Sustainability and Nutrition Support

January 04, 2023 5 min read

Sustainable healthy diets are dietary patterns that promote all dimensions of individuals’ health and wellbeing; have low environmental pressure and impact; are accessible, affordable, safe and equitable; and are culturally acceptable.1

A key part of a more sustainable diet is to consume more plant sources of protein in place of animal proteins. This will help reduce both the environmental and some of the health burdens associated with animal protein sources.

Principles of sustainable eating can also be applied in the context of clinical nutrition. In the clinical management of malnutrition, the food first principles focus on maximising energy and protein intake. High energy and protein containing foods primarily include dairy foods. However, due to changes in personal preferences for vegan or plant-based diets along with environmental concerns. There is a greater need for dietitians to be able to support patients with making sustainable dietary changes, including those patients who are malnourished.

This article discusses the basis of a plant-based diet, the different plant proteins and how plant-based diets can be applied to clinical nutrition.

Plant-based diets

The British Dietetic Association defines a plant-based diet as “a diet which is based on foods derived from plants, including vegetables, wholegrains, legumes, nuts, seeds and fruits, with few or no animal products.2

UK consumption of plant-based drinks such as those based on soya, oat, almond and rice is increasing.3 Changes in consumption trends to plant-based drinks have been attributed to lactose intolerance, cow’s milk protein allergy, taste preference and wishing to follow a sustainable diet.4,5

Increasing the proportion of proteins consumed from plant-sources is an important means of improving sustainability. Many dietary recommendations focus on this for both health and environmental reasons, including EAT-Lancet, EWG, World Cancer Research Fund and Heart UK.6

Plant proteins

Plant-based milk substitutes, or plant extracts, are water-soluble extracts of legumes, oilseeds, cereals or pseudocereals that resemble cow’s milk in appearance.7 However, these substitutes exhibit different sensory characteristics, stability and nutritional composition from cow's milk. Plant protein sources include cereals (wheat, rice, millet, maize, barley, and sorghum), legumes (pea, soybean, bean, faba bean, lupin, chickpea, and cowpea), pseudocereals (buckwheat, quinoa, and amaranth), nuts, almonds, and seeds (flaxseed, chia, pumpkin, sesame, and sunflower).8

The inclusion of plant proteins from whole sources such as legumes, nuts, pulses and grains has been shown to result in an improved fat profile, lower energy density and significantly increased fibre content.9 Processed plant-based protein sources are growing in popularity but can be high in fat and salt, so consumers should consider this when adding them to the diet, as an environmentally sustainable diet is not necessarily a healthy one.10

Protein quality and quantity is not compromised when switching to more plant sources. Plants contain all essential amino acids and diets entirely based on a variety of plant proteins which meet daily energy requirements can also meet all essential amino acid requirements.11,12 However, there are also other factors that affect the nutritional quality of crops, including soil condition, crop maturity, post-harvest handling, storage, use of fertilisers and pesticides, crop variety, and climatic condition.8

Two requirements for a protein to be considered high quality, or complete, for humans are having adequate levels of indispensable amino acids to support human growth and development and being readily digested and absorbed.13

Given that many whole food sources of plant-protein are less calorie-dense than animal sources of protein, greater overall food intake is needed to meet energy requirements which, in turn, helps meet indispensable amino acid requirements. In addition, it has now become much easier for consumers to boost intake of plant proteins via the availability of multiple plant-based protein isolates and concentrates (soy, pea, canola, potato, fava, etc.) in the food industry.12

Dietary protein intake stimulates muscle protein synthesis and the response to protein intake can vary substantially between different dietary protein types or sources. The muscle protein synthetic responses to the ingestion of plant-based proteins such as soy, compared to animal proteins, has been previously shown to be lower. However, a balanced combination of different plant-based proteins may provide a higher quality protein blend, thus improving muscle protein synthesis.14

Plant-based clinical nutrition

As plant-based diets are becoming increasingly common, it is likely that the number of patients under the care of a dietitian that may require guidance on how to make dietary change whilst considering the need for plant-based food choices will increase. One key area in dietetic practice where adaptations to advice is required for those following a plant-based diet is nutrition support.
In order to facilitate nutrition support in those individuals who wish to follow a plant-based diet, there are a number of considerations:

1. Plant-based milk alternatives

There are several plant-based milk alternatives available and there are some nutritional differences. Table 1 outlines the different plant-based milk alternatives compared to cow’s milk.15

Milk Energy content (average kcal/100ml) Protein content (average g/100ml)
Oat milk 47 0.8
Soya milk 42 3.2
Almond milk 37 0.6
Coconut milk 25 0.1
Rice milk 52 0.2
Cow’s milk (whole) 63 3.4

Dairy is a key provider of protein, vitamins B2 and B12, iodine and calcium.6 Therefore, non-dairy milk alternatives are commonly fortified with additional vitamins and minerals such as calcium, vitamins A, D, B-2, and B-12.16

2. Sources of proteins in oral nutritional supplements

There are a limited number of plant-based oral nutritional supplements. However, the plant-protein source used is soya protein isolate.

The nutritional value and abundance of branched chain amino acids (BCAAs) in dairy proteins means they still have a considerable role to play in the development of nutritional products and foods, especially in foods for special medical purposes (FSMP).17 The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is the standard measure of protein quality.18 Milk proteins have a PDCAAS score of 1.0. With the exception of soy proteins (PDCAAS 0.91–0.95), individual plant proteins have lower PDCAAS scores (<0.9).10 More recently the Digestible Indispensable Amino Acid Score (DIAAS) has been adopted to quantify dietary protein quality. However, there have been limitations of DIASS in relation to plant based proteins.19

Plant proteins are often described as incomplete, due to the insufficient amounts of all nine essential amino acids. Although protein content and amino acid composition vary between plant species, in general, protein found in legumes are limited in methionine and cysteine; cereals (lysine, tryptophan); vegetables, nuts and seeds (methionine, cysteine, lysine, threonine); seaweed (histidine, lysine).20

Claims that foods are a “source” or a “high source” of protein are permitted if protein contributes 12% and 20% of energy from protein, respectively.21

3. Plant-based food fortification

There are a number of plant-based protein sources that can be used in food fortification. These foods include nut butters, soya products (e.g. milk, yoghurts, cheese), vegan cheese, coconut yoghurt, plant-based and sustainable oils and hummus. In addition, plant-based protein powders such as soy or pea protein can be used to prepare nourishing drinks.


As dietary patterns change for both healthy and vulnerable people, it is important that dietitians and industry recognise the need for tailoring advice and products to meet the requirements of a plant-based diet. A key consideration in plant-based diets is ensuring an adequate nutritional intake and ensuring nutrient fortified foods are available. In the management of malnutrition through nutrition support, where protein requirements can often be raised, it is important to be aware of the different plant-based protein sources and the protein quality of these alternative foods.

  1. FAO and WHO. Sustainable healthy diets - Guiding principles. Rome : FAO, 2019.
  2. British Dietetic Association. 2017. Food fact sheet plant-based diets. Available from: Last accessed: October 2022
  3. Alae-Carew C et al. The role of plant-based alternative foods in sustainable and healthy food systems: Consumption trends in the UK. Sci Total Environ. 2022 Feb 10;807(Pt 3):151041. doi: 10.1016/j.scitotenv.2021.151041.
  4. Sethi S et al. Plant-based milk alternatives an emerging segment of functional beverages: a review. J Food Sci Technol. 2016 Sep;53(9):3408-3423. doi: 10.1007/s13197-016-2328-3.
  5. Clegg ME et al. A comparative assessment of the nutritional composition of dairy and plant-based dairy alternatives available for sale in the UK and the implications for consumers' dietary intakes. Food Res Int. 2021 Oct;148:110586. doi: 10.1016/j.foodres.2021.110586.
  6. BDA The Association of UK Dietitians. Policy statement: Environmentally Sustainable Diets. Jan 2021. Available online: Accessed October 2022
  7. Silva ARA et al. Health issues and technological aspects of plant-based alternative milk. Food Res Int. 2020 May;131:108972. doi: 10.1016/j.foodres.2019.108972.
  8. Langyan S et al. Sustaining Protein Nutrition Through Plant-Based Foods. Frontiers in Nutrition. 2021 ;8:772573. DOI: 10.3389/fnut.2021.772573.
  9. Scarborough P et al. Modelling the health impact of environmentally sustainable dietary scenarios in the UK. Eur J Clin Nutr. 2012 Jun;66(6):710-5. doi: 10.1038/ejcn.2012.34.
  10. Darmon N and Drewnowski A. Contribution of food prices and diet cost to socioeconomic disparities in diet quality and health: a systematic review and analysis. 2015, Nutrition Review, Vol. 73, pp. 643-660.
  11. Marsh KA et al. Protein and vegetarian diets. Med J Aust. 2013 Aug 19;199(S4):S7-S10. doi: 10.5694/mja11.11492.
  12. Young VR and Pellett PL. Plant proteins in relation to human protein and amino acid nutrition. Am J Clin Nutr. 1994 May;59(5 Suppl):1203S-1212S. doi: 10.1093/ajcn/59.5.1203S.
  13. Hertzler SR et al. Plant Proteins: Assessing Their Nutritional Quality and Effects on Health and Physical Function. Nutrients. 2020 Nov 30;12(12):3704. doi: 10.3390/nu12123704.
  14. Gorissen SHM et al. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids. 2018 Dec;50(12):1685-1695. doi: 10.1007/s00726-018-2640-5.
  15. Singh-Povel CM et al. Nutritional content, protein quantity, protein quality and carbon footprint of plant-based drinks and semi-skimmed milk in the Netherlands and Europe. Public Health Nutr. 2022 Feb 23:1-35. doi: 10.1017/S1368980022000453.
  16. Drewnowski A et al. Proposed Nutrient Standards for Plant-Based Beverages Intended as Milk Alternatives. Front Nutr. 2021 Oct 20;8:761442. doi: 10.3389/fnut.2021.761442.
  17. Prodhan UK et al. Altered Dairy Protein Intake Does Not Alter Circulatory Branched Chain Amino Acids in Healthy Adults: A Randomized Controlled Trial. Nutrients. 2018 Oct 15;10(10):1510. doi: 10.3390/nu10101510.
  18. Marinangeli CPF and House JD. Potential impact of the digestible indispensable amino acid score as a measure of protein quality on dietary regulations and health. Nutr Rev. 2017 Aug 1;75(8):658-667. doi: 10.1093/nutrit/nux025. Erratum in: Nutr Rev. 2017 Aug 1;75(8):671.
  19. Craddock, J.C et al. Limitations with the Digestible Indispensable Amino Acid Score (DIAAS) with Special Attention to Plant-Based Diets: a Review. Curr Nutr Rep 10, 93–98 (2021).
  20. Lonnie M et al. Protein for Life: Review of Optimal Protein Intake, Sustainable Dietary Sources and the Effect on Appetite in Ageing Adults. Nutrients. 2018 Mar 16;10(3):360. doi: 10.3390/nu10030360.
  21. European Commission. Regulation (EC) No 1924/2006 of the European Parliament and of the Council of 20 December 2006 on Nutrition and Health Claims Made on Foods. Official Journal of the European Union; 2006.