Food choices are so important in determining lifespan and quality of life.
Genetics perhaps determine about 20% of a person's health outcomes, and environment, including food choices, determine about 80%. This can be seen at a population level in the so called Blue Zones (1), which are areas of extended life span and health.
Main Ideas
For optimising health and longevity, try to choose a pattern of eating, by choosing foods that together are:
High in fibre
Low in saturated fat
High in polyunsaturated fat
Protein that in predominantly or exclusively from plant sources
Low in ultra- processed foods
In our community
Fibre is found in all plant foods such as vegetables, fruit, whole grains (such as whole wheat, oats, brown or wild rice, corn, quinoa and barley), lentils and legumes (green beans and peas and pulses), nuts and seeds.
Saturated fats are most concentrated in some processed foods, including processed meats, and red meat, poultry and dairy. They also are in tropical oils such as coconut and palm oil.
Unsaturated fats are in the most concentrated forms are sourced from fish and plant foods such as nuts, seeds, avocado, and olives. They can be found in olive oil and canola oil which are the cooking oils I most often recommend.
Plant sources of protein include whole grains, lentils and legumes, nuts and seeds.
What else about protein?
Plant protein is as good a source of animo acids as animal protein. All plants contain all essential amino acids (those our bodies cannot make). Plant sources may be inadequate in amino acids if there is not a range of foods eaten. For example, relying on only brown rice for protein. If another source was added, such as from vegetables or legumes, a complete source is expected.
Bioavailability of amino acids. If food is properly prepared and adequate protein is consumed from plant sources, muscle synthesis is as good. This has been well researched over the last years.
Animal sources of protein are more likely to come with saturated fats. This is because most of the meat sources we buy are farmed, and not sourced from game such as wild venison or bush meat from hunting. Swapping protein to plant sources has been shown to improve healthy aging, not have physical or mental limitations, and reduce the risk of chronic disease such as cardiovascular disease, kidney disease, lung disease and neurogenerative diseases. (2)
How much protein? I would recommend 1.5-1.6g of protein per kg of body weight for athletes and those training for strength or muscle performance. For most other people, 1.2g/ kg is very good. This includes older people who are at risk of frailty if protein intake is not adequate.
Note that muscles do not become stronger by eating more protein. They require stimulus with training.
Cholesterol, in particular LDL cholesterol, non HDL cholesterol or apolipoprotein B, is a biomarker for the risk of developing atherosclerotic vascular diseases such as heart disease and stroke, and also dementia. There is good research showing that red and white meat increase LDL cholesterol, and plant proteins do not.
In addition, when eating more plant protein sources, such as beans or tofu, you will eat more fibre which reduces cholesterol by getting rid of bile. Bile's main ingredient is cholesterol, so when the body recognises that bile has been reduced, it will make more and draws cholesterol from the blood stream.
Protein intake is optimised if taken in amounts across the day rather than when concentrated in one meal.
What else about fats?
Swapping saturated fat for polyunsaturated fat reduces the risk of a cardiovascular event by a significant amount. Long term observation studies show this, and is in line with all the government food guidelines that I am aware.
Linoleic acid is a common unsaturated omega-6 fat found in seed oils. People consuming more of these foods have less heart disease (this is not including polyunsaturated oils in ultra-processed foods which are also low in fibre, and high in refined carbohydrates and may contain other elements such as preservatives and colourings).
It is also important to remember that all oils and fats are equally high in calories. For those trying to lose weight, reducing total fat intake is an important strategy. Better sources of plant oils are high fibre sources such as nuts and seeds which are inefficiently absorbed from the gut.
Animal foods contain cholesterol. This is a smaller effect than the amount of saturated fat but it is recommended to limit cholesterol intake.
What else about fibre?
Perhaps the biggest fault in our community is the lack of fibre in our diet.
Fibre reduces transit time in the colon which means that our bowel habits are more regular and reduces the effect of carcinogenic compounds in the colon.
Fibre is the principal food supply for our microbiome, which is the trillions of microbes that live in our guts. The microbiome is incredibly important for our health, and has been shown to effect so many different functions in our body. We have evolved with these microbes in a symbiotic relationship and have out-sourced the digestion of complex carbohydrates (fibre) to them, and in return receive the metabolites which include short chain fatty acids. One of these is butyrate which provides a large proportion of the nutrients to our colon cells and is positively influential for our immune function. It has an anti-inflammatory effect in the body, reduces colonic inflammatory conditions by maintaining the junctions between cells (and avoiding leaky gut), reduces bowel cancer risk, improves the metabolism of glucose with improved insulin sensitivity, and is thought to be good for improving brain neuroplasticity and sleep quality.
Fibre slows down the absorption of nutrients in the blood including glucose which reduces the spike in blood glucose levels.
GLP1 is a hormone that our body makes. One of its effects is to reduce appetite. It has become better known with the publicity around Ozempic, a medication to lose weight. Consumption of fibre stimulates GLP1, thereby improving satiety.
If you are trying to increase the amount of fibre in your diet, it may be best to increase slowly as the microbiome may not be ready and the effect may be to cause bloating, cramping and gas. Including fermented foods in your diet, such as sauerkraut, yogurt or kimchi has been shown to be helpful. Having some resistant starch can be a good way of increasing fibre early or to avoid unpleasant symptoms. This can be made by cooking a starchy food such as potato or rice, letting it cool, and later reheating and consuming.
Increasing the variety of plant fibres, and including herbs and spices is a good goal. Simon Hill from The Proof podcast (3) has a practical way of looking at this. He talks about keeping a diary of different plant foods over a week, and trying to increase the number to 30.
If you get unpleasant symptoms with fibre, it may be that your microbiome is not very healthy. This could be due to not eating much fibre over the years, having lots of antibiotics, having an inflammatory bowel condition or even being born by Caesarian Section.
How to start?
If you are starting from scratch, try to first reduce or eliminate ultra- processed foods. It is important to note that changing from saturated fats to highly refined carbohydrates (such as white flour products or white rice) is not likely to be beneficial.
A Mediterranean style diet has been associated with good health outcomes. This is a predominant unprocessed plant food diet (supplying >80% of total calories), and if you are having animal protein, then oily fish, eggs or a fermented dairy food such as natural or Greek yogurt or some cheese would be preferable. The Danish Food Guidelines, one of the more recently published guidelines, take this position of plant dominant diet.
It is hard to argue for a plant exclusive or vegan diet for health reasons. Most of the benefits of having so many plant foods will be seen when they add to more than 80% of the total food intake. I would suggest that ethical arguments around the environment or the treatment of animals remain the best arguments for a plant exclusive diet.
The health of the planet. I like to think that this is important to consider. About 80% of the land that we use to grow food is for growing animal foods which only supplies less than 20% of our calories (energy). It uses so much land and is very inefficient. This means deforestation, loss of wildlife and biodiversity, increased water consumption, overuse of fertilisers, and increased greenhouse gases. "Food is the strongest lever to optimise human health and environmental sustainability on earth". (4)
To eat a nutrient balanced plant exlusive diet, it is necessary to have to have some information to achieve a healthy diet, to have access to a diversity of plant foods, and to store and cook these foods, knowing tasty recipes. Otherwise, it might be wise to achieve a high level of plant foods and to reduce to risk of having an unbalanced diet by including some animal foods as stated above.
A word on diabetes
Type 2 diabetes is a reversible condition if recognised early before the pancreas is damaged. It is a disease of caloric excess. It does not seem to be related to body weight in a linear way, but rather depends on the distribution of body fat. Those who store more fat in the subcutaneous tissues are not as affected as those who store fat around the middle, including visceral fat (fat in and around our abdominal organs). We know that the excess stores of fat in the liver and pancreas leads to increased blood glucose levels, which increases blood insulin levels. Over time this creates insulin resistance, which is fat cells not responding to insulin to take in glucose from the blood. The increasing insulin levels results in damaged beta cells in the pancreas, which further accents the inability to reduce blood glucose levels in a spiralling fashion. High glucose leads to increased inflammation which has negative effects including more pain in osteoarthritis, cardiovascular disease and cognitive decline.
Research (5) shows reversibility using caloric reduction, with meal replacement shakes, then transition to low calorie diet, and the Mastering Diabetes (6) outfit in US have had great success with whole food plant-based diets. Saturated fat in the diet will increase the fat in the liver, whereas unsaturated fats do not increase fat storage in the liver. It is also important to state that exercise will improve insulin sensitivity by consuming and lowering blood glucose without involving insulin.
References
1 Blue Zones see book by Dan Buettner (also is a Netflix series, which I haven't watched!)
2 Dietary protein intake in midlife in relation to healthy aging- results from the prospective
Nurses Health Study cohort. Andres V Ardisson Korat et al. Am J Clin Nutr. 2024 Feb
3 The Proof with Simon Hill. A podcast with well communicated information on health, especially nutrition.
4 Summary report of the EAT Lancet Commission
5 Nutritional basis of type 2 diabetes remission. Roy Taylor, professor ,Ambady Ramachandran, professor, William S Yancy Jr, physician, Nita G Forouhi, professor. BMJ 2021; 374 doi 07 July 2021
6 Mastering diabetes https://www.masteringdiabetes.org
Additional reading
A very good published scientific article expanding on some of the big themes is;
Plant-based diets for personal, population, and planetary health. Hemler EC, Hu FB. Adv Nutr. (2019)
10:S275–s283. doi: 10.1093/advances/nmy117