Besides a heart full of love and a big smile, romance can bring some positive health benefits.
Some scientific studies suggest that a loving relationship, physical touch and sex can bring health benefits.
Anything that exercises your heart is good for you, including sex. Sexual arousal sends the heart rate higher, and the number of beats per minute reaches its peak during orgasm.
But, as with most exercise, it depends how vigorously you do it. Some studies show the average peak heart rate at orgasm is the same as during light exercise, such as walking upstairs. That's not enough to keep most people fit and healthy.
Adults should do at least 150 minutes (2.5 hours) of moderate-intensity aerobic activity, such as cycling or fast walking, every week.
Unless you're having 150 minutes of orgasms a week, try cycling, brisk walking or dancing.
Having heart disease doesn't have to hold you back in the bedroom. Experts advise that you can usually have sex as long as you can do the everyday activities that have the same impact on your heart without causing chest pain, such as walking up two flights of stairs.
Source: Rerkpattanapipat P, Stanek MS, MN Kotler. Sex and the heart: What is the role of the cardiologist? European Heart Journal 2001;22: 201-208.
Embracing someone special can lower blood pressure, according to researchers.
In one experiment, couples who held each other's hands for 10 minutes followed by a 20-second hug had healthier reactions to subsequent stress, such as public speaking.
Compared with couples who rested quietly without touching, the huggers had:
So give your partner a hug -- it may help to keep your blood pressure healthy.
Similar effects have been found for non-sexual stroking, although this appears to only reduce blood pressure in women who are stroked, not men.
Source: Grewen KM, Anderson BJ, Girdler SS, Light KC. Warm partner contact is related to lower cardiovascular reactivity. Behavioural Medicine, 2003;29:123-30.
Sex could help you beat the stresses of 21st century living, according to a small study of 46 men and women.
Participants kept a diary of sexual activity, recording penetrative sex, non-penetrative sex and masturbation.
In stress tests, including public speaking and doing mental arithmetic out loud, the people who had no sex at all had the highest stress levels.
People who only had penetrative sex had the smallest rise in blood pressure. This shows that they coped better with stress.
Plenty of people find that intimacy or orgasm without penetration helps them feel relaxed, as do exercise or meditation. It doesn't have to be penetrative sex -- it's whatever works for you.
Try these 10 stress busters.
Source: Brody S. Blood pressure reactivity to stress is better for people who recently had penile-vaginal intercourse than for people who had other or no sexual activity. Biological Psychology, 2006;71:214-22.
There's a link between how often you have sex and how strong your immune system is, researchers say.
A study in Pennsylvania found students who had sex once or twice a week had higher levels of an important illness-fighting substance in their bodies.
Immunoglobulin A (IgA) was 30% higher in those who had sex once or twice a week than in those who had no sex at all. The lowest levels were in people who had sex more than twice a week.
But don't devise a sex calendar just yet. More research is needed before it can be proved that weekly sex helps your immune system.
Another study found stroking a dog resulted in raised IgA levels in students. Resting quietly or stroking a stuffed dog didn't.
Sources: Charnetski CJ, Brennan FX. Sexual frequency and salivary immunoglobulin A (IgA). Psychology Report , 2004;94:839-44.
Charnetski CJ, Riggers S, Brennan FX. Effect of petting a dog on immune system function. Psychology Report , 2004;95:1087-91.
It could be that people who feel healthier have more sex, but there seems to be a link between sexual activity and your sense of wellbeing.
A study of 3,000 Americans aged 57-85 showed that those who were having sex rated their general health higher than those who weren't.
And it's not just sex -- it's love, too. People who were in a close relationship or married were more likely to say they felt in "very good" or "excellent" health than just "good" or "poor".
It seems that emotional and social support can boost our sense of wellbeing.
Find out about five steps to mental wellbeing.
Source: Lindau ST, Schumm LP, Laumann EO, et al. A Study of Sexuality and Health among Older Adults in the United States. New England Journal of Medicine . 2007;357:762-74.
A happy marriage can help fend off angina and stomach ulcers -- at least, it can if you're a man.
One study of 10,000 men found those who felt "loved and supported" by their spouse had a reduced risk of angina.
This was the case even if they had other risk factors, such as being older or having raised blood pressure.
Similarly, a study of 8,000 men found there was more chance of them getting a duodenal ulcer if they:
Researchers suggest that stress, lack of social support and coping style can all affect a man's likelihood of developing an ulcer.
Sources: Medalie JH, Goldbourt U. Angina pectoris among 10,000 men. II. Psychosocial and other risk factors as evidenced by a multivariate analysis of a five-year incidence study. American Journal of Medicine , 1976;60:910-21.
Medalie JH, Stange KC, Zyzanski SJ, Goldbourt U. The importance of biopsychosocial factors in the development of duodenal ulcer in a cohort of middle-aged men. American Journal of Epidemiology , 1992;136:1280-7.
Spending an evening with friends is good for your health, too. One 10-year study of 1,500 people over 70 years old found those with stronger friendship networks lived longer than those with fewer friends.
Researchers thought this could be because friends may have a positive influence on lifestyle choices, such as smoking or exercise, and offer emotional support.
Source: Giles LC, Glonek GF, Luszcz MA, Andrews GR. Effect of social networks on 10-year survival in very old Australians: the Australian longitudinal study of aging. Journal of Epidemiology and Community Health, 2005;59:574-9.
A life without sex is no bar to excellent health. A long-term study into the health and ageing of a group of nearly 700 older nuns found many kept active and lived well into their 90s and past 100.
Since 1986, participants in The Nun Study had yearly checks on their physical and mental abilities. Researchers used convent records to obtain their social, family and educational background.
While they found some links between lifestyle and dementia -- for example, higher education or positive emotions in early life might cut the risk of dementia -- this isn't linked to sexual activity.
If you do have sex, using a condom will help protect you and your partner against sexually transmitted infections (STIs) and unplanned pregnancy.