All recommendations should be considered in the context of other WHO guidelines on healthy diets, including those on sugars (15), sodium (99), potassium (100), total fat (101), saturated fatty acids (102), trans-fatty acids (102), polyunsaturated fatty acids (32)1 and non-sugar sweeteners (103). An explanation of the strength of WHO recommendations can be found in Box 1.
WHO recommendations
WHO recommends that carbohydrate intake should come primarily from whole grains, vegetables, fruits and pulses (strong recommendation; relevant for all individuals 2 years of age and older).
In adults, WHO recommends an intake of at least 400 g of vegetables and fruits per day (strong recommendation).
In children and adolescents, WHO suggests the following intakes of vegetables and fruits (conditional recommendation):
2–5 years old, at least 250 g per day
6–9 years old, at least 350 g per day
10 years or older, at least 400 g per day.
In adults, WHO recommends an intake of at least 25 g per day of naturally occurring dietary fibre as consumed in foods (strong recommendation).
In children and adolescents, WHO suggests the following intakes of naturally occurring dietary fibre as consumed in foods (conditional recommendation):
2–5 years old, at least 15 g per day
6–9 years old, at least 21 g per day
10 years or older, at least 25 g per day.
Rationale and remarks
The following provides the reasoning (rationale) behind the formulation of the recommendations, as well as remarks designed to provide context for the recommendations and facilitate their interpretation and implementation.
Rationale for recommendation 1
- ▶
Recommendation 1 is based on evidence from seven systematic reviews that assessed the effects of higher compared with lower intakes of whole grains, vegetables and fruits, or pulses (19, 34–40). These systematic reviews found that higher intake of these foods reduced the risk of all-cause mortality and several NCDs. The overall certainty in the evidence for recommendation 1 was assessed as moderate.
Box 1Strength of WHO recommendations
WHO recommendations can either be strong or conditional, based on a number of factors including overall certainty in the supporting scientific evidence, balance of desirable and undesirable consequences, and others as described in the Evidence to recommendations section of the guideline.
Strong recommendations are those recommendations for which the WHO guideline development group is confident that the desirable consequences of implementing the recommendation outweigh the undesirable consequences. Strong recommendations can be adopted as policy in most situations.
Conditional recommendations are those recommendations for which the WHO guideline development group is less certain that the desirable consequences of implementing the recommendation outweigh the undesirable consequences or when the anticipated net benefits are very small. Therefore, substantive discussion amongst policy-makers may be required before a conditional recommendation can be adopted as policy.
The reasoning behind the strength of recommendations in this guideline is provided in the rationale for each recommendation. Additional information on assessing the strength of WHO recommendations can be found in the WHO handbook for guideline development (33).
For adults, findings supporting the recommendation include the following.
Evidence of moderate certainty overall came from a systematic review of prospective observational studies demonstrating associations between higher intakes of whole grains and reduced risk of all-cause mortality, CVDs, coronary heart disease, type 2 diabetes and colorectal cancer (34).
Evidence of moderate certainty overall came from a systematic review of prospective observational studies demonstrating associations between higher intakes of vegetables and fruits and reduced risk of all-cause mortality, CVDs, stroke, coronary heart disease, type 2 diabetes and cancer (19).
Evidence of moderate certainty overall came from a systematic review of prospective observational studies demonstrating associations between higher intakes of pulses and reduced risk of CVDs, coronary heart disease and type 2 diabetes (39, 40).
For children and adolescents, findings supporting the recommendation include the following.
Direct evidence for health effects of consumption of whole grains, vegetables, fruits and pulses by children and adolescents is limited. Because the health benefits of consuming these foods observed in adults are expected to also be relevant for children and adolescents, and the benefits observed in adulthood are likely to begin accruing in childhood, the recommendation as it pertains to children and adolescents is based on extrapolation of adult data without downgrading the strength of the recommendation. Limited evidence from a systematic review of prospective observational studies of intake of dietary fibre, whole grains, vegetables, fruits and pulses by children and adolescents is consistent with that observed for adults (35). Results from studies included in this review were not amenable to meta-analysis. Although several studies suggested benefit from consumption of whole grains, vegetables, fruits or pulses in terms of body weight, blood lipids and glycaemic control, results from some studies suggested no effect, and results from a very small number of studies suggested increased body weight with increased vegetable intake (very low certainty evidence for all outcomes).
- ▶
Recommendation 1 was assessed as strong because evidence for benefit was observed directly for a number of critical health outcomes, and indirectly in the results for dietary fibre; the main dietary sources of dietary fibre were whole grains, vegetables, fruits and pulses. Although assessed in adults, this evidence was also considered to be highly relevant for children and adolescents. With the exception of a small increase in risk of prostate cancer with higher whole grain intake (low certainty evidence), no undesirable effects were identified, and no mitigating factors were identified that would argue against including whole grains, vegetables, fruits and pulses as the primary sources of carbohydrates in the diet.
Rationale for recommendations 2 and 3
- ▶
Recommendations 2 and 3 are based on evidence of moderate certainty overall from a systematic review of prospective observational studies conducted in adults that assessed the health effects of higher compared with lower intake of vegetables and fruits (19). The systematic review found that higher intakes of vegetables and fruits were associated with reduced risk of all-cause mortality, CVDs, stroke, coronary heart disease, type 2 diabetes and cancer.
- ▶
The threshold of at least 400 g of vegetables and fruits per day was selected because a dose–response relationship was observed in the observational studies: risk for all outcomes except cancer decreased with intakes of vegetables and fruits up to 800 g per day, and the greater the intake, the greater the benefit. Evidence for intakes more than 800 g per day was limited. Although the greatest benefit was observed at intakes of 800 g per day, the steepest reduction in risk was up to 400 g per day, after which the effect levelled off for some outcomes. Furthermore, intakes of more than 400 g per day may be difficult to achieve in many settings. The threshold of 400 g per day was therefore selected as a feasible minimal level that would provide significant health benefits.
- ▶
Because evidence from studies conducted in children and adolescents is insufficient to derive quantitative recommendations on intakes for children, and the observed health benefits of consuming vegetables and fruits in studies of adults are expected to be relevant for all age groups, intakes for children and adolescents are extrapolated from values for adults, based on the different levels of energy intake at different stages of childhood and adolescence. Limited evidence from a systematic review of prospective observational studies in children and adolescents suggested that higher vegetable and fruit intakes are generally associated with improvements in body weight, blood lipids and glycaemic control (very low certainty evidence for all outcomes), with no evidence of undesirable effects (35). This further supports the recommended levels of vegetable and fruit intake for children.
- ▶
Recommendation 2 was assessed as strong because evidence for benefit was observed for a number of critical health outcomes across a wide range of intakes. The minimal value selected for vegetable and fruit intake was both associated with a significant benefit and an amount that many should be able to achieve. No undesirable effects were identified with consuming 400 g per day or more of vegetables and fruits, and no mitigating factors were identified that would argue against consuming vegetables and fruits at this level.
- ▶
Recommendation 3 was assessed as conditional because, although the evidence observed for benefit in adults is robust and is expected to also be relevant for children and adolescents, the values were calculated based on extrapolation of adult values. Because the values are based both on extrapolated data and mean reference energy expenditures, a conservative approach was taken, leading to a conditional recommendation.
Rationale for recommendations 4 and 5
- ▶
Recommendations 4 and 5 are based on evidence of moderate certainty overall from a systematic review of randomized controlled trials and prospective observational studies conducted in adults that assessed higher compared with lower intakes of dietary fibre (34). This systematic review found that higher intakes of dietary fibre led to favourable improvements in obesity and NCDs risk factors, and were associated with reduced risk of all-cause mortality, CVDs, stroke, coronary heart disease, type 2 diabetes and cancer.
- ▶
The threshold of at least 25 g per day was selected based on the dose–response relationship seen in the observational studies between dietary fibre intake and reduced risk for several NCD and mortality outcomes. This relationship was observed at intakes up to 40 g per day, but the number of studies reporting data began to taper off at 30 g or more per day. Evidence for intakes more than 40 g per day was scarce. In studies comparing individuals with the lowest fibre intakes with those consuming discrete ranges of increasing intake, the range that demonstrated greatest benefit for the largest number of health outcomes was 25–29 g per day.
- ▶
Because evidence from studies conducted in children and adolescents is insufficient to derive quantitative recommendations on intakes for children, and the observed health benefits of consuming dietary fibre in studies of adults are expected to be relevant for all age groups, intakes for children and adolescents are extrapolated from values for adults, based on the different levels of energy intake and energy expenditure at different stages of childhood and adolescence. Limited evidence from a systematic review of prospective observational studies in children and adolescents suggested that higher dietary fibre intake is generally associated with improvements in body weight, blood lipids and glycaemic control (very low certainty evidence for all outcomes), with no evidence of undesirable effects (35). This further supports the recommended levels of dietary fibre intake for children.
- ▶
Recommendation 4 was assessed as strong because evidence for benefit was observed for a number of critical health outcomes across a wide range of intakes. The minimal value selected for dietary fibre intake was both associated with a significant benefit and an amount that many should be able to achieve. With the exception of increased risk of endometrial cancer with higher intakes of dietary fibre (very low certainty evidence), no undesirable effects were identified with dietary fibre intakes of at least 25 g per day, and no mitigating factors were identified that would argue against dietary fibre intake at this level.
- ▶
Recommendation 5 was assessed as conditional because, although the evidence observed for benefit in adults is robust and is expected to also be relevant for children and adolescents, the values were calculated based on extrapolation of adult values. Because the values are based both on extrapolated data and mean reference energy expenditures, a conservative approach was taken, leading to a conditional recommendation.
Remarks
- ▶
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.
- ▶
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).
- ▶
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).
- ▶
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.
- ▶
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).
- ▶
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).
- ▶
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.
- ▶
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.
- ▶
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.
- ▶
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.
- ▶
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
- 1
WHO guidance on polyunsaturated fatty acids is currently being updated.
- 2
WHO recommends that infants should be exclusively breastfed for the first 6 months of life to achieve optimal growth, development and health. Thereafter, to meet their evolving nutritional requirements, infants should receive nutritionally adequate and safe complementary foods, while continuing to breastfeed for up to 2 years or beyond (113, 114).
