Dominique Glatt, student dietian, Queen Margaret Uiniversity.

Asparagus is an ancient vegetable, with its earliest cultivation dating back to the ancient Romans1; today it is eaten across the globe, is a fabulous source of fibre, folic acid, vitamins C and A, potassium2 and glutathione3, and is infamously know for causing “smelly pee”4. This beautiful green veggie is a member of the Asparagaceae family, native from Siberia to southern Africa1. We commonly think of garden asparagus (Asparagus officinalis) when we invasion this vegetable, which is grown for its tender young stalks (called “spears”)5. It is produced in most temperate and subtropical parts of the world, and is easily cultivated in the UK. Here, the harvest season starts in mid-April and lasts between 6-8 weeks (depending on local climate) when the shoots are approximately 15cm tall5. More details about growing your own asparagus can be found from the Royal Horticultural Society5. Historically asparagus was cultivated as an aphrodisiac (little supporting evidence), and is still used as a diuretic6.

FUN FACT: Less commonly known in the UK is the white asparagus, where the young growing shoots of the asparagus are covered with soil to prevent the development of chlorophyll (green colouring); white asparagus is a delicacy across continental Europe and its harvest season is greatly anticipated6.

One adult portion (80g) of asparagus will count as 1 portion of your daily 5 portions of fruit and vegetables as a part of the 5 A DAY (based on current UK government guidelines)7, which is roughly 5 fresh spears or 7 canned spears8. Although difficult to describe, fresh tender spears commonly have a mild, earthy taste; the older and more mature the spear gets the more bitter or sour the taste can get6.

The table shows the macronutrient and major micronutrient content of one portion of asparagus and the corresponding adult, adolescent and child reference nutrient intake (RNI); which is the recommended amount of nutrients to meet 97.5% of the populations needs9.

The total energy (kcal) derived from one portion of asparagus is very low at 21kcal with 1.12g of fibre (roughly 4% of the adult daily RNI)2,9. Choosing low-energy dense foods such as vegetables can add volume to a meal without adding extra calories, ideal for individuals looking to lose weight and/or prevent obesity. It can help you feel full while still maintaining an energy deficit10. Dietary fibre helps maintain healthy bowels by adding bulk and increasing transit time; it has been associated with a lower risk of developing colon cancer, cardiovascular disease and type 2 diabetes10.

Folate (or folic acid) is a B vitamin, and along with vitamin B12 works to produce our red blood cells; a lack of folic acid can lead to folate deficiency anaemia9. Sufficient folate intakes of expecting mothers also help prevent central nervous system defects (ex. spina bifida) in the unborn child9, however, women who are planning on becoming pregnant or are pregnant are recommended to take a 0.4mg folic acid supplement and should consult their GP11. Your body cannot store folic acid so it’s important to eat a healthy balanced diet rich in veggies; good vegetable sources include: broccoli, brussels sprouts, spinach, peas and chickpeas11. One portion of asparagus provides approximately 70% of an adult’s daily RNI2,9.

Vitamin A (or retinol) is a fat-soluble vitamin and is vital for a healthy immune system and infection prevention, low-light vision, and tissue development (very important in growing bodies)9,12. Your body can store vitamin A, meaning it’s not needed every day. Vitamin A (in the form of retinol) comes from dairy foods, eggs and oily fish12; however, our bodies are also able to convert plant-based beta-carotene into retinol9, which is the case for asparagus. Asparagus provides on average 52% of the RNI for adult women and 44% for adult men2,9. Other good beta-carotene sources are: leafy green vegetables, carrots, red peppers, mango, papaya and apricots12.

Vitamin C (or ascorbic acid) is known for its antioxidant properties in preventing free radical damage in our cells9. It aides in the maintenance of healthy connective tissue (preventing scurvy) and helps in wound healing9. It also increases the absorption of non-heam iron (plant sourced iron)9, so never forget to add a little lemon or orange juice to your kale or spinach smoothies. One portion of asparagus can provide roughly 20% of an adult’s daily RNI2,9. This water-soluble vitamin can’t be stored in your body so you’ll need vitamin C every day, however with a healthy balanced diet this is easy to achieve (some good sources include: citrus fruits and juices (150ml of 100% fruit juice can count as 1 of your 5 A DAY7), red and green peppers, broccoli, brussels sprouts, and strawberries13.

Potassium is a dietary mineral required for healthy nerve signalling in our muscles and controlling the amount of sodium in our cells, which influences their water content and as a result body fluid balance9,14. One portion of asparagus provides roughly 5% of an adult’s daily RNI2,9, its therefore important to include other potassium rich foods such as bananas, broccoli, parsnips, brussel sprouts and pulses14. It can also be found in nuts, seeds and meat sources14.

Glutathione is an antioxidant phytochemical which has been associated with anticarcinogenic properties3. While it is produced by our bodies, it is currently not seen as an essential dietary nutrient and therefor has not RNI9.

Asparagus can be lightly boiled, steamed, blanched or grilled and is often served with Hollandaise sauce or butter. It’s an ideal starter (wrapped in some prosciutto) or can be used as a side to a main dish. A more modern trend is to eat raw chopped or ribboned (very fancy!) asparagus as part of a salad, just be careful to remove any woody or tough parts and always remember to thoroughly wash your fresh fruit and veggies. If you want to go a little old school, there is a recipe for asparagus in Apicius’s De Re Coquinaria, the oldest surviving cook book6; however, you can also take a more Mediterranean inspired route and munch on a few balanced spears with a drizzle of extra virgin olive oil (adding a cardio-protective element)15. If you have a weaning youngster in the family, well-cooked asparagus is an ideal weaning food (mashed to the appropriate texture or as a natural finger food); introducing your baby to a more bitter tasting vegetable and expanding their taste and texture range16. If you’re worried about losing weight, roast your asparagus in a little butter (add some leek for added flavour) and blend it with some creamy stock for a warm hearty soup17.

The options are limitless with asparagus, just remember, the shorter the cooking time, heat exposure and the less chances of the nutrients leaching out (ex. boiling) the more nutrient packed your asparagus will be18!

 

References

  1. Encyclopædia Britannica (2016). Asparagus, Plant Genus. Available from: https://www.britannica.com/plant/Asparagus (Accessed: February 2017)
  2. McCance, R.A., and Widdowson. E.M., 2015. McCance and Widdowson’s The composition of foods: 7th summary edition [electronic resource].
  3. Guoyao Wu, Yun-Zhong Fang, Sheng Yang, Joanne R. Lupton, and Nancy D. Turner, 2004. Glutathione Metabolism and Its Implications for Health. J. Nutr. Vol. 134, pp. 489–492
  4. NHSChoices (2014). Smelly Urine. Available from: http://www.nhs.uk/conditions/smelly-urine/Pages/Introduction.aspx (Accessed: February 2017)
  5. The Royal Horticultural Society (2015). Asparagus. Available from: https://www.rhs.org.uk/advice/profile?PID=310 (Accessed: February 2017)
  6. Kew: Royal Botanical Gardens (2017). Asparagus officinalis (garden asparagus). Available from: http://www.kew.org/science-conservation/plants-fungi/asparagus-officinalis-garden-asparagus (Accessed: February 2017)
  7. Public Health England (2016). The Eatwell Guide. In association with the Welsh Government, Food Standards Scotland and the Food Standards Agency in Northern Ireland. Available from: https://www.gov.uk/government/publications/the-eatwell-guide (Accessed: February 2017)
  8. NHS Choices (2014). Rough guide – Fruit & vegetable portion sizes.

Available from: http://www.nhs.uk/Livewell/5ADAY/Documents/Downloads/5ADAY_portion_guide.pdf (Accessed: February 2017)

  1. Department of Health (1991). Dietary Reference Values for Food and Energy and Nutrients for the United Kingdom. Report of the Panel on Dietary Reference Values of the Committee on Medical Aspects of Food Policy.
  2. Gandy, J., 2014. Manual of Dietetic Practice, 5th edition, Wiley-Blackwell.
  3. NHS Choices (2015). Vitamins and minerals – B vitamins and folic acid. Available from: http://www.nhs.uk/Conditions/vitamins-minerals/Pages/Vitamin-B.aspx#folic-acid (Accessed: February 2017)
  4. NHS Choices (2015). Vitamins and minerals – Vitamin A. Available from: http://www.nhs.uk/Conditions/vitamins-minerals/Pages/Vitamin-A.aspx (Accessed: February 2017)
  5. NHS Choices (2015). Vitamins and minerals – Vitamin C. Available from: http://www.nhs.uk/Conditions/vitamins-minerals/Pages/Vitamin-C.aspx (Accessed: February 2017)
  6. NHS Choices (2015). Vitamins and minerals – other vitamins and minerals. Available from: http://www.nhs.uk/Conditions/vitamins-minerals/Pages/Other-vitamins-minerals.aspx#potassium (Accessed: February 2017)
  7. Estruch R, Martínez-González MA, Corella D, Salas-Salvadó J, Ruiz-Gutiérrez V, Covas MI, 2006. Effects of a Mediterranean-style diet on cardiovascular risk factors; a randomized trial. Ann Intern Med. Vol: 145, issue:1, pp.1-11.
  8. NHS Start for Life (2016). Choosing first foods. Available from: https://www.nhs.uk/start4life/choosing-first-foods (Accessed: February 2017)
  9. NHS Choices (2015). Keeping your weight up in later life. Available from: http://www.nhs.uk/Livewell/over60s/Pages/Underweightover60.aspx (Accessed: February 2017)
  10. AHA (2015). Cooking Technique: Healthy Sautéing. Available from: http://www.heart.org/HEARTORG/HealthyLiving/HealthyEating/SimpleCookingwithHeart/Cooking-Technique-Healthy-Saut%C3%A9ing_UCM_430100_Article.jsp#.WLAcuzhXVoA (Accessed: February 2017)