Archive for January 20th, 2019

On Food Choices, part 2: but is it healthy?

January 20, 2019
Once you are open to questioning rituals and time-honoured practices, you find that one question leads to another. (Carl Sagan)
Let food be thy medicine. (Hippocrates)

The central concern about a plant-based diet is this: is it healthy?

It’s a very reasonable question. Committing to any kind of dietary strategy without some understanding of it is to run a potentially dangerous experiment.

We all need to make decisions based upon evidence not dogma or wishful thinking, sometimes easier said than done since we’re creatures of emotion not pure reason.

I’ve been learning a lot lately. What I found is mostly good news but there are things to be aware of and I don’t want to sweep anything under the carpet.

I’m not a climate scientist, but I understand the fundamental science and accept the idea of evidence-based consensus.

I’m not a nutrition scientist or dietician either, but I can inform myself by reading, critical thinking and conversation.

By the same token, here’s a disclaimer: I am not a nutrition scientist or dietician! When I refer to publications, I am reporting what I have found. Everything else is my opinion, hopefully well-informed opinion based upon evidence and reason.

I read fairly widely for what follows but the main references are:

  • the 2013 Australian Dietary Guidelines of the National Health & Medical Research Council (NH&MRC)
  • a supplement to Issue 1999 volume 4 of the Medical Journal of Australia (MJA), and
  • a book by Peter Singer and Jim Mason titled “The Ethics of What we Eat”. Singer is a well known Australian philosopher.

The 2013 Australian Dietary Guidelines from the NH&MRC says this:

Appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthy and nutritionally adequate. Well-planned vegetarian diets are appropriate for individuals during all stages of the lifecycle.

Those following a strict vegetarian or vegan diet can meet nutrient requirements as long as energy needs are met and an appropriate variety of plant foods are eaten throughout the day.

It continues (my italics):

Those following a vegan diet should choose foods to ensure adequate intake of iron and zinc and to optimise the absorption and bioavailability of iron, zinc and calcium. Supplementation of vitamin B12 may be required for people with strict vegan dietary patterns.

Volume 199, Issue 4 supplement of the Medical Journal of Australia (October 9 2013) contains numerous articles about plant-based diets including this one: A plant-based diet — good for us and for the planet.

This issue of MJA also has articles dealing specifically with protein, vitamin B12, iron, zinc and omega-3 from plant-based sources including cereals, legumes, nuts, seeds, oils, and from foods fortified with some of these nutrients.

The MJA article Protein and vegetarian diets (my italics) has this to say:

If a vegetarian diet is planned to meet the requirements for essential micronutrients, including iron, zinc, calcium and vitamin B12, it is likely that protein needs will be exceeded. Most plant foods contain some protein, with the best sources being legumes, soy foods (including soy milk, soy yoghurt, tofu and tempeh), Quorn (mycoprotein), nuts and seeds. Grains and vegetables also contain protein, but in smaller amounts.

In relation to protein, Singer & Mason, in their book The Ethics of What we Eat (p 205, 206) comment that:

The first question most people ask vegans and vegetarians is “Where do you get your protein?” The prevalence of that question is a hangover from an earlier period, starting in the 1930s, when nutritionists believed we needed a high level of protein in our diet, and that a protein-deficient diet was a major cause of malnutrition.

The idea that we need high levels of protein was disproven in the 1970s, and health authorities reduced recommended protein levels to about a third of what had been thought to be required.

I didn’t know about that history before reading this book. A comment that I found a bit surprising is that with the reduced recommended protein intake from the 1970s “…even a diet consisting exclusively of bread, pasta, rice or potatoes will provide adequate protein.” (Singer & Mason, p 206).

Then again, rice underpins the diet of many people around the world. And apparently, contrary to the old saying, man can live by bread (or potatoes) alone. Of course, this says nothing about the other essential nutrients which must be taken into account, only protein, and I think it’s fair to say that there are malnourished people around the world who live on a diet that lacks variety.

The MJA article also has this to say:

While the lower protein intake and quality of protein in a vegetarian diet is often believed to be a concern, there is increasing evidence that consuming protein from plant rather than animal sources may, in fact, be one of the reasons why vegetarians generally have a lower risk of…obesity and chronic disease. In comparison to protein foods of animal origin, most plant protein sources are lower in saturated fat, free of cholesterol and haem iron, higher in fibre, and are good sources of antioxidants and phytochemicals, all of which may contribute to a reduced disease risk.

The MJA article goes on to say that a number of studies show that higher protein intake — animal protein in particular — in childhood may increase the risk of obesity later. It also has a useful table (Box 2) of recommended daily protein intake for different ages and genders.

One morning while taking a break from writing a draft of this post, I ate a nut bar containing 8g of protein. Added to the 3 serves of soy milk I typically have per day, that gives half of the required dietary intake of protein without much effort. A mix of fruits, vegetables, lentils/beans/chickpeas, meat substitutes if desired such as veggie sausages or burgers — there’s around 19g in 2 veggie sausages vs around 25g in a 100g beef steak — will help with the rest.

The MJA article concludes (my italics) with:

Vegetarians who eat a range of plant foods can easily meet their protein requirements, even though the protein content of vegetarian diets is usually lower than that of omnivorous diets. Most Australians eat significantly more protein than is required. The consumption of plant protein rather than animal protein may play a role in weight management and reducing chronic disease risk.

Moving on, Singer & Mason continue with this:

After protein, the nutrient that concerns most people when going on a vegetarian or vegan diet is iron. Many plant foods are rich in iron, including soybeans, molasses, pumpkin seeds, dried apricots, pinto beans, spinach, and raisins. Iron from plant foods may not, however, be as easily absorbed as iron in meat.

Taking vitamin C with iron rich foods makes the iron more available.

Vitamin C is not hard to come by in various fruits (e.g. oranges, strawberries) and juices. Singer & Mason also point out that coffee, tea, and calcium supplements inhibit the absorption of iron. So drinking coffee or tea with a meal makes it harder to absorb iron.

Vitamin B12 requires serious consideration since it is not generally present in plant matter and is necessary for nerve myelin integrity and DNA synthesis. It is created by bacteria and present in animal products such as meat, eggs and dairy, foods fortified with B12 like soy milk, some cereal, and dietary yeast.

Alternatively, a B12 supplement can be taken. Some people, such as those with low intrinsic factor (e.g. in my age group of over 50) or those with pernicious anaemia may need a supplement anyway due to a reduced ability to absorb B12. Some even choose to have B12 injections where there is a known deficiency or a high risk of deficiency.

Indeed, if there is concern about a possible deficiency of any of the important nutrients, a supplement (e.g. multi-vitamin or specific) can be used. On one occasion several years ago when donating blood I was told to take iron supplements before I could donate again. At that time I ate plenty of animal products.

There’s a lot written on the topic of vitamin B12, but the important thing is to be aware of the potential for deficiency, to think about whether you are consuming enough, and to get levels tested if concerned. What every vegan should know about B12 is an honest appraisal and there is also a good MJA article about B12.

The MJA articles don’t have a separate article about calcium but the 2013 NH&MRC guidelines point to fortified foods as sources, again, such as soy milk.

The MJA article about zinc makes a number of points, including:

  • Vegetarians appear to adapt to lower zinc intakes by increased absorption and retention of zinc.
  • Good sources of zinc for vegetarians include whole grains, tofu, tempeh, legumes, nuts and seeds, fortified breakfast cereals and dairy products.

  • Studies show vegetarians have similar serum zinc concentrations to, and no greater risk of zinc deficiency than, non-vegetarians (despite differences in zinc intake).

Sometimes it’s hard to see the forest for the trees. We are used to seeing a food pyramid. The 2013 NH&MRC guidelines present the same thing in a slightly different form:

The main message is:

  • mostly grains and vegetables
  • meat/poultry/fish/eggs or tofu/nuts/seeds/legumes
  • fruit
  • dairy or alternatives

The “in small amounts” parts of the figure are not very surprising either.

In 2006, The American Dietetic Association said that:

Well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life cycle including during pregnancy, lactation, infancy, childhood and adolescence. (Singer & Mason, The Ethics of What we Eat, p 202).

They add that vegetarians have lower rates of heart disease, type 2 diabetes, hypertension, and prostate and colon cancer.

Near the end of their chapter Is it unethical to raise children vegan?, Singer & Mason mention this:

Meanwhile, further evidence of the ability of a vegan diet to provide all the energy and stamina anyone needs was provided by Scott Jurek’s victory in the 2005 Badwater Ultramarathon, one of the toughest events in ultra-long-distance running, Jurek, a vegan, shattered by more than 30 minutes a course record that some thought unbreakable, finishing a full 2 hours ahead of his nearest rival… Along the way, he ate vegan energy bars, potatoes, rice balls and soy protein drinks. Jurek has plenty of predecessors, among them Carl Lewis, who won nine Olympic track and field gold medals between 1984 and 1996. Lewis became a vegan in 1990 and has written that ‘my best year of track competition was the first year I ate a vegan diet.’

This post has only scratched the surface of the question in the title. I obviously don’t have all the answers, but hopefully, this is a start towards allaying some concerns and I’ve tried to be honest about potential problems.

A plant-based diet — good for us and for the planet ends with this (my italics):

Not everyone needs to or wants to become vegetarian, but reducing our dependence on meat is a good recipe for our own health and also that of our planet. Diets dominated by plant foods are almost certainly the way of the future.

So, the decisions we make about what to eat depend, in part, upon the needs of people (personal preference, health, a fair price) and sustainability, the topics parts 1 and 2 were most focussed on.

The next post picks up where the first left off by considering the elephant in the room, so to speak.

Part 3: the elephant in the room