Cashews

100g (roasted, salted): 611 calories, 50.9g fat, 0.7g salt

With as much anaemia-protective iron and immune-boosting zinc as steak, cashews are a great choice for vegetarians. One handful (25g) supplies 10 per cent of a woman’s daily maximum of cholesterol-raising saturated fat though.

Hazelnuts

100g (kernels): 650 calories, 63.5g fat, negligible salt

Highly nutritious, a handful supplies 60 per cent of the recommended daily intake of vitamin E, an important antioxidant that protects cells. They are heart-healthy too: their fat content has the same composition as olive oil.

Almonds

100g (blanched): 612 calories, 5.8g fat, negligible salt

Another great nut with as much vitamin E as hazelnuts. They are low in saturated fats and packed with bone-building calcium and magnesium too.

Brazils

100g (kernels): 682 calories, 68.2g fat, negligible salt

Nibble these to boost your magnesium and selenium intake (selenium is a mineral to bolster your defence

against viruses). Quite high in saturated fat.

Pistachios

100g (kernels, roasted, salted): 601 calories, 55.4g fat, 1.3g salt

A rich source of potassium that helps keep blood pressure healthy. Go for salt-free versions. Having to remove the shell makes it more of an effort so you are less likely to eat too many.

Peanuts

100g (roasted, salted): 602 calories, 53g fat, 1g salt

A great source of niacin, needed for energy release, and biotin, important for healthy skin. Roasting reduces vitamin E and folic acid. The saturated fat intake can creep up if you eat a lot.
Macadamia nuts

100g (salted): 748 calories, 77.6g fat, 0.7g salt

The most fattening nut and lower in nutrients than some. Still good in moderation though and a handful supplies your daily manganese needs for healthy joints and bones.

The news is based on a large randomised controlled trial (RCT) that is about to start. The research follows a successful pilot study of a treatment called peanut oral immunotherapy (OIT), in which allergic children are repeatedly exposed to strictly controlled doses of peanut protein. Its success so far shows that it has good potential and the results from the upcoming RCT are greatly anticipated.

However, it is vitally important that no attempts are made to replicate the treatment at home as severe allergic reactions can be fatal. If the treatment works it will be offered to children with peanut allergies in the safe and controlled manner that will be necessary for its success.

It should be noted that this treatment is not a cure, and several unknowns need to be addressed, including whether this treatment works in adults and the nature of its long-term effects in children.

What is the basis for these current reports?

The news stories are based on research carried out by Dr Andrew Clark and colleagues from Addenbrooke’s Hospital in Cambridge. The team has had success in previous pilot studies with a technique known as peanut oral immunotherapy. This treatment aims to desensitise the immune system to the allergen (the substance that usually causes an allergic response) by gradually increasing its exposure.

A £1 million grant has now been given to Dr Clark and his team by the National Institute for Health Research, to carry out a larger RCT in more than 100 children with peanut allergies.

The results of the pilot studies and the new trial were presented by Dr Clark at the annual meeting of the American Association for the Advancement of Science.

Has this therapy been tested before?

Dr Clark announced the results of a previous trial in 23 children between 7 and 17 years of age. These children were given a very small amount of peanut flour in yoghurt every day, and the amount was increased every two weeks until the children could eat five peanuts a day. Most of the children had some reactions when the dose was increased, including oral itching and abdominal pain. However, by the end of the trial, 21 of the 23 children could eat five peanuts a day and one could eat two peanuts a day.

More information about peanut oral immunotherapy is available from another pilot study published in February 2009. This trial, in four boys with suspected peanut allergy, was covered by Behind the Headlines. Each boy had an allergic response to between 5 and 50mg of peanut protein (a fraction of the approximately 200mg present in a whole peanut). The boys were exposed to increasing daily doses of peanut flour, up to a maximum of 800mg of peanut protein. Each boy was given a personalised dosing schedule depending on their initial tolerance levels. After six weeks of carefully tailored daily treatment, all four boys were able to eat up to 800mg of peanut protein without any serious adverse effects.

More research is needed into this treatment, and the researchers have begun a larger RCT – the best way to establish the effectiveness of a treatment.

What is the new trial?

Dr Clark presented the plans for a larger study (an RCT) during his presentation to the AAAS conference. There is only limited information publicly available about the trial, but it is known that it is a large controlled trial involving 104 participants who will be randomised to peanut OIT or no treatment. The trial will cost £1 million, sponsored by the Department of Health’s Institute of Health Research, and will run for three years. Children will be given the equivalent of up to five nuts per day in a carefully controlled dosing schedule that depends on their initial tolerance.

Are peanut allergies common?

Dr Clark reports that between 1997 and 2007 there was an 18% increase in childhood food allergy. According to Clark, approximately 1 in 50 children have a nut allergy and 10% of reactions to peanuts will be severe ones. Aside from potentially fatal reactions and the fear of them, children with peanut allergies also experience restricted food choices that can affect their social behaviour. While most children will outgrow allergies to milk, eggs, soya and wheat, peanut allergies are more persistent and an estimated 80% of children remain allergic to peanuts for the rest of their lives.

Many people believe that deaths from food allergies are common and the NHS highlights this as a frequently held misconception. This may be due to the fact that the deaths receive a lot of media coverage when they do occur, but in fact, death from food allergies is very rare. For instance, there were six deaths recorded as a result of food allergies in 2008.

Conclusion

The previous success of this treatment shows that it has good potential for treating children with peanut allergy, and the results from the upcoming RCT are anticipated with great interest. Its strong study design will provide robust answers to questions about the efficacy and safety of this treatment for children with allergies.

It should be noted that this treatment is not a cure, and several unknowns need to be addressed, including whether this treatment works in adults and the nature of its long-term effects in children.

Dr Clark said in The Times: “I think in two or three years time we will be in a position where we have a treatment that works, but we are still working on a long-term cure.

“It’s likely to be a treatment that lasts at least two or three years, and we hope that once that’s over we can withdraw the treatment and maintain long-term tolerance, but we need a long-term study to find out.”

Most importantly, these trials are taking place under carefully controlled conditions and in no way should attempts be made to replicate them at home. Several safety precautions are in place should any of the children have an allergic reaction, and the amount of peanut given is carefully measured for each child’s own personal initial tolerance levels.

The short period of two to three years until a working treatment is encouraging. Until it is available, parents should continue to manage their children’s exposure as they have been doing. Peanut allergies can be successfully managed by vigilantly avoiding exposure and by treating accidental exposures with appropriate medications – antihistamines or adrenaline as advised by your doctor.

This news story is based on a pooled analysis of 25 studies, looking at the effects of experimental nut diets on blood cholesterol and fat levels. A nut-enriched diet was found to be associated with both reduced total cholesterol and LDL (“bad”)-cholesterol. On average, in people who consumed 67g of nuts a day, total cholesterol was reduced by 5.1% and LDL-cholesterol by 7.4%. Nut-enriched diets had a lesser effect on reducing the cholesterol levels of people with higher BMIs.

These diets lasted between three and eight weeks, so it is unclear whether this reduction in cholesterol has any effect on the risk of coronary heart disease in the long term. Although nuts are low in saturated fat, they are nevertheless very high in fat and calories. Plain, unsalted nuts should be eaten in moderation as part of a healthy diet.

Where did the story come from?

The study was carried out by researchers from Loma Linda University in California and the Instituto de Salud Carlos III in Barcelona. Funding came from Loma Linda University and the International Tree Nut Council Nutrition Research and Education Foundation. Some of the researchers have also received funding from the California Walnut Commission, the Almond Board of California, the National Peanut Board and the International Tree Nut Council. The study was published in the peer-reviewed medical journal Archives of Internal Medicine.

The research was generally covered well by the newspapers, which all included the advice that people who want to increase their nut intake should avoid salty nuts.

What kind of research was this?

The researchers say that previous epidemiology studies have shown that frequent nut consumption reduces the risk of coronary heart disease. The aim of this research was to see whether it was possible to estimate the effects of nut consumption on the levels of different types of fat in the blood.

The researchers carried out a systematic review and a pooled analysis, in which they grouped the data from various published trials on the effects of nut consumption on cholesterol levels and blood fat. They also wanted to see whether other factors, such as a person’s age or the type of nut, affected the outcomes.

What did the research involve?

The researchers carried out a systematic search of a medical research database for scientific papers which looked at the effect of nuts on blood fat and cholesterol levels, and had been published between January 1992 and December 2004.

To be included, studies had to be based on humans, and either to have had a control group or to have taken stable baseline fat measurements from participants before they started the experimental diet. The experimental diets had to be supplemented solely by nuts, and to have lasted at least three weeks. The participants’ weight also had to have remained the same during the diet. The researchers excluded studies in which participants had taken fat or cholesterol-lowering medication.

Twenty-five studies of various design were suitable for inclusion in the analysis. In studies that had used a crossover design, in which participants received the experimental diet followed by the control diet or vice-versa, participants contributed two data points, one from when they were a control and one where they were receiving the experimental diet. This resulted in a total 1,284 data points and 583 participants.

The researchers looked at whether age, gender, body mass index (BMI) type of nut and type of diet modified the effect of nut consumption on cholesterol and fat measurements in the blood. They also considered the type of study design and the degree of control that the study’s investigator had over the participants’ overall diet, and whether this impacted the effect of nuts on the blood measurements.

For some analyses, the participants’ data was classified into groups. For example, cholesterol was classified as (low) less than 130mg/dL, (medium) 130-160 mg/dL, or (high) greater than 160 mg/dL. Other fats (triglycerides) were classified as less than 150 mg/dL or more than 150 mg/dL, and BMI was classified as normal weight (less than 25), overweight (25-30) or obese (more than 30).

What were the basic results?

Compared with control diets, nut diets were associated with a reduction in total cholesterol and levels of low-density lipoprotein (LDL) (“bad”) cholesterol. Nut consumption did not have an effect on the levels of high-density lipoprotein (HDL) (“good”) cholesterol, but it did increase the ratio of HDL compared to total cholesterol (p < 0.001).

Nut diets did not appear to affect blood triglyceride levels, except in participants who had high blood triglyceride levels before the study began, in whom blood triglyceride levels were reduced following the diet (p<0.05).

Age, gender and the type of nut did not influence the effects of nuts on blood cholesterol. However, BMI did have an effect. Participants with a lower BMI at the beginning of the study had lower cholesterol as an effect of eating nuts. Participants with higher LDL-cholesterol at the start of the study had a greater decrease of total cholesterol at the end of the diet.

Participants with LDL-cholesterol greater than 160 mg/dL at the start of the study were associated with a decrease of 17.5 mg/dL (approximately 11%) at the end. Having LDL-cholesterol at less than 130 mg/dL at the study start was associated with a decrease of 5.0 mg/dl (approximately 4% of 130).

Nut diets were associated with a 7.4% reduction in cholesterol and 9.6% reduction in LDL-cholesterol, compared to a western diet, 4.3% and 6.7% compared to a Mediterranean diet, and 4.1% and 6.0% compared to a low-fat diet.

The researchers then made estimates of how differing amounts of nuts would affect blood fat and cholesterol levels. They suggested that if a participant ate 71g of nuts per day as part of a 2,000-kcal diet (20% of dietary energy), this was associated with a 4.5% decrease in total blood cholesterol, and a 6.5% decrease in LDL-C.

How did the researchers interpret the results?

The researchers say that their study suggests that “increasing the consumption of nuts as part of an otherwise prudent diet can be expected to favorably affect blood lipid (fat/ cholesterol) levels (at least in the short term) and have the potential to lower CHD risk”.

They attempt to explain the association by saying that “nuts are rich in plant sterols, natural compounds that might contribute to cholesterol lowering by interfering with cholesterol absorption”. However, they also say that “more research is needed to answer the important question of why nuts are less effective in lowering blood cholesterol concentration among subjects with obesity”.

Conclusion

This study conducted a pooled analysis of 25 studies, which looked at the effect that a nut-supplemented diet had on cholesterol and fat levels in the blood. A nut-enriched diet was found to be associated with a decrease in blood cholesterol. There are a few limitations which affect how these results can be interpreted:

* Although the data pooled results from 25 studies the overall population was relatively small. The small size increases the likelihood that the differences observed were due to chance.
* The 25 studies had different diets to which the nut supplementation was added. The researchers did not give details of the energy, fat and cholesterol content of these background diets, which may have varied, potentially affecting the collective results. In addition, the studies varied on the degree of dietary control that the researchers had over the participants, such as whether they checked compliance to the diets or advised on other foods that should be eaten or avoided during the experimental nut diet.
* The experimental diets were typically between three and eight weeks long, which is a relatively short period of time. It is unclear what effect a nut-enriched diet would have over the longer term.
* It is unclear whether the reductions in cholesterol and LDL-cholesterol would be enough to lower the risk of coronary heart disease. Further analysis is needed to assess how much an individual would need to lower their cholesterol in order to lower their risk of coronary heart disease in the long term.

These preliminary results warrant further investigation into how to optimise our diets to lower blood cholesterol levels. As many nuts are heavily salted or coated with sugar and other vegetable oils, people are advised to choose raw unsalted nuts. They should also be aware that although nuts are low in saturated fat, they are nevertheless very high in fat and calories, and should be eaten in moderation as part of a healthy diet.

The trend for healthy eating has sent sales soaring to £547million in 2009, market research analysts Mintel said.

A poll found 44 per cent – many over 45s – now buy cashews or other nuts as an alternative to crisps.

Nuts are packed with omega-6 which boosts brain power. And 36 per cent opt for dried fruit and not sweets.

Mintel food and drink expert, Amy Lloyd, said: “Consumers now want a nutritious snack.”

The vegetable has been shown to have a positive effect on glucose and fat levels, both of which play a role in type 2 diabetes.

This is the most common form of the disease, which occurs when the body makes too little insulin or cannot properly use the insulin it makes to mop up excess blood sugar.

Type 2 diabetes is linked to lack of exercise and being overweight. Turnip extract was given to laboratory mice with the condition.

Results showed it increased the speed with which fat was processed and lowered cholesterol, as well as reducing glucose levels.

‘Studies should now be carried out to develop turnip extract as a novel therapy for type 2 diabetes,’ say scientists from the National University in South Korea.