A study published this week in the BMJ has found, for the first time, that eating potatoes is associated with an increased risk of high blood pressure.
These findings have been widely reported in the media over the last couple of days.But before we banish bangers and mash from our dinner times, let's take a closer look at this study and work out whether we have reason to be concerned.The researchers from Harvard Medical School analysed data from more than 187,000 men and women from three large US studies over a 20-year period. It looked at people who ate four or more servings of mashed, baked or boiled potatoes, crisps or French fries per week, with those who ate less than one serving per week.The researchers controlled for numerous factors, including weight, smoking status, level of physical activity, and current dietary habits.The main findings of the study were as follows:
1. Women could be at greater risk
Eating four or more servings of mashed, baked, or boiled potatoes per week was linked to a 11% increased risk of high blood pressure in women, when compared with less than one serving per week. This effect was not observed in men.
2. French fries could be the worst offenders
Higher consumption of French fries was associated with a 17% increased risk of high blood pressure in both men and women.
3. Crisps were deemed innocent
Higher consumption of potato chips (crisps) did not display an increased risk for high blood pressure. In fact, strangely, the men who ate more crisps showed a reduced high blood pressure risk.
4. Making room for other veggies is a good shout
Replacing one serving of potatoes per week with a portion of non-starchy vegetables was associated with a 7% drop in blood pressure.
But there's no proof potatoes cause high blood pressure:
This study is what is known as an observational study. These examine the association between what is known, in scientific jargon, as an exposure (in this case, potatoes) and an outcome (in this case, high blood pressure). Because of all the other exposures that occur simultaneously in our lives, which can never be completely accounted for, this type of study cannot provide evidence of cause and effect. Rather, it can only provide evidence of a relationship between exposure and outcome (potatoes and high blood pressure. In other words, this research doesn't prove that eating more potatoes increases blood pressure; it has just shown an association between these two factors.
Remembering everything you've eaten is tricky
There were several limitations of this study design that were acknowledged by the researchers:
- The diagnosis of high blood pressure was based on information provided by the participants, rather than measurements taken during the study, so could have been open to error.
- The amount of potatoes the participants ate was self-reported. In one study, this was via a food questionnaire every 4 years, and recalling diet over that amount of time is open to inaccuracies. Also, people aren't always honest when reporting their food intake.
How you cook your potatoes can reduce health risks
The findings could have been affected by other dietary factors e.g. potatoes are often eaten with a lot of fat (butter or margarine) and salt, which could explain the association of boiled, baked and mashed potatoes with high blood pressure. Going easy on the salt and butter when preparing your spuds will make you meal instantly.