Rachel Whitehall, student dietitian, Glasgow Caledonian University.

 

Lettuce may be called ‘rabbit food’ by some however, it is so much more than that due to its nutritional benefits. Lettuce is one of the most popular vegetable greens and is commonly used in salads, sandwiches, soups and even juices nowadays. Although generally lettuce has a reputation for being a poor source of nutrients, this is not actually true. Lettuce does provide many of the same nutrients as other green vegetables, albeit in smaller quantities and has the benefit of being a low calorie food choice.1 Lettuce helps to enhance the taste of meals by providing a crisp, crunchy texture to dishes as well as providing a punch of several nutrients and minerals simultaneously.

Lettuce is part of the Asteraceae family of plants, also commonly referred to as the daisy family.2 There are many varieties of lettuce although the four most commonly eaten types are iceberg, butter, leaf and romaine.  Nutrient values differ slightly between the different sub-types of lettuce, and it should also be noted that the nutrient content differs depending on which part of the plant you choose to eat. The outer green leaves of any of the lettuce plants tend to be of higher nutrient value than the inner white leaves. 3 Table 1 displays the typical nutrient content of an average salad serving of iceberg lettuce.3

Table 1- Nutritional breakdown of iceberg lettuce                                                                                                               

Nutrient Average serving of iceberg salad (80g) Recommended Nutrient Intake (RNI) of nutrient/per day
Children

Aged 2-5 years

Children

Aged 5-11 years

Teens

11-16 years

 

Adults

 

Energy (kcals) 9
Carbohydrate (g) 1.1
Of which sugars (g) 1.1
Total Fat (g) 0.08
Protein (g) 0.96
Fibre (NSP) (g) 1.2 15 20 25 30
Vitamin A (µg) 8 400 400-500 600-700 600

(Women)

 

700

(Men)

Vitamin C

(mg)

1 25-30 30 35 40

 

* Fibre calculated using the AOAC method.

Lettuce is normally available year round in the United Kingdom, although peak season for whole head lettuce generally starts around mid May and finishes around October time. Purchasing lettuce in-season usually leads to fresher tasting produce and tends to be higher in nutritional value, as some vegetables nutritional content can decline if stored for long periods, such as some antioxidants and Vitamin C. 4 Also, purchasing in-season produce helps support local farming, which means less transportation and promoting a more environmental friendly lifestyle.  To get the best value and optimum flavour for your money, choose the best looking, least wilted lettuce heads. If it is brown and dry looking at the stem it is likely not to be the freshest vegetable on display.  Always ensure that you wash the raw lettuce leaves well before eating. Washing your lettuce thoroughly is by far the best thing you can do to reduce E.coli and Salmonella exposure. To keep the produce fresh, store lettuce in the refrigerator until meal preparation.

As seen in Table 1, lettuce is hugely popular due to its low calorie content, with an average salad serving providing only 9 calories.3 All types of lettuce have roughly similar amounts of calories per serving, usually between 9-15 calories per 80g portion. This is partly due to the high water content of lettuce, which helps give the green leafy vegetables bulk that help fill our stomachs up without increasing the calorie content.

Table 1 is not an extensive list of the nutritional content of lettuce, however it does highlight several nutrients that lettuce contains.  As well as being low in calories, lettuce contains no saturated fat or cholesterol, which have been linked to heart health. Lettuce does provide a moderate source of dietary fibre, containing 1.2 g per average serving. 3 Dietary fibre is important for maintaining good gut health, healthy bowel movements and lowering blood glucose and cholesterol levels. Dietary fibre also helps maintain a healthy weight as fibre helps fill us up and is slowly digested by the body, meaning it helps keep us fuller for longer. Research indicates that diets rich in fibre are associated with reduced risk of cardiovascular disease, type-2 diabetes and bowel cancers, whereas, conversely diets low in fibre are associated with poor digestive health.6 The UK adult population is recommended to consume 30g of dietary fibre daily and so, including a portion of lettuce alongside your meals or inside your sandwich will help support you in reaching your daily fibre target and give your meals some extra crunch. 5

Lettuce is also a source of Vitamin A, albeit providing a small quantity of around 2% of the recommended nutrient intake per average serving. 3 UK adults are recommended to consume 600-700 µg of Vitamin A daily and because it is one of the fat-soluble vitamins our bodies are able to store the nutrient in our fat tissues and liver. Vitamin A plays an important role in maintaining healthy vision, promoting a healthy immune system, reproduction and cellular communication. It also plays a vital role in promoting cell growth and differentiation, playing a crucial role in the normal functioning and maintenance of the heart, lungs, kidneys and other organs. However, Vitamin A can be toxic if consumed in very high doses, and so the recommended intakes have been proposed as seen in Table 1. Although, it is unlikely that you will exceed your requirements through diet alone, pregnant women should be aware of their intakes as high levels can be harmful to the unborn baby. If you are pregnant avoid liver products and pate, because they are very high in Vitamin A. 6

Lettuce contains around 3% of the recommended nutrient intake for Vitamin C for UK adults. 3 As Vitamin C is a water-soluble vitamin, our bodies are unable to store these vitamins and so it is important we follow a healthy well-balanced diet to ensure we are receiving adequate amounts.  Vitamin C plays an important role in the maintenance of healthy connective tissues, and helps in wound healing. Vitamin C is also widely known for its anti-oxidant properties in preventing free-radical damage in our bodies, which may assist in preventing disease. 6

In addition, lettuce is low in Sodium, which may be helpful for those looking to reduce their salt intake to promote lowered blood pressure. 7Lettuce also contains small amounts of several minerals such as iron, calcium, magnesium, and potassium.  Our bodies require different amounts of minerals depending on our age, sex and health status to help promote optimum bodily functioning and general wellbeing. 8 Although lettuce provides lower quantities of a variety of vitamins and minerals in comparison to other green leafy vegetables, it is important to remember that our bodies absorb nutrients more efficiently when supplied by foods instead of dietary supplements. Therefore, every little helps when trying to reach our daily, recommended nutrient intakes. The most efficient way to achieve a good nutritional status is to consume a well-balanced diet, including fruit and vegetables from a variety of sources as this will help support long-term good health.

When choosing between different lettuce types, it is worth noting that although iceberg lettuce contains the lowest amount of calories, it also contains the lowest amount of nutrients. Romaine, also known as cos lettuce, has higher amounts of Vitamin A present and also is a good source of Vitamin K, which is important for its blood clotting properties and role in promoting good bone health.6 Nutritionally, the other lettuce types sit somewhere between iceberg and romaine. All types of lettuce are great for increasing the bulk of meals without increasing the calorie content, and are also very cheap to purchase, which is why it is such a staple in salad dishes. The best way to maintain a healthy diet is to ensure you are including a variety of fruits and vegetables throughout your day. Eating the rainbow is the best motto you can follow for nutrient density, as each vegetable and fruit has their own unique nutritional composition and benefits. So incorporate lettuce into your diet regularly, however add extra ingredients into your salad for extra texture and taste and to reap the health benefits of a well-balanced diet.

 

References

[1] Katz, S. H., and W. W. Weaver. 2003. Encyclopedia of Food and Culture. New York: Schribner.

[2] Great Stems. 2017. Vegetable Families [online] [Accessed on 24/03/2017] Available from: http://www.greatstems.com/images/veggiefamilies.html

[3] McCance, R.A., Widdowson, E.M., Royal Society of Chemistry. Information Services, Public Health England, Institute of Food Research & Great Britain. Ministry of Agriculture, Fisheries and Food (2015), McCance and Widdowson’s the composition of foods, 7th summary edn, Royal Society of Chemistry.

[4] British Leafy Salads Association, 2017. Leaf Types [online] [Accessed on 24/03/2017] Available from: http://www.britishleafysalads.co.uk/know/leaf-guide.shtml

[5] SACN (Scientific Advisory Committee on Nutrition) 2015. Carbohydrates and Health. [online] [Viewed on 07/03/2017] Available at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/445503/SACN_Carbohydrates_and_Health.pdf

[6] British Nutrition Foundation, 2017. Vitamins [viewed on 17/02/2017] Available from: https://www.nutrition.org.uk/nutritionscience/nutrients-food-and-ingredients/vitamins.html?limit=1&start=5

[7] NHS, 2014. Salt: The Facts [online] [Accessed on 25/03/2017] Available from: http://www.nhs.uk/Livewell/Goodfood/Pages/salt.aspx

[8] British Nutrition Foundation, 2017. Minerals and Trace Elements [online] [Viewed on 23/02/2017] Available from: https://www.nutrition.org.uk/nutritionscience/nutrients-food-and-ingredients/minerals-and-trace-elements.html