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)

Mushroom	Vitamin D mcg/100 g serve
Regular retail mushrooms (sliced & whole)	2.3
Cooked regular mushrooms	3.1
Regular mushrooms after 1 hr in the winter sun	10
Vitamin D labelled mushrooms	26
Cooked Vitamin D labelled mushrooms	52

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.

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.

References:

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

Kefir: potential health benefits

Alberto Gómez from Buenos Aires wrote to me, wondering if kefir would be a useful sports drink. Well, I had never heard of kefir being downed by athletes. In fact I had never tried it myself, so I was about to get an education in taste and knowledge. Where I live kefir, a yogurt-style milk drink, is not widely available but I did track down a version made on the east coast of Australia (see pic). The plain version is too acidic for me, but the honey version hits the spot. It is too thick to work as a sports drink, unless diluted with water which is likely to reduce its palatability. I prefer to have it on cereal after my early-morning cycle training.

Alberto had also heard that kefir had a range of health benefits. Well, being a milk base with added Bifidobacterium and Lactobacillus bacteria, there is no doubt it will be similarly nutritious as yogurt. It originated in the Northern Caucasus mountains of Russia, its name taken from Turkish meaning “good feeling”. The fermentation process is started by “kefir grains” which contain bacteria and yeast in a carbohydrate matrix of granules. The granules have a popcorn or cauliflower shape and are visible to the naked eye.

Bumping out evil bacteria

There is quite a bit of research on the potential health benefits of kefir, as you would expect with a fermented food. The kefir bacteria are able to attach to the intestine lining to effectively “bump out” the pathogenic bacteria. They seem to also produce compounds that kill the nasty bacteria. Kefir seems to be effective in stopping the growth of Helicobacter pylori, a particularly nasty bacteria that is linked to chronic gastritis, ulcers and gastric cancer. Some other results suggest that it helps lower blood cholesterol levels.

In the laboratory kefir are able to kill and slow down cancer cell growth, and enhance the immunoglobulins that help your immune system function well. Anyway, you get the picture. And you can see why there is a keen interest in kefir.

I’m not sure that I have been consuming anything close to the kefir they enjoy in Eastern Europe, which is meant to be a little bit fizzy. Still, whether or not it is going to add years or minutes to my life, I thank Alberto for introducing me to this quite delightfully tasting style of yogurt.

References:

Guzel-Seydim ZB et al (2011). Review: Functional properties of kefir. Critical Reviews in Food Science &Nutrition

Nielsen B et al (2014) Kefir: a multifaceted fermented dairy product. Probiotics & Antimicrobial Proteins

Milk for rehydration

With warm weather and/or physical activity you lose perspiration, and the evaporation of the sweat from your skin cools the body. Before long, that sweat loss needs to be replaced. Water is good. You know from previous articles both coffee and tea can rehydrate the body. Sports drinks are specifically designed for rehydration, especially for athletes during sport.

After sweating did you ever consider a glass of milk for rehydration? Well, it is 90% water, just like fruit juice, so theoretically it should be a useful drink. Or, if you prefer, soy milk which is also 90% water. One Australian research group has just published their results on rehydration drinks.

  

Drink more fluid than you lose

If you perspire, say 1 litre (34 oz), it makes sense to drink the same volume to make up for the loss. Only problem is that the kidneys still want to make urine, so you might drink 1000mL of water and yet produce 350mL of urine, still leaving you 350mL short of the 1000mL replacement. This is why you hear coaches and sports dietitians encouraging athletes to drink more, 150% more, than they lost as sweat.

So what is happening here? If you replace sweat losses with just water it actually dilutes the blood because you sweat both water and salt, then replace it with just water and next-to-no salt. Not a problem for normal sweating as you will get your salt from the next snack or meal. If you sweat heavily, like in this study, then drinking just water dilutes the blood and the kidneys act to concentrate the blood by creating some pee. This is why sports drinks have some added salt – it helps you to retain more water absorbed from the gut, with less pee, after sweating.

The power of milk

This is where milk comes in. This was a study of 15 young males who were exercised until they lost about 2% of their body weight as sweat in a session on the exercise bike (that’s 1.5kg in a 75kg person; 3.3lb in 165lb). To rehydrate they were given either milk, soy milk, Sustagen Sport (a milk-based nutrition supplement), or the sports drink Powerade. The volume given was 150% of the amount lost as sweat, in other words, more than sufficient to replace sweat losses, on paper at least. The milk and soy-based drinks were chosen as their natural salts, sugars and protein all work to help retain the fluid in the body, meaning you produce less pee.

Sustagan Sport takes the title

 After drinking 1.5 litres of drink for every 1 litre lost as sweat the athletes were tracked for another four hours, taking blood and pee samples, while checking body weight. The least amount of urine production was after drinking Sustagen Sport, the flavoured milk-based supplement that is fortified with extra vitamins and minerals, and very popular with Australian and Kiwi athletes. Put another way, more fluid was retained from a flavoured milk supplement drink, making it very viable as a rehydration fluid.

In second place came milk and soy milk, with little to separate them. The sports drink was last, suggesting you need to drink much more than 150% of losses, probable twice as much, when replacing losses with a sports drink.

What does it all mean?

Remember, this is a study of fluid replacement after you have finished your workout. Let’s be very clear, water or a sports drink are still very good choices to have while you are perspiring. After the gardening, brick-laying, half-marathon or cycle training has finished there are other options to help replace the sweat.

What this study shows is that a milk-based drink will do an excellent job of replacing your fluid losses when the work is finished. After a long bike ride, I put the bike back in the shed, open the fridge and enjoy a coffee-flavoured milk (pictured). I’m getting:

1. Fluid
2. Carbs to replace my glycogen
3. Protein to help repair any muscle micro-damage; and
4. A great flavour
5. And a nice change after 2-3 litres of water on the bike.

Try it and see what you think.

Reference:

Desbrow et al (2014) Applied Physiology, Nutrition & Metabolism 39: 1366-1372

Cow blowing (insufflation) to encourage milk letdown

So, I’m reading this book on milk (Milk: A global history by Hannah Velten) when I come across this picture on the right and I’m thinking “OK, this is looking a bit strange, and is surely quite disconcerting for both species.”

The photo was taken in 1982. It is a young lad blowing, via a tube, air into the vagina of a cow to induce milk letdown. I have read that similar result can be achieved by blowing air into the anus.

I know what you are thinking:

1. No, no, no, you are kidding me, right? No. It’s true, and it’s called “cow blowing” or insufflation. It has been described in many parts of the world, and the “art” has been around for a long time. Back in 440 BC a bloke called Herodotus described this in horses: “... they insert a tube made of bone and shaped like a flute into the mare’s anus, and blow; and while one blows the other one milks.”

2. OK, who was the first person to think of this?

“Hey Dad, Daisy won’t let down any milk, what should we do?”

“Have you tried scratching behind her ear?”

“Yes. Didn’t work.”

“What about rubbing her tummy”.

“Doesn’t work either".

Dad, stuck for ideas, decides to play a joke on the kids. “Try blowing air up her backside.” And so the incredible discovery began.

Seriously, I would like to know the physiology behind this practice, but I had difficulty getting an answer. Is it a physical response or does the air stimulate the release of oxytocin? Anyway, there is a fascinating, although long, history of insufflation of cattle here. There is also a short TV news video here. When food is not always easy to come by you have to admire human ingenuity to get nutrition.