US researchers found that people who ate an average of 67g of nuts each day reduced their total blood cholesterol concentration by 5.1 per cent. People with high triglyce-ride levels also benefited from the diet.
Previous studies produced a mixed picture of potential benefits, prompting a more comprehensive review of the evidence.
A team from Loma Linda University in California attempted to quantify this beneficial effect using data from 25 nut consumption trials using 583 people.
Results showed that eating 67g of nuts a day lowered LDL cholesterol concentration by 7.4 per cent. The diet also cut blood triglyceride levels by 10.2 per cent in patients with high triglyceride levels.
The authors concluded that the findings 'supported the inclusion of nuts in therapeutic dietary interventions for improving blood lipid levels and lipoproteins and for lowering CHD risk'.
How significant are the findings?
Scientists already believed that eating nuts could protect against cardiovascular disease. A summary of four studies showed CHD risk fell 37 per cent among those who ate four servings of nuts per week, compared with those who did not.
But the researchers stressed their study was the first to assess this benefit across various population groups and between different types of nut.
They found the benefit to blood lipid levels occurred in a dose-related manner, although there was no difference between nut types.
The effect was particularly strong among patients with higher LDL cholesterol or lower BMI. But people with higher BMI were less likely to benefit.
Scientists believe plant sterols contained in nuts might reduce cholesterol by cutting the amount absorbed by the gut.
In obese people, cholesterol absorption is impaired. This means any benefit from plant sterols is muted as a result.
Should nuts be recommended to reduce cholesterol?
British Cardiovascular Society member and GP Dr George Kassianos said it was well known that eating nuts could reduce LDL cholesterol.
However, he added that 'one must consider the increase in calories that accompanies such a dietary intervention'.
Ellen Mason, senior cardiac nurse at the British Heart Foundation, said it was time nuts were reintroduced in the average, healthy diet.
'Apart from salted peanuts at the pub, nuts in sugary cereals or the traditional Christmas selection, nuts have been lacking in our diets in the UK,' she said, adding that eating more nuts in place of saturated fats could help to improve cholesterol levels for many people.
However, the charity warned against opting for salty nuts, instead recommending unsalted versions in small amounts.