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One of the original aims of updating the guidance on carbohydrate intake was to provide guidance on carbohydrate quality. Having considered the available evidence relating to food sources of carbohydrate and dietary fibre, starch digestibility and glycaemic response, as measured by glycaemic index and glycaemic load, the WHO NUGAG Subgroup on Diet and Health concluded that providing guidance on dietary fibre and food sources of carbohydrate with consistently demonstrated benefit in terms of important health outcomes was the most effective means of addressing carbohydrate quality.
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This guideline provides guidance on dietary fibre intake, and also updates the prior WHO recommendation on intakes of vegetables and fruits (32). The scope of this guideline does not include an update to the previously published range of carbohydrate intake as a percentage of total energy intake, which was determined largely by the energy intake remaining after defining amounts of dietary fat and protein intake (32). Consequently, this guideline does not include recommendations on the amount of carbohydrate that should be consumed, and carbohydrate intake should continue to be based on recommended levels of protein (32) and fat intake (101). Results from a 2018 meta-analysis suggest that a range of total carbohydrate intake appears to be compatible with a healthy diet (104). Intakes of approximately 40–70% of total energy intake as carbohydrate are associated with reduced risk of mortality compared with lower (<40%) or higher (>70%) intakes. This is largely consistent with the range of carbohydrate intakes resulting from current WHO guidance on protein intake (32) and updated guidance on total fat intake (101).
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In addition to the benefits of dietary fibre from whole grains, vegetables, fruits and pulses, these foods may also contain other compounds that have been associated with health benefits (105–107).
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The recommendations included in this guideline cover all types of whole grains, vegetables, fruits and pulses, with caveats relating to processing and preparation, as noted in the following remarks. A variety of such foods should be consumed, where possible.
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Although fresh vegetables and fruits are a good choice when and where they are available, in some settings they present a significant risk for foodborne illness. In areas where risk of foodborne illness is high, selecting vegetables and fruits with hard skins or peels that can be removed, thoroughly washing them with potable water, or consuming cooked or canned varieties can reduce the risk of illness (108).
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The recommendations covering vegetable and fruit intake are not limited to fresh vegetables and fruits. Evidence from the systematic reviews suggests health benefits from a wide range of vegetables and fruits, including those that are fresh, cooked, frozen or canned. However, an increased risk of all-cause mortality and CVDs was observed for tinned fruits in a small number of studies. Specific evidence for dried fruits and fruit juices in the systematic reviews is very limited, and results are inconsistent; however, both can be significant sources of sugars, as can fruit concentrates and fruit sugars (i.e. sugars and syrups obtained from whole fruits). All should therefore be consumed in accordance with WHO recommendations on free sugars intake (15). Similarly, although no specific evidence was identified for canned vegetables, some canned vegetables contain added sodium and should therefore be consumed in accordance with WHO recommendations on sodium intake (99).
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The method of preparation and the level of processing should be considered when consuming whole grains, vegetables, fruits and pulses, and should be compatible with other WHO macronutrient recommendations. For example, frying and addition of sauces or condiments can significantly increase the amount of fat, sugars or salt. Therefore, fresh foods, or foods that are minimally processed or modified beyond the treatment necessary to ensure edibility, without added fat, sugars or salt, are preferred.
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Whole grains contain the naturally occurring components of the kernel (i.e. bran, germ and endosperm). Some processed foods are labelled whole grain if these three components of the grain are included, regardless of the extent to which the grains have been processed, and highly processed products labelled as whole grain are becoming increasingly available (e.g. products containing flour from milled whole grains with added fat, sugar or salt). Because there is evidence to suggest that the naturally occurring structure of intact whole grains contributes to its observed health effects (109–111), minimal processing of whole grains beyond that necessary to ensure edibility is preferred.
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The source of dietary fibre in the prospective cohort studies included in the systematic reviews, upon which recommendations 4 and 5 are largely based, is fibre naturally occurring in foods and not extracted or synthetic fibre added to foods or consumed on its own (e.g. fibre supplements, capsules, powders). Although there was limited evidence for a reduction in total cholesterol with use of extracted or synthetic fibre, further research on disease outcomes associated with extracted or synthetic fibre is needed before conclusions on potential health benefits can be drawn. Therefore, the recommendations specifically cover dietary fibre that occurs naturally in foods.
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Plant-based foods – including whole grains, vegetables, fruits and pulses – contain some compounds that have been shown to inhibit absorption of certain nutrients, most notably minerals such as iron, zinc and calcium (112). These “antinutrients” include lectins, oxalates, phytates, goitrogens, phytoestrogens, tannins, saponins and glucosinolates, and many of these have also been shown to have health benefits unrelated to their impact on nutrient absorption. The extent to which an impact on nutrient absorption occurs varies from person to person. The inhibitory effect is generally observed only at very high intakes and in individuals with existing nutritional deficiencies; in the context of adequate, diverse diets, it is generally not significant. In addition, some simple methods of preparation, including soaking and heating, and more advanced methods, including germination and fermentation, appear to reduce the inhibitory potential. Therefore, most people can generally consume whole grains, vegetables, fruits and pulses with little to no risk. Those with nutritional deficiencies or at high risk for nutritional deficiencies – particularly undernourished children and those who rely heavily on foods containing these compounds as staple foods without much additional diversity in the diet – may need to adopt behaviours that minimize the ability of these compounds to inhibit absorption of other nutrients.
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These recommendations do not cover children under 2 years of age. However, whole grains, vegetables, fruits and pulses can be healthy sources of carbohydrates in complementary foods consumed by children from 6 months to 2 years of age, and are strongly preferred to foods containing free sugars.2
