Caffeine & Calcium

David asked if caffeine reduced calcium absorption from food. Well, if it does it is only a small effect. One review paper suggests that just a teaspoon (5 mL) of milk would offset any reduced absorption of calcium, so if you have milk in your tea and coffee (average 30 mL) then you are ahead in the calcium stakes. Sometimes you will hear that caffeine is associated with osteoporosis (brittle bones). This is not the case in those getting enough calcium each day, according the latest review papers.

As we have hinted in the past, caffeine is pretty innocuous and is certainly not the demon you heard about in the 1980s and 1990s.

Salt shaken

Think of salt and health and the first, and possibly only, association you can make is to link salt and high blood pressure. That’s understandable as anyone with hypertension is told cut out salt and choose salt-reduced foods. Having high blood pressure also increases the chances of having a stroke.

Salt, sodium?

It can get confusing when the words salt and sodium get interchanged. The easy thing to remember is that salt is sodium chloride, and it is the sodium part that seems to be the problem. About 10% of the sodium in our diet is found naturally in food; another 10% or so is added at the table or in the kitchen. Guess where the other 80% comes from? More on that later.

Salt effects more than blood pressure

Salt may be causing more problems than high blood pressure. A high salt diet is also known to be associated with osteoporosis because the extra sodium causes calcium to leach from the bones.

Collaborative work between researchers from Australia, New Zealand and the US found that high salt could be having an effect at the level of the artery wall too. Previous research on salt reduction in high salt consumers had shown an improvement in artery function. This was a small study of 34 adults designed to see if the opposite could happen, that is, did adding extra salt to the diet for four weeks cause artery damage?

The answer was “Yes”. The extra sodium in the diet caused artery walls to stiffen as well as causing an increase in blood pressure. What was interesting about this study was that the effect of the extra salt was independent of blood pressure. So, if you eat plenty of salt-laden foods, but your blood pressure is fine, you are likely to still be causing artery damage. Put another way, don’t wait for the doc to tell you that your blood pressure is high before you eat healthy and cut the salt.

What does it all mean?

We fret so much about fat, saturated fat, trans fatty acids and anything that hints of grease, yet not give even a sideways glance at the salt content of foods. I have met only two people who know the definition of a low salt food (one that has less than 120 mg sodium per 100g) and very few people know that “non-salty tasting” foods like bread, cheese and breakfast cereal can pack a fair sodium punch. I don’t want to unduly worry you, but I do think it is time to take note of the one food additive that can definitely affect your health.

Just don’t expect me to be perfect. I love olives and cheese.

Reference: American Journal of Clinical Nutrition. 2010; 91: 557- 564

Salt on the wane

When I tell people that the most dangerous food additive they are likely to eat is salt they get really disappointed because they expect me to say an artificial sweetener or flavour, neither of which probably has any effect on their health. Salt is off the radar; no-one cares about salt.

It’s easy to tell people to stop sprinkling salt on their meals, but in reality this does little to reduce overall salt intake as 80% of the salt in the diet has been put there by food manufacturers.

At the Public Health Association of Australia annual conference recently in Canberra, we were told that the Heart Foundation’s tick program has reduced salt levels by 12% on average in foods with the tick. Kelloggs’ 12 most popular cereals have dropped their sodium by 40% on average. For example, the Cornflakes people ate in the 1980s had one and a half times more salt than the Cornflakes today. Yikes!

By 2013 all the major bread manufacturers will reduce their salt content to a maximum of 400mg/100g. This is a significant step because bread is the main salt source in many people’s diet.

Even Smiths crisps have dropped their salt by 17% and Vegemite has gradually got less and less salt over the last two decades. I’m not suggesting that bread, crisps and Vegemite are, or will become, “low salt”, just that they have a lot less salt than before. Good to see the food industry taking a step in the right direction.

Pasteurisation and calcium

Hannah asked whether pasteurisation (a process that kills bugs) or homogenisation (evenly distributes the fat) of milk affects the calcium content.

Dietitian Helen Mair from Dairy Australia tells us that neither process has any effect, which does make sense because pasteurisation is a very rapid heating and cooling process and minerals like calcium are very stable compounds in food. Even UHT (Ultra High Temperature) milk has retained its calcium.

As mentioned in earlier blogs, low fat milks generally have a higher calcium content.

Skeleton in deposit

Although osteoporosis appears later in life, the process begins during childhood. If there is not enough calcium and vitamin D in the diet or, in the case of vitamin D, insufficient sunlight exposure, then not enough skeletal bone is created during our schooldays. Our bones reach peak mass by the age of 30 years and thereafter decline. The rate of the decline is greatly dampened if adequate calcium is consumed, you remain active, don’t smoke and get all your vitamin D needs through diet or sunshine.

Calcium & vitamin D

Your recommended calcium and vitamin D needs increase as you get older to help forestall the brittle bones of osteoporosis. A greater calcium intake slows down the rate of bone loss in the later decades, while the kidneys become less able to activate vitamin D so more D is needed. High calcium foods usually have their calcium levels mentioned on the label. You need about 1000 mg of calcium a day when you are youthful, increasing to 1300mg a day when you head to the retirement village.

Calcium, where art thou?

You know about milk, yogurt and cheese. There is next to no calcium in butter despite it being a dairy food. Calcium is found in the ‘watery’ part of milk, not the fatty part we call butter. Some canned fish can provide calcium providing you eat the soft bones; think of sardines, pilchards, tuna and salmon. Don’t assume other ‘milks’, like soy and rice milk, have calcium unless they specifically state on the label that they are calcium fortified.

The list below shows you how many serves of selected foods you need to eat to get the same amount of calcium found in a serve of milk or yogurt.

Milk, yogurt, 200g [1.0 serve]

Cheddar cheese, 40g [1.0]

Broccoli, ½ cup [5.5]

Brussel sprouts, ½ cup [8.3]

Cauliflower ½ cup [8.6]

Canned sardines, 100g [1.1]

Sesame seeds, 30g [13.0]

Soy milk (unfortified), 250 mL [31.0]

Soy milk (calcium fortified), 250 mL [1.4]

Almonds

You may recall that Annyca asked about the calcium in almonds. Although I knew their calcium content (about 70mg in a 30g handful) I wasn’t sure how much was likely to be absorbed. That took a little tracking down. Thankfully super-dietitian Helen Mair was able to help. She says you would need to eat about 170g of almonds to get the same amount of calcium as found in a 200 mL glass of milk. That’s about a cup of almonds.

What does it all mean?

Like so many aspects of health, it is what you do throughout life that minimises the risk of brittle bones. Waiting until the first hint of osteoporosis means leaving it too late. Women are more likely to get thin bones because they lose the protection of the hormone estrogen after menopause. In men, testosterone is the hormone that protects bone. Levels of testosterone tend to drop more slowly than does estrogen in women, where women can lose 20% of their bone mass in the decade after menopause. Think about your bones today.

Reference: Whitney & Rolfes. Understanding Nutrition. 10^th edition 2005

Magnesium and fat and calcium

John asked if magnesium had to be present as well for calcium to be absorbed. We know that vitamin D helps calcium to be absorbed from your food. I checked the texts and there was no mention of magnesium being critical for calcium absorption. Some sources of calcium are also pretty good for magnesium too. A cup of reduced-fat milk has about 35 mg magnesium and 200g of yogurt has around 40 mg, about 10% of your daily needs.

Hannah asked if removing fat from milk, making it skim milk, had any effect on calcium absorption. Had to get the sniffer dogs onto that one too. The word is that the fat content doesn’t influence the amount of calcium absorbed from milk. That’s good news because skim milk generally has a higher calcium content, and less kilojoules, compared to full cream milk.

What a waste

Last week I was at the Public Health Association of Australia annual conference in Canberra. I want to tell you something interesting I found out.

Amy White, a postgraduate teaching fellow at Bond University in Queensland told us that around 10-30% of all bananas grown are simply discarded, basically at a loss to the farmer. The sad part is that four out of five discarded bananas are perfectly edible and ideal for consumption. So why do they get thrown?

In this game you need to be bent; straight ones never get to market. Even slightly bent ones won’t make it; you need to be properly bent, but not too bent that you horseshoe. No __double pups__, those bananas that are conjoined, the Siamese banana. No minor blemishes on the skin, little birth marks that don’t affect the flesh. No single or double bananas either. Bananas have to go to market in hands of 3-9 bananas. Yet how often do you, or others, grab just one or two bananas at the shop?

When next you question the cost of fresh produce just think of the amount that gets wasted only because major supermarket chains lay down the law on what is the “perfect” fruit or vegetable. Like humans, bananas come in different shapes and skins; it’s what’s on the inside that counts.