Whole Grains and Health. Группа авторов
Cooked cereal foods
While bread and breakfast cereals make up the bulk of whole grain intake worldwide, a potentially substantial portion can come from meals that include whole grain pasta, noodles, pizza, tortillas or couscous, or “intact” grains such as brown rice, quinoa or wheatberries.
A standard dry weight serving of these foods is between 45–70 g, which is around the minimum (48 g) recommended intake of whole grains in the United States, and close to the 75 g/2000 kcal recommended in Denmark and Sweden. Since all cereals – from wheat, rye, barley and rice to pseudocereals such as buckwheat, amaranth and quinoa – can be easily incorporated “intact” into main dishes and salads, this category can contribute to greater diversity of whole grain consumption and enjoyment.
Unlike bread and breakfast cereals, whose whole grain content is hard to ascertain, “main meal” carbohydrates such as brown rice or quinoa are easily identifiable as 100% whole grain. Pasta is generally made from either 0%, 50% or 100% whole grain flour, while noodles can also be made from 100% whole grain flour, though sometimes “whole grain noodles” are made with less than 50% whole grain in order to maintain a similar texture to noodles made with 100% refined grain flour.
Fresh corn/maize is usually included as a vegetable in dietary surveys, although corn/maize is a cereal (and dried corn in the form of popcorn is included as a whole grain cereal). The contribution of fresh corn/maize to whole grain intake is not well established to date, and should be estimated (on a dry‐weight basis) as part of efforts to understand the intake and potential health impact of different cereal species. As for other whole grain foods, reporting on dry or wet weight can make a big difference to estimates of whole grain intake, especially for products such as fresh pasta or noodles, or frozen ready meals.
d. Sweet baked goods, snacks and other products
Although sweet foods are often not considered to be suitable for whole grain claims, many sweet foods such as buns and muesli/granola bars include whole grain ingredients, and determining intake from these sources is important for understanding how much they contribute to overall whole grain intake, and how this may impact on health. Generally, few pastries and cakes contain whole grain flour due to the difficulties in making pastry or batter with the desired properties.
Sweet products such as some types of biscuits/cookies or muesli/granola bars may contain a significant amount of whole grain per serving. In general, though, high levels of fat, sugar and inclusions like nuts and dried fruit mean that foods in this category contain relatively low amounts of whole grain as a percentage of weight as consumed (Table 5.1).
One of the most commonly consumed whole grains among “non‐whole grain” consumers is corn/maize in the form of popcorn. While not always recognized as a whole grain food, popcorn is a dried intact kernel of corn, and while the starch in the kernel expands and pops with heat, all the components of the grain are still generally attached. Some studies have found that popcorn intake is associated with reduced disease risk,(20,21) suggesting that popcorn deserves more attention as a healthy whole grain food. Other savory snack foods may also contain a relatively high amount of whole grains. This includes crisp‐type products (called snack chips in the United States) made from cereal flours and crackers. However, recommended serving sizes for whole grain snack foods are often limited, so as a category, should be considered fairly limited as a sole source of whole grains in a diet. However, it is positive that there are a wide range of whole grain snacks available as an alternative to those based on refined carbohydrate sources.
5.2.4 Measuring the whole grain content of foods
To date, there are no validated instrumental methods to independently determine the whole grain content of food. Thus, labeling claims for whole grains are difficult to police, and are ultimately dependent on the honesty of the food manufacturer – who may be tempted to “healthwash” a product, to make it seem healthy while still maintaining organoleptic properties similar to a non‐whole grain product. For both research and regulatory purposes, it would be useful to have a method for measuring whole grain intake by determining the amount of whole grain content in unknown samples.
There are no officially accepted methods for monitoring compliance to reported whole grain content or levels. The FDA in its whole grain health claim guidance directs that fibre content of at least 11% be used for this purpose, though this approach does not account for the wide range of dietary fibre contents in different cereal grains (e.g., wheat, used as a reference by the FDA as it is one of the most commonly consumed grains in the United States, has a dietary fibre content of around 10–11%, while brown rice has just 3–3.5% dietary fibre). A ratio of 10:1 carbohydrate to fibre has also been proposed as an index to help consumers choose foods with the highest whole grain content in foods(22) though this is essentially the same as the FDA proposal, and is not effective for foods with whole grain rice or corn/maize or foods with added fibre.
One simple method for regulators to monitor whether the whole grain content of foods matches that which is reported on packaging is to check the paper trail in relation to the making of that product – that is, following good manufacturing practice standards. In food manufacturing, there should be clear documentation detailing what ingredients have gone into making a batch of a product, including the weight. Thus, an audit of this documentation should reveal if the reported whole grain content accurately reflects what is in the product. This should work well where such record keeping is normal, but still requires a method that could highlight such products. Nor will it help in detecting the whole grain content in foods where the proportion of whole grains is not publicly available.
Independent methods are needed that can be used for both regulatory purposes and screening, including for food composition databases and work on whole grain intake. The major problem is finding a method that is able to differentiate between the addition of bran and whole grain flour. Measures such as that proposed by the USFDA that are based on dietary fibre are limited because of the inability of simple methods of measuring dietary fibre that distinguish between fibre from bran or other sources. Other more complex methods have been proposed for measuring the whole grain content of foods. These include the analysis of components that are derived from bran, germ and endosperm, and checking the relative ratios.(23) This has proven to be effective, but requires many different types of analyses so is expensive and too slow for screening or monitoring. Other more simple measures include the use of biomarker compounds such as the alkylresorcinols. These phenolic lipids are present as several homologues that differ between common wheat, durum wheat, rye, barley and quinoa, and represent a fingerprint that distinguishes between these cereals.(24,25) However, alkylresorcinols are not present in other cereals, and they are mainly present in the bran fraction, so they cannot distinguish between whole grain flour or flour with added bran. In Table 5.1, it is possible to see the potential problems of using alkylresorcinols as markers of whole grain content, as several whole grain foods contain no alkylresorcinols, while wheat bran‐based breakfast cereal has the highest amount by some margin, even though for wheat‐ and rye‐based products they are strongly correlated to whole grain content.(26)
The question of whether it is possible to develop a method that can distinguish between whole grain flour and flour with bran and germ added from another batch of flour, and is both rapid and cheap, remains open. That there are some methods available that are able to give some indication does at least help to reinforce measures such as auditing of good manufacturing practice documentation.
5.2.5 Reporting whole grain content in foods in clinical trials
The plethora of different ways of reporting whole grains in clinical trials has led to great difficulty in directly comparing different studies. This, in turn, hampers meta‐analyses pooling data from different studies to increase the statistical power for finding differences due to dietary interventions that include whole grains. Reports of whole grain intake