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If you're toying with the idea of a plant-based diet, there's some compelling evidence why you should. Nutritionist Diana Robinson reports.

There are many health benefits associated with a vegetarian diet, such as lowered cardiovascular risk factors and better bowel health. Meat produces carcinogenic compounds when it's cooked at high temperatures; a plant-based diet, on the other hand, results in a significant reduction in cancer risk. Going vegetarian also reduces the environmental effects of animal farming. However, it is important to be aware of potential ‘at risk’ nutrients that are either in lower concentrations or are less bioavailable in plant form.

Protein

This is a macronutrient made of single amino acids that are found in many different foods. Amino acids are classified as either essential (cannot made in the body) or non-essential (can be made in the body). All animal proteins contain both essential and non-essential amino acids, meaning that you eat what’s known as a complete protein. Plant-based proteins contain a range of different amino acids, meaning they give you partial protein. This simply means you need to include a good variety of plant protein to ensure you get all the amino acids needed to make a complete protein. Combining your protein throughout the day or over a few days exposes you to a variety of different amino acids , and is the most effective way to ensure you get enough protein in a vegetarian diet. Soy products like tofu and tempeh are the only vegetarian protein sources that give you a complete amino acid profile.

Macro-minerals

Iron: This essential mineral makes up around 70 percent of blood haemoglobin, which is responsible for transporting oxygen throughout the body. It is also a cofactor for many metabolic, neurological, and immune functions. Iron deficiency results in extreme fatigue, as well as hair loss, weak and splitting nails, poor cognitive function and ‘brain fog, and an increased risk of depression.
Iron is categorised as heme (animal-derived) and non-heme (plant-based). Heme iron is more bioavailable then non-heme forms, so people obtaining iron from plants need to be extra mindful about taking steps to ensure greater absorption. Squeezing lemon juice over food is a great way to promote iron absorption, as vitamin C is a cofactor for iron uptake. Good non-heme iron sources include soy products, black strap molasses, legumes, and green leafy vegetables.
Zinc is another extremely common deficiency, and plays an important role in regulating the immune system, maintaining skin, hair and nails, manufacturing stomach acid, and supporting neurological pathways. Zinc deficiency may result in frequent infections and colds that last longer than one week, poor complexion and slow-to-heal blemishes, poor digestion, and an increased risk of mood disorders, such as depression. Zinc is found in seeds and nuts, with pepitas (pumpkin seeds) yielding the highest concentration, although when eaten raw, the bioavailability is low due to natural enzyme inhibitors found in raw nuts, seeds, grains and legumes.
Calcium: If you are vegan or just don’t consume a lot of dairy, calcium can still be obtained through many plant sources. The amount of calcium that stays in your bones is also a reflection of the acidity of your blood: as calcium is a natural buffer, it is leached from bones to reduce blood pH when it becomes too acidic. A person’s blood can become acidic from a diet high that is high in sugar, animal protein, alcohol, and refined carbohydrates. Maintaining a healthy diet rich in green leafy vegetables is the best way to keep the blood alkaline and reduce calcium leaching. Good sources of calcium are broccoli, spinach, kale, almonds, sesame seeds (also tahini) and soy products (non GM).

Vitamin B12

This is used in protein metabolism and helps form red blood cells. It is known as 'the energy B’, being primarily associated with energy production, and deficiency can result in extreme fatigue associated with anaemia as well as numbness or tingling in the arms and legs. B12 is really only found in animal products, so if you're vegan you will need to supplement. It is found in small amounts in brewer's yeast and fortified products, but if you don't eat eggs, seafood or dairy regularly, you'll need to supplement and have regular blood tests to ensure you don't end up deficient.

Essential fatty acids (EFAs)

Omega-3 fatty acids are made up of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA is primarily responsible for the anti-inflammatory effects of omega-3s, while DHA is an important component of the brain and is involved in memory and cognitive function. The only plant-based source of DHA is from algae, usually consumed by fish. The fish get their DHA from the algae, and we get the DHA from the fish. However, if you don't eat fish, you will need to take a nutritional supplement containing a plant-sourced DHA to avoid deficiency. EFA deficiency signs include dry skin and eyes, poor memory and cognitive function, depression, degenerative diseases such as Alzheimer’s, increased inflammation and an increased risk of hypertension and high LDL (bad) cholesterol.

Tips and tricks

Phytic acid is found in the bran of wholegrains, the skin of legumes, and in nuts and seeds. Phytic acid binds to minerals like calcium, iron, zinc and magnesium, interfering with the absorption of these minerals. To get the most bioavailability out of your grains and legumes, soak them for 24-48 hours before cooking. For nuts and seeds, the process of activation (soaking and drying) will give you the greatest nutrient absorption. Tannins found in tea and coffee also bind to minerals, reducing the absorption through the small intestine. For best mineral absorption, drink tea and coffee 2 hours away from meals. Certain mineral supplements compete for absorption when taken at the same time at high doses: iron and zinc, and also calcium and magnesium, should be taken 2 hours apart.

Diana Robinson is a Melbourne based clinical nutritionist. www.dianarobinsonnutrition.com