On Monday, my blog looked at why nuts were generally such a good food for diabetics. And part of their attraction is that they are a food rich in protein and fat and low in carbohydrate. These nutritional qualities mean that nuts will liberate sugar in a tempered fashion into the blood stream (they have a low glycaemic index), which is ideal for diabetics who have limited capacity to regulate blood sugar levels.

What sorts of foods a diabetic eats is obviously important for optimising blood sugar control, but so is when food is eaten. Generally, I advocate a ‘little and often’ approach, which usually means breakfast, lunch and dinner, maybe with one or two healthy snacks between meals. For most individuals regular eating can help quell the appetite and naturally control the amount that is eaten at actual meal times. For any given type of meal, smaller volumes will be less disruptive to blood sugar levels than larger meals. Plus, when the appetite has not been allowed to run riot, healthier food choices are usually easier to make. In particular, it tends to make eschewing generally sugar-disruptive foods like bread, potatoes, rice and pasta much easier.

This week, however, saw the publication of a study which suggests that regular eating has another major boon for diabetics. Researchers from Newcastle University in the UK tested what is known as the ‘second meal effect’ [1]. Briefly put, the second meal effect is the effect a meal has on the blood sugar control of a meal eaten subsequently. What they did is test the blood sugar response to a set lunch in two settings in different days. On one day, the lunch was eaten preceded by breakfast some hours before. On another day, no breakfast was given and the same set meal was given.

The results of this study showed that having breakfast appeared to reduce rises in blood sugar levels post-lunch by 95 per cent.

Because the lunch was set in terms of type and size, this means that the presence of breakfast is exerting a strong and potentially important effect on blood sugar balance after a subsequent meal. This has profound significance I think, for diabetics.

But does it have potential ramifications for non-diabetics, too?

Well, I’m not aware of any specific science here, but my experience in practice leads me to believe that regular eating may have specific benefit for non-diabetic individuals. My observations concern people who have food cravings in the afternoon and/or tend to find themselves overeating at night. Generally speaking, I find these issues can often be significantly improved if not completely eliminated by establishing a half-decent breakfast if it wasn’t in place already.

So, how might this work? Well, one mechanism here relates to blood sugar balance. Recently I wrote about carbohydrate cravings (particularly in the afternoon) and their link with episodes of low blood sugar. Well, if breakfast causes less of a blood sugar spike after lunch, it might help to prevent the low blood sugar that can follow it later in the afternoon.

But this effect may also last into the evening. Because more stable levels of sugar throughout the afternoon and maybe into the early evening could also impact positively on eating behaviour in the evening. If this were true, then it might be that eating breakfast might have a positive domino effect on blood sugar levels (and appetite) right through the day.

With regard to what to eat for breakfast I strongly recommend what some regard as standard morning fare such as usually highly sugar disrupting and generally nutritionally inadequate toast/breakfast cereal combo. One good alternative is Bircher muesli – a usually homemade blend of oats, plain yoghurt, fruit, nuts and/or seeds. For some more generally decent breakfast ideas, see here.

References:

1. Jovanovic A, et al. The Second-Meal Phenomenon in Type 2 Diabetes Diabetes Care 2009;32:1199-1201

I saw this morning reports on a study which has found links between vegetarianism and a reduced risk of certain cancers. The study, which assess nutritional habits and cancer risk in more than 61,000 men and women in the UK found that compared to meat-eaters, vegetarians had a 53, 45 and 74 per cent reduced risk in bladder, blood and lymph system (eg. leukaemia and lymphoma) and stomach cancers respectively [1]. Looking at all cancers combined, risk reduction was found to be 12 per cent. Something tells me that those keen on the vegetarian way will wave this study around as yet more ‘proof’ that the vegetarian diet is healthiest for us.

I do not dismiss this evidence out of hand, but I think it is important to bear in mind that this study was epidemiological in nature, and can only then tell us about associations between diet and cancer. But just because two things are associated does not mean one is causing the other. The usual assumption with studies of this nature is that there’s something bad about meat that ups cancer risk. But it may be vegetables are cancer protective and vegetarians eat more of these. Or maybe it’s neither of these things. Or maybe, it’s nothing more than an association and eating meat/fewer vegetables does not cause cancer at all. We just don’t know.

One major problem with epidemiological studies is what are known as ‘confounding’ factors. So let’s say we find from a study less physically active people turn out to have a higher risk of lung cancer. We have found an association between two things that might cause people to conclude that a sedentary lifestyle causes lung cancer. But, imagine that sedentary people are more likely to smoke. Smoking is a potential confounding factor here, and may be the real reason for why sedentary individuals are at heightened risk of lung cancer. In epidemiological studies often an attempt is made to ‘control for’ potential confounding factors. It’s an imprecise science, for sure, but generally better than nothing.

Controlling for potential confounding factors is particularly important when comparing meat-eaters and vegetarians because, generally speaking, they are likely to be more health-conscious than meat-eaters. Meat-eating has an unhealthy reputation, right? And vegetarianism generally as a ‘healthy’ image too. So someone inclined to do what they can to protect or improve their health may be drawn towards eschewing meat. But these individuals may also be drawn to other habits too like smoking less and exercising more.

The study focused on here did control for a variety of potential confounding factors including age, smoking, alcohol intake, body mass index and physical activity level. But another way to level the playing field might be to attempt to compare vegetarians and non-vegetarians who have been matched for a similar level of health consciousness.

In one study, researchers attempted to counteract any confounding factors by focusing only on individuals who shopped in health food stores. The idea here is that all of these individuals are generally ‘health-conscious’, whether they are vegetarian or not. This allows, some would argue, a fairer appraisal of the impact of vegetarian or non-vegetarian eating.

This study did not focus on risk of individual conditions, but a much better marker for overall health: overall risk of death. This study found that compared to the general population, death rates in vegetarians and non-vegetarians were significantly lower than in the general population (which supports the notion that health food shoppers are a generally health-conscious bunch). Crucially, though, overall risk of death in vegetarians and non-vegetarians the same [2].

In another study, vegetarians were asked to recruit their friends and family into the study. Doing this was thought to help ensure that all individuals in the study were similarly health-conscious. Again, death rates for vegetarians and non-vegetarians were essentially the same [3].

In May this year, a study was published which assessed total mortality in a large group of vegetarians and non-vegetarians [4]. Confounding factors controlled for were age, sex, smoking, and alcohol consumption. The result? No difference in risk of death between vegerarians and non-vegetarians. Risk of death from heart disease was the same too.

I read here that Professor Tim Key, the lead author of the study being reported on today “said it was impossible to draw strong conclusions from this one single study”. He is quoted as saying, “At the moment these findings are not strong enough to ask for particularly large changes in the diets of people following an average balanced diet.” Even the study’s lead author seems to have poured cold water on its findings. Perhaps Professor Key is aware of the evidence which shows vegetarianism does not offer distinct health advantages? He should be, seeing as he’s the lead author of the studies mentioned above [2,4] that show that vegetarians have mortality rates the same as non-vegetarians.

References:

1. Key TJ, et al. Cancer incidence in British vegetarians. Br J Cancer. 2009 Jun 16. [Epub ahead of print]

2. Key TJA, et al. Dietary habits and mortality in 11000 vegetarians and health conscious people: results of a 17 year follow up. Br Med J 1996;313:775–9

3. Thorogood M, et al. Risk of death from cancer and ischemic heart disease in meat and non-meat eaters. BMJ 1994;308:1667–70

4. Key TJ, et al. Mortality in British vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Am J Clin Nutr. 2009;89(5):1613S-1619S