Asparagus is a popular food with a short harvesting season but is available frozen and canned. Some asparagus spears are a vibrant emerald-green, some are purple, while those that are white are produced by excluding light. Asparagus health benefits are many, but it does have some interesting side effects for some people!
Asparagus health benefits
Asparagus is a low calories source of antioxidants and fibre. A typical 100g serving contains only 22 kilocalories, zero fat (unless dressed in butter), and supplies significant amounts of vitamin C and vitamin A in the form of carotenoids.
Asparagus produces antioxidant polyphenols to protect it from UV sunlight.
Green and purple asparagus provide around 75mg polyphenols per 100mg, including one known as rutin which appears to boost metabolism when eaten to aid weight loss.
The rutin content of purple varieties of asparagus is higher than green varieties (23 mg/100g versus 15 mg/100g).
White asparagus has a lower total polyphenol content of around 14 mg/100g but produces no rutin as it is grown ‘forced’ with no exposure to sunlight. Instead, white asparagus has a high content of quercetin.
Asparagus side effects
Eating asparagus can give your urine an unpleasant odour of rotting cabbage due to the breakdown of asparagusic acid. Interestingly, the ability to produce this smelly side effect is a genetic trait that occurs in around 40% of people. Another genetic trait means that at least one in two of the population are unable to detect the smell of these asparagus breakdown products, even if they do produce them, due to a mutation in a cluster of genes that code for smell receptors. So, if you both produce smelly wee after eating asparagus, and can smell it, you are among the one in five people who is able to do both.
Asparagus and weight loss
Asparagus was traditionally used to aid weight loss due to its diuretic properties. Its effects on weight loss were investigated in a study involving 80 people with an average weight of 85kg (body mass index 29.9) who wanted to follow a low-calorie diet to start a longer-term weight loss and lifestyle change program.
Volunteers were asked to take psyllium fibre every morning, and for 7 days also replaced meals with low-calorie meal replacement juices made from elderberries and elderflower. They also took 2.7g asparagus powder tablets equivalent to 40.5 g dried asparagus per day.
Of the 80 people who completed the study, over a quarter admitted to having broken the diet. Even so, the average weight loss overall was 3.2 kg, with a reduction in BMI to 28.9 kg/m2. Those who broke the diet lost an average of 2.5kg compared to those who stuck to the diet, who lost an average of 3.5kg.
Blood pressure also decreased significantly from 129/80 mmHg down to 122/78 mmHg. All reported significantly improvements in well-being, and quality of life, too.
The researchers concluded that an elderberry and asparagus based low-calorie diet is a good way to start a long-term behavioural program that includes eating less and exercising more (at least 40 minutes per day).
Asparagus and stress
Asparagus extracts have been developed as an anti-stress functional food in Japan. In healthy male volunteers, asparagus extracts were found to enhance cell production of protective proteins (known as heat shock proteins) which are produced by cells to protect themselves from stressful conditions. In those who did not sleep well, asparagus extracts also reduced levels of cortisol hormone, and these rose when they weren’t taking the asparagus extracts.
Asparagus and skin ageing
A study investigating links between diet and skin wrinkling among native Australians found that those eating the most fruit and vegetables had the least wrinkles, with asparagus among the foods that offered the greatest protection. It was suggested that the antioxidant polyphenols that protect asparagus from UV light may offer similar protective effects in the skin when eaten.
Asparagus and liver health
Green asparagus polyphenols were shown to protect liver cell cultures from inflammation and to increase their survival. Interestingly, other researchers also found that asparagus extracts increased liver cell production of two enzymes (alcohol dehydrogenase and aldehyde dehydrogenase) needed to metabolise ethanol alcohol. Levels of these enzymes doubled within the liver cell cultures, suggesting that asparagus may have a future role in protecting against hangovers.
Asparagus and bowel cancer
Asparagus extracts were found to discourage the growth of several different types of cancer cells in laboratory culture studies. Extracts from white asparagus shoots were the most promising, and were shown to inhibit the growth of human colon cancer cells by 80%.
How to add asparagus to your diet
Steam asparagus lightly and eat it with your fingers, dipped in melted butter or creme fraiche and sprinkled with black pepper.
Asparagus can be chopped and added to risotto and stews, while asparagus soup was once considered the height of sophistication.
How to prepare asparagus
Once I discovered this knife-free method of preparing fresh asparagus by snapping the stem, everything suddenly became much easier! They always break in just the right place.