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The contents of this pages have been extracted from the pponline web site with acknowledgements and thanks. I have condensed, paraphrased and edited; I have not checked all the facts or all the details.
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As you get older, there will be some changes in how your body processes nutrients, and your need for particular nutrients may alter. Of particular relevance to the veteran athlete are possible diminishing calorie requirements and the need to ensure an adequate intake of calcium and iron. [I'm still just as hungry on trips ... RNC] There's a tendency, as you get older, for your daily energy (calorie) requirement to go down. There are three main components which make up the total daily calories you require. The largest (65-70 per cent) is resting energy expenditure (REE), the amount of calories required to keep your body ticking over and at a constant temperature when you're not active - this includes when you're asleep. You may also come across this referred to as basal metabolic rate (BMR). The effects of physical activity account for another 20-35 per cent, with the remaining 10-15 per cent of energy used up in digesting food. It has become accepted by nutritionists that the BMR slows down as people get older - by about 4 per cent for every 10 years over 25. Thus, many people will tend to gain weight if they continue to eat the same amounts as they always did. However, regular exercise may help to offset this insidious trend. Apart from the extra calories used up in exercise itself, there is pretty good evidence that regular activity increases the BMR too. In a study where men who were involved in endurance exercise were compared with men who did not take part in any regular activity, it was clearly
demonstrated that active older adults had a higher REE than sedentary ones ('Influence of age and endurance training on metabolic rate and hormones in older men', Poehlman et al, American Journal of Physiology 1990; 259, ppE66-E2). A number of other researchers have found that involvement in aerobic exercise offsets the age-related decline in REE. Resistive weight training has also been suggested as a way of maintaining REE, as REE goes up the higher your lean body mass. Ultimately, you are the only one who will know whether you need fewer calories now than you used to. If you're putting on weight without being aware that you're actually eating more food, a slower BMR may be the culprit. Exercise which is regular (as opposed to infrequent mega-sessions) is likely to boost your daily calorie requirement. The exercise doesn't need to be aerobic or endurance-related to have an effect, either - resistance exercise (eg, weight training, yoga) can also work. If you still find that you need to cut down on what you eat to keep to a desired weight, you will need to take more care over the quality of what you eat. If you're an endurance cyclist packing away 5,000 calories a day, you can get away with eating some foods that provide calories and not a lot else (eg, food rich in refined sugars), because you'll still have room to eat foods that will bring in the required amounts of vitamins and minerals. However, if you're dipping below the 2,000 calories a day mark, as an athlete you need to make sure that everything you eat is 'nutrient-rich'. There's another reason too for paying attention to the quality of your food as you get older. Changes in the gut as you age mean that you become less efficient at absorbing nutrients from food. Foods tend to be higher in vitamins and minerals the nearer they are to their natural state. This is particularly true for fruit, vegetables and cereal-derived foods. For example, the refining process which strips away the outer husk of wheat grain to make white flour also strips away significant amounts of B vitamins (these play a crucial part in converting carbohydrates into energy in the body), vitamin E, iron and zinc. Thus, choose whole-food varieties of foods when you can (see table above for comparisons). When cooking, vegetables fare best with minimal cooking - prolonged soaking and boiling lets vitamins (B 1 and C in particular) seep away. It's good practice to make a habit of eating raw fruit or vegetables at least once a day. Protein - no need to panic Lean body mass (which includes muscle) tends to decrease as we get older, which has led to the notion that older people need relatively more protein. In fact, the evidence seems to indicate that the decrease in lean body mass is largely due to decreased activity. If you spend most of your time sitting down, no amount of protein stuffing is going to make your muscles bulge. The only way to increase your lean body mass is to take more exercise, then your body will be able to use what protein there is in your diet to make muscle rather than fat. Inadequate calcium intake is linked with a number of disease states more common in older adults, such as osteoporosis, hypertension, and colon cancer. It's well-documented that the incidence of osteoporosis (thinning of the bones which leads to higher risk of bone breakages) increases with age, postmenopausal women being at particular risk. Bone mass begins to decrease between 20 and 40 years of age, and this loss may continue at a rate of 6 per cent to 10 per cent per decade. Exercise and calcium intake are two key factors which can thwart the incidence and progress of osteoporosis. For both older men and women, it's been found that those with stronger muscles also have greater bone mineral density ('Exercise, nutrition and aging', Evans WJ in Journal of Nutrition, 1992, vol 22: pp796-801). Several studies have shown that bone mineral density is improved by exercise programmes that increase muscular strength and/or endurance. [Use it or lose it. RNC] Although there's good evidence that a high calcium intake can help to maintain bone mineral density, a number of nutritional surveys have found that older people have calcium intakes below recommended amounts. In addition, as you get older, you will be at risk of absorbing less calcium from your food; this is an effect of the stomach production of acid tending to decrease with age. So, if you're taking part in regular exercise, you're taking good care of one side of the equation. Don't blow it with a poor calcium intake. Ways to boost calcium: Calcium supplements are generally a poor choice compared to calcium-rich milk products because the calcium from the supplements is absorbed less effectively than that from milk. People who have trouble digesting milk because they can't digest milk sugar (lactose) need to find alternate calcium sources. Some people who are milk-intolerant can tolerate yoghurt, hard cheeses, or even small amounts of milk. Non-dairy calcium sources include soya milk enriched with calcium, green vegetables, nuts and seeds. This section of the pponline article is not reproduced here. It contains a number of claims here about dehydration which the maintainer believes to be medically wrong. For instance:
Since water makes up such a huge proportion of your body weight, and you are unlikely to lose more than a couple of percent of your body weight through sweating under normal bushwalking conditions, the claim of 'treacle-like' seems grossly exaggerated. The reader is referred to the Food page and the page on Salt, Electrolytes and Sports Drinks where water consumption needs are discussed, with reference to medical articles by Dr Noakes. In particular, the hazards of serious over-drinking (of water!) include cases of death. As you get older you tend to become more prone to aches and pains - from non-specific twinges in the joints to conditions such as arthritis. If you have a medical condition causing you muscular and/or joint pain, take advice from your doctor as to how much and what type of exercise is best for you. Some joint pain has been shown to respond well to dietary treatment. One of the most promising is the use of fish oil. A number of trials have indicated that symptoms of rheumatoid arthritis can be relieved in some people by taking fish oil supplements. Fish rich in the specific type of oil include mackerel, salmon, sardines, pilchards, herrings, kippers and (uncanned) tuna. The liver of white fish is also rich in oil - hence cod liver oil. There is a potential biochemical explanation for this - fish oil contains a special type of fat (omega3 fatty acids) which when metabolised by the body interacts with the system responsible for inflammation, damping it down. Since some joint pain is caused by inappropriate inflammation, relief is brought about by decreasing the inflammation response. Another bonus of fish oil is that it seems to decrease the 'clottability' of the blood, thereby decreasing the risk of heart disease and strokes. [However, other research has shown that over-consumption of fish oil has its own medical problems. Once again, a broad diet of good foods is far better than the latest health fad. RNC] © pponline and Roger Caffin 1/3/2002Introduction
Metabolic go-slow
Iron and Anaemia
Iron deficiency anaemia is common among older adults. Risk factors for iron deficiency include a low-calorie diet, low protein consumption, impaired iron absorption, or blood loss due to injury or disease. Iron deficiency among older adults is often caused by gastrointestinal haemorrhage and/or poor iron intake. The best dietary sources of iron are organ meat (eg, liver) and red meat. There are vegetable sources of iron too (green vegetables, whole grains, pulses), but these are absorbed less easily. Absorption from these sources increases if you eat them at the same time as meat. But if you don't eat meat, or are trying to cut down, there is another way to raise vegetable iron absorption - that's by eating something rich in vitamin C at the same time, such as raw or lightly cooked vegetables, or fresh fruit juice. [My wife tried mixing bushwalking with a vegetarian diet. The result was pretty disasterous: acute aneamia and gross fatigue in the afternoons. A return to a 'normal' omnivore diet solved this in a few days. RNC]Calcium and Osteoporosis
Fluid requirements
The fluid in sweat is borrowed from a number of sources within the body, the most critical of which is the fluid lost from blood plasma. The result is a smaller and more sluggish blood volume, which gets increasingly treacle-like the more dehydrated you get.
Remedies for aches and pains
Conclusion
As a veteran athlete you need to follow general guidelines for sensible sports nutrition - ensuring that you have a good carbohydrate intake and eating plenty of fresh foods. If you're eating less than you used to, try to make sure that the food you do eat is pulling its weight in terms of its nutrient content - and in particular, watch out for calcium and iron.