Vegetarian Protein - Myths and Facts

Part 3: How Much Protein Do We Need?

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Protein needs vary with age, body-weight, health, circumstance, and stress levels, as well as dietary sources of protein. That's true for a vegetarian diet, as well as non-veg. Our bodies compensate to a large extent for these differences, in maintaining constant internal protein levels

Nitrogen recycling makes this possible. Excess protein can't be stored; it's either broken down and burned for energy (a function more efficiently and healthfully served by carbohydrates) or stored as fat (extra calories from any source are stored as fat). During burning or storage of excess protein, the nitrogen is excreted. Assuming that you're consuming enough calories, if you don't get enough protein in your diet, your body retains nitrogen, from which it makes protein.

How much protein do we need? Let's ask Dr. Science. The nitrogen balance test compares normal daily nitrogen losses (such as sweat, urine, feces, shed skin, lost hair etc.) with intake. A positive balance means more nitrogen coming in than going out, which means there is tissue growth. A negative balance means that more nitrogen is going out than coming into the body, or more protein is being lost than made by the body. This represents a net loss of body protein.

Here's the unscientific answer to how much protein we need: Do we look good, feel good, maintain optimum weight, and have good muscle tone? Do our hair and nails grow quickly? Do our wounds heal well? Are we generally healthy, and recover quickly from illness? If so, then we must be getting enough protein!

Our protein requirements can change dramatically when we're injured or sick. They may double in the short term. The body gets this extra supply mostly from muscle. It may take a month or more to restore the nutrients used up in the body while it fights off an infection or recovers from injury.

Increased protein needs during pregnancy and breast-feeding are usually met by the extra calories from eating more food. Because infants and children are growing they require more protein than adults in proportion to their body weight. Children on a varied, balanced diet usually get enough protein as long as they are getting enough calories.

Athletes and other physically active people don't need a diet higher in protein compared to the recommended balance with fats and carbohydrates. The extra protein needs for building muscle mass can usually be supplied by eating more food. Carbohydrates best supply the extra energy required for strenuous activity.

Protein requirements are affected by the amount of carbohydrate in the diet. One of the effects of carbohydrates is to "spare" protein. Nonessential amino acids can be made from glucose, for example. Sometimes a significant amount is made. The liver maintains minimum blood sugar levels, and it will break down protein to supply glucose if necessary. For example, brain tissue and red blood cells use 140 to 150 grams of glucose over the period of a day. The liver makes sure they get it, either from food, or from converting internal protein to sugar. If there are enough carbohydrates in the diet, there is less need for the liver to make glucose from proteins.

What's the daily protein requirement? The body loses about 0.34 g of protein per kg body weight per day. With a safety margin added, apparently we need .45 g/kg per day of "ideal" protein to replace what's lost. With additional safety margins for digestibility and protein quality, our protein requirement is in the neighborhood of .75g/kg, or about 56 grams of protein for a 70 kg man (160 lb, or an average sized guy). This figure varies widely, depending on where you look. In the end, the variations are not that important since we get enough anyway, often way more than enough. So don't worry too much about scientific determinations of adequate protein intake. That way you can avoid having to translate pounds of body weight into kilograms.

Protein Deficiency

There ARE ways to become protein deficient, but it's pretty difficult. One way is not to get enough food. In parts of the world where famine is real, we can see people with bloated bellies who are obviously protein deficient. But they don't just lack protein - they lack calories, iron, calcium, vitamins - everything. In other words, they're starving to death.

Another way to become protein deficient is to get almost all of your calories from alcohol and/or sugar. Sugar contains no protein! Hard liquor contains almost no protein (beer contains very small amounts). If you are an alcohol/sugar addict, you could become protein deficient.

Another possible cause of protein deficiency is that babies are given foods they can't digest, like cows milk, or inadequate substitutes for breast milk, such as watered down formula, or rice milk. By the way, breast milk, which has been the ideal food for human babies for hundreds of thousands of years, provides 6% of calories as protein - far less than cow's milk, which has 22% of calories as protein.

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