wholegrains and legumes
Their role in health and fat loss
From reduced risk of chronic disease to assistance with weight loss and even increased longevity, the case for including more wholegrains and legumes in your diet is hard to ignore, writes Dr Kate Marsh.
If you’ve been part of the high protein low carb craze, you may view wholegrains and legumes as the enemies to health and fat loss. Research doesn’t support this view, however: in fact it provides many reasons for including more of these important foods in our diets.
Grains commonly referred to as ‘cereals’ are the edible seeds of plants belonging to the cereal grass family. Wheat, oats and rice are the grains most commonly eaten in Australia with others such as rye, barley, corn, triticale and millet making a smaller contribution. ‘Pseudo-cereals’ such as amaranth, buckwheat and quinoa are generally considered grains since their overall nutrient composition is similar and they are prepared and used in the same way as true cereal grains. Wholegrains are defined as the intact grain or the dehulled, ground, milled, cracked or flaked grain where the components are present in the same proportion as is found in the whole cereal.
Wholegrains are low in fat, and are important sources of protein, dietary fibre, vitamins (especially B-group and vitamin E), minerals (magnesium, zinc) and phytochemicals. However, their role in a healthy diet appears to go beyond providing nutrients – there is strong and growing evidence that regular consumption of grain-based foods, especially wholegrains, can play a role in disease protection.
- Epidemiological studies in the US, UK and Europe consistently report that eating wholegrain foods reduces overall disease risk and all-cause mortality. For example, a large US study, which followed more than 15,000 individuals for 11 years, found those consuming the most wholegrains (three serves a day) had a 23 per cent reduction in mortality compared to those consuming little or no wholegrains.
- Eating two to three serves of wholegrain foods a day is consistently reported to reduce the risk of developing chronic disease – including cardiovascular disease, type 2 diabetes and certain cancers – by 20 to 30 per cent.
- A diet high in wholegrains is associated with a lower BMI, waist circumference and risk of being overweight; it can also help to reduce weight gain and assist in weight loss as part of an energy-controlled diet.
- Eating two to four serves of wholegrain foods a day can reduce the risk of heart disease by as much as 40 per cent – equal to the effect of the most common cholesterol-lowering drugs.
- Wholegrains can help to lower blood pressure. Replacement of white rice with brown rice, white bread with wholegrain bread, and low-fibre cereals with barley or whole wheat cereals led to a significant reduction in blood pressure over a five week period in one study of 25 overweight patients with high cholesterol.
- A review of 12 studies found that high intakes of wholegrain foods reduced the risk of developing type 2 diabetes by between 21 and 33 per cent while another review of 24 studies that incorporated wholegrain foods into the diets of those who already have type 2 diabetes found that, in all but two, there were improvements in glucose metabolism, including reduced fasting blood glucose and HbA1c levels and a reduction in insulin or diabetes medications.
- There is some evidence that wholegrain cereal foods and cereal fibre-rich foods may protect against colorectal cancers, gastric cancers and possibly also breast, endometrial and prostate cancer.
Surveys have shown that Australians don’t eat enough wholegrain foods and have actually reduced their intake. In 2008, Go Grains (now the Grains and Legumes Nutrition Council), in collaboration with the International Life Sciences Institute (ILSI) convened with an expert panel to establish an Australian daily target for wholegrain intake. After reviewing the scientific evidence, the expert panel agreed that 48g of wholegrains each day is an achievable, evidence-based Daily Target Intake (DTI) for adults, teens and older children (aged 9+ years). Table 1 shows the wholegrain content of some commonly eaten foods.
Versatile, economical, filling and nutritious, legumes (or pulses) are the edible seeds of plants from the Leguminose family and include dried beans, peas and lentils. Legumes are low in fat and kilojoules, and high in fibre, containing all three important sources of fibre (soluble, insoluble and resistance starch). They are a good source of plant protein, folate, B-group vitamins, and minerals including iron, zinc, potassium and magnesium. They are also a rich source of antioxidants and have a low glycemic index (GI). In their natural form they are low in sodium (although salt may be added to canned varieties) and when sprouted (e.g. mung beans) they are a good source of vitamin C.
Like wholegrains, legumes appear to have many health benefits.
- Research has shown that eating legumes regularly can lower total and LDL cholesterol levels and reduce the risk of heart disease. A large US study found that compared to those who ate legumes less than once per week, those who ate them four or more times per week had a 22 per cent lower risk of coronary heart disease and an 11 per cent lower risk of cardiovascular disease.
- Higher intake of legumes has been shown to reduce fasting blood glucose and insulin levels in people both with and without diabetes, and a large study of Chinese women found an inverse association between legume intake (including soybeans) and the incidence of type 2 diabetes. Those with the highest intakes of soybeans were almost half as likely to develop diabetes as those with the lowest intake, while those with the highest intakes of non-soy legumes had a 24 per cent reduced risk.
- Legumes appear to protect against bowel cancer. Both the Nurse’s Health Study and Shanghai Women’s Health Study showed a reduced risk of colorectal cancer with higher intakes of legumes. There is also some evidence of a benefit for stomach, prostate and breast cancers, the latter particularly with soy.
- The combination of fibre, protein and low GI carbohydrate in legumes means they can help with satiety and may assist with weight loss. A recent review found that four of five studies investigating the effects of legumes as part of an energy-controlled diet showed significant reductions in weight (3.6 to 8.1kg over 6 to 8 weeks) compared to diets without legumes.
- Legumes may even help you live longer. A large study published in 2004 found that legumes were the most important dietary predictor of survival in long-lived elderly people from a number of countries, including Australia. The researchers found that for every 20g/day increase in intake of legumes, your risk of dying reduced by 7 to 8 per cent.
Legumes can be bought either dried or canned. While the canned ones are ready to use, the dried legumes need to be soaked before cooking. The main reason most people don’t eat legumes is because they are not sure what to do with them. Fortunately they are a very versatile food and can be easily incorporated into meals (see box on previous page). Another reason some people avoid legumes is due to their unfortunate tendency to cause wind. The good news is that cooking them thoroughly in fresh water (not in the water you soaked them in) and rinsing the canned varieties helps, as does eating them regularly, which can improve tolerance.
Whichever way you look at it, there seem to be many reasons to include more of these important foods in your diet and to recommend them to your clients who are looking to improve their health and lose weight.
Dr Kate Marsh, PhD, MNutrDiet, BSc, Grad Cert DiabEdn&Mgt
Kate is an Advanced Accredited Practising Dietitian and credentialled diabetes educator with a nutrition practice in Sydney. Her main areas of expertise are vegetarian nutrition and the nutritional management of diabetes and PCOS. Kate is co-author of The Low GI Diet for PCOS, The Low GI Vegetarian Cookbook, Low GI Gluten-free Cooking and The Bump to Baby Diet and is a regular contributor to Diabetic Living magazine.