Wednesday, August 27, 2014

Calcium absorption

Calcium is a crucial part of the structure of bones and teeth. You knew that already. So how do you assess what food is a good source of calcium? You may just look for the number of milligrams of calcium there are in a serve, the more the better. Well that doesn’t always work as we shall see.

Or you could read some websites that give you counter-intuitive information, such as those claiming milk, yogurt and cheese being high in calcium, yet being a poor source of calcium. Let’s take a look at the data because Hannah Castledine, university nutrition student, was a bit annoyed when she went to presentation by a chef claiming that dairy just doesn’t cut it as a calcium source and we should rely solely on almonds and leafy vegetables.

Calcium absorption
During digestion the calcium is usually freed-up for absorption, although some calcium complexes can form which are difficult to absorb. That doesn’t mean that every atom of calcium gets absorbed into the blood. We still tend to absorb more calcium as more calcium appears in the diet, independent of its source.

At low amounts of dietary calcium, it is actively transported across the lining of the intestines and into the body. Once this system becomes saturated as we eat more calcium then the extra calcium is absorbed by passive diffusion.

Factors affecting calcium absorption
Vitamin D is needed for effective calcium absorption, and as you know many people are low in vitamin D. On average one in three adults are vitamin D deficient in North America, Australia and New Zealand, even more in the winter months.

Even if you get enough calcium in your food, a low vitamin D level is going to make it difficult to absorb enough. You will still absorb some calcium, but probably not enough for good bone mass.

As we get older our ability to absorb calcium declines, by about 1% every five years, with a slightly bigger drop in women at menopause. Hence, the reason for more calcium recommended for folk as they edge into their 60s.

The lactose in milk seems to give calcium an absorption “leg-up” by augmenting its passage across the intestinal wall. On the other hand, salt and caffeine can increase calcium losses through your pee. This is most likely to be a problem in people eating lots of salty processed food and gallons of coffee. If you eat well, avoid highly salted food and enjoy 3-5 cups of tea or coffee a day, then I wouldn’t change a thing.

Calcium sources
You absorb about 30% of the calcium from milk, yogurt and cheese sources, which is pretty impressive when compared to the 5% absorption from spinach. I mention this specifically because spinach is touted by the pop-nutritionist as a wonderful source of calcium. Much of the calcium in spinach is locked up in the form of calcium oxalate making it just too difficult to absorb. Same with the iron in spinach. Mostly bound to oxalate. As case of being high in calcium and iron but low in bioavailability.

I remember telling that to a men’s health group once, and one bloke did an air punch and said: “That’s going back to the missus”. I had to say that even if the calcium and iron in spinach goes down the loo it doesn’t make spinach a 2nd class veg – it is still high in folate and beta-carotene.

The calcium from Brassica vegetables is much easier to absorb. I’m talking broccoli, kale, bok choy and cabbage, for example. We can absorb about 50% of the calcium from the Brassicas, but beware that 1 cup of broccoli will have about 50 mg calcium (so 25 mg ends up inside you) while a cup of milk will have 300 mg calcium, with you absorbing about 90 mg of that.

If you don’t fancy milk, then I recommend you choose a calcium-fortified beverage in its place, such as a soy milk. How do you know if your milk substitute has added calcium? It will definitely be on the label. If there is no mention of calcium, then assume it is low.

I have previously written about food sources of calcium. Yes, almonds and tahini are other good sources of calcium, with 70 mg calcium in 30g almonds, and 30 mg calcium in a tablespoon of tahini.

The old days
Our ancestors may have got 1500mg of calcium each day through nuts, vegetables, seeds and beans, partly because they would be eating a lot more food than we do. Nowadays we do less activity, therefore need less food, so we need to make sure our food is high quality, and some of us will need to also make use of calcium-fortified foods.

What does it all mean?
I have tried to give you a fair and reasonable summary, free from food politics and bias. Yes, there are many who want to swing your views based personal nutrition evangelism. As you have heard many times from me, you are your own boss and your sources of calcium is your decision. If you are happy with dairy, then continue to make that a major source of calcium. If you are avoiding dairy for philosophical or allergy reasons, then there are other calcium sources.

Essentials of Human Nutrition, 4th edition p 142-145

Modern Nutrition in Health & Disease, 11th edition p 136-140

Wednesday, July 16, 2014

Gluten-free eating - when is it necessary?

When I was at dietitian school long ago we were taught that a gluten-free diet was only for those who had coeliac disease or an inflammatory skin condition called dermatitis herpatiformis. About one in 70 to 100 people have coeliac disease. The gluten triggers the immune system to breakdown the intestinal lining making it difficult to absorb the nutrients in food. That usually leaves you with uncomfortable intestines and difficulty in gaining weight or muscle.

Now it seems that gluten-free foods have become trendy. One US estimate is that one in 10 people have gone gluten-free at the moment. There are even supermarkets with gluten-free aisles (see the pic I took in Granada, Spain). Around 10% of all new food product launches around the world in 2013 were gluten-free. It is now a $5 billion global market, and just under $100 million market in Australia.
What is gluten?
Let’s clear up a few points. First know that gluten is a protein naturally occurring in grains like wheat, barley and rye. I had to point that out because there are some thinking that it is an evil additive or some toxin to be avoided. Not so. We’ve been eating it for millennia. The long, interconnected gluten proteins help bread to rise, providing the characteristic texture and springiness many enjoy.

Gluten-free does not mean “healthy”. Potato crisp/chips are usually gluten-free. Those gluten-free muffins are still high in Calories (fat and sugar are gluten-free). A diet without gluten might be a healthier diet if you are now eating more fruits, vegetables, nuts and legumes and dropped the croissants and donuts.

Gluten-free for weight loss?
If you are trying to trim up and decide upon the gluten-free diet as the way to do it, then you are likely to experience weight loss. That is not because gluten is fattening. It is because you will eliminate biscuits, cakes, pastries, bread (and therefore butter and margarine), pizza and most other take-aways, so weight loss and a better sense of well-being comes from an improved diet. This is the same reason why a low carbohydrate diet causes weight loss – many kilojoule-dense foods disappear and you are left pretty much with meat, fish and salad.

Non-coeliac gluten sensitivity
There may be people with symptoms similar to Irritable Bowel Syndrome who seem to respond to a gluten-free diet although they do not have gut lining atrophy on biopsy, yet they respond positively to a gluten-free diet or a wheat-free diet. It is not entirely clear if that is due to the gluten or to other compounds in grain such as fructans. If you have a science bent you may want to read a recent paper on the topic (use the link in the top right corner to download the full paper).

What does it all mean?
First, don’t go gluten-free just because your neighbour or best friend swears by it. If your guts are telling you that everything is not perfect, then see your doctor about testing for coeliac disease before you go on a gluten-free diet. If the test is positive, then a gluten-free diet is your solution. If the tests show that you do not have coeliac disease then see a qualified dietitian and do a proper trial on a gluten-free diet to see if symptoms improve. In this case, called gluten intolerance, you may find that gluten does not need to be totally eliminated, just reduced to a level that controls your symptoms.

CoeliacAustralia tells us that 80% of people with coeliac disease haven’t been diagnosed yet, which is 330,000 people by their estimate. You might be one of those that does feel better on a gluten-free diet, but make sure it is the lack of gluten that is making you feel better, not the lack of biscuits/cookies and cakes! If your guts are singing along beautifully then just eat well. And choose good quality gluten-containing foods.

Thursday, June 19, 2014

Brazil - do they have the best dietary guidelines ?

You may not even know that many countries have dietary guidelines. For some countries it is just a case of being able to feed their people. For the well-off democracies the guidelines are needed to combat over-eating and fashion food policy and education.

Earlier this year Brazil released their new dietary guidelines for public comment. When this happens, in English speaking countries, there is some outcry and lobbying for modifications, but the guidelines don’t change a great deal before they become official. Anyway, that to one side, lets take a look at the proposed guidelines.
Brazil’s proposed dietary guidelines
1. Prepare meals from staple and fresh foods.
2. Use oils, fats, sugar and salt in moderation.
3. Limit consumption of ready-to-consume food and drink products.
4. Eat regular meals, paying attention, and in appropriate environments.
5. Eat in company whenever possible.
6. Buy food at places that offer varieties of fresh foods. Avoid those that mainly sell products ready for consumption.
7. Develop, practice, share and enjoy your skills in food preparation and cooking.
8. Plan your time to give meals and eating proper time and space.
9. When you eat out, choose restaurants that serve freshly made dishes and meals. Avoid fast food chains.
10. Be critical of the commercial advertisement of food products.

Do you sense a soul, a sassiness, in these guidelines? To me, it sounds like a call to the days of past, when you ate more with family and friends, when you took pride in cooking a dish for others, when you took time out to eat, not to stuff something down in between meetings.

“Avoid fast food chains”? That wouldn’t get up in a country that relies on them for a few meals each week. “Be critical of food adverts”. Sure. Make that all ads. And best-selling diet books, weight loss programs and self-styled nutrition experts. You might have another view. Here is one US viewpoint.

Australian dietary guidelines
Compare them to the Australian Dietary Guidelines that came out last year.
1. To achieve and maintain a healthy weight, be physically active and choose amounts of nutritious foo and drinks to meet your energy needs.
2. Enjoy a wide variety of nutritious foods from the five groups every day: vegetables; fruit; grains; lean meats and poultry, fish, eggs, tofu, nuts, seeds, legumes; milk, yoghurt, cheese and/or alternatives.
3. Limit intake of foods containing saturated fat, added salt, added sugars and alcohol.
4. Encourage, support and promote breastfeeding.
5. Care for your food; prepare and store it safely.

There is a little more wording than I have given in the Australian guidelines, but the above captures the essence. They are pretty dry and emotionless don’t you think? Is that our national feeling about food? I doubt it, but taking the emotion away allows the focus on the food and nutrients, not the pleasure, the theatre, the cultural significance of food.

Breast milk is a critical food
Note guideline 4 above. I think Australia was the first country to mention breast feeding in their dietary guidelines over 20 years ago. Now Nigeria, Bangla Desh and India also recommend breast feeding for the first 6 months in their guidelines, but not China, Argentina, NZ, Canada or the US (as far as I can determine).

What does it all mean?
You will hear a lot about Brazil throughout the next three weeks. It will be all about the football world cup. In the meantime, add a bit of soul and sassiness to your personal dietary guidelines. Mine include: 
A. Cook most meals from (almost) scratch using simple recipes (because I have a simple mind) 
B. Leave loose change in the jar when you visit a cafĂ© after a long bike ride because the coffee always tastes better that way 
C. Always thank the cook (especially if it wasn’t you)

I’m sure you have you own dietary guidelines that should be considered by any government. Our big problem is that too many people have one dietary guideline: eat whatever is convenient, tastes nice without any discernable flavour beyond salty or greasy or sweet, and doesn’t require any washing up.

Do vegetarians and meat eaters smell different?

I live in a household of vegetarians, but not from my influence. The youngest never enjoyed the texture of meat well before she knew what a vegetarian was. The others came to their own views from the outside world. I still eat meat, but usually when on the road, so I guess I’m a flexitarian. Anyway, whenever the vegetarian vs omnivore discussion comes up, I have never heard the “odour card” played.

In a small study of men who either ate meat or a ‘non-meat’ diet for two weeks it seems that the ladies preferred the aroma of the vegetarian men. Seventeen young men had either a vegetarian diet for 10 days or ate 2 x 100g serves of red meat daily for 10 days. They weren’t allowed to use deodorants or aftershave or anything that gave a non-human smell, nor could they eat foods like garlic, blue cheese or fermented fish (this study was done in Prague, Czech Republic). However, they were given non-perfumed soap.

Near the end of the specified diet period they had to wear a cotton pad in the armpit for 24 hours, under a fresh new cotton T-shirt. Great lengths were taken to avoid any potential background odours. Within an hour of collecting the cotton pads 30 young ladies were asked to rate the body aroma of the men. The aroma of the vegetarian men was rated as more pleasant, more attractive and less intense. 

It wasn’t clear if the odour difference could be over-ridden by offering good quality chocolate to the ladies.