Soundbites: Having survived thousands of nautical miles, months at sea and successfully navigated the Cape of Good Hope many 16th century European explorers could do little more than drool at the meaty rabbit and game dishes in a land of plenty.
As luck would have it, these intrepid explorers who reached South Africa were toothless with scurvy. It's rare to come across scurvy, beri-beri or pellagra these days, but there are some subtle and some not-so-subtle pointers to poor nutritional status.
Psychological symptoms are often the first tell tale signs that food not only provides the nutrients to keep our bodies healthy and active, but food can also affect our mood and mental function.
Given the complexity of the brain's chemistry, it seems that even marginally poor intakes of certain nutrients can, over time, have significant effects on our temperaments.
Take the B vitamins for example. Increased irritability and depression are frequently reported in studies where diets are too low in thiamin (vitamin B1). These problems resolve when thiamine- rich foods are returned to the diet. Even people who meet the RDA for thiamin feel more clear-headed, composed and energetic after two months of supplementing their diets with additional thiamine.
Depression may also be the only overt symptom of a mild vitamin B12 deficiency. This vitamin is unique among vitamins in that it's found almost exclusively in foods of animal origin such as meat, poultry, fish, eggs or dairy products. As a result, strict vegetarians have an increased risk of B12 deficiency.
Older people may have low B12 intakes as well. This is because we need a protein called intrinsic factor to help us absorb B12.
We make B12 in our stomachs but older people may not produce enough due to wasting and deteriorating stomach glands. In this case, neither diet nor oral supplements will correct the problem and B12 must be injected or administered as a nasal spray.
In the US National Health and Nutrition Examination Survey, those people with a history of depression were also found to have lower folate levels than those who had never been depressed.
Current studies reviewing the efficacy of treatments for depression are now exploring the use of folic acid as an adjunctive therapy.
Apart from the B vitamins, your mineral status is also important. Poor mood is associated with a low selenium intake. Iron deficiency anaemia is associated with lethargy, problems of sustaining attention and poor mood.
Anaemic women experience more psychiatric symptoms such as anxiety and depression than women with sufficient intakes.
Mental functions are also affected by the larger macro-nutrients in our diets. Carbohydrate-rich foods are reputed to be mood foods - they help you to relax, whereas protein- rich foods perk you up when you're drowsy, and sugar and fat offer a quick fix when you're feeling down.
Having said that, these effects can certainly be more subtle than the effects of alcohol, drugs or caffeine!
As long as you haven't eaten in a few hours, a pure carbohydrate snack can give you that 'mellow' feeling. When you eat carbohydrates, your pancreas gets the signal to secrete insulin. In addition to helping process carbohydrates, insulin clears the blood of a variety of amino acids by carrying them into the tissues.
For some reason, the amino acid tryptophan gets left behind, and with all its competition gone, more tryptophan is able to make its way into the brain.
There it's converted into serotonin, a brain chemical that helps regulate your mood. The more carbohydrate you eat, the more serotonin you create, and the more relaxed you feel. That's the theory at any rate.
The problem is that you have to eat your pure carbohydrate snack on an empty stomach, without any protein or fat, and then wait half an hour for your body to process it. Fat is off limits because it slows your digestion, dampening or delaying the effect.
And protein will cancel the process by introducing too many new amino acids into the bloodstream.
Unfortunately, even the high carbohydrate foods (potato, rice and bread) contain sufficient protein to ensure that tryptophan levels do not rise all that significantly and the effects of eating carbohydrates are subtle to say the least. Then again it's pasta not Prozac!
Add a few meatballs to your bowl of pasta at lunch, and you'll avoid the serotonin surge altogether. Protein introduces a new batch of amino acids to your bloodstream that compete with tryptophan for entry into the brain, so you never get that sleepy mellow feeling.
Add in too many meatballs at the expense of the pasta and you're likely to experience increased anger, depression and tension. That may explain why many Atkins dieters are so irritable!
Arguably the food that has the greatest impact on mood is chocolate. Regarded by many as the surest route to food nirvana, chocolate contains a little caffeine and a similar substance called theobromine that may add a pleasant buzz to your endorphin high.
Interestingly, poor mood and stress can inversely affect how much we eat. Stress can make us comfort eat or binge eat lots of less nutritious foods; so called 'emotional eating'. On the other hand, other people react to stress by going off their food and not eating at all. Studies consistently find that those people who are trying to restrict their calories normally (slimmers) eat more when under stress.
In contrast, non-restrained eaters either do not change their food intake or eat less when under stress.
Funny that - I've never met an unstressed dieter!
Paula Mee is an independent food and nutrition consultant. She is co-presenter of RTÉ Television's Health Squad programme.