n4 nutrition

Why Tomatoes Are a Great Choice

Average Rating:
Number of Ratings:
0
To add you own rating or comments, you need to be a member. Join now, it's free!
Intro
Being a vegetable (although botanically classified as a fruit), tomatoes are automatically a healthy food. They are a good source of potassium, fibre and vitamins A and C. However, it is the high concentration of a particularly powerful antioxidant, lycopene that makes them a great everyday food.

What is lycopene?

Lycopene is a type of carotenoid antioxidant and is what gives tomatoes their red colour.  Several epidemiological studies have found that high blood levels of lycopene are associated with a number of health benefits, including a reduced risk of heart disease, diabetes and even certain cancers.

 

Healthy skin

As one of the most potent antioxidants, dietary intake of lycopene enhances the skin’s natural sun protection factor1, helping to protect the skin against sun damage (kind of like a mild sunscreen).  Lycopene also strengthens the skin by inhibiting the activity of collagenases2 (enzymes that break down collagen which plays an important role in maintaining the elasticity of the skin).

 

Cardiovascular system benefits

It is also this antioxidant activity that is thought to contribute to lycopene’s ability to protect against cardiovascular disease by slowing the process of atherosclerosis (hardening of the arteries) which occurs over time as cholesterol molecules become oxidised3. Tomatoes are also an excellent source of potassium, a nutrient known to help lower blood pressure4.

 

Cancer prevention

 There is also emerging evidence that other mechanisms, apart from tomato’s antioxidant action, are involved in its ability to reduce the risk of certain cancers. Lycopene has been shown to interfere with growth factors that stimulate cancer cell growth5, 6, as well as enhance the body’s immune defence system against cancer cells7.

 

Recommendations

Although there is currently no official recommended intake of lycopene, it would be fair to suggest the consistent inclusion of one to two servings of tomato or tomato-based products would confer health benefits, with one such study finding that those who consumed 10 or more servings on average of tomato products each week had almost a 35 per cent reduction in the risk of developing prostate cancer8. 

Whilst many nutritionists advocate the consumption of fresh produce, in the case of tomatoes, tinned or tomato paste from a jar may actually be better as lycopene becomes more bioavailable (more easily absorbed by the body) when cooked9. The cooking process breaks down the cell walls and fibre of raw tomato to free the lycopene. Cooking also lowers the vitamin C content to a certain extent, but the increase in lycopene bioavailablility well and truly makes up for the loss.

 

Food sources of lycopene:

Some easy ways to increase your consumption of tomato and lycopene include:

·       Opting for tomato-based pasta dishes, including tomato paste in homemade sauces and salad dressings.

·       Adding sundried tomato to salads, sandwiches, wraps.

·       Adding tomato paste to casseroles

·       Using tinned tomatoes in curries.

 

You can use the following as a guide for how much to use:

·       2 tablespoons (35g) tomato paste (12mg lycopene)

·       ½ cup (100g) canned tomato puree (15mg lycopene)

·       ½ cup (125ml) tomato juice (12.5mg lycopene)

·       1 medium (150g) fresh tomato (3.8mg lycopene).

As lycopene is a fat-soluble nutrient it is important to consume tomato-based products with a source of fat to aid absorption. This would be as simple as some avocado or a drizzle of olive oil over a salad containing fresh tomatoes or the use of a couple of teaspoons of oil in the cooking process of a meal containing tomato paste or tinned tomato.


One final note: although tomato sauce (ketchup) is technically a tomato-based product, be careful as the majority of commercial tomato sauces on the market are around 25 per cent sugar, with several popular brands containing 35 to 40 per cent sugar (the majority of which is added, not what is naturally occurring in tomato). To put things in perspective, the average chocolate sauce contains 40 to 50 per cent sugar.

 

Useful Links and references

1. Stahl and Sies (2012), ‘B-Carotene and other carotenoids in protection from sunlight’,American Journal of Clinical Nutrition, 96(5): 1179S-1184S.

2. Rizwan et al (2011), ‘Tomato paste rich in lycopene protects against cutaneous photodamage in humans in vivo: a randomized controlled trial’, The British Journal of Dermatology, 164(1): 154-162.

3. Hadley et al (2003), ‘The consumption of processed tomato products enhances plasma lycopene concentrations in association with a reduced lipoprotein sensitivity to oxidative damage’, The Journal of Nutrition, 133(2): 727-732.

4. Willcox et al (2003), ‘Tomatoes and cardiovascular health’, Critical Reviews in Food Science and Nutrition, 43(1): 1-18.

5. Sharoni et al (2012), ‘The role of lycopene and its derivatives in the regulation of transcription systems: implications for cancer prevention’, The American Journal of Clinical Nutrition, 96(5): 1173S-1178S.

6. Yang et al (2011), ‘Growth inhibitory efficacy of lycopene and B-carotene against androgen-independent prostate tumor cells xenografted in nude mice’, Molecular Nutrition and Food Research, 55(4): 606-612.

7. Preet et al (2013), ‘Lycopene synergistically enhances quinacrine action to inhibit Wnt-TCF signalling in breast cancer cells through APC, Carcinogensis 34(2): 277-286.

 

8. Giovannucci et al (1995), ‘Intake of carotenoids and retinol in relation to risk of prostate cancer’, J Natl Cancer Inst, 87(1): 1767-1776.

 

9. Gartner et al (1997), ‘Lycopene is more bioavailable from tomato paste than from fresh tomatoes’, American Journal of Clinical Nutrition, 66(1): 116-122.

 

Why Tomatoes Are a Great Choice
Rebekka Frazer
Accredited Practising Dietitian (APD)