When tomatoes are in season they are one of my favourite foods to eat in abundance. See my easy to make tomato soup recipe here. Tomatoes are a native to South America where they were enjoyed by Aztec and Incan cultures. In the last few hundred years tomatoes have risen in popularity to their place today, as one of the worlds’ most widely cultivated and consumed vegetable or fruits.
In this article I give my perspective on one of the most widely used arguments used in support of cooking versus raw food; the discovery that the powerful cancer fighting antioxidant in tomatoes, lycopene, is more available to the human body from processed and cooked tomatoes, than from eating tomatoes raw.
Some mistakenly believe a general rule that cooking food is necessary, in order to ‘release’ the nutrition it contains. This belief is supported by widely publicised information about the higher lycopene content of cooked, concentrated tomato products such as tomato paste or ketchup.
Taking the diet as a whole and the idea of cooking to improve food, this is generally not true and especially not true when we are discussing macro nutrients like proteins or fats. Vegetables and fruits contain many thousands of phytochemicals and many of them can only benefit us in the raw form. The carotenoids including beta carotene and lycopene are the partial exception to the rule. Heating foods containing these phytonutrients will enhance their availability, however raw versions of these foods do also provide these nutrients.
Lycopene is a member of the carotenoid family of antioxidant pigments, and gives its red or pink colour to tomatoes, goji berries, sea buckthorn, pink grapefruit and watermelon. It has attracted a lot of attention for its disease fighting properties.
Even though it is not considered to be an essential nutrient that we must get from our diet, numerous studies have illustrated its cancer fighting properties including for prostate and ovarian cancers, and also that it can play a part in preventing strokes. Lycopene’s antioxidant activity is considered to be more powerful than that of other carotenoids, such as beta-carotene.
More lycopene in cooked and pureed tomatoes
Research by Gärtner et al, published in the July 1997 issue of the American Journal of Clinical Nutrition, has shown that Lycopenes bioavailability in tomatoes increases by 2,5 times during cooking.
A further study reported in the Journal of Agricultural and Food Chemistry in May 2002 further confirmed this by showing that cooked tomatoes (eg, tomato sauce or tomato paste) increased the trans-lycopene content that can be absorbed by up to 164%, with the availability steadily increasing over 30 minutes. The overall antioxidant activity was seen to increase by up to 62%.
The main reason for this is because during cooking the cell walls are broken down and the lycopene inside becomes more available. As the water evaporates off during cooking, a tomato paste or sauce becomes relatively more concentrated, also increasing the lycopene content per gram.
However simply blending or juicing tomatoes also breaks down the cell walls, increasing the availability of the lycopene.
What else is in Tomatoes?
What these studies don’t take in to account is that lycopene, is just one interesting nutrient out of a whole array of nutrients found in tomatoes. By cooking the tomatoes you will lose many of the heat sensitive nutrients such as its abundant vitamin C, and B complex vitamins. It is important to remember that the array of nutrients you get from whole foods work synergistically together and likely enhance the disease preventative effects of any single phytonutrient.
The main nutrients in tomatoes include calcium, magnesium, phosphorous, potassium, sodium, zinc, iron, copper, manganese, vitamin C,Vitamins B1, B2, B3, B6, K and E, pantothenic acid, fibre and folate, as well as a small amount of lipids and amino acids. They also contain a long list of phytochemicals including beta carotene, lutein, zeaxanthin, curcumin, tocotrienols, phenol, flavonels such as kaempferol, quercetin and rutin, and flavanones.
The good news that eating raw and particularly blended or juiced tomatoes will still provide a significant amount of lycopene and by simply eating a few more of them, you quicky get equivalent amounts of lycopene in your diet.
While processed tomato sauces are shown to contain more lycopene, be careful when shopping. Many packaged products contain added sugar and it may be better to make your own sauces to avoid less desirable ingredients.
While there are many different varieties of tomato available, including yellow and green ones, only the red ones contain lycopene. The best choice is to buy tomatoes still growing on the vine.
Consume lycopene with fat
Lycopene is a fat-soluble nutrient, which means eating it with some oil, such as olive oil in a tomato sauce or another fat rich food, is necessary for it to be properly absorbed.
Other sources of lycopene
While so much attention has been given to the lycopene content of tomatoes, it is easy to forget that lycopene is also found in many other foods too, including watermelon, grapefruit, papaya, apricot, asparagus, red cabbage, red bell peppers, mangos and carrots. It is even found in a few non red coloured items such as parsley and asparagus.
The chart on this page shows the lycopene levels in 23 food sources.
Watermelon Has More Lycopene Than Raw Tomatoes
Compared to fresh tomato, an equivalent portion of fresh watermelon has 1.5 times the lycopene; 6 mg in watermelon compared to 4 mg in a tomato.
Interestingly, organic tomatos have been shown in studies to contain more nutrients than conventional tomatos. In particular one study showed a 55% percent increase in the Vitamin C content, and 139 percent more total phenolic content, when fully grown, compared to the conventionally-grown tomatoes.
Due to the abundant demand for tomatoes, modern agri business farmers have developed tomatoes which can be picked green and then treated with ethylene gas which ripens them. This artificial ripening process affects the flavour and texture of tomatoes, and will noticeably lack an odor. Naturally ripened tomatoes will have a distinct smell. Unripe tomatoes should never be stored in the fridge as this will hinder the eventual ripening process, but will ripen better at room temperature. Once ripe they can be kept at room temperature for 2-3 days, and then stored for more days in the fridge.
Consider growing your own tomatoes! Tomatos are easy to cultivate and can be grown in a pot on a balcony or sunny windowsill.
The most lycopene is available from pureed heated tomatoes.
In order to get the highest amount of lycopene (x 2,5) you would cook the tomatoes for 30 minutes losing a great deal of the other nutrients.
You can obtain an equal amount of lycopene from raw tomatoes by blending or juicing them, and by eating slightly more of them. This way you get the complete nutritional package from the raw whole food.
Organic tomatoes have more phenols and other nutrients than conventional.
Fresh watermelon contains more lycopene per gram than fresh tomatoes.
As a general rule you will receive more protective phytochemicals from eating most vegetables raw rather than cooked.
Author: Diana Store
For a delicious and simple tomato soup recipe see here
References and suggested further reading
Book: Prescription for Dietary Wellness by Phyllis A. Balch CNC