause, and from heart disease in particular. Each extra 3% of daily energy from plant protein went with a 5% lower risk of death.

Closer to home, researchers at Erasmus MC in Rotterdam followed almost 7,800 people in the Netherlands for a median of 13 years. The protein that stood out came from legumes, nuts, vegetables and fruit, which was linked to a lower risk of death. When they combined their results with other studies, more plant protein again meant lower risk.

Soy is a staple for many vegans and plant-based eaters, me included. A review of 23 studies with more than 330,000 people linked eating soy foods to a lower risk of dying from cancer and from heart disease.

The longevity question: can there be too much?

Protein raises a hormone called IGF-1, which helps the body grow and repair. That is useful when we are young or recovering, but research in ageing biology links lifelong high IGF-1 activity to faster ageing and to some cancers.

One well-known study followed American adults for 18 years. Among people aged 50 to 65, those who reported a high protein intake had a 75% higher risk of dying from any cause and four times the risk of dying from cancer. The link largely disappeared when the protein came from plants, and in people over 65 it reversed: higher protein went with lower risk.

This was an observational study, based on what people remembered eating on a single day, and it is still debated. It does not prove that protein causes cancer. Still, it matches what I now aim for: moderate protein in midlife, mostly from plants, and a bit more as we get older.

Ageing well

For me, the number of years matters less than staying healthy and mobile through them.

A study that followed almost 49,000 women from midlife asked who reached older age free of major chronic disease, with good physical and mental health and no problems with memory or thinking. Plant protein had the strongest link: each extra 3% of daily energy from plant protein went with 38% higher odds of healthy ageing.

After 65, the picture changes

As we age, the body gets less efficient at using protein to maintain muscle, and muscle is what keeps us strong and independent. An international expert group convened by the European Union Geriatric Medicine Society, the PROT-AGE Study Group, recommends 1.0 to 1.2 g/kg per day for people over 65, ideally combined with regular strength training. People with severe kidney disease are an exception and may need to limit protein.

Can plants cover it?

According to a review by researchers in Paris and at Stanford, yes for most adults. Plant-based diets that include legumes, nuts and seeds, fully vegan ones included, can cover protein needs, and worries about missing amino acids have been largely overstated. A more recent review adds a nuance for older vegans: plant proteins are a little less digestible on average, so variety and enough protein-rich foods at each meal matter more with age.

Where I have landed

Here is what I am doing for now:

1. Whole foods first. Tofu, tempeh, lentils, beans, chickpeas, nuts and seeds, spread across the day.
2. A moderate target. Around 0.8 to 1.0 g/kg of a healthy body weight, without chasing high numbers.
3. Pausing the daily protein powder. I do not need it to reach my target, and whole foods bring fibre and much more besides. No study shows that a moderate amount of plant protein powder is harmful, so I see this as a precaution.
4. Strength training twice a week. Protein works best together with muscles that are being used.
5. Less white bread. Swapping some of it for wholegrain or sourdough.
6. Revisiting this after 65, when the evidence says to eat a little more.

None of this is extreme, whether you call your diet vegan or plant-based. Mostly it means more beans, lentils, soy and vegetables on the plate, and less counting of grams.

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Sources (via PubMed)

• Rand WM, Pellett PL, Young VR. Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults. American Journal of Clinical Nutrition, 2003. doi:10.1093/ajcn/77.1.109
• Naghshi S, et al. Dietary intake of total, animal, and plant proteins and risk of all cause, cardiovascular, and cancer mortality. BMJ, 2020. doi:10.1136/bmj.m2412
• Chen Z, et al. Dietary protein intake and all-cause and cause-specific mortality: results from the Rotterdam Study and a meta-analysis. European Journal of Epidemiology, 2020. doi:10.1007/s10654-020-00607-6
• Nachvak SM, et al. Soy, soy isoflavones, and protein intake in relation to mortality from all causes, cancers, and cardiovascular diseases. Journal of the Academy of Nutrition and Dietetics, 2019. doi:10.1016/j.jand.2019.04.011
• Levine ME, et al. 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 Metabolism, 2014. doi:10.1016/j.cmet.2014.02.006
• Ardisson Korat AV, et al. Dietary protein intake in midlife in relation to healthy aging: the Nurses' Health Study. American Journal of Clinical Nutrition, 2024. doi:10.1016/j.ajcnut.2023.11.010
• Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people (PROT-AGE Study Group). JAMDA, 2013. doi:10.1016/j.jamda.2013.05.021
• Mariotti F, Gardner CD. Dietary protein and amino acids in vegetarian diets: a review. Nutrients, 2019. doi:10.3390/nu11112661
• Soh BXP, et al. Achieving high protein quality is a challenge in vegan diets: a narrative review. Nutrition Reviews, 2025. doi:10.1093/nutrit/nuae176