The health benefits of nuts

Although rates of cardiovascular disease (CVD) are declining in many developed countries, it remains the number one cause of death. In developing countries, CVD rates are increasing.

People with diabetes are two to four times more likely to develop CVD than people without diabetes. The prevention and treatment of CVD by diet is an important issue both for people with diabetes and those without. Dr Alexandra Chisholm explains the benefits of eating nuts as part of a healthy balanced diet.

Adding nuts to the diet can help to lower blood cholesterol levels.

Nuts are grown all over the world. They are an intrinsic part of traditional dietary patterns in many regions where both blood cholesterol levels and the incidence of heart disease are low.

A small serving of nuts four to five times per week has been observed to reduce the risk of CVD in population studies.

Intervention studies have shown that the addition of nuts to the diet can help to lower blood cholesterol levels, reduce the oxidation of low density lipoprotein (LDL) cholesterol and improve a number of other indices related to CVD risk.

Cholesterol is a type of fat or lipid

As cholesterol is carried in the blood stream by particles called lipoproteins, a distinction is made between cholesterol carried by low-density lipoproteins (LDL cholesterol, or 'bad' cholesterol) and that carried by high-density lipoproteins (HDL cholesterol, or 'good' cholesterol).

The level of total cholesterol is the sum of HDL and LDL cholesterol levels.

The Evidence - Epidemiology

Initial evidence of the benefit of nut consumption has come from population studies which looked at the diets of large numbers of people over long periods of time.

In four studies, the Adventist Health Study, the Iowa Women's Health Study, the Nurses' Health Study and the Physicians' Health Study, a total of over 160,000 men and women were followed up for between six and 14 years.

These studies showed very consistent indications for the health benefits of nuts. When compared with never eating nuts, the effect of eating small quantities of nuts (30g) four to five times per week or more was a reduction in CVD risk of between 18% and 51% (Kris-Etherton et al 2001).

Intervention studies

A number of studies have looked at the effect on blood lipids (fats) and lipoproteins of including nuts in the diet. Different population groups and both men and women have taken part in these research studies. The studies included participants with lipid levels in the normal range as well as those with hyperlipidemia (high levels of blood fat). The participants ranged in age from 18 to 81 years.

In spite of this diversity in subject characteristics and study design, reductions of between 9% and 31% in LDL cholesterol were observed. The quantities of nuts consumed in the studies varied from 30g to 100g per day.

Almonds, macadamias, pistachios, walnuts, pecans, and hazelnuts (tree nuts) have all been used in studies, as have peanuts, which are a legume (Kris-Etherton et al 2001).

Studies including persons with diabetes

Thirty volunteers with Type 2 diabetes took part in a recent study using almonds. Including almonds in the diet had no effect on glycaemia (blood sugar) but there was a drop in LDL cholesterol and a slight drop in high density lipoprotein (HDL) cholesterol. However, there was still a reduction in the ratio of total cholesterol to HDL cholesterol and in the ratio of LDL to HDL cholesterol.

It is thought that these ratios reflect CVD risk from blood cholesterol levels. Their highly significant reduction in this study indicates the beneficial effect of eating almonds as part of a healthy diet (Lovejoy et al 2002).

Further research involving the addition of nuts to the diets of post-menopausal women with Type 2 diabetes is in progress.

Studies relating to weight

Nuts have often had a 'bad press', being regarded as a fatty food to be avoided by those trying to reduce or control their weight. Two recent studies have shown that the inclusion of nuts in the diet did not lead to weight gain.

One study added almonds and the other peanuts. The participants were not asked to make any other changes in their diets and did not know that the researchers were studying body weight (Fraser et al 2002; Alper & Mattes 2002).

Include nuts in diet

The health benefits of nut consumption, particularly their cardio-protective effects are often under-recognised. Nuts provide a concentrated and palatable source of essential unsaturated fatty acids, fibre, and a number of other nutrients often in short supply in the modern diet. They are filling and can thus be useful in helping to prevent weight gain, and provide a concentrated source for those needing additional energy.

People with diabetes as well as those who do not have diabetes should be encouraged to include a small serving of nuts in their diet several times a week.

See recipe for hot basmati rice, lentil & cashew salad ...

Dr Alexandra Chisholm is a lecturer and research dietitian in the Department of Human Nutrition, University of Otago, Dunedin, New Zealand.

In a nutshell

Nuts make a wonderful snack, particularly in place of foods like cakes or biscuits. The ultimate healthy 'fast food', they are easy to carry.
Nuts are a good choice for a healthy fat exchange or a sustaining snack together with some carbohydrate.
Getting as much variety as possible into your diet is important and this applies to nuts as well as other foods.
To get the maximum benefit from eating nuts, it is important to make sure they are very fresh, and to keep them in a cool dark place (especially ground or chopped nuts).
As they contain enough of their own fat, simply roast nuts by putting them in a shallow dish in the oven at a low to medium heat, stirring frequently, until they have the desired crunch. Don't add salt or other fats or oils.

Diabetes Voice March 2003 Volume 48 Issue 1

^ Back to top