One of the most heated debates (pun intended) amongst nutritionists, scientists, and consumers alike is whether heating or cooking your greens affects their nutritional value.
We’ve been cooking, roasting, frying, basting, boiling, and grilling veggies for millennia, but does that mean it’s the right thing to do?
Are we depleting their nutrients by exposing them to heat?
Or is it actually perfectly fine?
Let’s find out.
What Does The Science Say?
As with most topics, if you look hard enough, you can find study after study supporting both sides of the argument; in this case, heating or not heating.
It is true that water-soluble nutrients and vitamins such as Vitamin C, B, and Enzymes all lose a certain amount of their nutritional value when exposed to heat. However, here’s where it gets tricky, cooking or heating your veggies can prove to have significant advantages for both the veggie and you.
When you cook veggies, unlimited scientific processes take place, which we don’t need to cover here; However, there are numerous nutrients, compounds, and enzymes that, after being heated, make them much much easier for the body to digest.
Amazingly in one recent study, researchers concluded that one cup of raw spinach contained 30mg of calcium; however, when cooked, the same amount ballooned to a massive 245mg. Scientists suggested that other veggies such as carrots, celery, asparagus, beans, and potatoes may also benefit significantly from being heated.
In another study conducted by the Health Sciences Academy, tomatoes also benefited greatly from being cooked and contain 35% more lycopene than when eaten raw. (1)
Benefits Of Cooking
Cooking as we know is absolutely essential to not only our lifestyle but our diets.
One of the most significant advantages of heating or cooking our food is that it allows us to much more easily digest the nutrients, meaning we expend much less energy in doing so. Besides from cooking, one of the most popular ways to consume vegetables is smoothies.. Smoothies or juicing, softens the food making it easier on our teeth and jaw, with the body quickly absorbing the nutrients.
An interesting study put out by the British Journal of Nutrition showed that a group who followed a diet of eating raw foods had normal levels of vitamin A yet comparatively high levels of antioxidants. The specific antioxidant beta-carotene is found in dark leafy greens. (2)
Lycopene is another highly potent antioxidant. Some scientists even suggest it’s more powerful than vitamin C. Lycopene can be found in vegetables and fruits such as red capsicums, watermelon, and papaya.
Tomatoes, as mentioned earlier, contain high amounts of lycopene, but when cooked at 190f/88c for 30 minutes, the levels of lycopene increase up to 35%. Many researchers believe this is because the heat helps break down the dense cell walls in certain vegetables, allowing the body to easily digest and uptake the nutrients.(3)
Steaming these vegetables acts as a preserver of antioxidants, specifically carotenoids. This means that cooking these particular vegetables supplies the body with more nutrients and has higher antioxidants levels. Other compounds such as ascorbic acid and polyphenols were also deemed higher after being exposed to heat. Antioxidants and polyphenols play a crucial role in the prevention of disease.
In some countries like Japan, where it’s popular to tempura fry vegetables, although this may seem relatively healthy, the oils cause high levels of free radicals. Free radicals as well know, are harmful and can have long-term adverse effects on the body.
Possible Adverse Effects
One of the most significant downsides of cooking or heating vegetables is that it can deplete up to 10% of the vitamin C content found in them.
Some studies have shown that cooking for longer than 2 minutes can drastically reduce the amount of Vitamin C; This is because vitamin C is highly sensitive and deteriorates rapidly when exposed to heat or water if boiling. Some scientists suggest that because vitamin C can be sourced from so many other fruits and vegetables, cooking certain amounts really doesn’t have a big impact overall.
Another green vegetable that is affected by heat is broccoli. In the case of broccoli, heat has an adverse effect, damaging myrosinase, which plays a vital role in breaking down glucosinates. The conclusion here is that eating dark leafy greens like spinach and broccoli, raw, pack a real punch.
Conversely, indole, which is an organic compound, is produced when cooking greens such as broccoli, cabbage, and cauliflower. Indole is crucial because it helps to kill cancerous cells before they become malignant.
As I said much earlier in the piece, if you look hard enough, you can find studies to support any number of arguments.
One case in point is a recent study found that boiling carrots increased levels of carotenoids, yet in another study, it was shown that boiling carrots led to a complete loss of polyphenols. This is why it’s essential to research thoroughly to make an informed decision.
Vegetables Best Eaten Raw?
In February 2014, the American Journal of Lifestyle Medicine published a report revealing that fresh, frozen, and even canned vegetables are all healthy.
Not surprisingly, though, the study found fresh veggies to be of the highest nutritional value yet concluded frozen and canned veggies were still an excellent cost-effective way of introducing veggies into the diet.
An interesting fact from a study by Frontiers in Psychology found that those people who regularly ate raw vegetables had an overall higher quality of life than those who didn’t. Eating raw vegetables seemed to reduce the chance of depression and increase positive moods and attitudes. (4)
Researches identified several fruits and vegetables that are best eaten raw; They include:
- Dark leafy greens
- Kiwi-fruits and
- Fresh berries
To me, it seems we have cooked vegetables for millennia, and even amongst well-known chefs like Jamie Oliver, frozen vegetables are highly recommended; by frozen meaning, they obviously need to be reheated yet still hold most or if not all of their nutritional value.
Some scientists suggest that because vitamin C can be sourced from so many other fruits and vegetables, cooking certain amounts really doesn’t have a big impact overall.
Most people are not thinking of how the nutritional value of specific vegetables will be affected when cooking, but what they are thinking of is taste. To be honest, the better they taste, the more vegetables we probably eat.
Sounds like a good trade-off to me.
I would suggest that even if they are cooked, grilled, boiled, steamed, or BBQ’d, the most important factor is the taste. If any of you have children, then you’ll know exactly what I mean.