I remember when rawism first came on the scene. I was about 16, and just starting to think about what I wanted to study beyond high school. I saw a TV segment on a raw restaurant in LA; they made ice-cream out of cashew juice, and dehydrated sweet potato until it resembled a chip. I was captivated by the creativity and the absurdity of only eating food kept under 49C/120F. This sprouted (pun intended) into a day-long raw challenge among my friends. None of us survived past lunch--watermelon and salad just doesn't cut it when you're 16.
Many years later 'going raw' is increasingly popular, with many supermarkets and restaurants now catering to the un- and under-cooked movement. Dedicated rawists will tell you that they feel better eating exclusively raw foods, but what does the science say?
Which nutrients are affected by cooking?
Yes, it’s true that some vitamins are sensitive to heat, and are lost during the cooking process. These nutrients include :
- Vitamin C: An antioxidant that supports immunity, and protects soft tissue.
- Thiamin: B-vitamin that helps convert carbs, fat and protein into energy and;
- Vitamin B6: Supports metabolism, brain function, oxygen transport, and DNA formation.
However, the extent of degradation is unclear. Studies show that thiamin and vitamin B6 losses during cooking vary from 7-70%, while vitamin C degradation ranges from 5-15% . Sure, these nutrients are partially degraded during cooking, but deficiency is unlikely if you have a healthy, varied diet. Vitamin C, thiamin and vitamin B6 are available in a wide variety of foods, and generally abundant in our food supply.
On the contrary, some nutrients become more concentrated during the cooking process. Lycopene, an antioxidant associated with prostate health, becomes more concentrated when tomatoes are cooked. Similarly, iron-rich foods cooked in a cast-iron pan are often richer in iron.
High temperature cooking may have more damaging effects...
Cooking at high temperatures such as searing or barbecuing/grilling changes the proteins in meat, poultry and seafood. High heat causes proteins to unravel and fat drippings to smoke, resulting in the formation of carcinogenic heterocyclic carbons (more on this here). This issue can largely be mitigated by cooking low and slow, and marinating your meat prior to cooking.
Similarly, fats with low smoke points such as olive oil, and coconut oil degrade at high temperatures, forming harmful free radicals. Again, this can be prevented by cooking at a lower temperature, or using an oil with a high smoke point like sunflower oil.
The pros + cons of being a rawist...
Going completely raw means subsisting off raw fruit and veggies, nuts, seeds and some sprouted grains, and largely eliminating grains, poultry, meat, and dairy.
- On the spectrum of dietary choices, the raw diet is one of the more restrictive, and difficult to follow.
- Extra care needs to be taken to get adequate protein, carbohydrate, calcium, zinc, iron, vitamin B12, and omega-3s, as well as Calories because the raw diet is typically low in these nutrients
- On the plus side, raw diets are often loaded with veggies, and rich in fiber, vitamin A, vitamin C, vitamin K, folate, potassium, and manganese.
In a nutshell...
At this point the best approach to eating appears to be one that incorporates a wide variety of both cooked and raw, minimally processed foods. Eating exclusively raw foods may feel healthier, but they're likely to miss out on important nutrients without diligent planning.
 Maximizing the nutritional value of fruits and vegetables. Barrett D. University of California, Davis. 2007.