Wednesday February 24 2016
Almonds contain a range of nutrients
"Desperate to lose weight?" asks the Mail Online. "Eat almonds! Handful a day 'wards off hunger and replaces empty calories from junk food'," it says, without any justification.
It's hard to see where the headline's over-excited promises of weight loss or reduced hunger come from. The study they write about showed an improvement in diet quality for a small number of people asked to eat almonds daily for three-weeks. However, it did not measure the effect of almonds on weight loss, dieting or hunger pangs.
The study, funded by the Almond Board of California, failed in its aims of showing improved bowel function, better bacteria in the gut, and signs of improved immune status.
While the study did show improvements of seven to eight points on a healthy eating scale (range 1 to 100), this was based on questionnaires for just 28 adults and 28 children, during a short period of eating almonds. Healthy changes to diets need to last for years, not weeks, to make a difference to health.
Like other so-called superfoods, there is no evidence in this study to suggest that almonds have any particular powers of helping people to lose weight. However, they are a good source of fibre and nutrients.
The NHS Choices weight loss guide can help you lose weight in a sensible way through a combination of diet and exercise.
Where did the story come from?
The study was carried out by researchers from the University of Florida and was funded by the Almond Board of California, which has a clear interest in promoting the health benefits of almonds.
The study was published in the peer-reviewed journal Nutrition Research on an open-access basis, so you can read it for free online.
The quality of reporting by the Mail Online and the Daily Express was below par.
In addition to the Mail Online's over-enthusiastic headline, the Daily Express suggested that eating almonds "could work wonders". Neither newspaper included any information about the study's failure to prove its hypothesis about immune function. The basic facts given in the stories were mainly correct, although uncritically and selectively reported.
The Mail claimed that people eating almonds "increased their protein and lowered their salt intake", although protein only increased on one measure (total protein foods) and not another (protein as a percentage of energy). Salt consumption was only lower for adults, with borderline statistical significance.
The obvious conflict of interest in terms of the study's funding was not reported.
What kind of research was this?
This was a randomised crossover study, where people were assigned to eat almonds or no almonds for three weeks, then switched to the opposite intervention after a wash-out period. The study was not blinded, meaning people knew when they were in the "almond" or "no almond" part, and there were no substitutes offered for almonds (such as another type of nut).
What did the research involve?
Researchers studied 28 parents and 28 children (one child per parent). They measured their bowel function (how many stools they passed in a week), any symptoms like constipation or bloating, the composition of bacteria in the gut (from stool samples), markers of immune function in blood and saliva tests, and overall diet quality (from questionnaires). The tests were repeated regularly during the study.
People were asked to eat 1.5 ounces (42g) of almonds (adults) or 0.5 ounces (14g) of almonds (children) for one of two three-week study periods, and no almonds in the other three-week study period. Researchers then compared the test results for the periods when they did or didn't eat almonds, to see if there were any differences.
The researchers aimed to recruit 30 pairs of parents and children, but only managed 29, and one pair dropped out of the study early on. They had calculated that they'd only need 15 individuals to show a change in gut bacteria, but it is not clear whether 28 pairs was enough to reliably show a change in diet quality or bowel function.
Dietary quality was measured by questionnaires about food eaten in the past 24 hours, which people filled out several times throughout the study, including while eating almonds, while not eating almonds, at the start of the study and the end. Results were mapped against a healthy eating scale to give a score from 1 to 100, and comparisons drawn between the scores while eating almonds and not eating almonds.
What were the basic results?
Both adults and children had an overall average dietary score of 53.7 while not eating almonds, and a score of 61.4 when eating almonds. Looking at individual parts of the healthy eating index, while eating almonds they consumed on average more total protein foods, seafood and plants protein, and fatty acids. Adults ate fewer foods classed as being "empty calories".
The researchers also reported "trends" for less empty calories for children and less salt for adults, but these differences were so small they could have been due to chance.
The researchers found no difference for any of their other planned measures – bowel function, gut symptoms, phyla of bacteria in stool samples, or immune markers. They say they found some difference in bacteria types, but not at the level they planned to measure. We don't know whether the small differences they found would have any effect on human health.
How did the researchers interpret the results?
The researchers said they had "rejected" their hypothesis that eating almonds would improve bowel function, because overall fibre levels did not rise and adults ate less fruit while eating almonds. They say their failure to find differences in gut bacteria or immune markers may be because the "dose" of almonds was too low.
However, they claim the study results, "confirm that incorporating almonds into a daily diet promotes improved diet quality".
Despite the excitement in the tabloid headlines, this is a very small study with not particularly surprising results. You would expect that adding a food with known nutritional value to a daily diet would increase the overall quality of that diet, for the time that people continued to eat the food in question. The researchers' more ambitious aims – to show that nuts improved immune system and bowel function – were not met.
In addition to its small size, the study had other limitations. As the people in the study were not blinded to the intervention period, this could have affected their answers to questionnaires. Also, the parents filled in the questionnaires for their children, which may have been appropriate, but has not previously been tested as an accurate method for these specific questionnaires. Most of the children were at child care or school, so the parent may not have known what they’d eaten during the day.
It is also reported that many children were less than enthusiastic about having to eat almonds, with complaints that they were "boring" and "dry and bland". Whether they would stick to the diet on a long-term basis is uncertain.
A major problem with this type of study is that changes to improve the quality of diet need to be long term if they are to have a significant effect on life-long health. Measuring the effects of adding one food to the diet for three weeks does not tell us anything about the potential effects of eating that food regularly for many years.
While this study may not have much to tell us about healthy eating, there are still plenty of good reasons to eat nuts, such as walnuts, brazil nuts, hazelnuts and almonds. Nuts and seeds contain healthy oils, protein and fibre. They make a good addition to a balanced diet, along with fresh vegetables, wholegrains, fruit, dairy products and fish. Choose unsalted nuts, so as not to eat too much salt.
Read more about the benefits of eating a balanced diet.