Tuesday, July 14, 2015

Cutting Calories in Rice

Reader Gillian Street alerted me to a news item suggesting that we had found a way to reduce the energy (Calories/kilojoules) in rice by 10%, and possibly by as much as 50% soon, and this would result in a “healthier rice”. Immediately I was sensing a headline and not a story. Why?

Creating resistant starch
Researcher Sudhair James reported at a conference that if you added coconut oil to simmering rice, then chilled the rice for 12 hours after cooking, the proportion of resistant starch increases.

To make sense of this first we need to know what is resistant starch (RS). We don’t digest all of the starch in food. Some of it is in a form that is resistant to digestion, hence the term. The undigested starch then goes into the large bowel to be consumed by the resident friendly bacteria. This is good, being the main role of dietary fibre too. Foods such as breads, pasta, legumes, bananas, potatoes and corn chips all provide a reasonable amount of RS.

RS benefits
We already knew that if you cool cooked rice, pasta and potatoes that the level of resistant starch rises, meaning that you digest less starch in a cold rice, pasta or potato salad than in hot stir-fried rice, spaghetti marinara or baked potatoes. The cooled starch becomes less soluble and harder to digest.

What are the potential benefits of RS? It helps lower the Glycemic Index of a meal, has a laxation effect, increases the satiety of the meal, and as the healthy bacteria in your large bowel chew through the RS they produce acids that protect the bowel lining, reducing the risk of bowel cancer. Pretty cool eh?

10% fewer Calories
OK, back to the rice story. Sudhair James’ cooking method reduced the kJs by about 10%, which is quite minor in the scheme of things. Why not just eat a little less rice or, even better, not eat that biscuit or pastry for morning tea, or not buy the Maltesers at the movies, or the cake with coffee. It’s quicker, easier and more effective than going through the cook-add-oil-chill-for-12-hours-then-microwave process of saving a few Calories. A cup of steamed rice is 960 kJs (230 Cals) so a 10% saving is 96 kJs (23 Cals) or about one-third of a chocolate biscuit. Get my drift?

Maybe a company will produce rice that has been pre-cooked with oil and dried before putting a packet, but a reduction of 10% kJs would have a net result of zero when it comes to body weight, in my opinion.

OK, but what if they get up to a 50% cut in kJs, wouldn’t that shatter the earth in some manner? Yes, I suppose so, but that is purely speculative for the sake of the story, in my view.

What does it all mean?
Right now we eat an average of 5g of resistant starch each day, yet our goal should be closer to 20g. A rice with more RS could have potential health benefits, no doubt. My guess is that it will come at a premium cost, and may even cause some gut discomfort with all that RS being eaten by bacteria creating gas as a by-product. In the meantime, I suggest you do something radical, yet exceptionally dull, which is to eat regular rice and serve with wholesome plant-based foods and maybe a little meat. No way that will get you a headline.

Kefir 2: made using grains and water

Alberto Gómez from Buenos Aires asked about kefir. He very politely pointed out that I had misunderstood his question about using kefir as a sports drink. So he wrote:

“When I mentioned that kefir could be used as an isotonic drink, I was referring to the kefir prepared with water, not milk. The way to prepare it is to have three spoons of kefir grains, a litre of filtered water, three spoons of brown sugar, a lemon split in halves and three dried plums or dates. You put all of them in a glass container leaving enough air on it and they cultivate in 1-3 days. I do it in two days.

Every day you have to stir the mix. After the time is over, you filter the mix, reuse the kefir grains which amount has increased (separate a portion and use the right proportion, the unused grains could be kept in the fridge for several days keeping them in water with sugar), squeeze the lemon and if you want some fizz just leave the juice in a tight recipient for few hours, put it on the fridge and...voilá!!! you have the isotonic beverage.”

One additional comment from Alberto: “Kefir grains for milk and water are not the same, they share same origin but are different. Advantage of kefir prepared with water is that there are no limits for consumption, the one prepared with milk is heavier and should be consumed with moderation.”

Let me add that I’m still using my milk-based kefir on my cereal in the morning. Adds a pleasant tart sweetness to the start of my day. Thanks again Alberto.

Vitamin D in Mushrooms

I work for the mushroom industry in Australia and very recently we did something not yet done anywhere else that I know of. I arranged a collection of retail mushrooms from a range of stores in five capital cities and had them sent to the National Measurement Institute in Melbourne for analysis of their vitamin D content.

First, I should say that mushrooms are the only non-animal food to naturally produce vitamin D. Just like you, they do it in response to exposure to a source of UV light (eg sunlight). Mushrooms labeled “Vitamin D Mushrooms” have at least the daily needs of D in a serve (10 mcg), because they are exposed to UV light post-harvest.

What surprised me is that regular retail mushrooms have 20-25% of your daily D needs. I suspect that they are producing D from the UV bandwidth in the fluorescent lights in-store.

Table. Vitamin D content of store-bought button mushrooms (100g)
Vitamin D mcg/100 g serve
Regular retail mushrooms (sliced & whole)
Cooked regular mushrooms
Regular mushrooms after 1 hr in the winter sun
Vitamin D labelled mushrooms
Cooked Vitamin D labelled mushrooms
Source: National Measurement Institute

Following the strict protocol set by Food Standards Australia New Zealand, the resulting data was placed on their website. From there you can download the report.

It is winter in the southern hemisphere as I write and about half the population in Australia and New Zealand (and probably Argentina, Chile and South Africa) will be vitamin D deficient. Mushrooms can be part of the solution.

Monday, April 27, 2015

Cooking oil: does heating cause health problems?

The thought comes up regularly – if you cook with oil does it lose all its healthy properties? Do unsaturated fats become saturated once they are heated? In other words should oil only be used for salad dressings? These are common questions. Let me try and make sense of this topic.

Frying oil at home
I have done a search of all the literature on cooking oils. OK, that’s a lie. I have actually read five extensive review papers on the effect of heating on oils. And they certainly tested out my chemistry. And none came to a simple solution to make my life easier. Let’s start with the one we can sort out quickly.

You may have heard that frying any oil will convert it to a saturated fat, making it bad for your heart. Let’s assume that you are referring to unsaturated cooking oils like olive oil or peanut oil (mainly monounsaturated), or safflower oil (mainly polyunsaturated). Let’s also assume you only use the oil once in frying, because you are using just enough to get the food cooked. What will happen during cooking? Nothing. The oil will remain pretty much as it was originally. Nothing I’ve read says any different.

Deep frying oil
Nevertheless, there is a potential problem when an oil is repeatedly used for deep-frying. I don’t know anyone who has a deep fryer anymore. We had one back in the late 60s for cooking chips (fries), fish and potato fritters. Don’t think it made it past 1975. So, I suspect the only source of a deep-fried food for any reader is from a fast-food venue.

Cooking oil at high temperatures for hours over many days does cause the fats in the oil to begin to oxidise (go rancid), which spoils the smell, taste and colour of the oil. When consumed, this rancidity can cause inflammation and damage to the artery linings and a rise in the risk of heart disease, including a rise in blood pressure. Long term heating also causes a loss of vitamin A and antioxidant compounds naturally present in oils like extra virgin olive oil.

How much cooking before an oil goes bad?
I would love to give you a specific cooking time that oils “turn bad”, but there are so many variables. Simply put, most studies show a decline in the oil quality (from a health perspective) after 5-10 hours of frying. The shorter time frame is for the polyunsaturated oils, according to the Heart Foundation. That means the once-off use of oil in cooking shouldn’t pose a problem, while repeatedly heated oil could be aging your blood vessels rather quickly.

The one thing nobody considers
When you buy your Extra Virgin Olive Oil do you ever give it a taste test (licking some off your finger)? If your olive oil was cheap-ish it is probably also old-ish, as in starting to go rancid. Now taste a good local olive oil. Probably full of fruit flavours. Dietitian Rosemary Stanton has written a lot on fats and has often said that European olive oil sold in Australia has been around too long and has rancid tones to its flavour. And she’s an official olive oil taster, so I’m going to believe her.

This is not just a problem in Australia and New Zealand. The Americans are being sold rancid olive oil and no-one seems to care.

Buying local olive oil is a good argument on many fronts - environmental, economic, and nutrition. There is plenty of great tasting oil in Australia, New Zealand and the US. No doubt the folk in Europe can get wonderful fresh Spanish, Greek and Italian olive oil.

What does it all mean?
Simple message – eat few deep-fried takeaways; enjoy more home cooking. (Note: some big take-away franchises use better quality oil, filter it regularly and top up with fresh oil, therefore lowering any health risk). When simply frying food, then purchase a cheaper unsaturated oil (eg Canola, Grapeseed). If you want some flavour in an Asian dish, then maybe some sesame oil. Save the top-end olive oil for the salad dressing or for drizzling on bread. Keep your oil cool, sealed and away from light, to slow down the oxidising process.

Santos CSP et al (2013). Effect of cooking on olive oil quality attributes. Food Research International 54: 2016-2024
Choe & Min (2007) Chemistry of deep-fat frying oils. J of Food Science 72: R77-R86
Stier RF (2013) Ensuring the health and safety of fried foods. Eur J Lipid Science & Technol  115: 956-964
Ng CY et al (2014) Heated vegetable oils and cardiovascular disease risk factors. Vascular Pharmacology 61: 1-9